Search Results (262)

This research explores the effects of milling on fecal sludge (FS) biochar with an emphasis on milling time (5, 10, and 15 min) and ball-to-powder ratio (BPR) (4.533 g/g, 9.067 g/g, and 10.5 g/g). FS biochar was prepared through slow co-pyrolysis of a 50:50 mixture (by weight) of fecal sludge and rice husk powder at 550 °C. The resultant FS biochar with good qualities was subjected to methylene blue (MB) dye adsorption at varying FS biochar weights (0.05 g, 0.1 g, and 0.15 g) and adsorption durations. The BSA peaked at 50 m²/g for a BPR of 10.5 g/g and a milling duration of 10 min. Prolonged milling (15 min) led to structural degradation and reduced BET surface area (BSA). The pore volume peaked at a BPR of 9.067 g/g for shorter milling times and 10.5 g/g for extended milling. The SEM revealed that a milling time of 10 min at a BPR of 9.067 g/g provided the best balance between particle size reduction and uniform morphology, minimizing agglomeration. MB adsorption revealed that FS biochar milled for 10 min and 9.067 g/g BPR demonstrated the best properties. These findings highlight the potential of FS biochar for applications in environmental remediation and agricultural fields, contributing to resource recovery from FS. Full article

Soil degradation, declining fertility, and rising greenhouse gas emissions highlight the urgent need for sustainable soil management strategies. Among them, biochar has gained recognition as a multifunctional material capable of enhancing soil fertility, sequestering carbon, and valorizing biomass residues within circular economy frameworks. This review synthesizes evidence from 186 peer-reviewed studies to evaluate how feedstock diversity, pyrolysis temperature, and elemental composition shape the agronomic and environmental performance of biochar. Crop residues dominated the literature (17.6%), while wood, manures, sewage sludge, and industrial by-products provided more targeted functionalities. Pyrolysis temperature emerged as the primary performance driver: 300–400 °C biochars improved pH, cation exchange capacity (CEC), water retention, and crop yield, whereas 450–550 °C biochars favored stability, nutrient concentration, and long-term carbon sequestration. Elemental composition averaged 60.7 wt.% C, 2.1 wt.% N, and 27.5 wt.% O, underscoring trade-offs between nutrient supply and structural persistence. Greenhouse gas (GHG) outcomes were context-dependent, with consistent Nitrous Oxide (N₂O) reductions in loam and clay soils but variable CH₄ responses in paddy systems. An emerging trend, present in 10.6% of studies, is the integration of artificial intelligence (AI) to improve predictive accuracy, adsorption modeling, and life-cycle assessment. Collectively, the evidence confirms that biochar cannot be universally optimized but must be tailored to specific objectives, ranging from soil fertility enhancement to climate mitigation. Full article

In response to the problem of high energy consumption caused by inefficient temperature control of energy storage aggregates in traditional building envelope structures, this study developed a decanoic acid–stearic acid composite phase-change ceramsite aggregate to improve the thermal performance of buildings and promote the utilization of solid waste resources. Based on the theory of minimum melting, composite phase-change materials were screened through thermodynamic models. The capric acid–stearic acid (CA-SA) melt system, whose theoretical phase-transition temperature falls within the building indoor thermal environment control range (18–26 °C), was preferred as the experimental object of this study, and its characteristics were verified through step cooling curves and thermal property tests. Subsequently, the ceramsite adsorption process was optimized, and the encapsulation process was studied. Finally, the encapsulation performance was evaluated through thermal stability and stirring crushing rate tests. The results showed that the phase-transition temperature of the decanoic acid–stearic acid melt system was 24.83 °C, which accurately matched the indoor thermal environment control requirements. The ceramsite particles treated by a physical vibrating screen can reach equilibrium after 30 min of adsorption at room temperature and pressure, which is both efficient and economical. The encapsulation layer of sludge biochar cement slurry with a water–cement ratio of 0.5 and a biochar content of 3% has both thermal conductivity and encapsulation integrity. The thermal stability test showed that the percentage of leakage of sludge biochar cement slurry and epoxy resin encapsulated aggregates was 0%, and the thermal stability rating was “very stable”. However, the percentage of leakage of unencapsulated and spray-coated encapsulated aggregates was as high as 193% and 40%, respectively. The results of the mixing and crushing rate test show that although the mixing and crushing rate of sludge biochar cement slurry encapsulation is slightly higher, its production cost is much lower than that of epoxy resin, and it is also environmentally friendly. This study improves the thermal performance of buildings by using composite phase-change ceramsite aggregate, and simultaneously realizes the resource utilization of sludge biochar, providing a solution for building energy saving and efficiency that combines environmental and engineering value. Full article

The rising demand for sustainable agriculture and circular resource management has intensified interest in converting wastewater sludge into value-added products. This review explores the transformation of sewage sludge into slow- and controlled-release fertilizers (CRFs), with a focus on biochar production and encapsulation technologies. Sewage sludge is rich in essential macronutrients (N, P, K), micronutrients, and organic matter, making it a promising feedstock for agricultural applications. However, its use is constrained by challenges including compositional variability, presence of heavy metals, pathogens, and emerging contaminants such as microplastics and PFAS (Per- and Polyfluoroalkyl Substances). The manuscript discusses a range of stabilization and conversion techniques, such as composting, anaerobic digestion, pyrolysis, hydrothermal carbonization, and nutrient recovery from incinerated sludge ash. Special emphasis is placed on coating and encapsulation technologies that regulate nutrient release, improve fertilizer efficiency, and reduce environmental losses. The role of natural, synthetic, and biodegradable polymers in enhancing release mechanisms is analyzed in the context of agricultural performance and soil health. While these technologies offer environmental and agronomic benefits, large-scale adoption is hindered by technical, economic, and regulatory barriers. The review highlights key challenges and outlines future perspectives, including the need for advanced coating materials, improved contaminant mitigation strategies, harmonized regulations, and field-scale validation of CRFs. Overall, the valorisation of sewage sludge into CRFs presents a viable strategy for nutrient recovery, waste minimization, and sustainable food production. With continued innovation and policy support, sludge-based fertilizers can become a critical component of the green transition in agriculture. Full article

To address the challenges of complex composition, high chemical oxygen demand (COD) content, and the difficulty of treating organic wastewater from brewery wastewater, as well as the limitations of traditional Fenton technology, including low catalytic activity and high material costs, this study proposes the use of biochemical sludge as a raw material. Coupled with iron salt activation and mechanical ball milling technology, a low-cost, high-performance iron-doped mesoporous nano-sludge biochar material is prepared. This material was employed as a particle electrode to construct a three-dimensional electro-Fenton system for the degradation of organic wastewater from sauce-flavor liquor brewing. The results demonstrate that the sludge-based biochar produced through this approach possesses a mesoporous structure, with an average particle size of 187 nm, a specific surface area of 386.28 m²/g, and an average pore size of 4.635 nm. Iron is present in the material as multivalent iron ions, which provide more electrochemical reaction sites. Utilizing response surface methodology, the optimized treatment process achieves a maximum COD degradation rate of 71.12%. Compared to the control sample, the average particle size decreases from 287 μm to 187 nm, the specific surface area increases from 44.89 m²/g to 386.28 m²/g, and the COD degradation rate improves by 61.1%. Preliminary investigations suggest that the iron valence cycle (Fe²⁺/Fe³⁺) and the mass transfer enhancement effect of the mesoporous nano-structure are keys to efficient degradation. The Fe-O-Si structure enhances material stability, with a degradation capacity retention rate of 88.74% after 30 cycles of use. When used as a particle electrode to construct a three-dimensional electro-Fenton system, this material demonstrates highly efficiency in organic matter degradation and shows promising potential for application in the treatment of organic wastewater from sauce-flavor liquor brewing. Full article

Second-, third-, and fourth-generation biofuels represent an important response to the challenges of clean energy supply and climate change. In this context, the Horizon 2020 “TO-SYN-FUEL” project aimed to produce advanced biofuels together with phosphorus from municipal wastewater sludge through a combination of technologies including a Thermo-Catalytic Reforming system, Pressure Swing Adsorption for hydrogen separation, Hydrodeoxygenation, and biochar gasification for phosphorous recovery. This article presents the environmental performance results of the demonstrator installed in Hohenberg (Germany), with a capacity of 500 kg per hour of dried sewage sludge. In addition, four alternative scenarios are assessed, differing in the source of additional thermal energy used for sludge drying: natural gas, biogas, heat pump, and a hybrid solar greenhouse. The environmental performance of these scenarios is then compared with that of conventional fuel. The comparative study of these scenarios demonstrates that the biofuel obtained through wood gasification complies with the Renewable Energy Directive, while natural gas remains the least sustainable option. Heat pumps, biogas, and greenhouse drying emerge as promising alternatives to align biofuel production with EU sustainability targets. Phosphorus recovery from sewage sludge ash proves essential for compliance, offering clear environmental benefits. Although sewage sludge is challenging due to its high water content, it represents a valuable feedstock whose sustainable management can enhance both energy recovery and nutrient recycling. Full article

This study presents the preparation of iron and nitrogen co-doped sludge-based biochar (FeCN-MSBC) and iron oxide-doped biochar (FeO-MSBC) by ball milling municipal sludge with different iron precursors (K₃Fe(CN)₆ and Fe₂O₃), followed by pyrolysis. These biochars were utilized to activate persulfate (PMS) for the degradation of phenolic pollutants. The results demonstrate that FeCN-MSBC, formed by the introduction of K₃Fe(CN)₆, contains Fe/N phases, with surface Fe sites exhibiting a lower oxidation state, which significantly enhances PMS activation efficiency. In contrast, FeO-MSBC, due to the aggregation of Fe₂O₃/Fe₃O₄, shows relatively lower catalytic activity. The FeCN-MSBC/PMS system degrades pollutants via a synergistic mechanism involving non-radical pathways mediated by ¹O₂ and electron transfer processes (ETP) catalyzed by surface Fe. Electrochemical oxidation and quenching experiments confirm that ETP is the dominant pathway. FeCN-MSBC, prepared at a pyrolysis temperature of 600 °C and an Fe loading of 3 mmol/g TSS, exhibited the best performance, achieving a phenol degradation rate constant (k_obs) of 0.127 min⁻¹, 4.5 times higher than that of undoped biochar (MSBC). FeCN-MSBC/PMS maintained high efficiency across a wide pH range and in complex water matrices, exhibiting excellent stability over multiple cycles, demonstrating strong potential for practical applications. This study provides an effective strategy for simultaneous Fe and N doping in sludge-derived biochar and offers mechanistic insights into Fe/N synergistic activation of PMS for practical water treatment. Full article

Catalytic methane decomposition (CMD) is an environmentally friendly method of hydrogen production that, unlike other conventional processes, such as steam methane reforming, partial oxidation of methane, and dry reforming of methane, can convert methane into hydrogen with a simultaneous generation of solid carbon without CO₂ emissions. This study mainly focused on the application of carbon-based catalysts derived from biomass and biowaste for the CMD process. For this purpose, eight catalysts were produced from three carbon materials (wood, sewage sludge, and digestate) through the subsequent processes of pyrolysis, leaching, and physical activation. The comparison of catalysts prepared from the slow pyrolysis of biowaste and wood indicated that carbon materials with a lower ash content achieved a higher initial methane conversion (wood char > digestate char > sewage sludge char). For feedstocks with a high initial ash content, such as digestate and sewage sludge chars, an improvement in the catalytic activity was observed after ash removal through the leaching process with HNO₃. In addition, physical activation through CO₂ fluxing led to an enhancement in the BET surface area of these catalysts, and consequently to a growth in methane conversion. The initial methane conversion was assessed for all chars under operating conditions of 900 °C, a gas hourly space velocity (GHSV) of 3 L/g/h, and a CH₄:N₂ ratio of 1:9, and it was 65.9, 59.1, and 42.6% v/v, respectively, for chars derived from wood, sewage sludge, and digestate; these values increased to almost 80% v/v when these chars were upgraded by chemical leaching and physical activation. Full article

Municipal wastewater treatment relies primarily on biological methods, yet effective disposal of residual sludge remains a major challenge. Converting sludge into biochar via oxygen-limited pyrolysis presents a novel approach for waste resource recovery. This study prepared sludge-based biochar (SBC) through one-step pyrolysis of sewage sludge and applied it to activate peroxymonosulfate (PMS) for degrading diverse contaminants. Characterization (SEM, XPS, FTIR) revealed abundant pore structures and diverse surface functional groups on SBC. Using Acid Orange 7 (AO7) as the target pollutant, SBC effectively degraded AO7 across pH 3.0–9.0 and catalyst dosages (0.2–2.0 g·L⁻¹), achieving a maximum observed rate constant (k_obs) of 0.3108 min^–1. Salinity and common anions showed negligible inhibition on AO7 degradation. SBC maintained 95% degradation efficiency after four reuse cycles and effectively degraded sulfamethoxazole, sulfamethazine, and rhodamine B besides AO7. Mechanistic studies (chemical quenching and ESR) identified singlet oxygen (¹O₂) and superoxide radicals (O₂^•− ) as the dominant reactive oxygen species for AO7 degradation. XPS indicated a 39% reduction in surface carbonyl group content after cycling, contributing to activity decline. LC-MS identified five intermediates, suggesting a potential degradation pathway driven by SBC/PMS system. ECOSAR model predictions indicated significantly reduced biotoxicity of the degradation products compared to AO7. This work provides a strategy for preparing sludge-derived catalysts for PMS activation and pollutant degradation, enabling effective solid waste resource utilization. Full article

Municipal sewage sludge represents a significant environmental challenge due to its large-scale production and limited disposal options. Pyrolysis, a thermal decomposition process, offers a promising approach for converting sewage sludge into biochar, a carbon-rich material with diverse environmental applications. Sewage sludge-derived biochars were prepared at pyrolysis temperatures of 300 °C, 500 °C, 700 °C, and 900 °C (denoted as B300 to B900) and evaluated for their structural, adsorption, and catalytic performance. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and energy dispersive X-ray spectrometry (EDS) analyses revealed a distinct temperature-dependent morphological evolution and mineral exposure. The B900 biochar exhibited a BET surface area of 83.8 m²/g and the highest pore volume of 0.101 cm³/g, indicating a well-developed mesoporous structure. In catalytic degradation tests using 20 mg/L persulfate and 500 mg/L B900, rapid oxidation was observed, achieving 91% methylene blue (MB) degradation in 30 min, highlighting its role in activating persulfate via surface-bound Fe and Al species. Optimization studies confirmed that MB removal efficiency was highest at 500 mg/L biochar and 40 mg/L persulfate, and the system was not significantly affected by the tap and synthetic wastewater matrices. This work demonstrates that biochar obtained from sewage sludge can serve as an eco-friendly and multifunctional material for resource recovery and environmental cleanup. Full article

Sewage sludge, a byproduct of wastewater treatment, can be converted into biochar, offering a sustainable solution for waste management and water treatment. Although biochars from biomass have been widely studied, sewage sludge-derived biochars remain underexplored. This study investigated the use of alkaline-treated sewage sludge-derived biochar (AlBC) as an adsorbent for three water pollutants: caffeine (CAF), carbamazepine (CBZ), and 17α-ethinyl estradiol (EE2). A comprehensive analysis was conducted to explore the kinetic and thermodynamic behaviors of these pollutants under varying conditions, such as different adsorbent dosage, temperature, and water matrix values. The AlBCSS showed enhanced surface area and improved adsorption capacity, with EE2 being preferentially adsorbed (q_e: 9.51 mg g⁻¹), followed by CAF (6.12 mg g⁻¹) and CBZ (4.58 mg g⁻¹). Adsorption followed the Langmuir isotherm for CAF and CBZ, and the Freundlich isotherm for EE2, while kinetics were best described by the pseudo-second-order and Elovich models. Thermodynamic analysis revealed that the adsorption process was spontaneous, primarily driven by physical interactions. Factors such as dosage, temperature, and pollutant concentration influenced adsorption, with no saturation observed at higher concentrations. The natural water matrix had a minimal effect on removal efficiency (40–100%), whereas AlBC exhibited promising results after four adsorption cycles. These results highlight the potential of sewage sludge-derived biochar as a sustainable adsorbent for emerging water pollutants, supporting circular economy practices in wastewater management. Full article

Although coagulation can enhance sludge dewatering performance, it often leads to dense flocs, hindered water release, and secondary pollution of the sludge cake. In this study, three types of biochar-based skeleton materials, tea waste-derived biochar (TB), PAC sludge-derived biochar (PB), and their mixture (MB), were employed in combination with polyaluminum chloride (PAC) to improve sludge permeability and water release capacity. The results showed that PAC alone reduced the water content (Wc) and capillary suction time (CST) of raw sludge (RS) from 79.07% and 97.45 s to 69.45% and 42.30 s, respectively. In contrast, biochar–PAC composite conditioning achieved further enhancement. Among them, the TBP group (10% DS TB + 4% DS PAC) exhibited the best performance, with Wc and CST reduced to 58.73% and 55.65 s, reaching the threshold for deep dewatering (Wc < 60%). Low-field nuclear magnetic resonance (LF-NMR) analysis revealed an enhanced transformation from bound to free water, improving water mobility. Zeta potential and particle size analysis indicated that biochar promoted electrostatic neutralization and adsorption bridging. Rheological and EPS measurements demonstrated significant reductions in yield stress and apparent viscosity, alongside the enhanced release of proteins and polysaccharides into soluble EPS (S-EPS). Scanning electron microscopy and pore structure analysis further confirmed that biochar formed a stable porous skeleton (pore diameter up to 1.365 μm), improving sludge cake permeability. In summary, biochar synergizes with PAC through a “skeleton support–charge neutralization–adsorption bridging” mechanism, reconstructing sludge microstructure and significantly improving deep dewatering performance. Full article

In response to the growing issue of iron and manganese pollution in water bodies, this study systematically investigated the adsorption performance of municipal sludge-derived biochar prepared at pyrolysis temperatures ranging from 300 to 700 °C for the removal of Fe²⁺ and Mn²⁺. Among the series of adsorbents (BC300–BC700), BC600—with its well-developed pore structure and high specific surface area—exhibited the best adsorption performance for both metal ions. Kinetic and isothermal adsorption experiments, in combination with XPS characterization, collectively revealed that (1) the adsorption mechanisms of Fe and Mn differ markedly, with Fe adsorption primarily governed by physical interactions, whereas Mn adsorption is largely controlled by chemical processes; (2) Fe²⁺ adsorption occurs mainly via electrostatic interactions and hydrogen bonding; and (3) Mn²⁺ forms carbonate precipitates with C=O groups during redox reactions. Thermodynamic analysis further indicated that the adsorption process was spontaneous and endothermic. Moreover, BC600 demonstrated excellent reusability for Fe adsorption across different water matrices, maintaining efficiencies above 95% after five cycles, although the adsorption performance for Mn declined. This study provides theoretical support for the application of sludge-derived biochar as a cost-effective and efficient adsorbent for metal ion remediation. Full article

An activated biochar was produced from post-coagulation sludge (also called water treatment residuals or water treatment sludge) in the pyrolysis process at 800 °C in a nitrogen atmosphere and chemical activation using NaOH. The produced adsorption material was characterised by an S_BET surface area of 439 m²/g, a total volume of pores of 0.301 cm³/g, and an average pore size of 1.4 nm. FTIR analysis reveals the presence of primarily C-H, C-O, N-H, C-N, and O-H groups on the activated biochar surface. The batch adsorption process was conducted for three dyes: Acid Red 18, Acid Green 16, and Reactive Blue 81. In the study, the effect of pH, contact time, adsorption kinetics, and adsorption isotherm was determined. The studies showed that, for all dyes, the highest efficiency of the process was achieved at a pH of 2. The results indicate the occurrence of a chemical adsorption process, as evidenced by the best fit to the experimental results obtained with the pseudo-second-order kinetics model and the Elovich model. In the case of the adsorption isotherm, the SIPS model best describes the adsorption for Acid Red 18 and Reactive Blue 81, and the Jovanovic model describes the adsorption of Acid Green 16. Full article

Heavy metals represent long-lasting contaminants that pose significant risks to both human health and ecosystem integrity. Originating from both natural and anthropogenic activities, they bioaccumulate in organisms through the food web, leading to widespread and long-lasting contamination. Industrialization, agriculture, and urbanization have exacerbated soil and water contamination through activities such as mining, industrial production, and wastewater use. In response to this challenge, biochar produced from waste materials such as sewage sludge has emerged as a promising remediation strategy, offering a cost-effective and sustainable means to immobilize heavy metals and reduce their bioavailability in contaminated environments. Here we explore the potential of phosphate-enriched biochar, derived from sewage sludge, to adsorb and stabilize heavy metals in polluted soils. Sewage sludge was pyrolyzed at various temperatures to produce biochar. A soil incubation experiment was conducted by adding phosphate-amended biochar to contaminated soil and maintaining it for one month. Heavy metals were extracted using a CaCl₂ extraction method and analyzed using atomic absorption spectrophotometry. Results demonstrated that phosphate amendment significantly enhanced the biochar’s capacity to immobilize heavy metals. Amending soils with 2.5 wt% phosphate-enriched sewage sludge biochar led to reductions in bioavailable Cd (by 65–82%), Zn (40–75%), and Pb (52–88%) across varying pyrolysis temperatures. Specifically, phosphate-amended biochar reduced the mobility of Cd and Zn more effectively than unamended biochar, with a significant decrease in their concentrations in soil extracts. For Cu and Pb, the effectiveness varied with pyrolysis temperature and phosphate amendment, highlighting the importance of optimization for specific metal contaminants. Biochar generated from elevated pyrolysis temperatures (500 °C) showed an increase in ash content and pH, which improved their ability to retain heavy metals and limit their mobility. These findings suggest that phosphate-amended biochar reduces heavy metal bioavailability, minimizing their entry into the food chain. This supports a sustainable approach for managing hazardous waste and remediating contaminated soils, safeguarding ecosystem health, and mitigating public health risks. Full article