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Tremendous amount of sludge is generated annually from freshwater treatment or sewage. The high temperature slagging co-gasification converts the sludge to slag showing the potential application for construction material. In this study, the physico-chemical properties of 4 types of slags generated from the co-gasification of municipal solid waste (MSW) with sludge from freshwater treatment or sewage, and ashes from sludge incineration are comprehensively analyzed. Leaching performance of the sludge-derived slag and mortar (with slag as the fine aggregate), as determined based on Toxicity Characteristic Leaching Procedure (TCLP), batch leaching and column leaching tests, indicates the slag can be considered safe for reutilization. Compressive strength test demonstrates that the mortars perform excellently and have the potential to replace sand in concrete production. The consolidation coefficient of slag (1.6 - 39.1 m 2 /year) is lower than the sandy silt but higher than clay. Additionally, the coefficient of permeability (∼1.96 × 10 -3 m/s), angle of shearing resistance (∼39°), and undrained shear strength (375.5 ± 54.8 kPa) of the slag are comparable to sand. The life cycle assessment (LCA) is also conducted to evaluate the environmental impacts and benefits of reutilizing sludge-derived slag as an alternative material for concrete production and land reclamation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, a gravity-driven membrane (GDM) filtration system and hydroponic system (cultivating basil and lettuce) were combined for nutrient recovery from primary municipal wastewater. The GDM system was optimized by increasing the periodic air sparging flow rate from 1 to 2 L/min (∼15 hr per 3-4 days), resulting in a ∼52% reduction of irreversible fouling. However, the total fouling was not alleviated, and the water productivity remained comparable. The GDM-filtrated water was then delivered to hydroponic systems, and the effects of hydroponic operation conditions on plant growth and heavy metal uptake were evaluated, with fertilizer- and tap water-based hydroponic systems and soil cultivation system (with tap water) for comparison. It was found that (i) the hydroponic system under batch mode facilitated to promote vegetable growth with higher nutrient uptake rates compared to that under flow-through feed mode; (ii) a shift in nutrient levels in the hydroponic system could impact plant growth (such as plant height and leaf length), especially in the early stages. Nevertheless, the plants cultivated with the GDM-treated water had comparable growth profiles to those with commercial fertilizer or in soils. Furthermore, the targeted hazard quotient levels of all heavy metals for the plants in the hydroponic system with the treated water were greatly lower than those with the commercial fertilizer. Especially, compared to the lettuce, the basil had a lower heavy metal uptake capability and displayed a negligible impact on long-term human health risk, when the treated water was employed for the hydroponic system., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Plastic disposal has become a challenge due to its challenging degradability, and plastics recycling is one of the ideal methods. The utilization of recycled plastic in building materials has been widely researched as a possible way to store plastics permanently. An investigation on the modification and incorporation of polyethylene terephthalates (PET) on fresh and hardened properties of mortar composites (MCs) is performed in the study. The work provides understanding of the synergistic effects of plastic modification methods with different types of PET additives on MC properties and to explain behavior of modified PET in mortar composites. Modification methods include microwave radiation, chemicals oxidation and alkaline hydrolysis. These methods are applied on three types of structural PET materials (hard particles, hard strips and soft yarns). The properties of 0.5%-3% PET added MCs include workability, compressive strength (CS), flexural strength (FS) and toughness are determined. At 28 days, 3% hydrolysis-treated PET yarns significantly increased FS by 69.6% and improved toughness by almost 15 times while CS with 3% PET particles modified by microwave radiation and chemicals oxidation were comparable to the control., Competing Interests: Declaration of competing interest The author declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Chemically activated biochar is effective in supercapacitors and water splitting, but low conductivity hinders its application as a carbon support in carbon dioxide reduction reaction (CO 2 RR). Based on the observed CO 2 RR performance from potassium hydroxide (KOH)-activated biochar, increased microporosity was hypothesized to enhance the performance, leading to selection of potassium carbonate (K 2 CO 3 ) for activation. K 2 CO 3 activation at 600℃ increased microporosity significantly, yielding a total Faradaic efficiency of 72%, compared to 60% with KOH at 800℃. Further refinement of thermal ramping rate enriched micropore content, directly boosting FE C to 82%. Additionally, K 2 CO 3 's lower activation temperature could preserve hydroxyl groups to improve ethylene selectivity. These findings demonstrate that optimizing microporosity and surface chemistry is critical for designing activated biochar-based CO 2 RR electrocatalysts. Despite lower electrical conductivity of activated biochar, selecting the appropriate activating agents and conditions can make it a viable alternative to carbon black-based electrocatalysts., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The removal of uranyl ions (UO 2 2+ ) from water is challenging due to their chemical stability, low concentrations, complex water matrix, and technical limitations in extraction and separation. Herein, a novel molybdenum disulfide/graphene oxide heterojunction (MoS 2 /GO-H) is developed, serving as an effective electrode for capacitive deionization (CDI). By combining the inherent advantages of electroadsorption and electrocatalysis, an innovative electroadsorption-electrocatalysis system (EES) strategy is introduced. This system utilizes interface polarization at the MoS 2 /GO-H electrode, with its extraordinary adsorption capacity of 805.57 mg g 2 /GO-H electrode, with its extraordinary adsorption capacity of 805.57 mg g -1 under optimal conditions, effectively treated uranium-laden wastewater from a mine, achieving over 90% removal efficiency despite the presence of numerous competing ions at concentrations significantly higher than UO 2 2+ . Employing density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, it is found that the MoS 2 /GO-H total charge density at the Fermi level, enhanced by interfacial polarization, surpasses that of separate MoS 2 and GO, markedly boosting conductivity and electrocatalytic effectiveness., (© 2024 Wiley‐VCH GmbH.)

Ion-selective electrodes (ISEs) have widespread use in the fields of clinical and environmental analyses. Tetrahydrofuran (THF) is the most used solvent for the preparation of modern ISEs, equipped with ion-selective membranes (ISMs). Until now, the influence of impurities in THF toward potentiometric instability of ion-selective membrane based ISEs was probably associated with the presence of either residual water or peroxide. To address this issue, most literature recommends redistilling THF prior to use in the preparation of the potentiometric membranes. Current study reveals that the actual THF impurity that is responsible for potential instability in the ISM includes products from the oxidation of THF, which contains the hydroxyl group and possibly carbonyl group with a boiling point of above 200 °C. The density functional theory calculation supported pathway of the chemical reaction of THF oxidation, hence, the chemical structure of the uncertain impurities was predicted. The underlying reason for the deteriorating potential stability of the ISEs is proposed as the significant hydrophilicity of these impurities that affect the partitioning of the ion sensing components in the membrane, thus enhancing the leaching of the membrane components from the membrane phase. This finding explains why redistillation of aged THF is advised.

Paper-based microfluidics combined with potentiometric measurement has emerged as an attractive approach for detecting various chemical ionic moieties. Detection of heavy metal ions, using paper substrates as solution sampling and delivery systems remains challenging despite efforts to introduce several physico-chemical paper substrate modifications to stop adsorption of ions onto the paper substrates. This study quantitatively investigates the adsorption of heavy metal ions on the paper substrates during paper-based potentiometric measurements and explains the super-Nernstian response of potentiometric sensors through local depletion of heavy metal ions from the solution. Consequently, based on the investigated ion adsorption, a corrective potential protocol was established for the electrodes coupled with paper-based solution sampling by predicting interference free sensor response from paper-based measurement. Furthermore, the ion adsorption was also recorded for mixed metal ion solutions to understand competitive primary/interfering ions adsorption onto the paper substrates and establish corrective measures to predict interference free sensor response. In this method, no modifications of the paper substrates are necessary before actual potentiometric measurements. The proposed corrective protocol allows prediction of sensor response based on the paper-based solution sampling potentiometric measurement, providing a simple methodological approach based on correction of potential readout of the potentiometric sensor, thus completely resigning from the need of modifying paper substrate for measurements of heavy metal ions.

Prolonged drought conditions are a critical challenge for agricultural advancement, threatening food security and environmental equilibrium. To overcome these issues, enhancing plant resilience to drought is essential for plant growth and sustainable agriculture. In this study, blue-emitting antioxidant carbon dots (B-CDs), synthesized from citric acid and ascorbic acid, emerged as a promising solution to enhance the drought resistance of peas ( Pisum sativum L.). B-CDs can efficiently scavenge reactive oxygen species (ROS), which are harmful in excess to plants under stress conditions. Through detailed experimental analyses and density functional theory (DFT) studies, it is found that these B-CDs possess structures featuring eight-membered aromatic rings with abundant oxygen-containing functional groups, providing active sites for reactions with ROS. The practical benefits of the B-CDs are evident in tests with pea plants exposed to drought conditions. These plants show a remarkable reduction in ROS accumulation, an increase in photosynthetic efficiency due to improved electron transfer rates, and significant growth enhancement. Compared to untreated controls under drought stress, the application of B-CDs results in an impressive increase in the fresh and dry weights of both the shoots and roots of pea seedlings by 39.5 and 43.2% for fresh weights and 121.0 and 73.7% for dry weights, respectively. This suggests that B-CDs can significantly mitigate the negative effects of drought on plants. Thus, leveraging B-CDs opens a novel avenue for enhancing plant resilience to abiotic stressors through nanotechnology, thereby offering a sustainable pathway to counter the challenges of drought in agriculture.

Leaching of potentially hazardous substances, especially the heavy metals from Incineration Bottom Ash (IBA) is a major problem in its recyclable usage. To address this concern, treatment of IBA is indispensable before it can be reused. IBA subjected to laboratory-scale treatment typically yields clearer conclusions in terms of leaching behaviors, benefiting from the controlled laboratory environment. However, the leaching behaviors of commercially treated IBA appear to be more ambiguous due to the complex and comprehensive nature of industrial-scale treatments, where multiple treatment techniques are involved concurrently. Furthermore, treatment efficiencies vary among different plants. In this study, three types of commercially treated IBA were sampled from leading waste treatment companies in Singapore. Characterization and leaching tests were performed on the treated IBAs in both standardized and modified manners to simulate various scenarios. Besides deionized water, artificial seawater was used as a leachant in leaching tests for simulating seawater intrusion. The results reveal the promoting effect of seawater on the leaching levels of several elements from three types of treated IBA, which may require special attention for IBA application and landfill near the coast. Furthermore, the elements examined in these three types of commercially treated IBA generally comply with the non-hazardous waste acceptance criteria outlined in Council Decision, 2003/33/EC (2003), except Sb. By combining two leaching tests, the elements were categorized into different types of leaching behavior, making it possible to prepare and respond to the concerning leaching scenarios in future engineering applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

With the proliferation of reverse osmosis technology, seawater reverse osmosis desalination has been heralded as the solution to water scarcity for coastal regions. However, the large volume of desalination brine produced may pose an adverse environmental impact when directly discharged into the sea and result in energy wastage as the seawater pumped out is dumped back into the sea. Recently, zero liquid discharge has been extensively studied as a way to eliminate the aquatic ecotoxicity impact completely, despite being expensive and having a high carbon footprint. In this work, we propose a new strategy towards the treatment of brine to seawater level for disposal, dubbed reclaimed seawater discharge (RSD). This process is coupled with existing resource recovery techniques and waste alkali CO 2 capture processes to produce an economically viable waste treatment process with minimal CO 2 emissions. In this work, we placed significant focus on the electrolysis of brine, which simultaneously lowers the salinity of the desalination brine (56.0 ± 2.1 g/L) to seawater level (32.0 ± 1.4 g/L), generates alkali brine from seawater (pH 13.6) to remove impurities in brine (Mg 2+ and Ca 2+ to below ppm level), and recovers magnesium hydroxide, calcium carbonate, chlorine, bromine, and hydrogen gas as valuable resources. The RSD is further chemically dechlorinated and neutralised to pH 7.3 to be safe to discharge into the sea. The excess alkali brine is used to capture additional CO 2 in the form of bicarbonates, achieving net abatement in climate change impact (9.90 CO 2 e/m 3 ) after product carbon abatements are accounted., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

A strategy for enhancing value creation from pyrolysis gas and oil, derived from plastic waste, through the generation of two additional outputs of solid carbon and hydrogen was investigated. Three types of hard-to-recycle plastic waste (marine plastic litter, household mixed plastics and cosmetic products packaging) were thermally treated in two stages: (i) decomposition of feedstock into gas and oil via pyrolysis at 600 °C; and (ii) thermolytic conversion of the pyrolysis gas and a fraction of oil into hydrogen and solid carbon at 1300 °C separately. The thermolysis of both pyrolysis gas and oil fractions predominantly resulted in the production of solid carbon (39-70 wt% per plastic feedstock and carbon content of 91.3-98.6 wt%) and H 2 -rich gas (H 2 yield of 5.9-10.8 wt% per plastic waste feedstock and H 2 content of 71.4-97.2 vol% per gas volume). The incorporation of pyrolysis oil into the thermolysis process could enhance the outputs of solid carbon and hydrogen. Characterizations of solid carbon and hydrogen obtained from pyrolysis gas and oil fractions were further conducted. The observed similar properties of H 2 and solid carbon from pyrolysis gas and oil supported the feasibility of introducing all the pyrolytic products together into the thermolysis process without condensation of oil. To enhance the value of these solid carbon derived from plastics for practical usage, we utilized the obtained solid carbon as a reinforcing agent for polymer composite foam development. The solid carbon reinforced composite foam displayed great abrasion resistance (wear loss: 240 mg), compression strength (0.347 MPa), and dynamic impact properties (energy returned: 124 J/m and energy absorbed: 57.3 J/m), emphasizing the viability of solid carbon as a nucleating agent and reinforcing filler in polymer foam for cushioning applications. Overall, the strategy of pyrolysis-thermolysis, which harnesses both pyrolysis gas and oil, unlocks additional value creation by producing two new outputs from plastic waste. Depending on the market prices for solid carbon and hydrogen, this can substantially change the economics of plastic waste management and create new revenue streams, incentivizing plastic waste collection and processing., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Globally waste incineration is becoming the predominant treatment method of solid waste. The largest fraction of solid residue of this process is incineration bottom ash (IBA) requiring further treatment before applications such as in the construction industry become feasible. In this study, vitrification of IBA was conducted in a demonstration-scale high-temperature slagging gasification plant fueled with MSW and biomass charcoal as a green auxiliary fuel. High IBA co-feeding rates of up to 491 kg/h (equivalent to 107% of MSW feeding rate) were achieved during the trials. A highly leaching-resistant slag immobilizing heavy metals in the glass-like amorphous structure and recyclable iron-rich metal granules were generated in the process. The heavy metal migration into the solid by-product fractions depended on the IBA feeding rates and process conditions such as cold cap temperature, charcoal-to-ash ratio, and gasifier temperature profile. Slaked lime and activated carbon powder were used in a dry flue gas treatment and stack gas emissions were kept well below Singapore's regulatory limits. Steam from the hot flue gas was generated in a boiler to drive a steam turbine. The application of biomass charcoal instead of fossil fuels or electricity lead to a lower carbon footprint compared to alternative vitrification technologies. The overall results reveal promising application of high temperature slagging gasification process for commercial-scale vitrification of IBA., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Switching from a linear mode of waste management to a circular loop by transforming plastic waste into carbon nanotubes (CNTs) is a promising approach to current plastic waste treatment. One of the many applications of CNTs is its use for electrocatalytic water splitting for hydrogen evolution. Existing methods of CNTs-based hydrogen evolution reaction (HER) electrode fabrication involve additives like polymeric binders and additional steps to improve CNT dispersion, which are detrimental to the CNT structure and properties. The in-situ fabrication approach can potentially be a one-pot solution to HER electrode synthesis. In this study, polyolefins pyrolysis gas and a Co:Ni:Mg catalyst were used to fabricate binder-free CNTs-based electrodes on different substrates for HER. The study assessed CNT quality on conductive carbon paper, semiconductive silicon, and dielectric glass substrates, evaluating their HER performance in 1 M KOH. A mixture of hollow-core, bamboo-like, and cup-stacked arrangement nanotubes were synthesized on the substrates, with CNTs on glass and carbon paper substrates possessing better graphitization than CNTs grown on silicon. This is in agreement with HER performance, whereby the as-prepared electrodes required overpotentials of 267 mV, 241 mV, and 216 mV for silicon, glass, and carbon paper, respectively, to achieve 10 mA/cm 2 . Despite being poorly conductive, the glass substrate electrode achieved a lower overpotential than the silicon electrode. Additionally, the as-prepared silicon electrode faced a delamination issue likely attributed to the lower surface energy of the silicon substrate surface, demonstrating the weaker adhesion between the CNTs and silicon surface. The proposed approach thus showed that the in-situ fabricated electrodes performed better than separately synthesized CNTs prepared into electrodes by 27.4% and 14.2% for carbon paper and glass substrates, respectively. The improved performance of the as-prepared, binder-free electrodes can be linked to the lower charge-transfer resistance and reduced contact resistance between the CNTs and substrate., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Acoustic agglomeration is a technique that leverages on sound waves to promote the collision of aerosol particulate matter, thus leading to the formation of larger particle agglomerates. In this study, this acoustics-driven phenomenon is demonstrated for its usefulness as an aerosol pre-conditioning method to significantly enhance the efficiency of filtration systems in particle treatment processes. Specifically, favorable changes in pressure drop across the filters are observed as a result of receiving less particle mass, for which filters are shown to be able to have their operational life extended remarkably by more than 50%. The involved ultrasonic aerosol agglomeration mechanisms are unveiled through numerical simulations, and the effects of residence time, sound pressure level, and initial particle number concentration on agglomeration performances are experimentally investigated. In addition, validations and measurements of filter pressure drop are obtained through a series of experiments. This study provides a comprehensive overview to the design and performance characterization of acoustics-agglomeration-enhanced filtration systems, which could potentially derive energy savings for fan power in ventilation systems and be scaled up for applications in industrial plants for reducing carbon emissions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Numerous efforts have been devoted to understanding the electron transfer process of uranium (UO 2 2+ ) on adsorbent materials, whereas the potential oxygen vacancies (OVs) in metal oxides have long been overlooked. Once these interactions are taken into account, the emerging molecular orbital effects undoubtedly affect the adsorption process. Here, we synthesized CC/γ-MnO 2 by growing MnO 2 on carbon cloth (CC), followed by the creation of oxygen vacancies (OVs) through electrochemical methods to form CC/γ-MnO 2 -OVs. The CC/γ-MnO 2 , with the maximum adsorption capacity increasing from 456.8 to 1648.1 mg/g (by a factor of 3.6). Theoretical calculations suggest that the generation of OVs leads to an increase in charge transfer and a decrease in adsorption energy between UO 2 2+ , with the maximum adsorption capacity increasing from 456.8 to 1648.1 mg/g (by a factor of 3.6). Theoretical calculations suggest that the generation of OVs leads to an increase in charge transfer and a decrease in adsorption energy between UO 2 2+ and CC/γ-MnO 2 , due to the interaction between Mn 3d orbital in CC/γ-MnO 2 and O 2p orbital in UO 2 2+ . The OVs in CC/γ-MnO 2 provide a spatial structure for anchoring the OU=O moiety of UO 2 2+ , while the surface van der Waals forces and the formation of chemical bonds between Mn-U contribute to charge interactions. This synergistic effect allows CC/γ-MnO 2 -OVs to exhibit favorable selectivity, a large adsorption capacity, and rapid adsorption kinetics towards uranyl ions. This work achieves enhanced UO 2 2+ separation by introducing OVs in CC/γ-MnO 2 through a facile electrochemical strategy, highlighting the great potential for nuclear waste processing., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Yuhui Liu reports financial support was provided by National Natural Science Foundation of China., (Copyright © 2023. Published by Elsevier B.V.)

Utilization of renewable raw materials as feedstock defossilizes industrial manufacturing while subsequent carbon capture reduces carbon footprint. We applied this concept to design a new pyrolysis-based process for synthesis of biogenic multi-walled carbon nanotubes (MWCNTs) and H 2 from biomass. It was demonstrated that the conversion of hydrocarbon compounds in pyrolysis gas into MWCNTs and H 2 is detrimentally influenced by accompanied CO 2 released from biomass decomposition. Capturing CO 2 with a calcium sorbent upgraded the pyrolysis gas into a suitable gaseous precursor for downstream production of MWCNTs and H 2 -rich gas. Furthermore, the results suggest that CO 2 capture with the sorbent has a potential to outperform a liquid alkaline scrubber owing to avoided liquid organic waste generation, sorbent regenerability and higher H 2 recovery from biomass pyrolysis gas., (© 2023 Wiley-VCH GmbH.)

The replacement of natural gas with plastic-derived pyrolysis gas can defossilize H 2 production, while subsequent capture, utilization and storage of carbon in a solid form can decarbonize the process. The objective of this study was to investigate H 2 production from three types of plastics using a process comprising pyrolysis (600 °C) and thermolysis stages (1200-1500 °C). Depending on the plastic feedstock and thermolysis temperature, the laboratory-scale setup generated 1000-1350 mL/min product gas with H 2 purity of 74.3-94.2 vol%. The recovery of 5-9 wt% molecular H 2 per mass of plastics was achieved. Other products included solid residue (0.1-12 wt%) and oil (8-52 wt%) from the pyrolysis reactor, solid carbon (36-53 wt%) and gas impurities (2-16 wt%) from the thermolysis reactor. The purity of H 2 gas was detrimentally influenced by polyethylene terephthalate in the feedstock due to the dilution of gas by CO. The decomposition of methane containing in the pyrolysis gas was the limiting reaction step during H 2 production and improved at higher thermolysis temperature. Three solid carbon structures were formed during the thermolysis stage regardless of the plastic type: carbon black aggregates, carbon black aggregates coated with a layer of pyrolytic carbon and a carbon film on the inner reactor wall. Among the three types of carbon, the highest valorization potential was identified for carbon black aggregates. Plastic feedstock composition had little if any effect on carbon black properties, while high thermolysis temperature (1500 °C) reduced the particle sizes and increased the surface area of aggregates., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A multiphase CFD-DEM model was built to simulate the waste-to-energy gasifying and direct melting furnace in a pilot demonstration facility. The characterizations of feedstocks, waste pyrolysis kinetics, and charcoal combustion kinetics were first obtained in the laboratory and used as model inputs. The density and heat capacity of waste and charcoal particles were then modelled dynamically under different status, composition, and temperature. A simplified ash melting model was developed to track the final fate of waste particles. The simulation results were in good agreement with the site observations in both temperature and slag/fly-ash generations, verifying the CFD-DEM model settings and gas-particle dynamics. More importantly, the 3-D simulations quantified and visualized the individual functioning zones in the direct-melting gasifier as well as the dynamic changes throughout the whole lifetime of waste particles, which is otherwise technically unachievable for direct plant observations. Hence, the study demonstrates that the established CFD-DEM model together with the developed simulation procedures can be used as a tool for the optimisation of operating conditions and scaled-up design for future prototype waste-to-energy gasifying and direct melting furnace., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Herein, five N, S-co-doped carbocatalysts were prepared from different carbonaceous precursors, namely sawdust (SD), biochar (BC), carbon-nanotubes (CNTs), graphite (GP), and graphene oxide (GO) and compared. Generally, as the graphitization degree increased, the extent of N and S doping decreased, graphitic N configuration is preferred, and S configuration is unaltered. As peroxymonosulfate (PMS) activator for ciprofloxacin (CIP) removal, the catalytic performance was in order: NS-CNTs (0.037 min -1 ) > NS-BC (0.032 min -1 ) > NS-rGO (0.024 min -1 ) > NS-SD (0.010 min -1 ) > NS-GP (0.006 min -1 ), with the carbonaceous properties, rather than the heteroatoms content and textural properties, being the major factor affecting the catalytic performance. NS-CNTs was found to have the supreme catalytic activity due to its remarkable conductivity (3.38 S m -1 ) and defective sites (I D /I G  = 1.28) with high anti-interference effect against organic and inorganic matter and varying water matrixes. The PMS activation pathway was dominated by singlet oxygen ( 1 O 2 ) generation and electron transfer regime between CIP and PMS activated complexes. The CIP degradation intermediates were identified, and a degradation pathway is proposed. Overall, this study provides a better understanding of the importance of selecting a suitable carbonaceous platform for heteroatoms doping to produce superior PMS activator for antibiotics decontamination., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Seed nano-priming is a promising technology employed in the agronomic field to promote seed germination and plant growth. However, the effects of carbon dots (CDs) on plant development via seed nano-priming remain unclear. In the present study, CDs synthesized from non-biodegradable plastic wastes were adopted as a nano-priming agent for pea (Pisum sativum) seed treatment. The results demonstrated positive effects of seed priming at all CD concentrations (0.25-2 mg/mL), including accelerated seed germination rate, increased shoot and root elongation, biomass accumulation, and root moisture level compared to the control groups. Surface erosion of seed coat was observed after CD priming, which effectively promoted seed imbibition capability. CD penetration, internalization, and translocation were confirmed using transmission electron microscopy. Furthermore, the CD-plant interaction significantly enhanced seed antioxidant enzyme activity, as well as augmented root vigor, chlorophyll content, and carbohydrate content. These findings exhibit great potential of waste-derived CDs as nano-priming agents for seed germination and seedling development in a cost-effective and sustainable manner., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Polymer foam that provides good support with high energy return (low energy loss) is desirable for sport footwear to improve running performance. Ethylene-vinyl acetate copolymer (EVA) foam is commonly used in the midsole of running shoes. However, EVA foam exhibits low mechanical properties. Conventional mineral fillers are usually employed to improve EVA's mechanical performance, but the energy return is sacrificed. Here, we produced nanocomposite foams from EVA and multi-walled carbon nanotubes (CNT) using a chemical foaming process. Two kinds of CNT derived from the upcycling of commodity plastics were prepared through a catalytic chemical vapor deposition process and used as reinforcing and nucleating agents. Our results show that EVA foam incorporated with oxygenated CNT (O-CNT) demonstrated a more pronounced improvement of physical, mechanical, and dynamic impact response properties than acid-purified CNT (A-CNT). When CNT with weight percentage as low as 0.5 wt% was added to the nanocomposites, the physical properties, abrasion resistance, compressive strength, dynamic stiffness, and rebound performance of the EVA foams were improved significantly. Unlike the conventional EVA formulation filled with talc mineral fillers, the incorporation of CNT does not compromise the energy return of the EVA foam. From the long-cycle dynamic fatigue test, the CNT/EVA foam displays greater properties retention as compared to the talc/EVA foam. This work demonstrates a good balanced of mechanical-energy return properties of EVA nanocomposite foam with very low CNT content, which presents promising opportunities for lightweight-high rebound midsoles for running shoes.

Removal of radioactive uranyl ions (UO 2 2+ ) from water by effective adsorbents is highly desired but remains a challenge. UO 2 2+ are easily combined with H 2 O, and the polarization of H 2 O affects the complexation between UO 2 2+ and the adsorbent. Thus, it is necessary to reconstruct the UO 2 2+ active site to improve the adsorption capacity. Herein ，an amphiphilic ligand, namely N, N-dimethyl-9-decenamide (NND), is successfully prepared. NND replace H 2 O in [UO 2 (H 2 active sites. The predicted maximum adsorption capacity increased from 50.7 to 500.7 mg g 5 ] 2+ by hydrogen bonding, thereby enhancing the adsorption capacity of MoS 2 particles in the reconstituted UO 2 2+ active sites. The predicted maximum adsorption capacity increased from 50.7 to 500.7 mg g - 1 (by a factor of 9.87) with the presence of NND, which is higher than other functional group-modified MoS 2 adsorbents. Furthermore, NND and MoS 2 can retain UO 2 2+ uptake under extreme conditions including high acid-base and gamma irradiation. Theoretical Calculations of NND through H bonding produces an increased amount of charge transfer and a reduced adsorption energy between UO 2 2+ and MoS 2 , which weakens the polarization effect of H 2 O. The findings showed that NND appeared to be a promising amphiphilic to improve the adsorption efficiency of UO 2 2+ from water., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests, Yuhui Liu reports financial support was provided by National Natural Science Foundation of China., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Paper-based microfluidic solution sampling is a viable option for potentiometric sensors to be used for the determination of analytes in samples with high solid-to-liquid ratios. Unfortunately, heavy metal sensitive electrodes cannot be easily integrated with paper-based solution sampling as heavy metals have strong physicochemical adsorption affinity towards paper substrates. In this work, paper substrates were modified with an ion-selective membrane (ISM) cocktail (used for the preparation of Pb 2+ -ion-selective electrodes (ISEs)) and coupled with model heavy metal Pb 2+ -ISEs. It was found that the super-Nernstian response of Pb 2+ -ISEs was eliminated when 10 to 50 mg ml -1 of the ISM cocktail was used for the modification of paper substrates. The modification of the paper substrates by Pb 2+ -ISM allowed the elimination of adsorption sites. In addition, it resulted in an improvement of sensor performance in terms of their detection limits to be similar to those for conditioned electrodes in standard beaker-based measurements. It is believed that the elimination of super-Nernstian response of the electrodes and improving the potentiometric responses and detection limits of ISEs were attributed to the compatibility improvement of the paper substrates and Pb 2+ -ISEs to the same type of ISM.

This study comparatively investigated the influence of changes in pyrolysis temperature on the physicochemical, structural, and adsorptive properties of biochars derived from a green waste (Cynodon dactylon L.). For this purpose, the biophysically dried green wastes were pyrolyzed at 400 °C, 600 °C, and 800 °C under the same pyrolysis conditions. The results revealed that the physicochemical and structural properties were varied, depending upon the pyrolysis temperatures. With the increase of pyrolysis temperature, the surface functional groups were escaped, the structure became more porous (pore volume of 0.089 ± 0.001), the metal oxides were remained consistent, and the biochars turned into more alkaline nature (pH of 11.9 ± 0.2). Furthermore, as referring to the adsorptive performance for potentially toxic elements, with experimental adsorption capacity of up to 33.7 mg g -1 and removal rate up to 96% for a multi-metals containing solution, the biochars pyrolyzed at high temperature (800 °C) was significantly (p < 0.05) higher than those pyrolyzed at low temperature (400 °C). According to the physicochemical and structural properties, and the adsorptive performances of the biochars, the optimal pyrolysis temperature was herein recommended to be 800 °C., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Current synthesis routes of bismuth oxide nanosheets (BiONS) are relatively complicated, requiring the use of halogens or metalloids. Herein, a facile method to synthesize BiONS without the addition of halogens or other metalloids was developed. The synthesized BiONS were identified to have flake-shaped structures (300-1000 nm in width) with the thickness of 6-10 nm, which were predominantly made of β-Bi 2 O 3 . Such BiONS were applied to modify the surface of screen-printed carbon electrodes (BiONS-SPCEs) for the development of a robust palladium (Pd 2+ ) sensor. After optimizing the electrochemical parameters of the sensor, it was found that the linear sensor response range and limit of detection for Pd 2+ were 40-400 and 1.4 ppb, respectively. The electrocatalytic activity of the Pd 2+ -sensor was validated in the competing environment of other metal and metalloid ions. Real samples collected during a Pd recovery process from pharmaceutical wastewater were used to verify the application of BiONS-SPCEs in control of palladium recovery process. The quantitative results of post recovery palladium concentrations obtained using BiONS-SPCEs in treated pharmaceutical wastewater samples were in good agreement with those obtained by inductively coupled plasma-optical emission spectrometry (ICP-OES). Thus, such Pd 2+ -sensor provided the possibility of on-site process control of complex industrial samples for obtaining near-instant information that would lead to better management of resources used in the process, and same time assure environmental standards for both recovered products and processed discharge., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Polyolefins such as polyethylene (PE) and polypropylene (PP) are abundant components of plastic waste. Chemical recycling of PE and PP via pyrolysis followed by chemical vapor deposition typically results in the growth of multi-walled carbon nanotubes (CNTs). Here, a tandem catalytic system for the growth of few-walled CNTs is reported. The successful synthesis of few-walled CNTs in the system relies on the catalytic processing of pyrolysis gas from plastics into intermediate gas mixtures containing mainly paraffins and hydrogen (700 °C, catalyst: 40 wt% Co, 10 wt% Mo and 50 wt% MgO). Under appropriate conditions (1000 °C, catalyst: Co 3 wt%, Mo 2 wt% and MgO 95 wt%, synthesis time: 20 min), the obtained intermediate gas mixture was selectively converted into few-walled CNTs with > 95% CNTs having small outer diameters of 1-7 nm, containing CNTs with as little as three walls and having distinct radial breathing mode in Raman spectra at wave lengths 100-400 cm -1 . The proposed synthesis process opens new opportunities for production of high value few-walled CNTs from plastic waste., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Fe 2 O 3 -Al 2 O 3 catalysts applied for conversion of polyolefin plastic waste into multi-walled carbon nanotubes (MWCNTs) and H 2 are typically produced by impregnation, co-precipitation or sol-gel synthesis at atmospheric pressure and temperatures below 100 °C. This study utilized hydrothermal conditions and established the role of precipitating agents (urea, N-methylurea and N,N'-dimethylurea) on properties and catalytic activity of Fe 2 O 3 -Al 2 O 3 catalysts (Fe-u, Fe-mu and Fe-dmu, respectively). The precipitating agent played a key role in tailoring the properties, such as crystallization degree, surface area and reducibility. The precipitating agents influenced the yield and outer diameters of MWCNTs but did not affect graphitization degree. Among the synthesized catalysts, Fe-u had the largest surface area and preferential formation of the highly reducible α-Fe 2 O 3 crystalline phase. As a result, Fe-u had the highest activity during conversion of pyrolysis gas from low-density polyethylene (LDPE) into MWCNTs, yielding 0.91 g·g -1 -catalyst MWCNTs at 800 °C as compared to 0.42 and 0.14 g·g -1 -catalyst using Fe-dmu and Fe-mu, respectively. Fe-dmu favored the growth of MWCNTs with smaller outer diameters. Fe-u demonstrated high efficiency during operation using a continuous flow of pyrolysis gas from a mixture of polyolefins (70 wt% polypropylene, 6 wt% LDPE and 24 wt% high density polyethylene) producing 4.28 g·g -1 -catalyst MWCNTs at 3.2% plastic conversion efficiency and a stable H 2 flow for 155 min (25-32 vol%). The obtained data demonstrate that the selection of an appropriate precipitating agent for hydrothermal synthesis allows for the production of highly active Fe 2 O 3 -Al 2 O 3 catalysts for the upcycling of polyolefin plastic waste into MWCNTs and H 2 ., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Slagging-gasification has received increasing attention as a municipal solid waste treatment technology. Compared with incineration, slagging-gasification can produce valuable syngas and generates by-products that can be easier reusable in different applications in some cases. Among these by-products, the gasification fly ash (GFA) is the only hazardous solid residue to be landfilled. To explore its potential recycling methods and maximize its recycling efficiency, the detailed physicochemical properties of GFA are crucial. This study conducted a comprehensive characterization of six GFA samples and the results were compared with one incineration fly ash (IFA) sample and available data of IFA collected in Singapore in literature. X-ray fluorescence (XRF), and microwave acid digestion (MAD) followed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectroscopy (ICP-MS) were carried out to determine the physicochemical composition of ashes. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were applied to identify their mineralogical composition. The hazard of the material was assessed through one-stage batch leaching tests. The results showed that the GFAs and IFA were both mainly composed of calcium compounds and chloride salts. However, GFA contained higher amounts of heavy metals especially lead (Pb) and zinc (Zn) than IFA. Zn contents in tested GFA samples were in a range of 1.4-3.0%, indicating the potential to recover Zn. The Ca(OH) 2 content in GFA samples was up to 24.1%, which could be recovered as a low-grade lime. Based on the characteristics of GFA, a reusing method combining civil engineering utilization and resource recovery was suggested., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

As 2-hydroxybenzoic acid (HBA) represents a typical pharmaceutical and personal care product (PPCP), constant releasing of HBA into the environment poses threats to the ecology, and thus it is critical to develop effective techniques to remove HBA from water. Recently, sulfate radical (SO 4 ‒ )-based advanced oxidation processes involved with monopersulfate (MPS) activation are proven as effective approaches for eliminating PPCPs from water, and Co 3 O 4 is recognized as a capable catalyst for activating MPS. Therefore, great interests have arisen to develop Co 3 O 4 -based catalysts with advantageous morphologies and characteristics for enhancing catalytic activities. Therefore, a special Co 3 O 4 -based material is proposed in this work. Through a surfactant-assisted strategy, a cubic Co-MOF is prepared and used as a precursor, which is etched to afford hollow structure, and then transformed into hollow porous Co 3 O 4 nanobox (PCNB). PCNB can exhibit distinct reactive surface with abundant surface oxygen vacancy as well as physical properties in comparison to the commercial Co 3 O 4 NPs (com-Co 3 O 4 NP), thereby leading to the outstanding catalytic activity of PCNB for activating MPS to degrade HBA. The activation energy (E a ) of 46.2 kJ/mol is also calculated using PCNB + MPS system, which is much lower than most of recent reported studies for activating MPS. PCNB could be also reusable over 5 consecutive HBA degradation cycles. The activation mechanism of MPS by PCNB and HBA degradation pathway are also comprehensively elucidated via experimental evidences and the theoretical calculation to offer insightful information of development of Co 3 O 4 for HBA degradation., (Copyright © 2021. Published by Elsevier Ltd.)

As bromate removal and reduction can be also achieved using metals, aluminum (Al) appears as the most promising one for reduction of bromate because Al is abundant element and exhibits a high reduction power. Reactions between bromate and Al shall be even enhanced through ultrasound (US) process because US can facilitate mass transfer on liquid/solid interfaces and clean surfaces via generating microscale turbulence to facilitate reactions. Therefore, the aim of this study is for the first time to investigate the effect of US on bromate removal by Al metal. Specifically, Al particle would be treated by HCl to afford HCl-treated Al (HCTAL), which is capable of removing bromate and even reducing it to bromide. Such a mechanism is also validated by density function theory calculation through determining adsorption energy as -152.8 kJ/mole, and oxygen atoms of bromate would be extracted and reacted with Al atoms, releasing bromide ion. US not only facilitated bromate removal by further increasing removal capacity under the acidic condition but also suppressed the inhibitive effect from basicity at relatively high pH. The spent HCTAL could still remove bromate and convert it to bromide after regeneration. These features indicate that US considerably enhances bromate removal by Al. PRACTITIONER POINTS: Bromate removed by Al is elucidated by DFT calculation with E absorption  = -152.8 kJ/mole. Oxygen atoms of bromate are extracted and reacted with Al atoms, releasing bromide ion. A higher power of ultrasound would substantially enhance bromate removal efficiency. Ultrasound also suppresses the inhibitive effect from basicity at relatively high pH. With ultrasound, the interference of co-existing anions on bromate removal is lessened., (© 2022 Water Environment Federation.)

Catalytic activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) (or collectively known as persulfate, PS) using carbocatalyst is increasingly gaining attention as a promising technology for sustainable recalcitrant pollutant removal in water. Single heteroatom doping using either N, S, B or P is widely used to enhance the performance of the carbocatalyst for PS activation. However, the performance enhancement from single heteroatom doping is limited by the type of heteroatom used. To further enhance the performance of the carbocatalyst beyond the limit of single heteroatom doping, multi-heteroatom doping can be conducted. This review aims to provide a state-of-the-art overview on the development of multi-heteroatom-doped carbocatalyst for PS activation. The potential synergistic and antagonistic interactions of various heteroatoms including N and B, N and S, N and P, and N and halogen for PS activation are evaluated. Thereafter, the preparation strategies to develop multi-heteroatom-doped carbocatalyst including one-step and multi-step preparation approaches along with the characterization techniques are discussed. Evidence and summary of the performance of multi-heteroatom-doped carbocatalyst for various recalcitrant pollutants removal via PS activation are also provided. Finally, the prospects of employing multi-heteroatom-doped carbocatalyst including the need to study the correlation between different heteroatom combination, surface moiety type, and amount of dopant with the PS activation mechanism, identifying the best heteroatom combination, improving the durability of the carbocatalyst, evaluating the feasibility for full-scale application, developing low-cost multi-heteroatom-doped carbocatalyst, and assessing the environmental impact are also briefly discussed., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Metal modified paper-based substrates were utilized for microfluidic paper-based solution sampling coupled with Pb 2+ -ion selective electrodes (ISEs) with the aim of controlling the super-Nernstian response which usually occurs when using unmodified paper substrates. Potentiometric responses of Pb 2+ -ISEs coupled with gold, platinum and palladium coated paper substrates were investigated. Potentiometric response time was found to be predominantly dependent on the thickness of metallic layer deposited at the paper substrates. Paper-based substrates coated on both sides with 38 nm gold layers were found to be the most advantageous in controlling the super-Nernstian response of ISEs at non-equilibrium conditions. Durability studies indicated that the lifetime of Pb 2+ -ISEs could be doubled when used with paper-based substrates in complex environmental samples with high solid-to-liquid content. Determination of lead in real samples using metal modified paper substrates coupled with Pb 2+ -ISEs was validated by inductively coupled plasma optical emission spectrometry (ICP-OES). Detailed life cycle assessments were performed for model screen printed potentiometric sensors with and without metal modified paper-based solution sampling substrates. The results confirmed that the use of modified paper substrates demonstrated lower environmental impact per potentiometric measurement of Pb 2+ -ISE in prepared simulated environmental sample as compared to sensors without the use of paper substrates., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Thermochemical conversion of plastic wastes into carbon nanotubes (CNTs) and hydrogen is a promising management option to eliminate their hazardous effect. The yields and morphologies of CNTs strongly depend on the catalyst design and reaction conditions. To boost the efficiency, tuning of bimetallic nanoparticles as catalyst is an effective approach. For that reason, A-site-deficient perovskite La 0·8 Ni 1-x Co x O 3-δ (LN 1-x C x , x = 0.15, 0.5, 0.85) was developed and used as a catalyst precursor to achieve in situ formation of bimetallic Ni-Co nanoparticles. At an optimized Ni-to-Co ratio, the LN 0.5 C 0.5 exhibited the highest yields of multi-walled CNTs, namely 840 and 853 mg/g catalyst from high density polyethylene and polypropylene, respectively. This could be attributed to the higher catalytic capability of LN 0.5 C 0.5 catalyst for the decomposition of hydrocarbons into hydrogen and carbon. In both cases, multi-walled CNTs had regular shapes when the reaction temperature was 700 °C. At higher reaction temperatures, the morphological changes of carbon products were observed from multi-walled CNTs to carbon nano-onions. The Raman spectra showed that compared with the commercial multi-walled CNTs, the as-prepared multi-walled CNTs had a lower degree of defects., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

It is very important to develop green composite materials owing to increasing global environmental issues. One of the alternative raw materials for the production of green composites is biomass. Bagasse sorghum is a promising alternative raw material for the manufacturing of particleboard composites. The influence of sorghum accessions on the performance of particleboard composites was analyzed in this study. In addition, the particleboard quality was made using maleic acid (MA) adhesive and compared with citric acid (CA) and phenol-formaldehyde (PF) adhesives. Three accessions of sorghum, 4183A, super 1, and Pahat, were used as raw materials in particleboard manufacturing. The 20 wt% MA adhesive was applied in particleboard manufacturing. The board dimensions and density targets were 30 × 30 × 0.9 cm 3 and 0.8 g/cm 3 , respectively. The particle mat was pressed 200 °C for 10 min with a maximum of 6.5 MPa. For reference, the JIS A 5908-2003 was used to evaluate physical and mechanical properties, SNI 7207-2014 was used for the resistance against termites, and JIS K 1571-2004 for evaluated the particleboard against decay. The results showed that the sorghum accession in this research did not affect the quality of the particleboard. The thickness swelling (TS), internal bond (IB), modulus of elasticity (MOE), and modulus of rupture (MOR) of particleboard satisfied JIS A 5908-2003 type 8. The particleboard using MA was comparable with those bonded with CA and had better durability against termites and decay than PF adhesives. The ester linkages were formed due to the reaction between MA (carboxyl groups) and the sorghum bagasse (hydroxyl groups) after being analyzed using Fourier transform infrared (FTIR). Therefore, particleboard in this study has good quality., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Nickel nanoparticles (NiNPs) supported on activated multi-walled carbon nanotubes (MWCNTs) were used as an adsorbent applied towards Pb(II), As(V) and Cd(II) remediation from industrial wastewater. The result revealed the hydrophilic surface of MWCNTs-KOH was enhanced with the incorporation of NiNPs enabling higher surface area, functional groups and pore distribution. Comparatively, the removal of Pb(II), As(V) and Cd(II) on the various adsorbents was reported as NiNPs (58.6 ± 4.1, 46.8 ± 3.7 and 40.5 ± 2.5%), MWCNTs-KOH (68.4 ± 5.0, 65.5 ± 4.2 and 50.7 ± 3.4%) and MWCNTs-KOH@NiNPs (91.2 ± 8.7, 88.5 ± 6.5 and 80.6 ± 5.8%). Using MWCNTs-KOH@NiNPs, the maximum adsorption capacities of 481.0, 440.9 and 415.8 mg/g were obtained for Pb(II), As(V) and Cd(II), respectively. The experimental data were best suited to the Langmuir isotherm and pseudo-second order kinetic model. The fitness of experimental data to the kinetic models in a fixed-bed showed better fitness to Thomas model. The mechanism of metal ion adsorption onto MWCNTs-KOH@NiNPs show a proposed electrostatic attraction, surface adsorption, ion exchange, and pore diffusion due to the incorporated NiNPs. The nanocomposite was highly efficient for 8 adsorption cycles. The results of this study indicate that the synthesized nanocomposite is highly active with capacity for extended use in wastewater treatment., (Copyright © 2021 Elsevier B.V. All rights reserved.)

During high temperature slagging gasification of municipal solid waste (MSW), coal coke is typically used as an auxiliary fuel to maintain the high temperature in the gasifier and convert ashes into slag. Herein, biomass charcoal was utilized as a greener and more sustainable auxiliary fuel to replace the coal coke during stable and continuous gasification of MSW. Several monitoring characteristics were assessed, like operating conditions of the gasifier, influence of local MSW properties generated in Singapore, environmental impacts, and main by-products (slag, fly ash and metals). The performance data revealed that the replacement of coal coke with biomass charcoal provided significant environmental benefits. The use of biomass charcoal resulted in 78% less SO 2 emissions, and 22% less generated fly ash because the lower sulfur content in biomass charcoal resulted in a 32% reduced use of sorbent for flue gas treatment. Furthermore, there was clear evidence of a 22% carbon footprint reduction due to replacing fossil fuel as auxiliary fuel. In addition, the slag characteristics demonstrated lower heavy metals leaching as compared to the incineration bottom ash generated from the conventional MSW incineration plant suggesting its great potential in the application as clean and green waste-derived material in the construction industry., (Copyright © 2021 Elsevier B.V. All rights reserved.)

While cobalt (Co) stands out as the most effective non-precious metal for activating monopersulfate (MPS) to degrade organic pollutants, Co nanoparticles (NPs) are easily aggregated, losing their activities. As many efforts have attempted to immobilize Co NPs on supports/substrates to minimize the aggregation issue, recently hollow-structured carbon-based materials (HSCMs) have been regarded as promising supports owing to their distinct physical and chemical properties. Herein, in this study, a special HSCM is developed by using a special type of ZIF (i.e., ZIF-L) as a precursor. Through one-step chemical etching with tannic acid (TA), the resultant product still remains leaf-like morphology of pristine ZIF-L but the inner part of this product becomes hollow, which is subsequently transformed to ultrafine Co-NP embedded hollow-structured N-doped carbon (CoHNC) via pyrolysis. Interestingly, CoHNC exhibits superior catalytic activities than CoNC (without hollow structure) and the commercial Co 3 O 4 NPs for activating MPS to degrade phenol. The E a value of phenol degradation by CoHNC + MPS was determined as 44.3 kJ/mol. Besides, CoHNC is also capable of effectively activating MPS to degrade phenol over multiple-cycles without any significant changes of catalytic activities, indicating that CoHNC is a promising heterogeneous catalyst for activating MPS to degrade organic pollutants in water., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Laboratory scale recycling of marine plastic litter consisting of polyethylene terephthalate (PET) bottle sorting, pyrolysis and chemical vapor deposition (CVD) was conducted to identify the technical and environmental implications of the technology when dealing with real waste streams. Collected seashore and underwater plastics (SP and UP, respectively) contained large quantities of PET bottles (33.2 wt% and 61.4 wt%, respectively), suggesting PET separation was necessary prior to pyrolysis. After PET sorting, marine litter was converted into pyrolysis oil and multi-walled carbon nanotubes (MWCNTs). Water-based washing of litter prior to pyrolysis did not significantly change the composition of pyrolysis products and could be avoided, eliminating freshwater consumption. However, distinct differences in oil and MWCNT properties were ascribed to the variations in feedstock composition. Maintaining consistent product quality would be one of challenges for thermochemical treatment of marine litter. As for the environmental implications, life cycle assessment (LCA) demonstrated positive benefits, including improved climate change and fossil depletion potentials. The highest positive environmental impacts were associated with MWCNT production followed by pyrolysis oil and PET recovery. The benefits of proposed approach combining PET sorting, pyrolysis and CVD allowed to close the waste loop by converting most of the marine litter into valuable products., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Size and magnetic separation of incineration bottom ash (IBA) are common for ferrous metals recovery, however, their influences on the mineral phase and the element redistribution, and subsequently the induced variation of metal leaching potential herein remain limited understanding. The lack of research in this field may misunderstand IBA performances, cause confused results for comparison among various studies, and potentially lead to biased conclusions. We herein quantitatively investigate the effects of size and magnetic separation on the IBA based on element distribution, leaching behavior, morphology, and mineralogy with statistical analysis. For preparation, sieving was performed with the original IBA (to obtain 7 size-fractions termed as OR1-7, respectively), followed by magnetic separation of each, to further yield magnetic fractions (MF1-7) to discriminate nonmagnetic fractions (NF1-7). In this study, we show that size and magnetic separation may pose significant yet different impacts on different fractions, which would affect their leaching potential concerning their respective downstream applications., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Metal Organic Frameworks (MOFs) represent a promising class of metallic catalysts for reduction of nitrogen-containing contaminants (NCCs), such as 4-nitrophenol (4-NP). Nevertheless, most researches involving MOFs for 4-NP reduction employ noble metals in the form of fine powders, making these powdered noble metal-based MOFs impractical and inconvenient for realistic applications. Thus, it would be critical to develop non-noble-metal MOFs which can be incorporated into macroscale and porous supports for convenient applications. Herein, the present study proposes to develop a composite material which combines advantageous features of macroscale/porous supports, and nanoscale functionality of MOFs. In particular, copper foam (CF) is selected as a macroscale porous medium, which is covered by nanoflower-structured CoO to increase surfaces for growing a cobaltic MOF, ZIF-67. The resultant composite comprises of CF covered by CoO nanoflowers decorated with ZIF-67 to form a hierarchical 3D-structured catalyst, enabling this ZIF-67@Cu foam (ZIF@CF) a promising catalyst for reducing 4-NP, and other NCCs. Thus, ZIF@CF can readily reduce 4-NP to 4-AP with a significantly lower E a of 20 kJ/mol than reported values. ZIF@CF could be reused over 10 cycles and remain highly effective for 4-NP reduction. ZIF@CF also efficiently reduces other NCCs, such as 2-nitrophenol, 3-nitrophenol, methylene blue, and methyl orange. ZIF@CF can be adopted as catalytic filters to enable filtration-type reduction of NCCs by passing NCC solutions through ZIF@CF to promptly and conveniently reduce NCCs. The versatile and advantageous catalytic activity of ZIF@CF validates that ZIF@CF is a promising and practical heterogeneous catalyst for reductive treatments of NCCs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Over two decades have passed since polymeric membrane ion-selective electrodes were found to exhibit sufficiently lower detection limits. This in turn brought a great promise to measure trace level concentrations of heavy metals using potentiometric ion sensors at environmental conditions. Despite great efforts, trace analysis of heavy metals using ion-selective electrodes at environmental conditions is still not commercially available. This work will predominantly concentrate on summarizing and evaluating prospects of using potentiometric ion sensors in view of environmental determination of heavy metals in on-site and on-line analysis modes. Challenges associated with development of reliable potentiometric sensors to be operational in environmental conditions will be discussed and reasoning behind unsuccessful efforts to develop potentiometric on-site and on-line environmental ion sensors will be explored. In short, it is now clear that solely lowering the detection limit of the ion-selective electrodes does not guarantee development of successful sensors that would meet the requirement of environmental matrices over long term usage. More pressing challenges of the properties and the performance of the potentiometric sensors must be addressed first before considering extending their sensitivity to low analyte concentrations. These are, in order of importance, selectivity of the ion-selective membrane to main ion followed by the membrane resistance to parallel processes, such as water ingress to the ISM, light sensitivity, change in temperature, presence of gasses in solution and pH and finally resistance of the ion-selective membrane to fouling. In the future, targeted on-site and on-line environmental sensors should be developed, addressing specific environmental conditions. Thus, ion-selective electrodes should be developed with the intention to be suitable to the operational environmental conditions, rather than looking at universal sensor design validated in the idealized and simple sample matrices., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Transmembrane ion fluxes have earlier been identified as a source of potential instability in solid contact ion-selective electrodes (SC-ISEs). In this work, foamlike structures were intentionally introduced into a potassium-sensitive plasticized poly(vinyl chloride) ion-selective membrane (ISM) near the membrane|solid contact interface by controlling the temperature during membrane deposition. Foamlike structures in the ISM were shown to be effective at physically tailoring the transport of ions in the ion-selective membrane, greatly reducing the flux of interfering ions from the sample to the membrane|solid contact interface. The drifts during a conventional water layer test were hence able to be greatly mitigated, even with SC-ISEs incorporating a relatively hydrophilic poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) solid contact. In solutions with a high background concentration of interfering ions, equilibrated ion-selective electrodes with foamlike membranes were able to reproduce their initial potentials within 0.6 mV uncertainty ( n = 3) from 0 to 18 h. This was achieved despite sensor exposure to solutions exceeding the selectivity limit of the ISEs in 3 h intervals, allowing improvement of the potential reproducibility of the sensors. Since the introduction of foamlike structures into ISM is linked to temperature-controlled membrane deposition, it is envisaged that the method is generally applicable to all solid contact ion-selective electrodes that are based on polymeric membranes and require membrane deposition from the cocktail solution.

Polymeric reverse osmosis (RO) membranes are widely used worldwide for production of fresh water from various sources, primarily ocean desalination. However, with limited service life, exhausted RO membrane modules often end up as plastic wastes disposed of predominantly by landfilling. It is imperative to find a feasible way to upcycle end-of-life RO membrane modules into valuable products. In this paper, the feasibility of RO membrane recycling via pyrolysis and subsequent conversion of resulting char into carbon dots (CDs) through H 2 O 2 -assisted hydrothermal method was investigated. RO membrane module pyrolysis at 600 °C produced oil (28 wt%), non-condensable gas (17 wt%), and char (22 wt%). While oil and gas can serve as fuel and chemical feedstock due to rich hydrocarbon content, char was found a suitable precursor for the synthesis of functional CDs. The resulting CDs doped with N (4.8%) and S (1.8%) exhibited excellent water dispersibility, narrow size distribution of 1.3-6.8 nm, high stability, and strong blue fluorescence with a quantum yield of 6.24%. CDs demonstrated high selectivity and sensitivity towards Fe 3+ in the range of 0-100 μM with the limit of detection of 2.97 μM and were capable of determining Fe 3+ in real water samples (tap water and pond water)., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this study, industrial wastewater and groundwater were comparatively investigated for their physicochemical properties, concentrations of potentially toxic elements (PTEs), human health risks and pollution source(s). Every month, 34 wastewater samples and 26 groundwater samples were collected, for a duration of one year. The results showed that the physicochemical parameters and concentrations of PTEs in the industrial wastewater exceeded the maximum permissible limits of Pakistan Environmental Protection Agency (2000). Specifically, it was found that total dissolved solids (5%), total suspended solids (190%), chemical oxygen demand (107%), five-days biochemical oxygen demand (5.7 times), grease/oil (27.1 times), Fe (67%), Zn (29%), Mn (32%), Cu (27%), Ni (16%), Cr (8%), Pb (106%), and Cd (80%) were higher than the permissible limits. The carcinogenic and non-carcinogenic dermal health risks for wastewater irrigation group were significantly higher than the groundwater irrigation group. The hazard index of irrigation with industrial wastewater was 180 times higher than the groundwater. The principal component analysis indicated that industry was the main polluting source. The cluster analysis results of all PTEs (except Fe) were found in the same clade in the dendrogram, which showed a strong similarity within the monthly data set of the whole year. The study recommends using adjacent groundwater instead of industrial wastewater for irrigation purposes., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The oxidation state of ions is a crucial aspect that often has been overlooked when determining the toxicity of chromium (Cr) species in environmental samples. In this study, a novel electrochemical sensor array based on gold-silver nanoparticles modified electrodes was developed for simultaneous determination of the two main chromium species (Cr(III) and (VI)). Specifically, the working electrodes of screen-printed carbon electrodes (SPCEs) were modified with silver-gold bimetallic nanoparticles through electrochemical deposition for detection of Cr(VI). The silver-gold bimetallic nanoparticles were further oxidized to form stable silver-gold bimetallic oxide nanoparticles for the detection of Cr(III). The results showed that the addition of silver with a theoretical value of 1% of gold could contribute to the formation and stabilization of oxides on the surface of gold nanoparticles. After characterization, the two kinds of electrodes were integrated as an electrochemical sensor array for selective and sensitive detection of Cr(VI) and Cr(III). The linear range and limit of detection (LOD, identified by three times of signal-to-noise ratio) were found to be 0.05-5 ppm and 0.1 ppb for Cr(VI), and 0.05-1 ppm and 0.1 ppb for Cr(III), respectively. Finally, the electrochemical sensor array was proven for successful detection of Cr(VI) and Cr(III) in tap water, artificial saliva and artificial sweat samples, and monitoring of Cr(VI) and Cr(III) in chromium-containing wastewater treatment process. Combined with a handheld dual-channel electrochemical device, the simultaneous determination of Cr(VI), Cr(III) and total chromium contents can be easily achieved for various samples., (Copyright © 2021. Published by Elsevier Ltd.)

Voltammetric sensors based on screen-printed electrodes (SPEs) await diverse applications in environmental monitoring, food, agricultural and biomedical analysis. However, due to the single-use and disposable characteristics of SPEs and the scale of measurements performed, their environmental impacts should be considered. A life cycle assessment was conducted to evaluate the environmental footprint of SPEs manufactured using various substrate materials (SMs: cotton textile, HDPE plastic, Kraft paper, graphic paper, glass, and ceramic) and electrode materials (EMs: platinum, gold, silver, copper, carbon black, and carbon nanotubes (CNTs)). The greatest environmental impact was observed when cotton textile was used as SM. HDPE plastic demonstrated the least impact (13 out of 19 categories), followed by ceramic, glass and paper. However, considering the end-of-life scenarios and release of microplastics into the environment, ceramic, glass or paper could be the most suitable options for SMs. Amongst the EMs, the replacement of metals, especially noble metals, by carbon-based EMs greatly reduces the environmental footprint of SPEs. Compared with other materials, carbon black was the least impactful on the environment. On the other hand, copper and waste-derived CNTs (WCNTs) showed low impacts except for terrestrial ecotoxicity and human toxicity (non-cancer) potentials. In comparison to commercial CNTs (CCNTs), WCNTs demonstrated lower environmental footprint and comparable voltammetric performance in heavy metal detections, justifying the substitution of CCNTs with WCNTs in commercial applications. In conclusion, a combination of carbon black or WCNTs EMs with ceramic, glass or paper SMs represents the most environmentally friendly SPE configurations for voltammetric sensor arrangement., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

As bisphenol A (BPA) is an extensively used chemical for manufacturing plastic products, discharge of BPA into the environment has caused serious threats to ecology. Therefore, -based chemical oxidation methods have been employed for eliminating BPA. Because monopersulfate (MNP) has become a popular reagent for obtaining , and Co is the most efficient metal for activating MNP, it is critical to develop heterogeneous Co catalysts for easier implementation and recovery. Herein, a unique Co-based catalyst is proposed by utilizing tubular-structured N-doped carbon substrates, derived dicyandiamide (DCDA), to confine Co nanoparticles (NPs). Through simple pyrolysis of a mixture of Co/DCDA, DCDA would be transformed into N-doped carbon nanotubes (CNT) to wrap the resultant Co NP, and, interestingly, this N-doped CNT would exhibit a special bamboo-like morphology. More importantly, as Co NPs are mono-dispersed and singly-confined in N-doped CNTs, forming CoCNT, CoCNT exhibits significantly higher catalytic activities than Co 3 O 4 , for activating MNP to degrade BPA. The enhancement of catalytic activities in CoCNT would be possibly ascribed to the synergistic effects between Co NP and the N-doped CNT which not only acts as the support/protection but also provides active sites. Therefore, CoCNT + MNP could lead to a much lower E a (i.e., 13.8 kJ/mol) of BPA degradation than the reported E a values. Besides, CoCNT is still effective for eliminating BPA even in the presence of high-concentration NaCl and surfactants. CoCNT is also reusable over many cycles and retains its catalytic activity with 100% BPA removal, demonstrating that CoCNT is an advantageous and robust catalyst for MNP activation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Engineered biochar is increasingly regarded as a cost-effective and eco-friendly peroxymonosulfate (PMS) activator. Herein, biochar doped with nitrogen and sulfur moieties was prepared by pyrolysis of wood shavings and doping precursor. The doping precursor consists of either urea, thiourea or 1:1 w/w mixture of urea and thiourea (denoted as NSB-U, NSB-T and NSB-UT, respectively). The physicochemical properties of the NSBs were extensively characterized, revealing that they are of noncrystalline carbon with porous structure. The NSBs were employed as PMS activator to degrade organic pollutants particularly methylene blue (MB). It was found that NSB-UT exhibited higher MB removal rate with k app  = 0.202 min -1 due to its relatively high surface area and favorable intrinsic surface moieties (combination of graphitic N and thiophenic S). The effects of catalyst loading, PMS dosage and initial pH were evaluated. Positive enhancement of the MB removal rate can be obtained by carefully increasing the catalyst loading or PMS dosage. Meanwhile, the MB removal rate is greatly influenced by pH due to electrostatic interactions and pH dependent reactions. The NSB-UT can be reused for several cycles to some extent and its catalytic activity can be restored by thermal treatment. Based on the radical scavenger study and XPS analysis, the nonradical pathway facilitated by the graphitic N and thiophenic S active sites are revealed to be the dominant reaction pathway. Overall, the results of this study show that engineered biochar derived from locally available biowaste can be transformed into PMS activator for environmental applications., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The impact of different biochars (BCs) on the physicochemical properties and immobilization of potentially toxic elements (PTEs) in contaminated soil irrigated with industrial wastewater for the last three decades was studied. Furthermore, the efficacy of applied BCs in reducing geostatistical risks was also evaluated. For this purpose, BCs were prepared from green waste (Cynodon dactylon L.) for the first time at different pyrolysis temperature (400 °C, 600 °C and 800 °C), and amended the contaminated soil in pots with two different ratios of 2% and 5% (w/w) under controlled conditions. The BCs amended soil samples were analyzed after five months (equivalent to the life span of a wheat crop). The physicochemical impacts of applied BCs on the soil showed that the acidic soil was changed to basic. A tremendous increase in water holding capacity, cation exchange capacity, dissolved organic carbon, carbon, phosphorus and potassium contents was observed. The PTEs concentrations and geostatistical risks were significantly (p ≤ 0.05) decreased by all the BCs. Among them, BC prepared at 800 °C and applied at a ratio of 5% was showed the best effects by reducing the bioavailable concentrations of Cd, Pb, Cr, Ni, Cu, Mn, Fe, As, Co and Zn in 88%, 87%, 78%, 76%, 69%, 65%, 64%, 63%, 46% and 21%, respectively. Similarly, significant (p ≤ 0.05) reductions in geoaccumulation index, enrichment factor, contamination factor, and ecological risk were recorded. Therefore, BC prepared at 800 °C and applied at a ratio of 5% is recommended for soil remediation., (Copyright © 2021. Published by Elsevier Ltd.)