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Chemical activation in molten salts is a recent development in the field of tailoring activated carbon, where a combination of activating agents is used rather than a single compound. However, a comprehensive understanding of differences in catalytic activity is lacking. So, the question remains which chemical activation method is more beneficial. This research compares the catalytic effect of ZnCl2 as a single activating agent and its eutectic mixture of ZnCl2-KCl-NaCl (60:20:20 mol %). Pinewood shavings were chemically activated at 400 °C in a mass ratio of 5 to 1 (salt to biomass) and then washed to remove the activating agent. Obtained materials were subsequently physically activated using CO2 at 800 °C in an attempt to further increase their surface area. Properties of obtained carbons were characterized by elemental and proximate analyses, ICP-AES, FTIR, gas adsorption (N2, CO2), and adsorption (iodine, methylene blue, and molasses). Chemical activation with ZnCl2 and the eutectic mixture resulted in a surface area of respectively 910 m2/g and 917 m2/g with significant differences in porosity. The eutectic mixture created a greater proportion of micropores. ZnCl2 was more beneficial for mesoporosity which was formed over a broad range, whereas the eutectic mixture created mesopores in a narrower size range (19–27 nm). Subsequent CO2 gasification widened the pores and lowered the surface area, decreasing the adsorption capacity. This study illustrates that employing mixtures of molten salts has several advantages over a single activating agent and might lead to further development of tailor-made activated carbons. [ABSTRACT FROM AUTHOR]

The exploration of abundant and sustainable biomass materials for energy conversion applications is an environmental approach. In the present work, we prepare activated carbons (ACs) from coconut shells at a low temperature (230 °C) carbonization process followed by various chemical activation approaches. KOH and ZnCl2 were used as activating agents and their effects on the physical and chemical properties were studied. The formations of ACs were confirmed by XRD and FTIR. The degrees of defects were studied via Raman spectroscopy, which shows that KOH-based AC (ACK) gives better electrocatalytic properties than ZnCl2-based AC (ACZ). Morphological scrutiny was done by FE-SEM and the high level of porosity in ACK material was observed. BET reveals a large amount of macro and mesopores present in ACK facilitates the transportation and diffusion of electrolyte ions in the electrolyte-counter electrode interface. ACK exhibits an oxidation peak current density of 3.5 mA/cm2, which is higher than ACZ based electrodes. The maximum power conversion efficiency of 13.1% is achieved by using ACK as counter electrode material in DSSC under 800 lux illumination. Our research suggests that biomass-derived KOH-activated carbon with hierarchical pores is a promising material for the cost-effective counter electrode and sustainable for indoor photovoltaic applications. [ABSTRACT FROM AUTHOR]

The cashew nut shell is an agricultural residue generated in the production of cashew nuts. This residue is a hard-management biomass that can be efficiently transformed using pyrolysis, into a biochar. Conversely, potable water security requires the development of efficient adsorbents using novel and renewable materials. Then, in this work, a pyrolysis-derived carbon was chemically activated with KOH to remove phenol from an aqueous solution at 200 ppm that could represent health risk for life. The activated carbon was characterized rigorously, whereas adsorption kinetics and adsorption isotherms were evaluated to determine the suitability of this material to remove phenol. The activated carbon presented a chemical composition of 64.4 wt%; 33.2 wt%, and 1.98 wt% of carbon, oxygen, and hydrogen, respectively. Also, it presented a surface adsorption area of 863 m2/g, with a pore volume of 0.476 cm3/g. The surface chemistry presented -OH groups and the morphology revealed an organized material with the occurrence of porosity. The pseudo-second-order adequately described the kinetics of adsorption (80.93 mg/g and 0.0044 g/mg min, for equilibrium concentration (qe), and adsorption rate constant (kPSO), respectively). Additionally, the Toth isotherm model described reasonably the adsorption mechanism suggesting that a monolayer chemisorption that is independent of concentration of phenol took place for activated carbon. The efficiency of phenol uptake in the present work was about 79%, indicating that activated carbon derived from cashew nut shells has the potential for water remediation. [ABSTRACT FROM AUTHOR]

In this work, biochar was synthesized by carbonizing spent coffee grounds by conducting oxygen-limited pyrolysis in a muffle furnace. Six varieties of biochar have been synthesized at 550 ℃ and 750 ℃ with a ramp rate of 10 ℃/min and carbonization time of 120 min. Acid- and alkali-activated biochars were produced by carbonizing the activated biomass at 550 ℃ and 750 ℃. ZnCl2 and KOH were used as activating agents for acid and alkali activation, respectively. All the synthesized biochar yield was recorded as 40–60 wt% of the biomass weight. BET surface area increased significantly after activation and the values varied between 1.01 and 720.52 m2/g. The process of chemical activation has resulted in increased BET surface area in comparison with the pristine biochar. Other characterizations include FESEM analysis, elemental analysis through EDX, FTIR, UV–visible spectroscopy, XRD analysis, TGA, and Raman spectroscopy. Raman spectra and UV–visible spectra of activated samples revealed a higher graphitic quality and absorbance, respectively, whereas XRD analysis demonstrated the changes in structural phases. Activated carbon based on spent coffee grounds has displayed higher thermal stability and better surface chemistry than pristine biochar, enabling its application in various domains that foster circular economy. [ABSTRACT FROM AUTHOR]

Soybean husks were used as a precursor to prepare activated carbon (SHAC) by chemical activation with ZnCl2 under different experimental conditions. The best operational conditions for SHAC production were determined using a 23 factorial design and variance analysis (ANOVA). The best results were achieved with an impregnation ratio of 1 g ZnCl2/g soybean husks, a residence time of (180 min), and a temperature of (650ºC), resulting in SHAC with a high surface area (1150 m2/g) and pore volume (0.5933 cm3/g). The selected SHAC was used to adsorb malachite green (MG) from aqueous solutions. The MG adsorption process followed pseudo-second-order kinetics and Langmuir isotherms, with maximum adsorption capacities of 152.53 mg/g, 153.29 mg/g, and 166.83 mg/g at 30°C, 40°C, and 50°C, respectively. Furthermore, the pH of the point of zero charge of the selected SHAC was close to neutral, making it suitable for adsorbing cationic species in basic pH solutions. [ABSTRACT FROM AUTHOR]

The essential target of this work was to exploit some locally obtainable hard bio-wastes viz. date pits and pistachio shells, in preparing varioufigs activated carbons (ACs) via the optimised ZnCl2 and H3PO4 activation routes. After preparing ACs from an equal blend of the hard bio-waste, the best samples were identified for their BET surface area and pore volume, X-ray diffraction (×RD), Fourier Transform Infra-Red spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM) with Energy Dispersive X-ray (EDX). The ACZnCl2 exhibited a higher BET surface area (895.53 m2/g) than the ACH3PO4 (419.60 m2/g). The optimal ACs were implemented in the adsorptive elimination of dibenzothiophene (DBT) from model gasoline. The DBT trials were optimized by investigating the impact of the initial concentration of DBT (25–200 mg/L), ACs mass (0.05–0.40 g), temperature (0.0–60 °C), and working period (5.0–80 minutes). The highest elimination of DBT by ACZnCl2 reached 97.78% using 0.30 g of it at 40°C for 60 minutes employing 25 mL of 200 mg/L DBT, while ACH3PO4 revealed the superlative elimination of DBT (88.46%) utilising 0.35 g of it at 40°C for 70 minutes using 25 mL of 200 mg/L DBT. Besides the kinetics investigations, isothermal studies indicated that the Freundlich isotherm and the pseudo-2nd-order kinetic best described the DBT adsorption by the ACs more than the other models. In a batch process, the adsorption capacities of DBT by both ACZnCl2 and ACH3PO4 were 26.31 mg/g and 20.23 mg/g, respectively. The typical adsorption conditions for each adsorbent were employed to eliminate S- compounds from commercial gasoline and DBT in a fixed-bed system. In conclusion, the ACs above could be reutilised for 5 successive runs with an insignificant loss in their desulphurisation ability. They can thus be recommended for the desulfurization of fuels on an industrial scale. [ABSTRACT FROM AUTHOR]

Activated carbon production via chemical activation followed by surface functionalization with metal groups aims to achieve surface functionalization for CO2, aromatic/metallic organic compounds, and dye adsorption. The prepared activated carbon possesses a porous structure containing metal functional groups with adsorptive properties. This work proposed integrating two synthesis steps to simplify the process and reduce resources and impact. The preparation of palm kernel shell (PKS) derived AC (PKSdAC) through a concurrent activation and surface modification (CAM) process combines sulphuric acid (H2SO4) activation (5–10% mass loading) with barium chloride (BaCl2) modification (10 wt.%) at an activation temperature of 400–700 °C. The barium (Ba) is produced through the reduction process. Incorporating Ba into PKSdAC is vital to initiate chemical CO2 and other related component adsorption. The optimization study identified that 7.5% H2SO4, 10 wt.% BaCl2, and 700 °C was optimal in obtaining a high 1.50 wt.% Ba impregnated in PKSdAC. CAM-PKSdAC synthesized at optimal conditions exhibited a sponge-like cubic meso-microporous carbon structure containing BaSO4 crystals with a surface area of 420 and 423 m2 g−1 for its micropore and mesopore structure. A total pore volume of 0.19 cm3 g−1 and an average pore diameter of 1.78 nm were achieved. Conventional surface modified-activated PKSdAC prepared at optimal conditions has a cubic porous structure and a crack surface containing little BaSO4 crystals with a higher surface area of 565 m2 g−1 and total pore volume of 0.18 cm3 g−1 and an average pore diameter of 1.27 nm. [ABSTRACT FROM AUTHOR]

In the waste oil recycling industry, large amounts of oil-containing sludge are still generated, thus posing a resource depletion issue when disposed of or incinerated without energy recovery or residual oil utilization. In this work, chemical activation experiments using phosphoric acid (H3PO4) were performed at a low temperature (600 °C) for 30 min to produce porous carbon products. From the results of the pore property analysis, an increasing trend with an increasing impregnation ratio from 0.5 to 2.0 was observed. Based on the Brunauer–Emmett–Teller (BET) model, the maximal BET surface area was about 70 m2/g, which was indicative of the hysteresis loop and the type IV isotherms in the resulting carbon product. In addition, the enhancement in the pore properties of the carbon products obtained through acid-washing was superior to that achieved through water-washing and without post-washing. From observations made using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), the carbon products featured a porous structure and inherent magnetism due to their richness of iron oxides. In this regard, they can be used as efficient adsorbents or catalyst supports due to their simple recovery (or separation) when exhausted. [ABSTRACT FROM AUTHOR]

On a global scale, there is a growing need to find green and sustainable solutions to environmental issues. Waste tyres have become a serious environmental and health issue because of its being dumped into landfills or stored in stockpiles. Reuse of waste tyres is extremely important because of the problems and damage they cause. In this research, characterisation of activated carbon that was prepared from carbon black obtained by the pyrolysis of waste tyres was undertaken. The chemical activation method using potassium hydroxide as the activating agent was used in this study. The activated carbon was characterised by field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) methods. The FE-SEM analysis indicated that the produced AC is a highly porous material and provides a large surface area to which contaminants could adsorb. The elemental analysis using EDS indicated that carbon black from waste tyres was rich in carbon, and hence is suitable for preparation of activated carbon. The AC also was observed to have a high amount of carbon content. The surface area, pore volume and pore diameter of the activated carbon was found to be 235.86 m2 g−1, 0.845 cm3g−1 and 14.33 A°, respectively. The activated carbon thus denoted microporous and mesoporous characteristics, indicating that it would possess good adsorption properties, identical to that of commercially available activated carbon. Hence, it is expected that the activated carbon obtained from waste tyres will function as an effective adsorbent material in applications like wastewater treatment. [ABSTRACT FROM AUTHOR]

The increasing pollution from the textile industry, particularly organic azo dyes, presents a significant environmental challenge, necessitating the development of effective and sustainable treatment methods. This study investigates the adsorption potential of hazelnut shells (raw—RHSs; modified—MHSs) for the removal of organic azo dyes from aqueous solutions. As biomass, hazelnut shells are biodegradable and represent a sustainable alternative to synthetic adsorbents, thereby reducing the ecological footprint. Through a series of batch adsorption experiments, the influence of various parameters, including pH, contact time, concentration, and temperature, on adsorption capacity was examined. Characterization of the hazelnut shells was conducted using optical microscopy and ATR-FTIR, XRF, and XRD spectroscopy, confirming its suitability as a biosorbent. The analyzed isotherms showed that adsorption onto RHSs was best fitted by the Freundlich model, while adsorption onto MHSs was best fitted by the Temkin model. Kinetic studies demonstrated that the adsorption process is well described by the pseudo-second-order model, suggesting that chemical adsorption plays a significant role. The maximal adsorption capacity was 62.11 mg/g for RHSs and 80.65 mg/g for MHSs, highlighting the potential of hazelnut shells as an abundant, low-cost, and eco-friendly adsorbent. Furthermore, recycling studies indicated the feasibility of the adsorbent, underscoring its practical applicability in real scenarios. [ABSTRACT FROM AUTHOR]

Zinc-ion hybrid capacitors (ZIHCs), which combine the advantages of batteries and supercapacitors, are very competitive in the field of advanced energy storage applications. However, their performance is limited by carbon cathodes that have a low specific surface area and inferior porous structure. Here, we report a N-doped porous carbon cathode prepared by high-temperature calcination and chemical activation based on a soft C3N4 template. The as-prepared N-doped porous carbon cathode shows a hierarchical nano structure with micropores and mesopores, which can provide additional active sites for zinc-ion adsorption, reduce charge-transfer resistance, and enhance kinetic performance. The ZIHCs assembled by using this N-doped porous carbon cathode exhibits a specific capacitance of 166 mAh g–1 at a current density of 0.1 A g–1, an energy density of up to 124 Wh kg–1, and an 82.4% capacitance retention after 5000 cycles at a current density of 5 A g–1, showing a great potential for practical applications. Our work provides a way for developing high-performance zinc-ion hybrid capacitors. [ABSTRACT FROM AUTHOR]

In this study, porous activated carbon was produced from coffee waste and used as an effective adsorbent for the removal of humic acid (HA) from seawater and methyl orange (MO) dye from aqueous solutions. Phosphoric acid H3PO4 was used as an activating agent for the chemical activation of these agricultural wastes. The characterization of the activated carbon obtained using a scanning electron microscope (SEM), Fourier-transform infrared (FTIR) spectroscopy analysis, X-ray diffraction (XRD) and the Brunauer–Emmett–Teller (BET) method revealed that the activated carbon products exhibited high porosity and the formation of various functional groups. The effects of different parameters were examined using batch adsorption experiments, such as the adsorbent masses, pH, initial pollutant concentration and contact time. The results show that the performance increased with an increased adsorbent mass (up to 0.25 g/L) and decreased initial concentration of the adsorbent tested. On the other hand, this study clearly showed that the adsorption efficiency of the MO on the raw spent coffee grounds (SCGs) waste was around 43%, while no removal was observed for the humic acid. The experiments demonstrated that the activated carbon synthesized from the used coffee grounds (the efficiency was compared with commercial activated carbon (CAC) with a difference of 13%) was a promising alternative to commercially available adsorbents for the removal of humic acid from seawater. To understand and elucidate the adsorption mechanism, various isothermal and kinetic models were studied. The adsorption capacity was analyzed by fitting experimental data to these models. The experimental data for methyl orange dyes were analyzed using Langmuir and Freundlich isothermal models. The Freundlich isotherm model provided a superior fit to the equilibrium data, as indicated by a higher correlation coefficient (R2) than that of the Langmuir model. The maximum adsorption was observed at pH 3. The Freundlich adsorption capacity was found to be 333 mg/g adsorbent. The PAC showed a high adsorption capacity for the MO and HA. The PAC showed the highest adsorption capacities for the HA and MO compared with the other adsorbents used (SCGs and CAC) and would be a good material to increase the adsorption efficiency for humic acid removal in the seawater pretreatment process. In addition, the prepared AC BET surface area was 520.40 m2/g, suggesting a high adsorption capacity. This makes the material potentially suitable for various applications that require a high surface area. These results indicate that high-quality sustainable activated carbon can be efficiently produced from coffee waste, making it suitable for a wide range of adsorbent applications targeting various pollutants. [ABSTRACT FROM AUTHOR]

This research paper analyses the adsorbent properties of a unique biomass i.e. horse chestnut shell (Aesculus hippocastanum L) activated carbon synthesized by chemical activation of KOH produced under optimized carbonization conditions for Fe3+. Research was done to look into the characteristics of the made activated carbon and its systematic effects of process parameters. Characterizations like SEM, BET, FTIR, XRD, TGA, EDX, proximate and ultimate analysis, calorific value was performed. Also effect of process parameters like initial Fe3+ ion content, contact time, dosage and temperature of system was studied for mechanism of adsorption at pH (6) of Fe3+ in an aqueous solution. Data on equilibrium and kinetic isotherms from experiments were examined, for kinetics pseudo 1st order reaction, pseudo 2nd order reaction and intraparticle diffusion has been utilised. System was fairly fitted by pseudo-2nd-order reaction. Adsorption isotherms such as Halsey, Harkin Jura, Temkin, Freundlich, and Langmuir and Dubinin Radushkevich were used and Langmuir adsorption isotherm turned out best suitable match as R2 value was found out to be 0.99. The maximum Fe3+ adsorbing ability of the HCAC4 was 138.88 mg/g at 25 °C. Thermodynamical evaluation concluded the process to be spontaneous and heat-releasing. Highlights: Horse chestnut shell biomass was converted to activated carbon using KOH activation. Characterization (SEM, BET, FTIR, XRD, TGA, EDX) revealed favourable structural and compositional properties. Investigated effects of Fe3+ ion content, contact time, dosage, and temperature, achieving 138.88 mg/g adsorption at 25 °C. Pseudo-second-order kinetic model and Langmuir isotherm (R² = 0.99) best described the adsorption process. The process was spontaneous and exothermic, showing high potential for Fe3+ removal in water treatment. [ABSTRACT FROM AUTHOR]

This study focuses on the preparation of activated carbon using a petroleum-residue-based pitch, as well as the HCl gas adsorption properties of the resulting activated carbon pellets relative to their specific surface area and pore structure. Activated carbon was prepared under various oxidation and chemical activation conditions using pitch with a softening point of 220 °C. The activated carbon was mixed with distilled water, an acrylic binder, and carboxymethyl cellulose in a specific ratio to form pellets. These pellets were then dried in an oven at 80 °C. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller analyses were performed to evaluate the surface structure and specific surface area of the finalized pellets. HCl gas was adsorbed at a concentration of 50 ppm while examining the adsorption characteristics relative to the pore structure and specific surface area. [ABSTRACT FROM AUTHOR]

The activation process is a key step in preparing porous carbon. Herein, three kinds of green activators were separately used to successfully prepare N-doped porous carbons through a two-step strategy: hydrothermal carbonization and chemical activation using microcrystalline cellulose as the carbon source and urea as the nitrogen source. Palladium was deposited on these N-doped microcrystalline cellulose-based carbons (NMC-X, where X represents the activator) via a traditional deposition–precipitation method, and the resulting Pd nanoparticle catalysts (Pd/NMC-X) showed high activity in the selective hydrogenation of quinoline under mild conditions, particularly Pd/NMC-ZC (ZC, zinc carbonate), which achieved complete conversion of quinoline within 100 min at 40 °C and 4 atm H2. Characterization results suggest that the high activity of Pd/NMC-ZC is mainly attributed to the special electronic structure of its Pd species, particularly the distribution of valence states and reducibility of Pd and the high hydrogen spillover capacity between Pd and NMC-ZC. The chemical activation by ZC leads to the formation of multiple defect sites on the carbon skeleton, modifying the carbon surface properties to enhance hydrogen spillover. This also provides an excellent environment for Pd nanoparticle anchoring, thus increasing the Pd-support interactions and regulating the electronic structure of Pd. [ABSTRACT FROM AUTHOR]

To enhance the interfacial adhesion between poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) film and functional coatings, such as silver (Ag) coating, among others, the surface activation of FEP film has to be performed. Among various activation strategies, chemical activation, such as using naphthalene sodium system, is one of the most efficient methods. However, the effect of chemical activation on the interface interaction between the activated FEP and functional coating is rarely investigated. Herein, the FEP film was activated by naphthalene sodium solution under different conditions, and then the Ag layer was coated onto its surface by vacuum Ag deposition. Based on experimental results and density function theory (DFT) calculation, it is indicated that oxygen-containing functional groups (such as C=O and C–OH groups), introduced onto the surface of FEP by the chemical activation, play a key role in boosting the interface interaction, which is due to the strong interaction between the oxygen-containing functional groups and Ag atoms. In addition, the concentration of naphthalene sodium solution, activation time, and winding speed of Ag- deposition can have a significant impact on the microstructures of Ag coating and the interfacial adhesion between the activated FEP and Ag coating. Under the conditions of high concentration (0.9 M), medium activation time (15 min), and high winding speed (0.8 m min−1), there is the best interface adhesion. [ABSTRACT FROM AUTHOR]

Peels make up a considerable proportion of solid waste generated from fruit and vegetable production and processing. If not properly managed, they could contribute to environmental degradation through the dispersion of nutrient-rich leachate and the release of various greenhouse gases. Alternatively, these peels could be transformed to biosorbents, which could assist in the removal of pollutants of environmental and human health concerns from wastewaters. Using peels as raw material for biosorbent production is an environmentally friendly and cost-effective option for waste disposal. Peels also contain bio-activators, which can be used to activate the biosorbent produced, minimizing the use of synthetic chemicals for biosorbent activation. This review considers the different physicochemical characteristics of vegetable and fruit peels that make them suitable raw materials for biosorbent production. Additionally, their transformation to biosorbents using hydrothermal carbonization and pyrolysis is discussed. The review concludes with a discussion on the efficiency of peel-based biosorbents in the removal of diverse types of pollutants from wastewater. [ABSTRACT FROM AUTHOR]

Environment remediation is one of the primary goals of sustainable development and anthropogenic activities, and the use of fuels in various industrial processes through combustion has led to an increase in CO2 as well as big damage to the atmosphere by the greenhouse effect. Biochar has been used for the capture of carbon dioxide due to its high surface area. In this study, we obtained biochar from soursop seeds. The materials were synthesized by pyrolysis of precursor materials and chemical activation with chlorides of Ca and Mg at a concentration of 5% w/v. The effect of the defatting process of the soursop seeds on the obtained carbon was also researched. The absorbed solids were characterized through thermogravimetric analysis, X-ray diffraction, and CO2 adsorption, followed by infrared spectroscopy, N2-physisorption, CO2-physisorption, CO2, XPS, DRIFTS and TPD of NH3. The type of activating agent and pretreatment conditions used were more favorable than the defatted process at obtaining carbons with N2 surface areas between 26 and 220 m2g−1. The biochars were analyzed by CO2 surface area to describe the microporous framework, and the solid with the best CO2 surface area was the one with the highest CO2 adsorption. According to the statistical analyses conducted, the evaluated models Langmuir, Freundlich, and Redlich-Peterson presented good fits to the experimental data. However, the Redlich-Peterson model showed the lowest values for the residual variance, which were of the order of 0.001 or less in all cases based on the CO2 adsorption isotherms on the studied activated carbons. However, the carbons obtained by defatting showed favorable hydrophilic behavior along with adsorption capacities in the bioremediation process and affinity towards of this GHG. [ABSTRACT FROM AUTHOR]

The exploration of renewable energy in the twenty-first century emerged as the world-leading movement to support energy sustainability, leading to the paramount necessity for energy storage systems (ESSs). The porous carbon-derived electrode has been a long-pursued aim in supercapacitor applications, which feature their availability, renewability, environmental friendliness, rapid ion transport, and tunable surface chemistry. In this regard, chemical activation is one of the most highly praised and compatible strategies for synthesizing porous carbon in energy storage applications. Nevertheless, the most challenging issue to reconcile has been using environmentally hazardous, unsustainable activators. NaNH2 emerges as a greener solution to the synthesis of porous carbon. Additionally, it presents as a dual-function activator, serving as a nitridation and activating agent. This dual role promotes the development of micropores and mesopores in the pore architecture and active sites for effective ion transport, highlighting the critical facets in the fabrication of supercapacitor electrode materials. Herein, this paper discussed the promising use of NaNH2-activated porous carbon in electrochemical applications that covered the synthesis of porous carbon to the proposed activation mechanism, the impact of variations in design parameters, and the electrochemical properties of the resultant porous carbon. Ultimately, the recent challenges and future outlooks were comprehensively highlighted. [ABSTRACT FROM AUTHOR]

With the growing rise in CO2 emission, resulting in accelerated global warming, there is an increased utilization of lignocellulosic waste biomass to synthesize inexpensive CO2 adsorbents, via hydrothermal carbonization (HTC) of biomass followed by chemical activation (CAC) to create porous activated hydrochar that can capture CO2. However, despite analogous thermochemical conversion (HTC and CAC) conditions, the activated hydrochars derived from different biomass precursors exhibit dissimilarity in surface morphology and its corresponding CO2 capture capacity. Hence, finding the fundamental key underlying this discrepancy is of interest where biopolymer constituents' composition is hypothesized to be the determining factor. This study, therefore, explored the biopolymer model compounds of cellulose, hemicellulose, lignin, and glucose which were independently hydrothermally carbonized and KOH-activated to develop porous adsorbents. The findings of this study highlighted discrete porosity development in the biopolymer-derived activated hydrochar ranging from 591 m2/g for glucose precursor to as high as 2279 m2/g for that cellulose. On the other hand, lignin-based activated hydrochar demonstrated the lowest microporosity (0.084 cm3/g), reflecting its reluctance in transforming the hydrochar carbon matrix into substantially rich micro-cavities, at moderate HTC and CAC conditions. CO2 capture was observed to be the lowest of 1.45 mmol/g for glucose and highest of 2.45 mmol/g for cellulose-derived activated hydrochars, reflecting the direct influence of surface porosity on CO2 adsorbed. Literature data of other lignocellulosic biomass-derived activated hydrochars were combined with results of this study where a statistical analysis revealed the inhibiting role of glucose in pore creation while micropore creation was favored by cellulose and hemicellulose, benefitting CO2 capture. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI)) is a highly toxic form of chromium, which can be found in industrial effluents from various sectors, such as the metallurgical, tanning, and pigment industries. The presence of Cr(VI) in the environment is a concern due to its negative effects on human health and the ecosystem since it is carcinogenic, mutagenic, and can cause damage to the respiratory, renal, hepatic, and dermatological systems. Adsorption is a sustainable alternative for the removal of Cr(VI) from the environment since it is an efficient, low-cost technique and can be adjusted according to specific environmental conditions. The use of algae biomass activated with chemical agents can be a promising solution to improve the adsorption capacity of the material and contribute to the mitigation of contamination by Cr(VI) and the protection of human health and the environment. The results of the study indicate that the activation of the red macroalgae Gelidium sp. with zinc chloride (ZnCl2) resulted in improvements in the adsorbent properties of the material for the removal of Cr(VI) in aqueous solutions. The physical characteristics of the material were analyzed, and it was observed that the surface area increased from 2.90 to 3.12 m2 g−1 after activation with ZnCl2. Furthermore, changes in the surface structure of the material were observed, with the presence of irregularities, mainly after the adsorption of Cr(VI). The analysis of functional groups indicated that the main groups present in the native biomass remained after activation with zinc, and new diffraction peaks also appeared, indicating the chemical modification of the material. The adsorption experiments were carried out under different conditions, such as pH, dosage, temperature, Cr(VI) concentration, and contact time. It was observed that the adsorption was favored under acidic conditions, with a dose of 0.05 g L−1 of activated biomass. Equilibrium was reached quickly in the first few minutes, and the general kinetic model best fitted the experimental data. The kinetic adsorption capacity was higher for the activated material (226 mg g−1) compared to the native material (114 mg g−1). Increasing the concentration of Cr(VI) in the solution resulted in an increase in the adsorption capacity, indicating that the driving force gradient was greater at higher concentrations of the contaminating ion. The isothermal data were well fitted by the Koble-Corrigan heterogeneous surface model, and the maximum adsorption capacities were estimated at 126 mg g−1 and 240 mg g−1 for native and activated biomass, respectively, at the highest Cr(VI) concentration studied (150 mg L−1). The results indicate that the activation of the red macroalgae Gelidium sp. with zinc chloride improved its adsorbent properties for the removal of Cr(VI) ions, with high adsorption capacity and efficiency, demonstrating a high potential for application in the removal of Cr(VI) metal ions in aqueous solutions. [ABSTRACT FROM AUTHOR]

Cooked rice and the vegetables like lettuce are common kitchen waste, which are carbonaceous materials and have the potential as feedstock for the production of activated carbon. Cooking is similar to hydrothermal treatment (HTC), which might impact the subsequent activation of kitchen waste. In this study, the HTC of lettuce, rice, or their mixture and the activation of the resulting hydrochars were conducted. The results indicated that cross-polymerization between the N-containing organics from lettuce and the sugar derivatives from rice took place in their co-HTC, which significantly increased the hydrochar yield. Activation of the hydrochar from the co-HTC generated the AC with a yield of 2 times that from direct activation of mixed lettuce/rice. However, the co- HTC facilitated aromatization, reducing reactivity with K2C2O4 in activation and producing the AC with main micropores and low specific surface area. Activation of the hydrochar from HTC of rice followed the above trend, while that from lettuce was the opposite. The organics in lettuce were thermally unstable and could not undergo sufficient aromatization. The activation of hydrochar from HTC of lettuce thus generated the AC with the lowest yield, but the highest specific surface area (1684.9 m²/g), abundant mesopores, and superior capability for adsorption of tetracycline. However, the environmental impacts and energy consumption for the production of AC from the hydrochar of lettuce were higher than that from hydrochar of co-HTC. [ABSTRACT FROM AUTHOR]

Lentil shell (LS) on modification with sulfuric acid (LSAC), formaldehyde (LSFM), and on calcination (LSCL) were used for the adsorption of methylene blue dye in the present study. The sulfuric acid treated LS adsorbent has shown maximum adsorption. The batch adsorption experiments were studied with the effect of adsorbent dose (10–60 mg), pH (4–10), dye concentration (10–80 mg/L), contact time (10–60 minutes), and temperature (303–333 K). The maximum removal of methylene blue was found at pH 10 with adsorption time 60 minutes. The maximum adsorption capacity is measured for LSAC, LSCL, LSFM, and LS untreated (LSUN) are 49.56, 45.79, 42.24, and 42.09 mg/g respectively for 60 mg adsorbent dose with 60 mg/L of initial methylene blue dye concentration. The biosorbents were characterized with Fourier Transform Infrared spectra, Scanning Electron Microscopy, Transmission Electron Microscopy, BET-N2 adsorption, and Energy Dispersive X-ray analysis. The adsorption isotherm was studied at the temperature of 303, 313, 323, and 333 K. It was found that the higher temperature suitable for maximum adsorption. Langmuir model and Freundlich model were studied from the obtained results for adsorption mechanism. The pseudo second order kinetic model was found suitable for the present adsorption study in comparison with pseudo first order model and intraparticle diffusion model. The data obtained from the present work showed that LS could be employed as an efficient adsorbent for the adsorption of the dye. [ABSTRACT FROM AUTHOR]

Lignin is a nature's wonder most abundant aromatic biopolymer and a promising precursor for a wide range of sustainable carbon materials (CMs). However, the effects of lignin structural heterogeneity on the properties and performance of lignin-based CMs are still poorly understood. In this paper, we address the influence of the lignin structural heterogeneity on the properties of lignin-based activated carbons (ACs). Taking two structurally different kraft (KL) and hydrolysis (HL) lignins, we show that they result into ACs with different properties and electrochemical performance in supercapacitor application. In similar carbonization and activation conditions, ACs from HL showed higher specific capacitances than ACs from KL. The difference between the two groups of ACs could not be solely attributed to the difference in their specific surface areas. They were rather found to result from different particle morphologies, pore size distributions, pore wall nanostructures, and surface chemistries, as revealed by multivariate data analyses. Moreover, we observed that KL and HL had different thermophysical behaviors and reactivities during the thermal treatment, which would have influenced the porosity development and surface oxygenation levels and consequently the electrochemical performance of the derived ACs. This work also shows that it is possible to engineer ACs from HL with electrochemical performance close to the commercial YP-50F Kuraray AC, which implies that less pure, carbohydrate-containing lignins are no less advantaged compared to purer KL to produce high-performance ACs for supercapacitor application. [ABSTRACT FROM AUTHOR]

In this study, the adsorption of phenoxyacetic acid (PAA) and its chlorinated derivatives, including 4-chlorophenoxyacetic acid (4CPA) and 2,4-dichlorophenoxyacetic acid (2,4-D), on activated carbons (ACs) from corn kernels (AC-K), corn leaves (AC-L), and corn silk (AC-S) were investigated. The adsorption kinetics followed the pseudo-second-order model, and the film diffusion was the rate-limiting step. The adsorption rate increased in the order PAA < 4CPA < 2,4-D and was correlated with the porous structure (mesopore volume) of these ACs. The Langmuir isotherm models best fit the experimental data; PAA was adsorbed least and 2,4-D most preferentially. The observed trend (PAA < 4CPA < 2,4-D) was positively correlated with the molecular weight of the adsorbates and their hydrophobicity while being inversely correlated with their solubility in water. The adsorption for 2,4-D, according to the Langmuir equation, is equal to 2.078, 2.135, and 2.467 mmol/g and SBET 1600, 1720, and 1965 m2/g, respectively. The results for other herbicides showed a similar correlation. The adsorption of phenoxy herbicides was strongly pH-dependent. The ACs produced from corn biomass can be an eco-friendly choice, offering sustainable products that could be used as efficient adsorbents for removing phenoxyacetic herbicides from water. [ABSTRACT FROM AUTHOR]

The dependencies of the electrophysical characteristics of nanoporous carbon material (NCM) on the compaction degree of its particles have been investigated in the presented study. It has been found that the maximum value of the electrical conductivity is achieved at a pressure of 2.5 MPa. Furthermore, it has been revealed that the formation of O-compounds on the surface of the studied materials leads to a decrease in electrical conductivity. The correlation between structural-adsorption and electrical-conductive properties of NCMs has been established. Moreover, it has been demonstrated that an increase in the amount of potassium hydroxide results in a decrease in electrical conductivity due to the breakdown of small carbon particles and an increase in contact resistance, while the specific surface area enlarges due to the development of porosity and an increase in the total pore volume. [ABSTRACT FROM AUTHOR]

Semisynthesis using recombinant polypeptides is a powerful approach for the synthesis of proteins having a variety of modifications. Peptide thioesters, of which the peptide C-terminus is activated by a thioester, are utilized for coupling peptide building blocks. Biological methods employing intein have been a center for the C-terminal thioesterification of recombinant polypeptides. Chemical activation has emerged as an alternative methodology for synthesizing peptide thioesters from recombinant polypeptides. Chemical reactions are compatible with various solutions containing organic solvents, chaotropic reagents, or detergents that are generally incompatible with biomolecules such as intein. Despite the potential utility of chemical activation, available methods remain limited. This article introduces the methods for the chemical activation of a peptide C-terminus applied to the chemical synthesis of proteins. By showcasing these methodologies, we aim to accelerate the advancement of new chemical reactions and methodologies and broaden the frontiers for the chemical synthesis of proteins. [ABSTRACT FROM AUTHOR]

The carbon content of biomass waste makes it usable as a precursor in the production of activated carbon. The purpose of this work was to investigate the influence of lignocellulosic composition (i.e., lignin, cellulose, hemicellulose) in biomass waste on the microstructure and dye adsorption characteristics of microwave-assisted ZnCl2 activated carbon. Three biomass wastes with significant differences in lignocellulosic composition (i.e., pineapple leaf, cocoa shell, and coconut shell) were used as model substances. Carbonization experiments were conducted at 500 °C for two hours in a muffle furnace while the activation process was carried out at 600 W for 6 min in a microwave oven. The results showed that the composition of hemicellulose, cellulose, and lignin in biomass has an effect on the character of activated carbon. It was also found that cellulose is responsible for the formation of porosity so the high cellulose content in the biomass increases the specific surface area of the activated carbon obtained. It is in contrast with lignin which is responsible for the presence of functional groups and pore size. Activation using ZnCl2 coupled with microwave heating creates a template effect, resulting in uniform pores in activated carbon. As a result, the adsorption of dye increases with an increase in the impregnation ratio. The best adsorption ability was found in activated carbon with the highest cellulose content. Under the conditions of pH 3, an adsorption time of 180 min, and an adsorbent dose of 0.3 g per 50 mm−3 dye solution, the adsorption ability of all activated carbons was the best (adsorption rate reached 99% for the initial concentration of methyl violet dye of 100 mg.dm−3). All activated carbons exhibited the best fit with the Langmuir isotherm model. [ABSTRACT FROM AUTHOR]

The use of coal-derived activated carbon (AC) for water treatment applications demands more sustainable production methods, with chemical activation emerging as a promising alternative to thermal activation due to its higher AC quality, lower carbon burn-off, and higher yield. The study explored the effect of surface area, particle size and acid washing on the quality of AC derived from three seams of lower-rank Collie coal under the same activation conditions with potassium hydroxide (KOH). The quality of AC was determined by surface area and iodine number. The study demonstrates that Collie coal, suitable for AC production via KOH activation, yielded iodine numbers of 640 and 900 mg/g, with yields of 53 and 57 wt.%. Particle size influenced AC yield, with finer particle sizes yielding AC at 57–59 wt.%, whereas coarser ones yielded around 58–65 wt.%. SEM analysis shows the well-developed porous structure in Collie coal-derived activated carbons, with cleaner particles after acid washing. A positive correlation exists between coal surface area and AC iodine numbers, with higher values in coal samples correlating to increased iodine numbers in resulting AC. The regression model's predicted values yield a coefficient of determination (R²) of 0.99. [ABSTRACT FROM AUTHOR]

During the last century, benzene (C6H6) has been a highly studied substance, with some acute and chronic exposures leading directly to hematologic effects detected in humans. This work reports on preparing and examining biomass-derived activated carbons (HPACs) featuring high benzene adsorptive capacity. The fundamental goal of this paper is to propose a green approach for generating HPACs from Heracleum platytaenium Boiss. (Cow parsnip) as woody biomass using a low-cost approach. The characterization showed that chemical activation elicits more enhanced mesoporous structure, a higher degree of graphitization, and bulk porous structure with higher specific surface area and pore volume. To minimize the use of chemicals in the manufacture of high-performance HPACs, an essential pre-pyrolysis step was implemented prior to the chemical activation of biomass by NaOH. The samples were carbonized at different temperatures (500–900 °C) and named as HPAC500, HPAC600, HPAC700, HPAC800, and HPAC900. Considering micropore volume and total surface area, HPAC600 was superior, and maximum benzene adsorption capacities were: HPAC600 (127 mg/g) > HPAC700 (117 mg/g) > HPAC800 (101 mg/g) > HPAC500 (80 mg/g) > HPAC900 (59 mg/g) at selected conditions. Freundlich, Langmuir, and pseudo-first-order (PFO) and pseudo-second-order (PSO) models were used to mathematically describe HPAC600-vapor benzene sorption on HPAC600. The kinetic findings fitted PFO with optimal values of R2 = 0.999, and the isotherm model adsorption fitted Freundlich model (R2 = 1.000). The finding revealed that H. platytaenium is a useful material for producing adsorbents, and successful testing outcomes demonstrate that H. platytaenium products serve as a suitable benzene absorbent. [ABSTRACT FROM AUTHOR]

In this study, novel adsorbents were synthesized via the activation and magnetization of carbon spheres, graphene, and carbon nanotubes fabricated from plastics to improve their surface area and porosity and facilitate their separation from aqueous solutions. Fourier transform infrared spectroscopy "FTIR", X-ray diffraction "XRD", energy-dispersive X-ray spectroscopy "EDX", transmission electron microscope "TEM", and X-ray photoelectron spectroscopy "XPS" affirmed the successful activation and magnetization of the fabricated materials. Further, surface area analysis showed that the activation and magnetization enhanced the surface area. The weight loss ratio decreased from nearly 60% in the case of activated graphene to around 25% after magnetization, and the same trend was observed in the other materials confirming that magnetization improved the thermal stability of the fabricated materials. The prepared carbonaceous materials showed superparamagnetic properties according to the magnetic saturation values obtained from vibrating sample magnetometry analysis, where the magnetic saturation values were 33.77, 38.75, and 27.18 emu/g in the presence of magnetic activated carbon spheres, graphene, and carbon nanotubes, respectively. The adsorption efficiencies of methylene blue (MB) were 76.9%, 96.3%, and 74.8% in the presence of magnetic activated carbon spheres, graphene, and carbon nanotubes, respectively. This study proposes efficient adsorbents with low cost and high adsorption efficiency that can be applied on an industrial scale to remove emerging pollutants. [ABSTRACT FROM AUTHOR]

Biochar from agro-industrial residues has been reported as an excellent adsorbent material for metal ions due to its physical–chemical characteristics and he low cost of raw material. In this work, the synthesis and activation pathways of biochar produced from brewery waste and its capacity to adsorb iron ions in aqueous solutions were investigated. The synthesis was performed by pyrolysis in an oxygen deficient atmosphere. Biochar was chemically activated using solutions of sodium hydroxide, hydrochloric acid, and calcium chloride. The biochar samples as well as the raw material were characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and determination of the surface area and total pore volume by adsorption of N2 (BET) with the aim of evaluating the physicochemical changes in the material. The biochar activated by NaOH (B-NaOH) had the highest Fe adsorption capacity, followed by B-CaCl2, brewery waste (BW), raw biochar (RB), and B-HCl. Pyrolysis increased the surface area and pore volume of all biochar compared to the in natura sample (0.108 m2/g), with emphasis on the RB (0.832 m2/g) and B-NaOH samples (1067 m2/g). The maximum adsorption capacity of Fe2+ was obtained for B-NaOH (q = 21.5 mg/g) with 2 g/L of sample, 16 h of contact, and neutral pH. The Langmuir and Freundlich models fitted the experimental equilibrium data obtained for B-NaOH sample (R2 > 0.960). The kinetic curves showed equilibrium conditions after 300 min, and the pseudo-second-order model presented a better correlation with the data for all curves (R2 > 0.998). Biochars produced in this study can be effectively applied in processes involving iron ion removal. [ABSTRACT FROM AUTHOR]

This work aimed at optimizing the preparation of activated carbon (AC) from Kraft lignin for the adsorption of methylene blue (MB) and amoxicillin (AMX) from water. A full factorial design of three factors (precursor:activating agent (H3PO4) ratio, pyrolysis temperature, and residence time) at two levels was used to optimize the AC production. Eight AC products were obtained and evaluated considering the following responses: product yield, specific surface area (SBET), energy consumption, and adsorptive removal of the contaminants under study. The produced AC presented satisfactory SBET, ranging between 750 and 1335 m2 g−1, and efficient adsorption of MB and AMX from water, achieving up to 99% removal under the studied experimental conditions (100 mg L−1 of MB and AMX solution and material dose of 1 g L−1). Statistical analysis showed that product yield and energy consumption for AC production were influenced by temperature and residence time. The determination of a desirability function indicated a precursor/H3PO4 ratio of 1:2, pyrolysis at 700 °C, and residence time of 60 min as the optimal production conditions. The optimized AC presented SBET 1335 m2 g−1 and maximum adsorption capacity of 210 and 280 mg g−1 for MB and AMX, respectively. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate how the amount of ZnCl2 and temperature affect the process of converting waste wheat bran, known for its hemicellulose struc-ture, into porous material. The characterization of the wheat bran was done using proximate and primary component analysis, and Thermogravimetric analysis (TG) test, Fourier Transform Infrared Spectroscopy (FT-IR) spectra, Energy-dispersive X-ray spectroscopy (EDS) results, and Scanning electron microscopy (SEM) images. The influence of temperature on the surface areas of activated carbons is more significant than the impact of varying the amount of ZnCl2. When the carbonization temperature reached 500 °C, porous structures developed, and the highest surface areas achieved for all impregnation ratios (1:1, 2:1, and 3:1) were 1234, 1478, and 1422 m²/g, respectively. Activated carbon was found to have acidic (0.88 mmol/g) and basic (0.54 mmol/g) functional groups on its surface, after being synthesized through carbonization at 500 °C using ZnCl2 at a 2:1 impregnation ratio in accordance with Boehm titration. This promising activared carbon made from wheat bran, activated by ZnCl2, is efficient and environmentally friendly, and it is a potential solution for water pollution treatment. [ABSTRACT FROM AUTHOR]

Domestic wastewater treatment plants produce large amounts of waste sludge. Sludge can be used to produce activated carbon using potassium hydroxide (KOH) as an activating agent. However, KOH is expensive (relative to the cost of waste carbide lime), making the conversion of waste into valuable products unsustainable. This study explored the utilization of a solid waste by-product, carbide lime waste, as a replacement for KOH to produce sludge-based activated carbon (SBAC). The effects of activation conditions on the characteristics of SBAC were investigated and its performance for methylene blue (MB) removal from a solution was assessed. Post-production analyses using scanning electron microscopy and Fourier-transform infrared spectroscopy indicated that the SBAC produced had a porous surface rich in hydroxyl, aromatic, and alkyl functional groups. Among the tested cases of SBAC prepared using carbide lime, the highest removal of MB (240 mg/g) was achieved for the SBAC prepared at 700 °C with a 1:1 impregnation ratio when activated for 60 min and post-treated with 5M hydrochloric acid. The equilibrium adsorption of MB on SBAC was nonlinear. A strong correlation was found between the pore volume and adsorption capacity of the SBAC produced. The findings of this study suggest that the use of carbide lime waste for SBAC production is a viable alternative to an analytical-grade KOH activator. [ABSTRACT FROM AUTHOR]

The increasing emissions of gaseous pollutants of anthropogenic origin, such as carbon dioxide (CO2), which causes global warming, have raised great interest in developing and improving processes that allow their mitigation. Among them, adsorption on porous materials has been proposed as a sustainable alternative. This work presents a study of CO2 equilibrium adsorption at low temperatures (0, 10, and 20 °C) over a wide range of low pressures, on activated carbon derived from Eucalyptus (ES) and Patula pine (PP) forest waste, and carbonaceous material derived from waste tires (WT). The precursors of these materials were previously prepared, and their physicochemical properties were characterized. ES and PP were thermochemically treated with phosphoric acid, and WT was oxidized with nitric acid. Additionally, these materials were used to obtain monoliths using uniaxial compaction techniques and different binding agents, with better results obtained with montmorillonite. A total of six adsorbent solids had their textural and chemical properties characterized and were tested for CO2 adsorption. The highest specific surface area (1405 m2 g−1), and micropore properties were found for activated carbon derived from Eucalyptus whose highest adsorption capacity ranged from 2.27 mmol g−1 (at 0 °C and 100 kPa) to 1.60 mmol g−1 (at 20 °C and 100 kPa). The activated carbon monoliths presented the lowest CO2 adsorption capacities; however, the studied materials showed high potential for CO2 capture and storage applications at high pressures. The isosteric heats of adsorption were also estimated for all the materials and ranged from 16 to 45 kJ mol−1 at very low coverage explained by the energetic heterogeneity and weak repulsive interactions among adsorbed CO2 molecules. [ABSTRACT FROM AUTHOR]

BACKGROUND: This study aimed to produce activated carbon (AC) from spent coffee (Coffea arabica) grounds by chemical activation using zinc chloride (ZnCl2) and nitric acid to remove bentazone from aqueous solutions. RESULTS: The fresh spent coffee grounds were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and the AC by X‐ray diffraction (XRD), infrared spectroscopy (FTIR), Brunauer–Emmett– Teller (BET), point of zero charge, scanning electron microscopy (SEM) and the Boehman method. Adsorption experiments were carried out in a batch system. The results showed a 70% efficiency in bentazone removal using ZnCl2 carbon. Kinetic studies indicate that the adsorption rate increased slowly up to 720 min; the first‐ and second‐order models fitted the experimental data at a concentration of 50 mg L−1. The adsorption equilibrium is represented by the Langmuir model with a high adsorption capacity of 279.33 ± 6.29 mg mg−1. The adsorption efficiency was also confirmed by toxicity analysis of the effluent with bentazone at 50 mg L−1, using the Allium cepa bioassay, a high‐sensitivity test for pollutants in water. CONCLUSION: Before adsorption, the effluent caused significant cytogenotoxicity to onion root meristems. After adsorption, the generated effluent no longer caused toxicity to the test system, and the results obtained were similar to the control with distilled water. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Microporous carbon adsorbents with high surface area and porosity were synthesized from lignin using an acrylic acid pretreatment strategy. Lignin was grafted with acrylic acid via hydrothermal treatment to introduce carboxyl groups, as verified by NMR and FT-IR spectroscopy. The incorporated carboxyls enabled ion exchange reactions between lignin and potassium during subsequent potassium hydroxide (KOH) activation. This optimized the dispersion of potassium, allowing effective activation even at low KOH levels. The effects of process parameters, including acrylic acid content, hydrothermal time, and KOH ratio, were investigated. Optimal conditions of 5 wt% acrylic acid and 6 h hydrothermal reaction produced a carbon adsorbent with exceptional Brunauer–Emmett–Teller (BET) surface area of 1708 m2/g and pore volume of 0.82 cm3/g at a lignin:KOH:acrylic acid ratio of 1:0.5:0.05. Characterization by FE-SEM, XRD, EDS, and Raman spectroscopy confirmed the successful synthesis of an optimized microporous carbon material. The carbon exhibited an outstanding lead ion adsorption capacity of 371 mg/g by Langmuir modeling. Adsorption kinetics followed pseudo-second-order, indicating chemisorption as the rate-controlling step. Thermodynamic analysis revealed the endothermic nature of lead adsorption, further enhanced at higher temperatures. Overall, the acrylic acid pretreatment approach enabled sustainable production of high surface area microporous carbon adsorbents from lignin using minimal KOH activation. The adsorbents demonstrated tremendous potential for removing lead ions via chemisorption mechanisms. [ABSTRACT FROM AUTHOR]

A series of new granular carbonaceous adsorbents was prepared via single-stage physical and chemical activation of walnut shells. Their suitability for removing various types of organic pollutants (represented by dyes, surfactants and water-soluble polymers) from the liquid phase was assessed. The activation of the precursor was carried out with CO2 and H3PO4 using conventional heating. Activated biocarbons were characterized in terms of chemical composition, acidic–basic nature of the surface, textural and electrokinetic properties as well as thermal stability. Depending on the type of activating agent used during the activation procedure, the obtained biocarbons differed in terms of specific surface area (from 401 to 1361 m2/g) and the type of porous structure produced (microporosity contribution in the range of 45–75%). Adsorption tests proved that the effectiveness of removing organic pollutants from the liquid phase depended to a large extent on the type of prepared adsorbent as well as the chemical nature and the molecular size of the adsorbate used. The chemically activated sample showed greater removal efficiency in relation to all tested pollutants. Its maximum adsorption capacity for methylene blue, poly(acrylic acid), poly(ethylene glycol) and Triton X-100 reached the levels of 247.1, 680.9, 38.5 and 61.8 mg/g, respectively. [ABSTRACT FROM AUTHOR]

This article describes the production of bioadsorbents coming from seven different kinds of organic waste, produced in huge quantities in households, in a two-stage process. In order to determine the influence of the process parameters of carbonization (I stage) and activation with potassium hydroxide solution (II stage), the following analysis of the physicochemical properties of each sample at each stage processing was performed: base elemental composition, structure properties, surface morphology, thermal stability, crystallinity, and transmittance spectra characteristic bands. There was a lack of research on samples after each stage of waste processing in the literature. Addressing this allowed us to evaluate the transformative potential of each kind of organic waste included in the research and select the best waste for the production of bioadsorbents commonly used in environmental protection. Moreover, the results were compared with the ones in the literature. The utilization of particular kinds of organic waste seems to be especially important taking into account the strategy of waste management and sustainable development. [ABSTRACT FROM AUTHOR]

The aim of this study was to obtain nitrogen-enriched activated carbons from orthocoking coal. The initial material was subjected to a demineralisation process. The demineralised precursor was pyrolysed at 500 °C and then activated with sodium hydroxide at 800 °C. Activated carbon adsorbents were subjected to the process of ammoxidation using a mixture of ammonia and air at two different temperature variants (300 and 350 °C). Nitrogen introduction was carried out on stages of demineralised precursor, pyrolysis product, and oxidising activator. The elemental composition, acid-base properties, and textural parameters of the obtained carbon adsorbents were determined. The activated carbons were investigated for their ability to remove nitrogen dioxide. The results demonstrated that the ammoxidation process incorporates new nitrogen-based functional groups into the activated carbon structure. Simultaneously, the ammoxidation process modified the acid-base characteristics of the surface and negatively affected the textural parameters of the resulting adsorbents. Furthermore, the study showed that all of the obtained carbon adsorbents exhibited a distinct microporous texture. Adsorption tests were carried out against NO2 and showed that the carbon adsorbents obtained were highly effective in removing this gaseous pollutant. The best sorption capacity towards NO2 was 23.5 mg/g under dry conditions and 75.0 mg/g under wet conditions. [ABSTRACT FROM AUTHOR]

Activated carbon monoliths (ACMs) are single-piece, three-dimensional (3D) hierarchical porous structures with good permeability, high stability, and swift mass transfer features. Production of activated carbon monoliths from biomass has been identified as promising and sustainable for process development. In this study, ACM was synthesised from African locust bean pods and polystyrene resin. The pods were chemically activated using potassium hydroxide and then carbonised in a locally fabricated auto-thermal biomass-powered reactor for 100 minutes. The activated carbon was then hand-mixed with an organic binder, expanded polystyrene resin, and the product was thermally cured to form the ACM. The ACM was then characterised to determine its properties. Elemental determination revealed the ACM was mostly composed of carbon (63%), potassium (18%), oxygen (4%), and a host of other metals. SEM micrographs showed that the ACM's surface is composed of irregular or heterogeneous-sized carbon materials firmly held by the resin with well-developed visible micropores. Some of the functional groups inherent in the ACM include hydroxyl, alkene, carbonyl, and alkyne. The ACM has a BET surface area of 237 m2/g, a pore diameter of 2.86 nm, and a Young modulus of 1.064 MPa. The synthesised ACM can be utilised as an adsorbent for pollution control, as a catalyst, and for electrochemical applications. [ABSTRACT FROM AUTHOR]

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Recently, to protect the health of aquatic life and, indirectly, all living things, biomass-based substances have been increasingly applied as biosorbent materials to remove micropollutant agents from an aquatic environment. However, these studies are under development, and the search for more successful materials continues. Here, the biosorption of a common micropollutant, methylene blue, from an aquatic environment was investigated using the chemically activated biomass of a widely available plant species, Pyracantha coccinea M. J. Roemer. The biosorption efficiency of the biosorbent material was improved by optimizing the experimental conditions, including the contact time, micropollutant load, pH, and biosorbent material amount, and the highest performance was observed at t = 360 mins, C0 = 15 mg L−1, pH = 8 and m = 10 mg. The pseudo-second-order kinetics model and Freundlich isotherm model were in good agreement with the experimentally obtained results. The thermodynamic study suggested that the micropollutant biosorption was a favorable, spontaneous, and physical process. The micropollutant-biosorbent interaction mechanism was presented using SEM and FTIR studies. The maximum Langmuir biosorption capacity of the biosorbent was determined to be 156.674 mg g−1. The activation operation more than doubled the biosorption potential of the biosorbent material. Thus, the present study showed that the chemically activated plant biomass-based material could be a promising biosorbent for the effective removal of the micropollutant from water environment. The biosorption of a common micropollutant, methylene blue, from a water environment was studied using chemically activated biomass of Pyracantha coccinea M. J. Roemer. The activation operation more than doubled the biosorption potential of the biosorbent material. It exhibited higher micropollutant biosorption performance compared to most other biosorbents. These results indicated that the chemically activated biomaterial could be a very effective biosorbent for the micropollutant biosorption from an aqueous medium. [ABSTRACT FROM AUTHOR]

The preparation of iron ore tailings (IOTs) into supplementary cementitious materials (SCMs) is an effective approach to achieve value-added utilization of industrial solid waste. This study systematically investigates the hydration pattern and strength development of Portland cement systems with the incorporation of IOTs, steel slag (SS), granulated blast-furnace slag (GBFS), and fly ash (FA) under the action of different chemical additives. The hydration products, and microstructure and pore structure of the SCMs are analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and mercury intrusion porosimetry. The findings of this study demonstrate that chemical activation plays a significant role in the strength development of SCMs. Among the five chemical activators tested, Triethanolamine (TEA) had the greatest influence on mechanical properties. The maximum compressive strength of the SCMs at 28 days was 42.9 MPa at a dosage of 1%. Specifically, the addition of TEA promotes volcanic ash reactions, and the high fineness of SCM provides nucleation sites for hydration products. Interactions between the volcanic ash reaction and the complexation reaction of TEA have a positive effect on compressive strength development. This research expands the potential for IOTs SCMs through chemical activation methods for value-added applications. [ABSTRACT FROM AUTHOR]

The study investigated the adsorption behaviour of different activated carbon samples for pertechnetate under diverse conditions. Characterizations of A-CF-F and A-CF-Z samples were done using BET, FTIR, XRD, XRF and SEM–EDX methods. In batch experiments, maximum adsorption occured at pH 2, with a swift process and an optimal phase mixing time determined as 1 h for all of the samples. Analyzing experimental data using Langmuir and Freundlich adsorption models revealed coefficients of determination R2 exceeding 90%. The Freundlich isotherm was found to be more suitable for describing the adsorption process. [ABSTRACT FROM AUTHOR]

The persistent increase in the atmospheric concentration of carbon dioxide (CO2), the primary anthropogenic greenhouse gas contributing to global warming, makes research directed towards carbon capture and storage (CCS) imperative. In the past few years, among the available adsorbents, biochar has drawn significant interest as a promising carbon-based material for low-temperature CO2 capture from flue/fuel gas (such as biogas or gasification-derived syngas) owing to its environmentally friendly nature, cost-effective and facile preparation method, and sustainable adsorption performance. This work provides a review of recent studies on the development of biochar from biomass feedstocks and its subsequent modification through various approaches, including physical, chemical and physicochemical activations for post-combustion CO2 capture. An overview of the factors, including pyrolysis temperature, heating rate and time, and different modification methods, affecting the physicochemical attributes of biochar such as surface area, microporosity, surface properties and functional groups is presented. Biochar with a large micropore volume, a narrow microporosity (0.3–0.8 nm) and basic surface characteristics would be effective in adsorbing CO2 molecules. In this regard, physical modification of biochar is closely related to pore formation, whereas chemical modification emphasizes the creation of oxygen and nitrogen-containing functional groups; hence, they contribute to the enhanced CO2 capture through porosity development and surface chemistry alteration, respectively. Biochar has presented a strong selectivity towards CO2 compared to other gasses and has revealed a sustainable performance in multi-cycles of CO2 adsorption–desorption; these are crucial features to ensure the large-scale application of biochar for CO2 capture. [ABSTRACT FROM AUTHOR]

The aim of this study was to obtain a series of activated carbon samples by the chemical activation of low-rank coal. The precursor was impregnated with a NaOH solution. Activated carbons were characterized by determining their textural parameters and content of surface oxygen functional groups and by using an elemental analysis. The carbons were tested as potential adsorbents for the removal of liquid pollutants represented by rhodamine B. The effectiveness of rhodamine B removal from water solutions depended on the initial concentration of the dye, the mass of rhodamine B, and the pH and temperature of the reaction. The isotherm examination followed the Langmuir isotherm model. The maximum adsorption capacity of the rhodamine B was 119 mg/g. The kinetic investigation favored the pseudo-second-order model, indicating a chemisorption mechanism. The thermodynamic assessment indicated spontaneous and endothermic adsorption, with decreased randomness at the solid–liquid interface. The experiment revealed that a 0.1 M HCl solution was the most effective regenerative agent. [ABSTRACT FROM AUTHOR]

The waste of algae in the water filtration plants is to be considered waste and thrown away. This study reveals that the waste of algae biomass in the water filtration plant can be converted into a useful product such as aluminosilicate (AS). AS has been used for the preparation of gases separation membranes. In this study, waste of algae biomass was collected from the Arisu Water Filtration Plant in Seoul, South Korea. The energy-dispersive X-ray spectroscopy (EDX) results reveal that the Arisu water filtration algae contains Al = 10.34%, Si = 29.74%, C = 23.00, and oxygen = 29.32% by its nature. According to EDX results, this composition is favorable for converting waste of algae biomass into AS. Therefore, in this article, AS was prepared from waste algae biomass by using a combustion process. Two chemical activation agents, ZnCl2 and FeCl3, are used for chemical activation. Chemical activation takes place in the muffle furnace at 550 °C. The properties of the prepared aluminosilicate were analyzed by characterization techniques such as scanning electron microscopy, EDX, Brunauer–Emmett–Teller, X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR). The XRD results of the ZnCl2 chemical activation process reveal the amorphous structure of the aluminosilicate peak at an angle of 20–35 degrees. TGA analysis is carried out to find out the thermal stability of the prepared AS. Furthermore, FT-IR analysis was analyzed to figure out the attached surface functional groups of the prepared aluminosilicate. [ABSTRACT FROM AUTHOR]