Search Results (123)

Conventional powdered biochar encounters severe bottlenecks in practical water treatment, such as difficult separation, easy loss, and potential secondary pollution. This work aimed to develop recyclable and high-performance adsorbents by preparing iron-doped biochar/sodium alginate composite microspheres (BC/MBC500-ALF) through Fe³⁺ cross-linking. Using corn stalk biochar and KMnO₄-modified biochar as adsorbent components and sodium alginate (SA) as a green shaping matrix, SA formed a stable egg-box hydrogel network to convert powdered biochar into uniform microspheres. Batch adsorption experiments revealed that the optimal pH for oxytetracycline (OTC) adsorption was 9, with adsorption capacities of 136.28 mg/g for BC500-ALF and 182.91 mg/g for MBC500-ALF. Kinetic analysis showed that BC500-ALF followed pseudo-first-order kinetics (R² = 0.983) dominated by physisorption, while MBC500-ALF fitted pseudo-second-order kinetics (R² = 0.994) dominated by chemisorption. The maximum Langmuir adsorption capacities at 308 K were 220.75 mg/g and 495.05 mg/g, respectively. Thermodynamic parameters confirmed a spontaneous and endothermic process. The adsorption mechanisms involved hydrogen bonding, π–π stacking, electrostatic attraction, metal-bridging complexation, and Fe–Mn oxide-mediated redox reactions. SA exerted dual functions in structure stabilization and adsorption enhancement. This composite provides an efficient and eco-friendly approach for tetracycline antibiotic pollution control in aqueous environments. Full article

Excessive phosphorus discharge from aquaculture effluent significantly contributes to coastal eutrophication, while conventional adsorbents exhibit limited phosphorus removal efficiency in high-salinity, weakly alkaline seawater effluent. This study developed iron/calcium co-modified chlorella biochar (FCBC) through co-impregnation and high-temperature pyrolysis, optimizing the preparation process via the Box–Behnken response surface method. The optimal conditions were identified as an iron concentration of 2.5 mol/L, a calcium concentration of 2.0 mol/L, a pyrolysis temperature of 717 °C, and a duration of 113 min. Under these conditions, FCBC achieved a phosphorus removal rate of 93.23% within 3 h, which was significantly higher than that of the unmodified Chlorella biochar (BC, <8% within the same reaction time). The Fe/Ca co-modification endowed FCBC with a positively charged surface, an increased average pore size of 22.773 nm, and good magnetic responsiveness (saturation magnetization of 6.68 emu·g⁻¹). FCBC demonstrated remarkable adaptability, achieving over 97% phosphorus removal across a pH range of 3 to 11, salinity levels of 5 to 40‰, and phosphorus concentrations of 1 to 15 mg/L. Its adsorption kinetics conformed to pseudo-second-order kinetics (R² = 0.987) and the Freundlich model (R² = 0.971), with efficient phosphorus removal primarily attributed to iron–calcium synergistic effects. FCBC presents significant potential for phosphorus treatment in marine aquaculture effluents. Full article

In this work, iron–phosphorus-based composite biochar (FPBC) was prepared by modification with the leachate of spent LiFePO₄ batteries. The effects of solution pH, dosage, adsorption time, initial concentration, and temperature on the adsorption performance of FPBC were investigated by batch adsorption experiments with Pb(II) and Sb(III) as the target pollutants, and the adsorption mechanism was explored using SEM, BET, XPS, FTIR and XRD characterization. The results indicated that as the initial pH of the solution increased, the removal efficiency of FPBC for Pb(II) gradually increased, while the removal efficiency for Sb(III) remained largely unchanged. The removal of Pb(II) and Sb(III) by FPBC fitted the pseudo-second-order kinetic model and the three-step intraparticle diffusion model, indicating that their removal was primarily controlled by chemical adsorption. Isothermal adsorption studies revealed that FPBC adsorption of Pb(II) better fitted the Langmuir and D-R models, suggesting a monolayer-dominated adsorption process. In contrast, adsorption of Sb(III) fitted the Langmuir, Freundlich, and Temkin models, suggesting a combination of monolayer and multilayer adsorption characteristics. The maximum adsorption capacities of FPBC for Pb(II) and Sb(III) were 312.54 mg·g⁻¹ and 219.20 mg·g⁻¹ at 30 °C, which were approximately 12.85 and 3.37 times those of commercial corn stalk biochar (BC). Thermodynamic analysis confirmed that the removal of Pb(II) and Sb(III) by FPBC was a spontaneous and endothermic process. In addition, FPBC demonstrated strong selective adsorption of Pb(II) in the binary co-adsorption system of Pb(II) and Sb(III). Mechanism studies indicated that Pb(II) removal primarily occurred through co-precipitation, complexation, ion exchange, and electrostatic adsorption, while Sb(III) was mainly adsorbed by FPBC via redox reactions and complexation. Therefore, this work not only provides a low-cost, high-performance adsorbent for the remediation of water contaminated with Pb(II) and Sb(III), but also opens up new avenues for the resource recovery of the leachate of spent LiFePO₄ batteries. Full article

Arsenic (As) pollution has become a global concern, and the search for effective and sustainable As remediation methods has attracted much attention. Sustainable and cost-effective technologies for As remediation are essential to protect public health. This study aligns with the United Nations Sustainable Development Goals (SDGs), specifically SDG 6 (Clean Water and Sanitation) and SDG 12 (Responsible Consumption and Production), by transforming agricultural waste into value-added biochar for environmental remediation. Currently, studies on the remediation of As pollution using iron-modified biochar (Fe-BC) and cerium-modified biochar (Ce-BC) have demonstrated promising application potential. Although there is an established research foundation regarding their remediation performance and mechanisms, comparative studies evaluating their performance and mechanisms under unified experimental conditions remain limited. As in this study, Fe-BC and Ce-BC were prepared and systematically investigated. The As remediation performance and mechanisms of the two biochars were compared and analyzed through material characterization, aqueous adsorption experiments, and soil remediation assessments. The results showed that the specific surface areas of Fe-BC and Ce-BC were 94.380 m²·g⁻¹ and 36.388 m²·g⁻¹, respectively, both higher than that of the original biochar (BC). The Langmuir and Freundlich models adequately fitted the As adsorption processes of all three materials. Fe-BC and Ce-BC exhibited a tendency toward monolayer adsorption for As(III). The Freundlich distribution coefficient K_F of Fe-BC was 0.1604, which was higher than that of BC and Ce-BC, indicating superior adsorption performance for As(III). In the pot experiment, when Fe-BC and Ce-BC were applied at 5%, the As content in ryegrass decreased by 78.38% and 77.15%, respectively. Fe-BC reduced the available As content in soil by 63.1% and decreased As accumulation in ryegrass by 78.38%. The reduction in available As content achieved by Fe-BC was greater than that achieved by Ce-BC. Fe(III) oxides supported on Fe-BC immobilized As through complexation and precipitation mechanisms. Fe⁰ and Fe₃O₄ in the materials altered the redox potential of the local microenvironment, affecting the transformation and stabilization of As species. Ce-BC primarily oxidized As(III) to As(V), and Ce⁴⁺ facilitated the formation of CeAsO₄ precipitates due to its high redox potential. Full article

Biochar is a porous material which can be produced by biomass waste pyrolysis and modified using metal oxide to improve its adsorption performance. Activated biochar (AB) was synthesized from patchouli biomass waste to study the effect of calcination tempera-ture on its potency as a drug pollutant adsorbent. Research processes included the bio-mass pyrolysis with CoCl₂ activator, AB impregnation with FeCl₃, FeCl₃/AB calcination at various temperatures, product characterizations (X-ray diffraction, FTIR spectrometry), and paracetamol adsorption test at various concentrations. The paracetamol concentra-tions were analyzed using UV–Vis spectrophotometry. The adsorption data was treated using Langmuir, Freundlich, and Dubinin–Radushkevich (DR) models. The diffracto-grams indicated the α-Fe₂O₃, γ-Fe₂O₃, FeFe₂O₄, and carbon turbostratic structures. The Fe_xO_y crystallinity increased by increasing temperature. The FTIR spectra significantly indicated the functional group changing at 600 °C. In the adsorption test, the Fe_xO_y/AB-800 compo-site gave the highest adsorption capacity of 53.087 mg/g (Langmuir) with a correlation co-efficient of 0.964 (very high correlation), and the physical adsorption mechanism based on adsorption energy of 530.330 J/mol (DR) and 1/n value of 0.62 (Freundlich) provided the favorable adsorption based on both the RL of 0.457 (Langmuir) and the n constant of 1.579 (Freundlich). Thus, the Fe_xO_y/AB-800 composite has potential as an adsorbent of organic pollutants such as paracetamol. Full article

An exorbitant amount of organic fractions of the municipal solid waste, i.e., fruit and vegetable waste (FVW), generated from farm to fork are being treated through anaerobic digestion (AD). Anaerobic digestion (AD) of FVW only achieves <60% methane potential due to methanogen loss and indirect electron transfer. Hence, the technology necessitates further improvements in performance to maximise the methane gas yield by stabilising the methanogens using a potential additive. Magnetic biochar is a budding and promising additive in anaerobic digestion that amplifies biomethanation performance. This study focuses on the role of magnetic biochar in enhancing the viability of the AD system in biogas production from organic waste fractions. Herein, the magnetic biochar was produced using a FeCl₃-impregnated walnut shell and then characterized. The derived magnetite was identified as the major crystalline phase in biochar with the presence of several oxygenated functional groups. The specific surface area, pore volume, and pore diameter were found to be 360.99 m² g⁻¹, 0.089 cm³ g⁻¹, and 0.98 nm, respectively. The SEM and TEM images illustrated a good dispersion of the material, with size ranging between 18.2 and 46.6 nm, thus indicating the porous nature of the magnetic biochar. The incorporation of magnetic biochar in the CN ratio modified the AD system with enhanced methane production and the highest volume (1523.4 mL) reported in treatment, with a CN ratio of 25:1 and 0.5% magnetic biochar. The resulted gas yield is 35% more than the control (1125 ML) with reduced lag phase (4 vs. 12 days). It concludes that walnut shell MBC uniquely combines DIET conduits and biofilm support and enhances methane production from FVW. However, 16S rRNA confirmations of syntrophs, continuous reactor validation, and magnetic biochar recovery and reuse potential studies are essential for further scaleup. Full article

Heavy metal pollution is characterized by long-term accumulation and recalcitrance to degradation, which poses a serious threat to soil ecosystems and groundwater environments. To improve the remediation efficiency of biochar for cadmium (Cd)-contaminated soil, this study took unmodified biochar (BC) as the control and systematically explored the remediation potential of NaOH–KMnO₄–FeCl₃ composite-modified biochar (GBC). Combined with a Brassica napus L. pot experiment, the effects of modified biochar on soil Cd passivation, soil physicochemical properties, and B. napus biomass were analyzed. After composite modification, GBC had its surface ash removed and exhibited a more regular pore structure, with successful loading of iron–manganese oxides. Although partial changes in the microporous structure caused a decrease in CO₂ adsorption, the number of surface-active sites increased. Both biochars significantly increased soil carbon content, nitrogen and phosphorus nutrient levels, and electrical conductivity, while promoting B. napus biomass accumulation and reducing its Cd enrichment. Among them, the GBC-1.5 treatment group exhibited the most significant increase in B. napus biomass, which was 33.66% higher than that of the control group (CK). However, soil pH increased with the increase in BC but decreased with the increase in GBC application rate. In terms of Cd passivation effect, both biochars showed excellent remediation performance. When the application rate was 3%, the Cd passivation rate of the GBC-3 treatment group reached 35.87%, which was 5.29% higher than that of the BC-3 treatment group. The loading of iron–manganese oxides further enhanced the effectiveness and stability of chemical adsorption. This study provides an important reference for achieving sustainable utilization of soil heavy metal remediation. Full article

Background: Traditional methods exhibit an extremely low removal efficiency for antibiotics in water, making an efficient and energy-saving approach urgently needed. Methods and Results: In this study, a novel catalytic approach based on the in situ generation of high-valent iron (Fe(IV)/Fe(V)) has been developed by adding biochar instead of modifying the electrode materials (in previous studies) for the efficient removal of sulfamethoxazole (SMX) from water. Fe(IV)/Fe(V) was produced by the anodic oxidation of low concentrations of Fe(III) and subsequently activated by nitrogen-doped corn stalk biochar (NBC). The results showed that the degradation efficiency increased from 50.83% to 90.67% within 60 min after the addition of nitrogen-modified biochar. The abundant defect structures, graphitic N and oxygen-containing functional groups in NBC endowed the catalyst with excellent activation capability. Quenching experiments and methyl phenyl sulfoxide (PMSO) probe experiments revealed that singlet oxygen (¹O₂) and Fe(IV)/Fe(V) were the main contributors to SMX degradation. Degradation pathways were inferred based on transformation products (TPs) and density functional theory (DFT) calculations. Ecotoxicity prediction using the ECOSAR program indicated that the TPs formed in the E/Fe(III)/NBC system exhibited markedly lower toxicity to aquatic organisms than the parent SMX. Furthermore, the E/Fe(III)/NBC system maintained a high degradation efficiency for SMX in real aquatic environments. Additionally, the E/Fe(III)/NBC system showed high removal rates for other sulfonamides such as sulfadiazine (SDZ), sulfamethoxypyridazine (SMP), sulfathiazole (STZ) and sulfadoxine (SDX). Conclusions: Overall, the E/Fe(III)/NBC system was demonstrated to be a highly efficient and sustainable technology for removing various antibiotics from water. Full article

Nanoplastics (NPs) have emerged as pervasive aquatic pollutants due to their small size, high surface activity, and potential ecological and health risks. Although sludge-derived biochar is a sustainable adsorbent for NP removal, the relative importance of coexisting adsorption mechanisms remains poorly quantified. Here, iron-modified sludge biochar (FeBC) was synthesized and evaluated for NP removal from water. Batch experiments showed that FeBC significantly outperformed pristine biochar, achieving a maximum removal efficiency of 96.09%. Adsorption was strongly pH-dependent, with enhanced removal under acidic conditions due to surface protonation and strengthened electrostatic attraction toward negatively charged NPs. SEM, BET, FTIR, and XPS analyses indicated that electrostatic interactions, hydrogen bonding, π–π interactions, and pore adsorption jointly contributed to NP capture. Importantly, structural equation modeling quantitatively disentangled these mechanisms, revealing electrostatic interactions as the dominant driver (52.6%), followed by hydrogen bonding (23%), pore adsorption (16.6%), and π–π interactions (7.9%), and further identified synergistic and antagonistic relationships among them. These results demonstrate that surface charge regulation governs NP adsorption efficiency, providing a quantitative mechanistic basis for the rational design of biochar-based adsorbents. This study advances a multi-mechanistic framework for understanding and optimizing NP removal while promoting sludge resource valorization. Full article

This study investigated the remediation effects of iron-modified biochar (FeBC-1 and FeBC-2) on arsenic (As) and cadmium (Cd) co-contaminated paddy soil and elucidated the underlying mechanisms from the perspectives of rhizosphere microbial ecology and plant As and Cd accumulation. A pot experiment with rice was conducted, comprising a control (CK) and iron-modified biochar treatments (FeBC-1 and FeBC-2). Parameters such as As and Cd speciation in rhizosphere soil, bacterial community composition, and the abundance of As-related functional genes were analyzed. The results demonstrated that iron-modified biochar reduced As and Cd accumulation in rice grains by promoting the formation of iron plaques on root surfaces. Meanwhile, the iron-modified biochar significantly enhanced the alpha diversity of bacterial communities and altered their composition. Quantitative analysis of functional genes revealed that the abundance of the As oxidase gene (aioA) increased from 3.54 × 10⁵ in the CK treatment to 7.20 × 10⁵ in FeBC-1 and 7.14 × 10⁵ in FeBC-2, and the abundance of the As efflux gene (arsA) decreased in the biochar-treated groups. These results indicate reduced As bioavailability in the rhizosphere and enhanced transformation of As(III) to As(V). Full article

To explore the effects of Fe/P-loaded biochar on neutral Cd-contaminated paddy soils and the potential synergistic effects between biochar and modifying materials, a pot experiment was conducted using neutral paddy soil with a total Cd concentration of 1.10 mg/kg. Ball milling was employed for modified biochar production. Specifically, iron-loaded biochar (PBCFe) and phosphorus-loaded biochar (PBCP) were prepared using Fe₂O₃ and K₃PO₄, respectively. Results showed that PBCP significantly increased rice biomass while effectively inhibiting Cd uptake and accumulation in rice grains. Compared to the control (CK), P (K₃PO₄), and PBC treatments, the Cd content in rice grains under PBCP treatment decreased by 69.20%, 52.13%, and 56.06%, respectively. Moreover, compared with the treatments using single modifiers, PBCP and PBCFe effectively reduced Cd uptake and accumulation in rice tissues, especially in leaves and stems. In contrast, PBCP was more effective than PBCFe in enhancing iron plaque formation and Cd adsorption onto iron plaque. This promoted Fe uptake in rice roots, which might inhibit the upward translocation of Cd from roots to stems. Further analysis with FTIR and XPS results indicated that PBCP might be more compatible in immobilizing Cd in soil by inducing Cd-P co-deposition. Therefore, phosphorus-loaded biochar (PBCP) could be a more promising amendment for remediating Cd-contaminated alkaline rice paddy soils and improving rice quality. Full article

Conventional bioretention systems face challenges in effectively removing dissolved nutrients, heavy metals, and emerging contaminants from stormwater runoff. This study investigates the application of thermally modified steel slag (700 °C) as a functional bioretention matrix for comprehensive stormwater purification. Three pilot-scale systems were evaluated over 120 days: Control (biochar-zeolite), Unmodified (raw steel slag-biochar-zeolite), and Modified (thermally modified steel slag-biochar-zeolite). The modified system demonstrated superior and stable removal efficiencies for NH₄⁺-N (95.3 ± 1.3%), TN (85.7 ± 1.8%), TP (90.5 ± 1.5%), Cu²⁺ (96.1 ± 0.7%), Cr⁶⁺ (90.5 ± 1.2%), Pb²⁺ (92.2 ± 1.1%), enrofloxacin (65.6 ± 2.1%), and norfloxacin (62.6 ± 2.4%). Performance remained robust under varying hydraulic conditions, with high removal maintained across rainfall return periods (0.5–2 years) and antecedent dry periods (2–8 days). Mechanistic investigations revealed synergistic effects: (1) Enhanced physical adsorption through increased surface area (2.338 m²/g) and pore volume (0.109 cm³/g); (2) Chemical precipitation via Ca²⁺/Fe³⁺ release at alkaline pH (8.2–8.5); (3) Enriched microbial communities with 35% higher Shannon diversity, particularly Hydrogenophaga (12.3%) for autotrophic denitrification using Fe²⁺ as electron donor. The modified slag matrix creates a “triple-barrier” removal mechanism combining physical, chemical, and biological processes, offering an efficient solution for multi-pollutant stormwater treatment. This study demonstrates that thermally modified steel slag represents a high-performance, cost-effective bioretention matrix for comprehensive stormwater treatment while promoting industrial byproduct utilization and aligning with circular economy principles. Full article

Arsenic (As) contamination in paddy soils poses a serious risk to rice safety and human health. To mitigate this issue, we developed a low-temperature, partially pyrolyzed Fe/Mn/Mg-modified biochar (FMM-BC) and evaluated its performance and mechanisms for remediating As-contaminated soil through a pakchoi–rice rotation pot experiment, aiming to reduce As accumulation in rice grains and pakchoi. The results indicated that FMM-BC application altered soil physicochemical properties and As speciation, reducing both water-soluble and bioavailable As and promoting its transformation from exchangeable to more stable organic-bound and residual fractions. Compared with the control, FMM-BC application reduced arsenic content in rice stems, leaves, and brown rice to 1.94 mg∙kg⁻¹, 5.24 mg∙kg⁻¹, and 1.21 mg∙kg⁻¹, respectively. In contrast, unmodified biochar (BC) increased As bioavailability and plant uptake, underscoring the importance of Fe/Mn/Mg modification. FMM-BC also enhanced the translocation of Fe, Mn, and Mg within rice plants, thereby modifying internal As transport dynamics and suppressing its accumulation in aboveground tissues. Under FMM-BC treatment, arsenic content in pakchoi stems and leaves decreased to 1.19 mg∙kg⁻¹ (vs. 1.96 mg∙kg⁻¹ in the control), and brown rice declined to 0.27 mg∙kg⁻¹ (vs. 1.49 mg∙kg⁻¹ in the control)—well below the national food safety threshold (0.35 mg∙kg⁻¹). These findings demonstrate that FMM-BC effectively stabilizes As in contaminated soils and reduces its transfer to edible plant parts, with Fe/Mn/Mg playing a key role in enhancing As immobilization and limiting its mobility within the soil–plant system. Full article

Remediating cadmium (Cd) contamination in aquatic and terrestrial environments has become an urgent environmental priority. Biochar has been widely employed for heavy metal removal due to its wide availability, strong adsorption capacity, and potential for recycling agricultural waste. In this study, samples of alkali–Fe-modified biochar (Fe@NaOH-SBC, Fe@NaOH-HBC, and Fe@NaOH-MBC) were prepared from agricultural wastes (ginger straw, Sichuan pepper branches, and kiwi leaves) through NaOH and FeCl₃·6H₂O modification. A comprehensive characterization confirmed that the alkali–Fe-modified biochar exhibits a higher specific surface area, richer functional groups, and successful incorporation of the iron oxides Fe₃O₄ and α-FeOOH. The fitting parameter qmax from the Langmuir model indicates that the alkali–Fe modification of carbon significantly enhanced its maximum capacity for Cd²⁺ adsorption. Furthermore, a synergistic effect was observed between iron oxide loading and alkali modification, outperforming alkali modification alone. Furthermore, a 30-day soil incubation experiment revealed that the application of alkali–Fe-modified biochar significantly increased soil pH, SOM, and CEC while reducing the available cadmium content by 13.34–33.94%. The treatment also facilitated the transformation of highly bioavailable cadmium species into more stable, less bioavailable forms, thereby mitigating their potential entry into the food chain and the associated human health risks. Moreover, short-term spinach seed germination experiments confirmed that treatments with varying additions of alkali–Fe-modified biochar mitigated the inhibition of seed physiological processes by high concentrations of available cadmium to varying degrees. Overall, this study provides a sustainable and effective strategy for utilizing agricultural waste in the remediation of cadmium-contaminated water and soil systems. Full article

Biohydrogen production can be derived from low-value lignocellulosic biomass; however, in many biohydrogen producing systems, xylose is utilized less efficiently than glucose, which limits overall substrate conversion. To address this issue, Fe/Mn-modified biochar was employed to enhance dark fermentation of glucose–xylose mixed sugars, and its performance was compared with other inoculum treatments. The biochar addition achieved a hydrogen yield of 2.57 ± 0.10 mol-H₂/mol-sugar, representing 14.6% enhancement over untreated controls, while enabling complete substrate utilization across varying xylose proportions. Biochar supplementation also reduced the lag phase by 24.4% and increased hydrogen productivity by 47.3% in mixed-sugar cultivation. Integrated analyses of the experimental data revealed the dual role of Fe/Mn-modified biochar in constructing conductive extracellular polymeric substance networks and directing metabolic flux toward high-yield butyrate pathways. This work establishes Fe/Mn-biochar as a multifunctional microbial engineering tool that alleviates carbon catabolite repression and promotes the enrichment of hydrogen-producing bacteria (HPB), thereby providing a practical and effective strategy for enhanced biohydrogen production from lignocellulosic biomass. Full article