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Low-cost and green preparation of efficient sorbents is critical to the removal of organic contaminants during water treatment. In this study, the co-pyrolysis of macroalgae and oyster shell was designed to synthesize nitrogen-doped porous biochars for sorption removal of atrazine from water. Oyster shell played a significant role in opening pores in macroalgae-derived biochars, resulting in the surface area of the macroalgae (Enteromorpha prolifera and Ulva lactuca) and oyster shell co-pyrolyzed carbonaceous as high as 1501.80 m2 g−1 and 1067.18 m2 g−1, the pore volume reached 1.04 cm3 g−1 and 0.93 cm3 g−1, and O/C decreased to 0.09 and 0.08, respectively. The sorption capacity of atrazine to nitrogen-doped porous biochars (the Enteromorpha prolifera, Ulva lactuca and oyster shell co-pyrolyzed carbonaceous) reached 312.06 mg g−1 and 340.52 mg g−1. Pore-filling, hydrogen bonding, π-π or p-π stacking and electrostatic interaction dominated the multilayer sorption process. Moreover, the nitrogen-doped porous biochars showed great performance in cyclic reusability, and the Enteromorpha prolifera, Ulva lactuca and oyster shell co-pyrolyzed carbonaceous sorption capacity still reached 246.13 mg g−1 and 255.97 mg g−1, respectively. Thus, this study suggested that it is feasible and efficient to remove organic contaminants with the nitrogen-doped porous biochars co-pyrolyzed from macroalgae and oyster shell, providing a potential green resource utilization of aquatic wastes for environmental remediation. Highlights: Nitrogen-doped porous biochars (NPBs) were derived from natural wastes. Oyster shell enhanced the micropore and mesopore structures of NPBs. Physical sorption dominated atrazine sorption onto the NPBs. [ABSTRACT FROM AUTHOR]

As a common necessity, masks have been used a lot in recent years, and the comprehensive utilization of waste masks has become a research priority in the post-COVID-19 pandemic era. However, traditional disposal methods suffer from a range of problems, including poor utilization and insecurity. To explore new solution ideas and efficiently utilize waste resources, waste masks and biomass wastes were used as raw materials to prepare mask-based biochar (WMB), bio-oil, and pyrolytic gas via oxygen-limited co-pyrolysis in this study. The obtained solid–liquid–gas product was systematically characterized to analyze the physicochemical properties, and the adsorption properties and mechanisms of WMB on the environmental endocrine bisphenol A (BPA) were investigated. The co-pyrolysis mechanisms were also studied in depth. Furthermore, the strengths and weaknesses of products prepared by co-pyrolysis and co-hydrothermal synthesis were discussed in comparison. The results indicated that the waste masks could shape the microsphere structure, leading to richer surface functional groups and stable mesoporous of WMB. Here, the risk of leaching of secondary pollutants was not detected. The theoretical maximum adsorption of BPA by WMB was 28.73 mg·g−1. The Langmuir and Pseudo-second-order models optimally simulated the isothermal and kinetic adsorption processes, which are a composite of physicochemical adsorption. Simultaneous pyrolysis of mask polymers with biomass polymers produces bio-oil and pyrolytic gas, which is rich in high-quality aliphatic and aromatic compounds. This could have potential as an energy source or chemical feedstock. The co-pyrolysis mechanisms may involve the depolymerization of waste masks to produce hydrocarbons and H radicals, which in turn undergo multi-step cleavage and oligomerization reactions with biomass derivatives. It is recommended to use the co-pyrolysis method to dispose of waste masks, as the products obtained are significantly better than those obtained by the co-hydrothermal method. This work provides a new contribution to the resourcing of waste masks into high-quality products. [ABSTRACT FROM AUTHOR]

A carbon material Cu-corn straw-sludge biochar (Cu-CSBC) was prepared by hydrothermally modifying sewage sludge and corn stover. The composite coupled to ultrasound can effectively catalyze the activation of PS for organic pollutants degradation, and the removal rate of 20 mg/L TC reached 89.15% in 5 min in the presence of 0.5 g/L Cu-CSBC and 3 mM PS. The synergistic effect between the factors in the system, the reaction mechanism, and the efficient removal of TC in the aqueous environment were explored in a Cu-CSBC/US/PS system established for that purpose. Quenching experiments and electron paramagnetic resonance analysis both demonstrated the Cu-CSBC/US/PS system generated •OH, SO4–•, 1O2, and O2- •, which involved in the reaction. The Cu, carboxyl, and hydroxyl groups on the Cu-CSBC surface promoted the generation of radicals and non-radicals for the degradation process, which was dominated by both radical and non-radical pathways. The degradation pathway is proposed by measuring the intermediate products with LC-MS. Finally, the stability of the Cu-CSBC/US/PS system was tested under various reaction conditions. This study not only prepared a novel biochar composite material for the active degradation of organic pollutants by PS but also provided an effective method for the resource utilization of solid waste and sludge treatment. HIGHLIGHTS Cu-CSBC prepared from co-pyrolyzed biomass–sludge to activate PS.; US and Cu-CSBC have a positive synergistic effect on the system.; The TC removal efficiency of the Cu-CSBC/US/PS system exceeded 99%.; The US can promote the production of free radicals in the system.; The main intermediates and pathways of TC degradation were identified.;

With the increasing production of municipal sewage sludge (MSS) worldwide, the development of efficient and sustainable strategies for its management is crucial. Pyrolysis of MSS offers several benefits, including volume reduction, pathogen elimination, and energy recovery through the production of biochar, syngas, and bio-oil. However, the process can be limited by the composition of the MSS, which can affect the quality of the biochar. Co-pyrolysis has emerged as a promising solution for the sustainable management of MSS, reducing the toxicity of biochar and improving its physical and chemical properties to expand its potential applications. This review discusses the status of MSS as a feedstock for biochar production. It describes the types and properties of various co-substrates grouped according to European biochar certification requirements, including those from forestry and wood processing, agriculture, food processing residues, recycling, anaerobic digestion, and other sources. In addition, the review addresses the optimization of co-pyrolysis conditions, including the type of furnace, mixing ratio of MSS and co-substrate, co-pyrolysis temperature, residence time, heating rate, type of inert gas, and flow rate. This overview shows the potential of different biomass types for the upgrading of MSS biochar and provides a basis for research into new co-substrates. This approach not only mitigates the environmental impact of MSS but also contributes to the wider goal of achieving a circular economy in MSS management. [ABSTRACT FROM AUTHOR]

Plant available potassium (K) content is very low in K-bearing mineral ores present in Sri Lanka and that restrict their use in crop production as K fertilizer sources. Heating of minerals can increase their plant available forms of nutrients. The objective of this experiment was to study the effect of direct heating of K-bearing minerals at different temperatures and co-pyrolyis with poultry litter (PL) at different rates on their total and available K contents. Poultry litter was co-pyrolyzed with 0, 1 and 5% (w/w) of feldspar and mica at 350, 500, 650 and 900 ℃. K-bearing minerals were also directly heated at these temperatures. With direct heating the mineral, total K contents of feldspar (6.2%) and mica (4.5%) were significantly (p<0.001) increased by 10% and 18%, respectively at 500 ℃ and then decreased by 33 and 65%, respectively at 900 ℃. Available K contents in feldspar (0.05%) and in mica (0.03%) either decreased significantly (feldspar) or did not change (mica) upon direct heating. Increasing pyrolysis temperature up to 650 ℃ increased both total (4.2 to 6.4%), and available K (3.2 to 6.1%) contents in poultry litter biochar (PLB). Co-pyrolysis of PL with feldspar or mica at 1 or 5% rates did not improve the total or available K contents in PLB at these temperatures. We concluded that heat treatment of locally available feldspar and mica or co-pyrolyzing them with PL are not effective technologies to increase their utilization in agriculture. [ABSTRACT FROM AUTHOR]

Co-pyrolysis of chicken manure with tree bark was investigated to mitigate salinity and potentially toxic element (PTE) concentrations of chicken manure-derived biochar. The effect of tree bark addition (0, 25, 50, 75 and 100 wt%) on the biochar composition, surface functional groups, PTEs and polycyclic aromatic hydrocarbons (PAH) concentration in the biochar was evaluated. Biochar-induced toxicity was assessed using an in-house plant growth assay with Arabidopsis thaliana. This study shows that PTE concentrations can be controlled through co-pyrolysis. More than 50 wt% of tree bark must be added to chicken manure to reduce the concentrations below the European Biochar Certificate-AGRO (EBC-AGRO) threshold. However, the amount of PAH does not show a trend with tree bark addition. Furthermore, co-pyrolysis biochar promotes plant growth at different application concentrations, whereas pure application of 100 wt% tree bark or chicken manure biochar results in decreased growth compared to the reference. In addition, increased plant stress was observed for 100 wt% chicken manure biochar. These data indicate that co-pyrolysis of chicken manure and tree bark produces EBC-AGRO-compliant biochar with the potential to stimulate plant growth. Further studies need to assess the effect of these biochars in long-term growth experiments. [ABSTRACT FROM AUTHOR]

Leucaena leucocephala, an invasive toxic tree species, has threatened the survival of native plants in the Hengchun Peninsula, southern Taiwan. Due to the small-to-medium diameter, the utilization and processing of L. leucocephala is highly restricted, while its discarding accelerates carbon dioxide emission to the atmosphere. Biochar, produced from the pyrolysis of biomass under an inert atmosphere, is considered an effective carbon sequestration technique with high stability, which is important for long-term carbon storage and soil improvement. L. leucocephala biomass and montmorillonite were co-pyrolyzed under inert conditions, aiming to investigate the effects of different pyrolysis temperatures and montmorillonite blending ratios on biochar yield and carbon retention. Results showed improved biochar yield and carbon retention with increasing montmorillonite addition. Thermogravimetric analysis, nuclear magnetic resonance spectroscopy, and Fourier-transform infrared spectroscopy demonstrated enhanced stability of the modified biochars. The production of modified L. leucocephala biochar represents a promising technique for carbon dioxide sequestration and biochar stabilization, enabling the development of L. leucocephala utilization approaches.

The co-pyrolysis (at 300°C and 600°C) of municipal sewage sludge (SS) with zero-valent iron (Fe0: 1.5% and 3%) was investigated to reduce the toxicity of arsenic (As) and zinc (Zn) in SS. The BCR sequential extraction method, desorption kinetic analysis, and material characterization techniques (Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, X-ray diffraction) were used to evaluate the effects of the treatments on Zn and As behavior. The results showed that co-pyrolysis significantly reduced the acid-soluble fraction (18–43% for Zn; 83–95% for As) and mobility factor (45–85% for Zn; 86–96% for As) of Zn and As compared to untreated SS. Desorption experiments indicated a significant reduction in Zn and As release in treated samples, particularly in the co-pyrolysis sample at 600°C and Fe0 3% (67% for Zn; 88% for As) in comparison with untreated SS. Co-pyrolysis of Fe0 and SS led to the formation of new functional groups (Si–O, aromatic), a more porous surface morphology, and highly stable chemical crystals (ferric arsenate, zinc arsenide), which played a crucial role in Zn and As stabilization. The findings of this study suggest that co-pyrolysis is a promising approach for mitigating As and Zn toxicity in SS. However, additional field testing with plant-based systems is necessary for confirmation.

[Display omitted] • The release of Zn and Pb were mitigated by the synergistic effect. • Bioavailable fractions of HMs were reduced by SiO 2 and Al 2 O 3 from the sludge. • Bioavailable phosphorus was increased from 18.79 to 49.69 mg/g by co-pyrolysis. Phosphate tailings (PT) was used to reduce the release of heavy metals (HMs) during pyrolysis and the leachable rate of residual HMs, and simultaneously improve the bioavailability of phosphorus in the sludge-based biochar. The concentration of heavy metals and the fractions determined by BCR method was used to investigate the release and the transformation of Zn, Pb, Mn, Ni and Cu during pyrolysis involved with the effects of temperature and the addition of PT. The respective pyrolysis experiments shows that the release of Zn and Pb increases with temperature for both sewage sludge (SS) and PT, and the bioavailable fractions (F1 + F2) of Mn, Ni, and Cu increases with temperature for PT. During co-pyrolysis, blended samples released lower quantities of Zn and Pb and presented lower bioavailability of HMs than the individual SS or PT. A synergistic effect of co-pyrolysis was evident for volatile Zn and Pb. The decomposition of CaMg (CO 3) 2 from PT produced CaO, by which the volatile ZnCl 2 and PbCl 2 were transformed into ZnO and PbO with less volatility and higher reactivity with SiO 2 and Al 2 O 3 than the chlorides. Then SiO 2 and Al 2 O 3 from SS acted as the final stabilizer to immobilize the oxides. The final product combined with SiO 2 and Al 2 O 3 , such as ZnSiO 4 and ZnAl 2 O 4 , were detected. The addition of PT also introduced more Ca and P into sludge to produce biochar with higher concentration of apatite phosphorus with higher bioavailability. [ABSTRACT FROM AUTHOR]

The municipal sludge in mountainous cities and the sludge was co-pyrolyzed with agricultural and forestry wastes including rice stalk, rice husk, eucalyptus brand and eucalyptus leaf.The effects of co-pyrolysis on the physicochemical properties and Cu (II) adsorption properties of biochar were investigated, and the synergistic effect of co-pyrolysis on Cu (II) adsorption properties was discussed.The results showed that compared with sludge biochar, the C contents of biochar derived from co-pyrolysis of sludge with rice husk, rice stalk, eucalyptus branch and eucalyptus leaf were increased by 0.64 times, 0.87 times, 1.04 times and 1.22 times, respectively; the O contents were increased by 1.11 times, 1.25 times, 2.01 times and 2.17 times, respectively; the maximum adsorption capacities of Cu (II) were enhanced by 28.4%,60.3%,82.7% and 99.7%,respectively.Co-pyrolysis had a significant synergistic effect on the adsorption capacity of Cu (II) on biochar, and the synergistic value of the maximum Cu (II) adsorption capacity of biochar derived from co-pyrolysis of sludge with eucalyptus leaf was the highest (90.13%). [ABSTRACT FROM AUTHOR]

In this study, coffee ground (CG), a kind of solid waste, was co-pyrolyzed with native microalgae consortium (NMC) of which the main population were Spirogyra sp., Cladophora sp., Microspora, and Rhizoclonium at various mass ratios to improve the biochar qualities such as biochar yield, pH, nitrogen content, and BET surface area. The biochar production was undertaken from 150 g raw material in a slow pyrolysis cylindrical fixed bed reactor at 5–10 °C/min heating rate with 100 ml/min flow rate of nitrogen as sweeping gas. The reactor temperature was heated up to 400 °C with a holding time of 1 h. Increase of NMC resulted in higher percentage of biochar yield but in terms of higher heating value (HHV), the biochar from pure CG gave a high HHV of 32.14 MJ/kg which was suitable to be used as solid fuel and the value decreased with the NMC composition. The pH value and nitrogen content in the biochar were found to be improved with the increase in NMC content or decrease in CG/NMC ratio. The pores generated in the co-pyrolyzed biochars were mesopores of which the specific surface area and the total pore volume increased with the NMC content then the biochars were suitable for soil amendment and taken as adsorber to remove some toxic organic and inorganic pollutants in water and air treatments. In the case of the biochar electrical conductivity, since the value of the was higher with the increase of NMC content, the amount of the biochar having NMC composition for soil amendment should be carefully estimated to avoid high soil salinity and nutrient imbalances. [ABSTRACT FROM AUTHOR]

Biomass and plastics are two of the most common municipal solid wastes globally that have continuously placed a burden on the environment. It is therefore important that they are properly recycled. Thermochemical coconversion offers a valuable opportunity to recycle biomass and plastics simultaneously into biochar, which reduces the time and cost of recycling them individually while producing a material with a wide range of applications. This study is a review of published literature that discusses the thermochemical co-processing of biomass and plastic wastes into biochar. It was observed that co-pyrolysis and co-hydrothermal carbonization are the most commonly utilized technologies for this process. The characteristics of different biomass and plastics that have been thermochemically converted into biochar were compared. The properties of the resulting biochar are affected by the feedstock composition, pre-treatment and blending ratio, the reactor's configuration, reaction temperature, and the presence of a catalyst. Most studies found that treating the feedstocks separately resulted in a lower yield of biochar than processing them together. The biochar created by this procedure has been used as a soil additive and as an adsorbent for water treatment. Future perspectives and suggestions, such as the necessity for some technical advancement, biochar's economic benefits, improved government participation, and raised social awareness, were also made. These factors have the potential to propel this field of study to great horizons. [ABSTRACT FROM AUTHOR]

Hazardous waste stream needs to be managed so as not to exceed stock- and rate-limited properties of its recipient ecosystems. The co-pyrolysis of Chinese medicine residue (CMR) and textile dyeing sludge (TDS) and its bio-oil, biochar, and ash quality and quantity were characterized as a function of the immersion of K 2 CO 3 , atmosphere type, blend ratio, and temperature. Compared to the mono-pyrolysis of TDS, its co-pyrolysis performance with CMR (the comprehensive performance index (CPI)) significantly improved by 33.9% in the N 2 atmosphere and 33.2% in the CO 2 atmosphere. The impregnation catalyzed the co-pyrolysis at 370°C, reduced its activation energy by 77.3 kJ/mol in the N 2 atmosphere and 134.6 kJ/mol in the CO 2 atmosphere, and enriched the degree of coke gasification by 44.25% in the CO 2 atmosphere. The impregnation increased the decomposition rate of the co-pyrolysis by weakening the bond energy of fatty side chains and bridge bonds, its catalytic and secondary products, and its bio-oil yield by 66.19%. Its bio-oils mainly contained olefins, aromatic structural substances, and alcohols. The immersion of K 2 CO 3 improved the aromaticity of the co-pyrolytic biochars and reduced the contact between K and Si which made it convenient for Mg to react with SiO 2 to form magnesium-silicate. The co-pyrolytic biochar surfaces mainly included -OH, -CH 2 , C=C, and Si-O-Si. The main phases in the co-pyrolytic ash included Ca 5 (PO 4) 3 (OH), Al 2 O 3 , and magnesium-silicate. [Display omitted] [ABSTRACT FROM AUTHOR]

Biochar is currently used as a phosphate adsorbent in water and subsequently as a soil amendment. In this study, modified biochar was prepared directly by co‐pyrolysis of MgO and rice straw, and a preliminary ecotoxicological assessment was performed before the application of modified biochar to soil. The effects of single factors, such as pyrolysis temperature, dosage, pH, and coexisting ions, on phosphate adsorption performance were investigated. In addition, after phosphate adsorption, the effects of modified biochar leachate on the germination of corn and rice seeds were examined. The results showed that phosphate adsorption by the modified biochar first increased and then decreased as the pyrolysis temperature increased, with modified biochar prepared at 800 °C showing the greatest adsorption. In addition, a comprehensive cost analysis showed that the best phosphate adsorption effect of modified biochar was achieved at a dosage of 0.10 g and a solution pH of 3. In contrast, the presence of competitive coexisting ions, Cl−, NO3−, CO32−, and SO42−, reduced the phosphate adsorption capacity of the modified biochar. The adsorption kinetics results revealed that the process of phosphate adsorption by the modified biochar was more in line with the pseudo‐second‐order model and dominated by chemisorption. Moreover, the adsorption isotherm results indicated that the process was more in line with the Langmuir model and dominated by monomolecular layer adsorption, with a maximum adsorption of 217.54 mg/g. Subsequent seed germination tests showed that phosphate‐adsorbed modified biochar leachate had no significant effect on the germination rate of corn seeds, whereas it improved the germination rate of rice seeds. Together, these results provide guidance for the application of modified biochar firstly as an adsorbent of phosphate and subsequently as a soil remediator. [ABSTRACT FROM AUTHOR]

Global waste is a rising problem that requires attention. Pyrolysis is a process that converts waste into valuable products like biochar, bio-oil, and gas by heating feeds above 300 °C. Pyrolysis studies mostly concentrate on fuel production and characterization, while biochar studies lack parametric analysis, especially for co-pyrolysis. Little attention is given to the effects of blending ratio and particle size on biochar yield. This research focuses on the pyrolysis of biosolids obtained from gas-to-liquid wastewater treatment, waste cardboard, and co-pyrolysis of blended samples. Pyrolysis was performed using a muffled furnace at temperatures ranging from 350–850 °C , heating rates of 3–10 °C /min, and residence times of 30–180 min to examine biochar yield and properties. Particle sizes and blending ratios were also studied. Proximate and ultimate analyses, metal composition, surface area, and surface charge studies were conducted on biochar samples utilizing analytical instruments. Biosolids had the highest yield followed by mixed samples and cardboard for all conditions, with temperature and blending ratio having the greatest impact on yield. Regarding surface area, the maximum was found to be at 650 °C revealing 10.34, 170.4, and 124.8 m2/g for biosolids, cardboard, and mixed samples, respectively. A significant effect with change in blending ratio and a minimal effect by varying particle size was observed on the biochar yield. For future applications, temperatures below 550 °C can be considered in terms of biochar yield, ash, and metal contents; as heating rate and residence time showed minimal effects on yield, lower points are preferred to conserve energy during pyrolysis. Overall, mixing waste improved quality and yield, making it environmentally beneficial for applications. [ABSTRACT FROM AUTHOR]

Recent studies have reported that Fenton sludge and biochemical sludge contain high concentrations of toxic substances and heavy metals (HMs), whereas improper treatment can pose serious threats to environmental safety. Pyrolysis is considered an efficient technology to replace conventional sludge treatment. This study investigated the pyrolysis and kinetic processes of Fenton sludge and biochemical sludge, revealed the physicochemical properties of sludge biochar, and highlighted the role of co-pyrolysis in sludge immobilization of HMs and environmental risks. Results showed that Fenton sludge and biochemical sludge underwent three stages of weight loss during individual pyrolysis and co-pyrolysis, especially co-pyrolysis, which increased the rate of sludge pyrolysis and reduced the decomposition temperature. The kinetic reaction indicated that the activation energies of Fenton sludge, biochemical sludge, and mixed sludge were 11.59 kJ/mol, 8.50 kJ/mol, and 7.11 kJ/mol, respectively. Notably, co-pyrolysis reduced the activation energy of reactions and changed the specific surface area and functional group properties of the biochar produced from sludge. Meanwhile, co-pyrolysis effectively immobilized Cu, Pb, and Zn, increased the proportion of metals in oxidizable and residual states, and mitigated the environmental risks of HMs in sludge. This study provided new insights into the co-pyrolysis properties of sludge biochar and the risk assessment of HMs. [ABSTRACT FROM AUTHOR]

Co-pyrolysis is an important method to transform hazardous waste into new materials, and composites based on biochar and metal oxides could constitute new types of adsorbents for volatile organic compounds (VOCs). In this study, residual biomass (corn cob, rapeseed and walnut shell) was co-pyrolyzed at 650OC with aluminum slag (AlS), and different composites were synthesized. Biocomposites have been used as adsorbents for the removal of VOCs (such as acetone and toluene). The results showed that the biocomposite obtained from corn cob and AlS has a higher adsorption capacity for acetone, while the composite obtained from walnut shell and AlS showed a higher adsorption capacity for toluene. All prepared composites showed a higher adsorption rate than the corresponding pure biochars. After eighth cycles of adsorption/desorption, the results obtained showed the sample AlS 650 -Na/BC CC presented a good adsorption performance for acetone (318 mg/ g) in the first three cycles, and then the adsorption capacity decreased slowly, with the increase in the number of adsorption cycles. However,the adsorption capacity of 254.41 mg/g was still high after the eighth cycles.A similar behavior was presented by the AlS 325 -Na/BC WS composite for toluene adsorption.Therefore,AlS/BC composites could be used as a potential adsorbents in VOCs removal. [Display omitted] [ABSTRACT FROM AUTHOR]

Wastewater treatment plants produce solid and semi-solid sludge, which treatment minimises secondary environmental pollution because of wastewater treatment and obtaining new bioproducts. For this reason, in this paper, the co-pyrolysis of biogenic biomasses recovered from a biological reactor with immobilised fungal and bacterial biomass and a tertiary reactor with Chlorella sp. used for dye-contaminated wastewater treatment was carried out. Biogenic biomasses mixed with pine bark allowed the production and characterisation of two types of biochar. The raw material and biochar were on the "in vitro" germination of Lolium sp. seeds, followed by adsorption studies for malachite green (MG) dye using the raw material and the biochar. Results showed that using 60 mg L−1 of a cationic coagulant at pH 6.5 allowed for the recovery of more than 90% of the microalgae after 50 min of processing. Two biochar resulted: BC300, at pH 5.08 ± 0.08 and BC500, at pH 6.78 ± 0.01. The raw material and both biochars were co-inoculated with growth-promoting bacteria; their viabilities ranged from 1.7 × 106 ± 1.0 × 101 to 7.5 × 108 ± 6.0 × 102 CFU g−1 for total heterotrophic, nitrogen-fixing and phosphate-solubilising bacteria. Re-use tests on Lolium sp. seed germination showed that with the post-coagulation effluent, the germination was 100%, while with the biochar, with and without beneficial bacteria, the germination was 98 and 99%, respectively. Finally, BC500 adsorbed the highest percentage of malachite green at pH 4.0, obtaining qecal values of 0.5249 mg g−1 (R2: 0.9875) with the pseudo-second-order model. [ABSTRACT FROM AUTHOR]

Algal biomass is a promising pyrolysis feedstock, however, large amounts of nitrogen‐containing compounds (NH3, HCN,...) are emitted during its conversion. These emissions can be decreased by incorporating nitrogen in the biochar's carbon matrix via co‐pyrolysis. This study investigates whether adding glucose (GL) to the microalgae, Arthrospira sp. (SP), increases the nitrogen fixation in the solid biochar. Moreover, scalable (co‐) pyrolysis experiments are linked with micro‐scale pyrolysis. Using hyphenated pyrolysis (Py–GC–MS, TG‐IR) and characterization (CHNS, XPS, and Raman) techniques the phenomena associated with the incorporation of nitrogen in the biochars are unraveled. Co‐pyrolyzing SP and GL increased biochar yields and nitrogen retention, which is attributed to Maillard reactions occurring in the initial pyrolysis stages. In conclusion, this study provides evidence that co‐pyrolysis of microalgae and reducing sugars is a more sustainable strategy to produce algae‐based biochar. [ABSTRACT FROM AUTHOR]

As a common necessity, masks have been used a lot in recent years, and the comprehensive utilization of waste masks has become a research priority in the post-COVID-19 pandemic era. However, traditional disposal methods suffer from a range of problems, including poor utilization and insecurity. To explore new solution ideas and efficiently utilize waste resources, waste masks and biomass wastes were used as raw materials to prepare mask-based biochar (WMB), bio-oil, and pyrolytic gas via oxygen-limited co-pyrolysis in this study. The obtained solid–liquid–gas product was systematically characterized to analyze the physicochemical properties, and the adsorption properties and mechanisms of WMB on the environmental endocrine bisphenol A (BPA) were investigated. The co-pyrolysis mechanisms were also studied in depth. Furthermore, the strengths and weaknesses of products prepared by co-pyrolysis and co-hydrothermal synthesis were discussed in comparison. The results indicated that the waste masks could shape the microsphere structure, leading to richer surface functional groups and stable mesoporous of WMB. Here, the risk of leaching of secondary pollutants was not detected. The theoretical maximum adsorption of BPA by WMB was 28.73 mg·g−1. The Langmuir and Pseudo-second-order models optimally simulated the isothermal and kinetic adsorption processes, which are a composite of physicochemical adsorption. Simultaneous pyrolysis of mask polymers with biomass polymers produces bio-oil and pyrolytic gas, which is rich in high-quality aliphatic and aromatic compounds. This could have potential as an energy source or chemical feedstock. The co-pyrolysis mechanisms may involve the depolymerization of waste masks to produce hydrocarbons and H radicals, which in turn undergo multi-step cleavage and oligomerization reactions with biomass derivatives. It is recommended to use the co-pyrolysis method to dispose of waste masks, as the products obtained are significantly better than those obtained by the co-hydrothermal method. This work provides a new contribution to the resourcing of waste masks into high-quality products.

With the increasing production of municipal sewage sludge (MSS) worldwide, the development of efficient and sustainable strategies for its management is crucial. Pyrolysis of MSS offers several benefits, including volume reduction, pathogen elimination, and energy recovery through the production of biochar, syngas, and bio-oil. However, the process can be limited by the composition of the MSS, which can affect the quality of the biochar. Co-pyrolysis has emerged as a promising solution for the sustainable management of MSS, reducing the toxicity of biochar and improving its physical and chemical properties to expand its potential applications. This review discusses the status of MSS as a feedstock for biochar production. It describes the types and properties of various co-substrates grouped according to European biochar certification requirements, including those from forestry and wood processing, agriculture, food processing residues, recycling, anaerobic digestion, and other sources. In addition, the review addresses the optimization of co-pyrolysis conditions, including the type of furnace, mixing ratio of MSS and co-substrate, co-pyrolysis temperature, residence time, heating rate, type of inert gas, and flow rate. This overview shows the potential of different biomass types for the upgrading of MSS biochar and provides a basis for research into new co-substrates. This approach not only mitigates the environmental impact of MSS but also contributes to the wider goal of achieving a circular economy in MSS management.

[Display omitted] • The effect of temperature and CaO on migration of heavy metals during co-pyrolysis process was studied. • Co-pyrolysis promoted the immobilization and stable migration of heavy metals. • The addition of CaO further reduces the potential environmental risk of heavy metals. • The migration mechanism of heavy metals during co-pyrolysis was revealed. To relieve the secondary contamination of heavy metals (HMs), the synergistic effect of co-pyrolysis of textile dyeing sludge (DS)/litchi shell (LS) and CaO on the migration of HMs was demonstrated in this study. The proportions of Cu, Zn, Cr, Mn, and Ni in the F4 fraction increased to 75%, 55%, 100%, 50%, and 62% at the suitable CaO dosages. When 10% CaO was added, the RI value of DLC-10% was reduced to 7.89, indicating low environmental risk. The characterizations of the physicochemical properties of biochar provided support for the HMs immobilization mechanism. HMs combined with inorganic minerals or functional groups to form new stable HMs crystalline minerals and complexes to achieve immobilization of HMs. The pH value and pore structure also play an important role in improving the immobilization performance of HMs. In conclusion, the results provided a new direction for the subsequent harmless treatment of HMs-enriched waste. [ABSTRACT FROM AUTHOR]

The safe disposal and resource utilization of Fenton sludge (FS) are challenges due to the presence of heavy metals (HMs). Co-pyrolysis with biomass waste can effectively increase biochar quality and immobilize HMs, but research focusing on heavy metal stabilization from Fenton sludge using the co-pyrolysis approach is scattered. In this study, the co-pyrolysis of FS and pomelo peel (PP) was developed as a strategy to reduce the environmental risk of HMs. The results showed that co-pyrolysis greatly increased the pH and aromaticity of biochars, and the maximum specific surface area was 6.5 times higher than the corresponding FS-based biochar due to the sponge-like structure of PP, which was likely conducive to adsorbing HMs during pyrolysis. Meanwhile, the addition of PP promoted the enrichment of HMs in co-pyrolyzed biochars as well as induced the transformation of bio-available HM fractions to stable forms, especially at high temperatures. Finally, the presence of PP led to the decline in HM leachability in biochars; thus, the potential ecological risks of HMs decreased from considerable pollution levels to moderate and even clean levels. This study demonstrated that co-pyrolysis with PP is a promising approach to reduce the toxicity of HMs and improve the functionality of biochar for industrial sludge management. [ABSTRACT FROM AUTHOR]

In this study, the effect of oyster shell powder as a substitute for calcium chemical reagents to modify straw biochar for enhancing removal of phosphate and ammonium from aqueous solution was investigated. The results showed that the biochar composite (OSB3:1) with the maximum capacity (151.37 mg·P/g and 0.8 mg·N/g) was synthesized at optimum mass ratio of oyster shell-to-straw (3:1) and pyrolysis temperature (800°C). The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetic models, and it achieved excellent performance at pH 2.0-11.0. According to the thermodynamic analysis, the adsorption reaction was an endothermic and spontaneous process, and increasing the temperature increased the adsorption capacity. The removal mechanisms for phosphate included the formation of hydroxyapatite precipitation, ligand exchange, surface complexation and electrostatic attraction, while for ammonium only electrostatic attraction. The modified biochar can effectively remove phosphate (over 85%) from real domestic sewage within 3 h. Reuse of P-laden biochar as heavy metal adsorbent was proposed, as it exhibited a good removal efficiency for Cd, Zn and Cu, especially application for acidic wastewater. [ABSTRACT FROM AUTHOR]

Titanium dioxide (Titania) nanoparticle-coated biochar derived through co-pyrolysis of COVID-19 waste face mask (WFM) and Moringa oleifera seed cake (MO) provides an effective way to alleviate toxic metal in wastewater. This study investigates the effects of Biochar/titania photocatalyst preparation, characterization, and its photoreduction of Cr(VI). The morphological and functional modifications in the catalyst were identified using X-Ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, ultraviolet spectrophotometer, surface area analysis, and Raman spectrophotometer, respectively. The influencing parameters, namely, pH, photocatalyst dosage, initial pollutant concentration, and visible light irradiation time, have been investigated. The findings reveal that the Cr(VI) reduction by the photocatalyst was highly facilitated by photocatalytic process. The prepared photocatalyst shows higher and faster reduction rate of Cr(VI) and also improves the catalyst stability. The photoreduction of Cr(VI) ensembles well with pseudo-first order kinetics. At 180 min of reaction time, maximum Cr(VI) reduction of 98.65% was achieved at pH 2, 0.3 g/L catalyst dosage, and 10 ppm initial concentration, respectively. The synthesized photocatalyst shows excellent recycling performance up to 7 times, and these studies proved that the prepared catalyst is cost-effective and efficiently employed for removing pollutants. [ABSTRACT FROM AUTHOR]

Taking rubber and ginkgo biloba leaves as raw materials (the mass ratio is 5 : 2), this study prepared biochar by co‐pyrolysis at 700–900 °C and explored its adsorption performance on the emerging water pollutant ciprofloxacin. The pyrolysis behaviors of rubber, ginkgo biloba leaves, and their mixture were investigated using a thermogravimetric analyzer. The microstructure and physicochemical properties of the co‐pyrolysis biochar prepared in this study were probed through scanning electron microscopy (SEM), Brunauer‐Emmett‐Teller (BET) and element analysis. Meanwhile, the internal mechanism of prepared co‐pyrolysis biochar adsorbing ciprofloxacin was investigated using adsorption kinetics models and isotherm adsorption models. The results show that there is a synergistic effect between rubber and ginkgo biloba leaves during the co‐pyrolysis process. Due to the addition of ginkgo biloba leaves, the maximum mass loss rate of rubber reduces from −5.80 %/min to −4.98 %/min, the corresponding pyrolysis temperature decreases from 335.11 °C to 319.57 °C, and the calculated thermogravimetric analysis (TG) and differential thermogram (DTG) curves after mixing the two raw materials deviate from the experimental curves. As the pyrolysis temperature increases from 700 °C to 900 °C, the yields of biochars decrease from 28.62 % to 19.21 %, while the specific surface area significantly increases (337.5042 m2/g). The processes of co‐pyrolysis biochars prepared at different temperatures absorbing ciprofloxacin conform to the pseudo‐second‐order model (R2=0.9847, 0.9404 and 0.9772, respectively). The Langmuir‐Freundlich model describes the isotherm adsorption behaviors of co‐pyrolysis biochars prepared at different temperatures on ciprofloxacin excellently (R2=0.9976, 0.9995 and 0.9993). The co‐pyrolysis biochar prepared at 900 °C has the highest adsorption capacity for ciprofloxacin, 306.6 mg/g. This study provides an essential reference for the application of co‐pyrolysis biochar of low‐cost and environment‐friendly in the removal of water pollutants. [ABSTRACT FROM AUTHOR]

Co-pyrolysis characteristics of rice husk and cow manure using SnCl2, ZnCl2 and Fe3O4 as an additive were studied in a fixed tubular furnace. The effects of additive loading amount (0–20 wt.%) on the pyrolysis processes were investigated. The thermogravimetric-derivative thermogravimetric results showed that the weight loss rate was increased with the increase of additive content. There was no obvious shoulder peak appeared after the addition of Fe3O4, while the peak of weight loss was moved to the low-temperature region with the ZnCl2 addition. Gas yield was increased with the increase of Fe3O4 content while it was decreased after the addition of SnCl2 and ZnCl2. The highest gas yield (0.39 Nm3/kg) was obtained at 20% Fe3O4. At the same time, the additives could obviously improve the quality of syngas which promoted H2 content and reduced CO content. The H2 content was increased by 7.9%, 8.88%, and 4.44%, respectively, for SnCl2, ZnCl2, and Fe3O4. The results of GC/MS showed that the additives promoted hydrogen bond breaking and the cracking of macromolecules resulting in an increase of small polycyclic aromatic hydrocarbons production. Meanwhile, the additives made a great influence on the oxygen-containing functional groups in the biochar, which increased the content of O–H and O–C–O functional groups. [ABSTRACT FROM AUTHOR]

Abstract The increase in mineral and ash-rich waste biomass (MWB) generation in emerging economies poses critical environmental problems and bottlenecks the solid waste and wastewater treatment systems. Transforming these MWB such as sewage sludge from wastewater treatment (SSW) to biochar can be a sustainable method for their disposal and resource recovery. However, such biochar has limited applicability due to the relatively low organic content and possibly contaminated nature of SSW. This may be offset through combined pyrolysis with other MWB, which can also support municipal solid waste management. Studies on this MWB co-pyrolysis are lacking and have not yet seen successful long-term implementation. This work is the second part of authors’ research encompassing an analytical and lab-scale investigation of biochar production from MWB through pyrolysis for the case of Chennai city, India. Here, the physicochemical properties of biochar derived from lab-scale co-pyrolysis of SSW with other MWB such as anaerobic digestate from waste to energy plants of food, kitchen or market waste fermentation, and banana peduncles (BP) collected from vegetable markets and their thermolysis mechanism are comprehensively investigated for purpose of carbon sequestration. Also, a novel preliminary investigation of the effect of sample weight (scaling effect) on the analytical pyrolysis of biomass (BP as model substrate) is undertaken to elucidate its impact on the heat of pyrolysis and carbon distribution in resultant biochar. The maximum carbon sequestration potential of the derived biochar types is 0.22 kg CO2 kg−1 biomass. The co-pyrolysis of MWB is exothermic and governed by the synergetic effects of the components in blends with emission profiles following the order CO2 > CH4 > CO > NH3. Co-pyrolysis reduced the heavy metal enrichment in SSW biochar. The derived biochars can be an immediate source of N, P and S in nutrient-deficient acidic soils. The biochar has only up to 4-ring polyaromatic compounds and a residence time longer than 1 h at 500 °C is necessary to improve carbonization. The heat released during analytical pyrolysis of the model biomass and distribution of carbon in the resultant biochar are significantly influenced by scaling effects, drawing attention to the need for a more detailed scaling investigation of biomass pyrolysis.

Irreversible pollution by heavy metals such as lead (Pb) and cadmium (Cd) adversely affects the ecological environment and human health. Due to its high adsorption, microporosity, and specific surface area, biochar possesses excellent potential for use in heavy metal pollution remediation. The preparation of mixed-based biochar from sludge and cotton stalk can solve the problems inherent to pure sludge biochar, such as undeveloped pore structure and a small specific surface area, while resourcefully utilizing both waste biomass types. This study investigated the adsorption capacity for Pb2+ and Cd2+ of mixed-based biochar prepared at different pyrolysis temperatures, different pyrolysis residence times, and different cotton stalks percentages. Response surface experiments revealed the optimum process conditions for preparing mixed-based biochar, which included a pyrolysis temperature of 638 °C, a pyrolysis residence time of 86 min, and an addition ratio of 50% for cotton stalks. The isothermal adsorption experiments revealed that the maximum adsorption capacities of mixed-based biochar for Pb2+ and Cd2+ were 111.11 and 86.21 mg/g, respectively. Our findings suggest the co-pyrolysis of sludge and cotton stalk as a green and sustainable method for safely disposing of Pb and Cd. [ABSTRACT FROM AUTHOR]

The remediation of cadmium (Cd) contaminated cropland has been related to food safety and public health. While biochar derived from sewage sludge (SS) has been widely used for soil remediation due to its high efficiency of Cd immobilization, it has a low specific surface area and the ecological risk of heavy metals. Co-pyrolysis of straws and SS could resolve these issues. To date, little is known about the effect of biochar from SS/rice straw (RS) on Cd immobilization in soils. Here, we explored the soil remediation efficiency and mechanism of biochar derived from different mixing ratios (1:0, 3:1, 2:1, 1:1, 1:2, 1:3 and 0:1) of RS and SS named as RBC, R3S1, R2S1, R1S1, R1S2, R1S3 and SBC. It was shown that R1S2 amendment had the most efficiency of Cd immobilization among all amendments, which decreased the bioavailable Cd by 85.61% and 66.89% compared with RBC and SBC amendments. Results of biochar after soil remediation revealed that cation-π interaction, complexation, ion exchange and precipitation were the key mechanisms of Cd immobilization by biochar. All biochar amendments indirectly promoted Cd immobilization through increasing soil pH values, cation exchange capacity (CEC), soil organic carbon (SOC) and available phosphorous (AP). Compared with RBC, R1S2 reduced bioavailable Cd mainly through the increased soil pH, CEC and AP. However, the enhanced efficiency of Cd immobilization in R1S2 amendment than that in SBC amendment because of the more developed pore structure, functional groups and larger specific surface area of R1S2. Overall, our study showed a new type of biochar for the effective remediation of Cd-contaminated soil. [ABSTRACT FROM AUTHOR]

[Display omitted] • Various K-enriched biochars were produced from Canna indica by pyrolysis. • Co-pyrolysis with bentonite promoted the transformation of K to exchangeable K. • Co-pyrolysis and pelleting enhanced the K slow-release potential of biochars. Potassium (K) is one of the essential macronutrients for plant growth, while most agricultural soils are suffering from K deficiency worldwide. Therefore, it is a promising strategy to prepare K-enriched biochar from biomass waste. In this study, various K-enriched biochars were prepared from Canna indica at 300–700 °C by pyrolysis, co-pyrolysis with bentonite, and pelletizing-co-pyrolysis. The chemical speciation and release behaviors of K were investigated. The derived biochars showed high yields, pH values, and mineral contents, which were affected by the pyrolysis temperatures and techniques. The derived biochars contained a significant amount of K (161.3–235.7 mg/g), which was much higher than the biochars derived from agricultural residues and wood. Water-soluble K was the dominant K species in biochars with a proportion of 92.7–96.0%, and co-pyrolysis and pelletizing promoted the transformation of K to the exchangeable K and K silicates. In comparison with the C. indica derived biochars (83.3–98.0%), the bentonite-modified biochar showed a lower cumulative release proportion of K (72.5% and 72.6%) in a 28-day release test, meeting the Chinese National Standard for slow-release fertilizers. In addition, the pseudo-first order, pseudo-second order, and Elovich models well described the K release data of the powdery biochars, and the pseudo-second order model was the best fit for the biochar pellets. The modeling results indicated that the K release rate decreased after the addition of bentonite and pelletizing. These results indicated that the biochars derived from C. indica could be used as potential slow-release K fertilizers for agricultural application. [ABSTRACT FROM AUTHOR]

Highlights A new type of biochar was prepared by co-pyrolysis of corn stalks and alkali-fused fly ash for Pb(II) removal from wastewater. The high surface area and Pb(II) adsorption capacity of adsorbents made them suitable for wastewater treatment. The main Pb(II) adsorption mechanisms were physisorption, precipitation, cation exchange, and complexation.

[Display omitted] • Wheat straw, rice husk, pig manure, and oyster shell were used for co-pyrolysis. • Co-pyrolysis promoted syngas heat value and biochar characteristics. • Co-pyrolysis biochar was superior to limestone for soil remediation. • Application of COPB could be financially viable due to yield increase of cabbage. Co-pyrolysis is a potentially effective method for both biomass waste management and multi-functional biochar-based product design. It involves the thermochemical decomposition of biomass waste under anoxic conditions, which can reduce the cost of disposal and produce biochar with beneficial properties. Herein, this study aimed to investigate the properties and environmental applications of biochar from single- and mixed- feedstocks of wheat straw, rice husk, pig manure, and oyster shell at 450 ℃, respectively. A pot experiment with Chinese cabbage was carried out to compare the effects of biochars with limestone on soil Cd and Pb immobilization at two harvest periods. The results indicated that co-pyrolysis of various biomasses exhibited synthetic effects on promoting the calorific value of syngas and enhancing the quality of produced biochar. The pot experiment revealed a significant promotion on soil pH, soil organic matter, cation exchange capacity, and soluble Ca, which consequently reduced Cd and Pb availability. In contrast with limestone treatment, soil amendment with single biomass-derived and co-pyrolysis-derived (COPB) biochars had a significant positive impact on soil fertility and microbial biomass. Application of COPB at a 0.5% dosage consistently and most effectively enhanced the shoot biomass, increased leaf Vitamin C content but reduced leaf content of nitrate and heavy metals in both harvests. Using COPB for soil remediation would be financially visible due to the enhancement of crop yield. Therefore, this study proposes a strategy for targeted enhancement of the functions of biochar derived from co-pyrolysis of selected biomass waste for soil remediation and agricultural production. [ABSTRACT FROM AUTHOR]

This effort aimed to explore the activation and catalytic graphitization mechanisms of non-toxic salts in converting biomass to biochar from the perspective of pyrolysis kinetics using renewable biomass as feedstock. Consequently, thermogravimetric analysis (TGA) was used to monitor the thermal behaviors of the pine sawdust (PS) and PS/KCl blends. The model-free integration methods and master plots were used to obtain the activation energy (E) values and reaction models, respectively. Further, the pre-exponential factor (A), enthalpy (ΔH), Gibbs free energy (ΔG), entropy (ΔS), and graphitization were evaluated. When the KCl content was above 50%, the presence of KCl decreased the resistance to biochar deposition. In addition, the differences in the dominant reaction mechanisms of the samples were not significant at low (α ≤ 0.5) and high (α ≥ 0.5) conversion rates. Interestingly, the lnA value showed a linearly positive correlation with the E values. The PS and PS/KCl blends possessed positive ΔG and ΔH values, and KCl was able to assist biochar graphitization. Encouragingly, the co-pyrolysis of the PS/KCl blends allows us to target-tune the yield of the three-phase product during biomass pyrolysis. [ABSTRACT FROM AUTHOR]

Co-pyrolysis technology is an effective method to reduce heavy metal concentration in biochar produced from biosolids. In the current study, the effect of co-pyrolysis feedstock on product yield and properties was studied by mixing Biosolids (BS) with Wheat Straw (WS) and Canola Straw (CS) in a 3:1 mass ratio and carrying out thermal decomposition at 700 °C in a fluid bed reactor. This study found that the feedstock ash content and the volatile matter had a significant effect on biochar, oil, and gas yields from co-pyrolysis. The results also indicated that the addition of WS and CS feedstock notably reduced As, Cd, Cr, Cu, Ni, Pb, Se, and Zn concentrations in the biochar, due to the net effect of dilution and synergistic effects. BS-WS and BS-CS co-pyrolysis reduced Cu concentration in biochar by 61.6% and 63.3%, respectively, and Zn concentration by 66.4% and 64.4%, respectively. Lignocellulosic biomass addition also reduced biochar yield and improved C, H, and N content, along with the calorific value and the thermal stability of biochar. C content was increased by 36.9% in BS: WS biochar and 43.3% in BS: CS biochar compared to solely biosolids' biochar. The calorific value of biochar was increased by 43.5% and 52.9% in BS-WS biochar and BS-CS biochar compared to biosolids' biochar. During co-pyrolysis, CS addition produced oil with the lowest mole percentage of nitrogenated compounds. However, the addition of WS and CS increased co-pyrolysis oil acidity. Biosolids co-pyrolysis with WS and CS also increased the gas yield and the heating value compared to biosolids pyrolysis. Furthermore, the synergistic effect between biosolids and co-feedstocks resulted in increased gas yields and decreased oil and biochar yields. [ABSTRACT FROM AUTHOR]

The co-pyrolytic biochar was prepared by co-pyrolysis of peanut shell biochar and phosphate rock powder with different weight ratios. The influences of solution PH value, biochar dosage, initial concentration of heavy metal ions and adsorption time on the adsorption of Pb2+ by co-pyrolytic biochar were investigated through batch experiments. Langmuir and Freundlich isothermal adsorption models as well as quasi-first-order and quasi-second-order adsorption kinetic models were used for fitting analysis. The results showed that the optimum pH value of co-pyrolysis biochar for Pb2+ adsorption was 5. Under the conditions of biochar dosage of 2 g/L and adsorption time of 120 min, Pb2+ reached adsorption equilibrium, the maximum adsorption capacity was 62.438 mg/g, and the adsorption process was in accordance with Freundlich isothermal adsorption model and quasi-second-order adsorption kinetics model. The results showed that the adsorption capacity of co-pyrolysis of peanut shell and phosphate rock powder to Pb2+ was obviously better than that of peanut shell biochar, which had broad research prospects. [ABSTRACT FROM AUTHOR]

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The increase in mineral and ash-rich waste biomass (MWB) generation in emerging economies poses critical environmental problems and bottlenecks the solid waste and wastewater treatment systems. Transforming these MWB such as sewage sludge from wastewater treatment (SSW) to biochar can be a sustainable method for their disposal and resource recovery. However, such biochar has limited applicability due to the relatively low organic content and possibly contaminated nature of SSW. This may be offset through combined pyrolysis with other MWB, which can also support municipal solid waste management. Studies on this MWB co-pyrolysis are lacking and have not yet seen successful long-term implementation. This work is the second part of authors' research encompassing an analytical and lab-scale investigation of biochar production from MWB through pyrolysis for the case of Chennai city, India. Here, the physicochemical properties of biochar derived from lab-scale co-pyrolysis of SSW with other MWB such as anaerobic digestate from waste to energy plants of food, kitchen or market waste fermentation, and banana peduncles (BP) collected from vegetable markets and their thermolysis mechanism are comprehensively investigated for purpose of carbon sequestration. Also, a novel preliminary investigation of the effect of sample weight (scaling effect) on the analytical pyrolysis of biomass (BP as model substrate) is undertaken to elucidate its impact on the heat of pyrolysis and carbon distribution in resultant biochar. The maximum carbon sequestration potential of the derived biochar types is 0.22 kg CO2 kg−1 biomass. The co-pyrolysis of MWB is exothermic and governed by the synergetic effects of the components in blends with emission profiles following the order CO2 > CH4 > CO > NH3. Co-pyrolysis reduced the heavy metal enrichment in SSW biochar. The derived biochars can be an immediate source of N, P and S in nutrient-deficient acidic soils. The biochar has only up to 4-ring polyaromatic compounds and a residence time longer than 1 h at 500 °C is necessary to improve carbonization. The heat released during analytical pyrolysis of the model biomass and distribution of carbon in the resultant biochar are significantly influenced by scaling effects, drawing attention to the need for a more detailed scaling investigation of biomass pyrolysis. [ABSTRACT FROM AUTHOR]

The huge amounts of sewage sludge produced by municipal wastewater treatment plants induce major environmental and economical issues, calling for advanced disposal methods. Traditional methods for sewage sludge disposal increase greenhouse gas emissions and pollution. Moreover, biochar created from sewage sludge often cannot be used directly in soil applications due to elevated levels of heavy metals and other toxic compounds, which alter soil biota and earthworms. This has limited the application of sewage sludge-derived biochar as a fertilizer. Here, we review biomass and sewage sludge co-pyrolysis with a focus on the stabilization of heavy metals and toxicity reduction of the sludge-derived biochar. We observed that co-pyrolyzing sewage sludge with biomass materials reduced heavy metal concentrations and decreased the environmental risk of sludge-derived biochar by up to 93%. Biochar produced from sewage sludge and biomass co-pyrolysis could enhance the reproduction stimulation of soil biota by 20‒98%. Heavy metals immobilization and transformation are controlled by the co-feed material mixing ratio, pyrolysis temperature, and pyrolysis atmosphere. [ABSTRACT FROM AUTHOR]

In the context of resource utilization, the applications of waste biomass have attracted increasing attention. Previous studies have shown that forming biochar by heat treatment of sludge could replace the traditional sludge disposal methods, and sludge biochar is proved to be efficient in wastewater treatment. In this work, the pyrolysis, hydrothermal carbonization and microwave pyrolysis methods for preparing sludge biochar were reviewed, and the effects of different modification methods on the performance of sludge biochar in the synthesis process were comprehensively analyzed. This review also summarized the risk control of heavy metal leaching in sludge biochar, increasing the pyrolysis temperature and use of the fractional pyrolysis or co-pyrolysis were usually effectively meathods to reduce the leaching risk of heavy metal in the system, which is crucial for the wide application of sludge biochar in sewage treatment. At the same time, the adsorption mechanism of sludge biochar and the catalytic mechanism as the catalytic material in AOPs reaction, the process of radical and non-radical pathway and the possible impacts in the sludge biochar catalytic process were also analyzed in this paper. [ABSTRACT FROM AUTHOR]

The unsustainable management of sewage sludge induces environmental and economic issues, yet sewage sludge is a promising feedstock for the production of biofuels by pyrolysis. Actual challenges include poor chemical stability, high water content, high viscosity, high concentrations of nitrogen, and the presence of oxygen in the produced biofuels. Moreover the produced biochars contain elevated amounts of toxic metals and, as a consequence, may not be used in agricultural soils. Here we review the co-pyrolysis of sewage sludge with other materials to enhance bio-oil quality. Several studies show that co-pyrolysis of sewage sludge with non-biomass materials reduces water, oxygen and nitrogen contents, activation energy, and enthalpy; and increases the calorific value. [ABSTRACT FROM AUTHOR]

Waste stream valorization is a difficult task where the economic and environmental issues must be balanced. The use of complex metal-rich waste such as red mud is challenging due to the wide variety of metal oxides present such as iron, aluminum, and titanium. The simple separation of each metal is not economically feasible, so alternative routes must be implemented. In this study, we investigated the use of red mud mixed with hemp waste to produce biochar with high conductivity and good magnetic properties induced by the reduction of the metal oxides present in the red mud through carbothermal processes occurring during the co-pyrolysis. The resulting biochar enriched with thermally-reduced red mud is used for the preparation of epoxy-based composites that are tested for electric and magnetic properties. The electric properties are investigated under DC (direct current) regime with or without pressure applied and under AC (alternating current) in a frequency range from 0.5 up to 16 GHz. The magnetic measurements show the effective tailoring of hemp-derived biochar with magnetic structures during the co-pyrolytic process. [ABSTRACT FROM AUTHOR]

Vegetables tend to have higher content of inorganics and might involve in co-pyrolysis and impact characteristics of pyrolytic products. This was investigated by co-pyrolysis of lettuce or spinach with noodles at 600 °C. The results showed that the inorganics and/or the volatiles from lettuce/spinach interacted with noodles-derived organics, enhancing gasification, which produced more gases while diminished biochar formation. The inorganics in lettuce or spinach also catalyzed cracking of themselves to form more organics with π-conjugated structure in bio-oil. Moreover, the activation energy (Ea) in the pyrolysis of noodles or nascent biochar of higher aromatic nature was much higher than that in pyrolysis of spinach or lettuce. However, exposure of more inorganics from vegetable-derived biochar, at only high feedstock conversion (>20 %), significantly involved in the pyrolysis, reducing Ea in the co-pyrolysis. The co-pyrolysis enhanced combustion performances and also densification of biochar structures with lowered environmental impacts. [Display omitted] • Inorganics in vegetables enhance gasification, promoting gases formation in co-pyrolysis. • Maillard reactions between noodle-derived sugars with organics from lettuce/spinach make biochar N-rich. • Inorganics from vegetables reduce Ea in the co-pyrolysis but only at high feedstock conversion. • Ash-rich lettuce/spinach forms hydrophilic biochar of fragmented surface and low combustion performance. • Co-pyrolysis forms biochar of densified structures, superior combustion behaviors and reduces environmental impacts. [ABSTRACT FROM AUTHOR]

Co-pyrolysis of lignocellulosic biomass with a feedstock having a high hydrogen content, such as plastics, is one of the most efficacious and promising approaches to ameliorate bio-oil yield and quality. Polystyrene, a common thermoplastic, is an attractive feedstock for co-pyrolysis as it contains almost 99 wt% of volatile matter based on proximate analysis. A comprehensive review of the co-pyrolysis of different types of lignocellulosic biomass and polystyrene is provided here, with the primary focus on the reactor configurations, along with the quantity and quality of targeted products of interest. Kinetic modeling has been used to elucidate the role of polystyrene on the relevant activation energies and reaction mechanisms. Most of the experimental studies have employed a fixed bed reactor but a few have employed a fluidized bed reactor. The environmental and economic aspects of the process with respect to feedstock and products are considered. Finally, future perspectives and challenges in the commercialization of the co-pyrolysis process for the two types of feedstock are discussed. [Display omitted] • Most co-pyrolysis studies employed TGA and fixed bed reactors followed by fluidized bed reactors. • Co-pyrolysis of biomass and polystyrene provides a higher liquid yield than that obtained by using other plastics. • Blending ratio is the most significant parameter among the operating conditions. • Alkali metals entail a catalytic effect during the co-pyrolysis of lignocellulosic biomass and polystyrene. • Co-pyrolysis of biomass with plastics could address issues of energy crisis and plastic waste. [ABSTRACT FROM AUTHOR]

In this work, a novel nitrogen-doped biochar bentonite composite was synthesized by a single-pot co-pyrolysis method. Batch studies were conducted to evaluate the performance of the developed composite in eliminating synthetic dyes from the aqueous matrix. Energy dispersive X-ray spectroscopy analysis and field emission scanning electron microscopy imaging confirmed the N doping and bentonite impregnation into biochar. X-ray photoelectron spectroscopy analysis revealed that the N atoms were doped interstitially into the carbon matrix of biochar in the form of pyridinic and pyrrolic nitrogen. Simultaneous heteroatom doping and bentonite impregnation reduced the specific surface area to 41.721 m2 g−1 but improved the adsorption capacity of biochar for dye adsorption. Further experimental studies depicted that simultaneous bentonite impregnation and N doping into the biochar matrix is beneficial for direct blue-6 (DB-6) and methylene blue (MB) removal and maximum adsorption capacities of 53.17 mg. g−1 and 41.33 mg. g−1 were obtained for MB and DB-6, respectively, at varying conditions. Adsorption energetics of the dyes with the developed composite portrayed the spontaneity of the process through negative ΔG values. The Langmuir and Freundlich isotherm models fitted the best for MB and DB-6 adsorption. The monolayer adsorption capacity and favourability factor for MB and DB-6 adsorption were calculated to be 54.15 mg. g−1 and 0.217, respectively from the best-fitted isotherms. Based on density functional theory calculations and spectroscopic studies, major interactions governing the adsorption were predicted to be charge-based interactions, π-π interactions, H-bonding, and Lewis acid-base interactions. [Display omitted] • Heteroatom-doped biochar-clay composite was synthesized using green modifying agents. • Performance of modified biochars was assessed in anionic and cationic dye removal. • Doped N atoms were in the form of pyridinic and pyrrolic nitrogen. • Maximum adsorption efficiencies of 95.44% and 96.5% were achieved for MB and DB-6. [ABSTRACT FROM AUTHOR]

• Potential migration mechanism of HMs revealed during co-pyrolysis of modified kaolin with DS. • Pyrolysis and "dilution effect" synergistically influence the immobilization of HMs. • The addition of modified kaolin increases the proportion of stable HMs, thus reducing the environmental risk. • Phase transitions, pore structure, functional groups, and interactions between inorganic minerals and HMs may play a critical role. The existence of heavy metal in texting and dyeing sludge is one of the potential ecological pollutions. In this study, a series of modified kaolin was applied to co-pyrolysis with DS. The biochar characterization and heavy metal analysis reveal the effects of modified additives on the heavy metal behavior and potential mechanisms. Compared to raw texting and dyeing sludge, the total content of Cu, Zn, Cr, Mn, and Ni increased to a maximum value of 170.63, 451.85, 147.86, 731.69, and 57.91 mg/kg in biochar. The proportion of Cu, Zn, Mn, and Ni in stable fractions increased to 99.23 %, 88.71 %, 53.89 %, and 94.04 %, and the potential ecological risk index of biochar experienced a substantial reduction from 154.45 in DS to 11.18 in DAK. Co-pyrolysis and dilution effects synergistically reduced the leaching of heavy metals and promoted their enrichment in biochar. The Al/Si structural phase transition, pore structure, functional groups, and interactions between inorganic mineral components and heavy metals also were affected by acid-base modification. This resulted in the enhancement of heavy metal stabilization fractions and the reduction of environmental risks. This study aims to present an eco-friendly and efficient strategy to further mitigate the environmental risks associated with HMs in hazardous wastes. In addition, it also provides ideas for the application of modified mineral additives in the field of pollutant control. [ABSTRACT FROM AUTHOR]

• Co-pyrolysis of guava seeds and beetroot peels for synthesis a novel Co-biochar. • The co-biochar is functionalized by Mg/Al layered double hydroxide (Gs-Bp@Mg/Al LDH). • High efficiency and durability of nitrate removal by Gs-Bp@Mg/Al LDH. • Gs-Bp@Mg/Al LDH has potential for industrial practicability of nitrate treatment. Increased concentration levels of nitrate in various water resources and supplies have alarmingly increased worldwide owing to severe pollution problems. The growing usage and implementation of nitrogenous fertilizers were identified as the main sources of such serious impact and contribution to the high nitrate levels in domestic wastewater. Therefore, the removal of nitrate pollutants from water using low-cost and eco-friendly materials and techniques is a major concern. Therefore, this study was designed to assemble and prepare a novel co-biochar-double-layered hydroxide nanocomposite (Gs-Bp@Mg/Al LDH) by co-pyrolysis of guava seeds and beetroot peels, followed by functionalization with MgAl double-layer hydroxide (LDH). Various techniques were employed to characterize the assembled composite, confirming its successful synthesis and loading of LDH layers on the surface of co-biochar. The nanocomposite was evaluated as a potential adsorbent for nitrate removal from wastewater using batch experiments. The results showed that the removal efficiency of nitrate using Gs-Bp biochar was 49.1 % at pH 6.0, whereas the corresponding value for Gs-Bp@Mg/Al LDH was 94.9 % at pH 5.0 for 5 mg L-1 after 30 min. The kinetics followed the pseudo-second order model, and the equilibrium condition was reached within 30 min. The adsorption isotherms were well-defined by Freundlich and Langmuir. Thermodynamic parameters indicate that the adsorption process is both spontaneous and exothermic. Furthermore, Gs-Bp@Mg/Al LDH demonstrated excellent removal efficiency for nitrate from different water samples, ranging from 86.2 % to 100 %. In addition, recyclability tests indicated the validity of Gs-Bp@Mg/Al LDH for potential nitrate removal for several cycles without a significant decline in adsorption performance. Overall, (Gs-Bp@Mg/Al LDH) holds promise as an effective adsorbent for the treatment of nitrate-contaminated wastewater. [ABSTRACT FROM AUTHOR]