The development of effective and affordable adsorption materials for CO2 capture is a crucial issue. Biochar can play a significant role in CO2 capture, alongside other available adsorbents. In this research, biochar was made from the agricultural waste corn cobs through a pyrolysis process. Biochar itself has a limited capacity for capturing CO2. It needs to be modified to increase its CO2-capturing efficiency. This research aims to improve the CO2-capturing efficiency of corn cob-based biochar by incorporating magnesium and sodium metals into its structure with heat treatment under N2. The physicochemical properties of biochar were characterized by pore volume (25%), specific surface area (346.2 m2/g), average particle size (0.52 nm), and point zero charge (pH = 5.12). The XRD results showed that incorporating metals into biochar improved crystal structure formation and boosted the degree of carbon structure ordering. SEM analysis revealed that the biochar surface impregnated with metal oxide had a distribution of spotted activation centers. The adsorption of CO2 onto biochar was in the order of Mg metal-incorporated biochar > Na metal-incorporated biochar > pristine biochar at 25 °C and 1 atm. The elemental analysis employed by EDX indicates that the Mg-incorporated biochar has a higher CO2 uptake capacity. The XPS spectrum and13C NMR also agreed with the EDX results. The CO2 adsorption efficiency of Mg-incorporated biochar reached an impressive 94.6%, the highest reported in the literature to date. This efficiency was also higher than that of Na-loaded biochar (81.20%) and pristine biochar (64.43%). We can conclude that corn-cob-based biochar, which is made from agricultural waste, is both economically viable and effective in CO2-capturing systems.

Removal mechanisms of polycyclic aromatic hydrocarbons in biochar and its effects on plant growth.

ABSTRACT Aquatic plants used in lake remediation accumulate heavy metals, turning biomass into waste. Herein, biochar (M-AcBC) derived from metal-laden Acorus calamus was combined with sodium percarbonate (SPC) and UV light to degrade tetracycline (TC). M-AcBC contained dispersed CuO, ZnO, and Fe3O4, exhibited defect structures, higher graphitization, and larger surface area than pristine biochar. Under optimal conditions (1.0 g/L M-AcBC, 0.3 mM SPC, pH 3, 900 µW/cm² UV), 90% TC removal was achieved. During the dark phase (0–40 min), functional groups, persistent radicals, and Fe₃O₄ activated SPC to generate •OH, • O 2 - , and 1O2. Upon UV irradiation (40–120 min), ZnO produced electron-hole pairs that further formed •OH and • O 2 - . The system exhibited synergistic effects, good reusability, broad applicability to various antibiotics, and reduced ecotoxicity of intermediates. This work provides a waste-to-resource strategy and new insights into the M-AcBC/SPC/UV system for water treatment.

The treatment and disposal of excess sludge, a major solid byproduct of wastewater treatment processes, pose significant environmental and public health challenges, making its rational utilization crucial for promoting resource recycling. This study presents a one-step synthesis of a magnetically responsive bifunctional biochar composite (Fe-SDB600) derived from excess sludge for the simultaneous and enhanced removal of tetracycline (TC) and copper ions (Cu2+) from aqueous solutions. Characterization confirmed the successful loading of nanoscale iron oxide particles onto the biochar surface, resulting in a hierarchical porous structure. Under optimized conditions, Fe-SDB600 exhibited significantly improved adsorption capacities for TC (269.39 mg/g) and Cu2+ (271.65 mg/g) compared to the pristine biochar. The composite demonstrated excellent resistance to interference from common coexisting ions and maintained a high TC removal efficiency of 83.28% after four adsorption-desorption cycles, with minimal iron leaching. Adsorption kinetics were best described by the pseudo-second-order model, and isotherm data fitted the Langmuir model, indicating a chemisorption-dominated process. Density functional theory (DFT) calculations provided atomic-level mechanistic validation, confirming the spontaneous coordination of Cu2+ to surface Fe-OH sites with a high binding energy of -2.05 eV and identifying the A-ring of TC as the dominant moiety for π-π electron donor-acceptor interactions with an adsorption energy of -1.85 eV. Furthermore, in the binary system, a metal-bridging effect was identified, where preadsorbed Cu2+ enhanced TC uptake by forming ternary complexes. This work provides a sustainable and efficient strategy for sludge valorization and the coremoval of organic and inorganic pollutants, highlighting the potential of sludge-derived adsorbents in practical wastewater treatment.

Phosphoric acid (H3PO4) pretreatment is an effective method to improve biochar properties, yet its evolution mechanism remains incompletely elucidated. This study investigated the synergistic pyrolysis of H3PO4 and mottled bamboo at different temperatures in a fixed-bed reactor. Results showed that during impregnation, H3PO4 promoted the partial dissolution of hemicellulose and reduced cellulose polymerization, resulting in a decrease in the activation energy of the fast pyrolysis stage from 96.72 kJ/mol (pristine bamboo biochar, MB) to 75.75 kJ/mol (H3PO4-modified bamboo biochar, MB/H3PO4). With increasing temperature, the pore structure of the modified biochar was enhanced while its graphitization degree decreased, owing to the catalytic effect of H+ and the cross-linking action of the acid. Meanwhile, the addition of H3PO4 facilitated the rearrangement of oxygen-containing heterocycles, and the incorporation of small-molecule benzene rings further improved the aromatization degree of the modified biochar. In conclusion, it functions as a catalyst, reactant, and pore-expanding agent during pyrolysis. This study further broadens the understanding of biochar evolution mechanisms regulated by phosphorus-containing additives, and provides a theoretical basis for optimizing biochar properties and producing phosphorus-rich biochar.

Enhancing soil health and phosphorus use efficiency with modified biochar amendment.

Modified biochar mitigates nitrogen loss in distilled grain waste composting by modulating microbial community assembly and function.

Nitric acid-modified biochar enhances saline-alkali soil remediation and cotton growth via regulating soil-plant homeostasis.

Nutrient losses through leaching and low nutrient use efficiency are major challenges limiting crop productivity and causing environmental pollution. Biochar has been widely studied as a soil amendment to improve nutrient retention; however, the combined effects of pyrolysis temperature and post-production oxidation on soil nutrient dynamics and plant performance remain unclear. In this study, wheat straw and wood residue biochars were produced at two pyrolysis temperatures (350 and 450 °C) and subsequently modified by hydrogen peroxide (H2O2) oxidation to enhance surface functionality. A pot experiment with fava bean (Vicia faba L.) was conducted to evaluate the effects of pristine and oxidized biochars on soil chemical properties, nutrient leaching, and plant nutrient uptake. Results showed that pristine biochars increased soil pH from 6.82 (control) to 8.73–9.12 and EC from 2.15 to 3.06–4.71 dS m−1, with wheat straw biochars having stronger alkalizing effects. In contrast, oxidized biochars decreased soil pH to 5.62–5.93 due to the introduction of oxygen-containing functional groups. All biochars reduced NO3−-N, NH4+-N, and PO43−-P leaching, with the most pronounced reductions observed in oxidized wheat straw biochar produced at 450 °C (O-BWS450). Improved nutrient retention translated into higher plant nutrient uptake: fava bean plants grown in O-BWS450-amended soil achieved the greatest N (6.71%) and P (3.89%) uptake, significantly higher than the control. These findings highlight the potential of oxidation-modified biochars, particularly wheat straw biochar produced at moderate pyrolysis temperature, to improve soil nutrient conservation and enhance crop nutrition simultaneously. Such modifications represent a promising approach for developing biochar-based soil amendments that promote sustainable nutrient management.

Biochar is widely acknowledged as an environmentally efficient adsorbent for removing heavy metals from wastewater. However, its practical application is often limited by insufficient adsorption capacity. This limitation primarily arises from low surface area, suboptimal selection and utilization of chemical activating agents, and inadequate development of surface functional groups, leading to reduced stability. To address these challenges, the present study focuses on the synthesis and application of phosphoric acid-activated non-edible coco peat biochar (PMCB) for the efficient and stable removal of Cu²⁺ and Ni²⁺ from both aqueous solutions and real wastewater systems. Thus, this study focuses on the synthesis and application of phosphoric acid-impregnated non edible coco peat biochar (PMCB) for efficient and stable removal of Cu²⁺ and Ni²⁺ from both aqueous and real systems. The PMCB was prepared at combined optimal conditions (Pyrolysis temperature and H3PO4 impregnation ratio), which improved its physicochemical properties compared to that of pristine biochar. The PMCB exhibited superior adsorption capacities of 566.6 mg/g and 551.7 mg/g for Cu2+ and Ni2+ in batch tests and 794.5 mg/g and 691.4 mg/g in column studies. The adsorption data by PMCB were well fitted by the Langmuir isothermal and pseudo-second-order kinetic models, indicating monolayer chemical adsorption controlled the adsorption process. Characterisation using XPS and FTIR confirmed the presence of -PO3 and -PO4 functional groups in the modified biochar. These functional groups enhance metal adsorption through precipitation, physicochemical adsorption, surface complexation, ion exchange, and electrostatic interactions. PMCB demonstrated 99% removal efficiency for metals and pollutants in single-component and real-world systems. Stability tests showed PMCB’s reusability for up to 20 cycles with a 96.0% desorption rate. Additionally, the spent biochar proved effective as a bio-fertilizer. Cost analysis confirmed PMCB to be economically viable at 1.56 USD/kg (130.7 INR/kg), making it a cost-effective, sustainable, and low-energy solution for industrial heavy metal removal and wastewater treatment.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-20743-x.

Biochar shows potential for regulating nitrogen cycling in cold-region soils, but the roles of its different fractions during freeze-thaw cycles (FTCs) remain unclear. To elucidate the regulation of cold-region soil environments by biochar at the fraction scale, we examined the effects of biochar and its fractions (dissolved and undissolved) on soil nitrogen forms and microbial communities under simulated FTCs. The experiment included a constant-temperature control, a freeze–thaw control, and three biochar treatments with pristine biochar (PBC), dissolved biochar fraction (DBC), and undissolved biochar fraction (UBC), respectively, maintained in triplicate at five FTC frequencies (0, 1, 5, 10, and 20). Changes in soil physicochemical properties and nitrogen forms were measured at five FTC frequencies, and microbial community composition was analyzed by high-throughput sequencing after the 20th cycle. Both biochar fractions reduced inorganic nitrogen, with ammonium nitrogen decline resulting from joint action and nitrate nitrogen (NO3−-N) reduction dominated by UBC. PBC alleviated microbial biomass nitrogen stress by relying primarily on its undissolved fraction to enhance soil water retention, organic carbon, and total nitrogen. Redundancy analysis indicated that total nitrogen and NO3−-N were the key factors affecting microbial community composition. Partial least squares structural equation modeling results suggested that soil physicochemical properties influenced microbial community structure characteristics more strongly than nutrient properties. These findings provide a new perspective on the regulatory mechanism of biochar on the agricultural soil environment in cold regions.

Batch adsorption experiments were carried out to evaluate the removal of Rhodamine B (RhB), a cationic dye, from synthetic wastewater using a multi-walled carbon nanotube/titanium dioxide (MWCNT/TiO2)-modified biochar composite (CBTM), with pristine biochar (CCB) as a reference. The effects of solution pH, contact time, adsorbent dosage, temperature, and initial dye concentration on adsorption performance were systematically investigated. Maximum RhB removal occurred at pH 3, with equilibrium achieved after 180 min. Under these conditions, CBTM exhibited a higher adsorption capacity (31.43 mg·g−1) than CCB (17.31 mg·g−1) at 313 K. Equilibrium data were best described by the Freundlich isotherm, indicating multilayer adsorption on heterogeneous surfaces, while kinetic analysis showed that the pseudo-first-order model provided the most accurate fit, suggesting a physisorption-dominated process. Thermodynamic parameters (ΔG°, ΔH°, ΔS°) confirmed that the adsorption was spontaneous and endothermic. Interestingly, while CBTM demonstrated superior dye removal, antimicrobial assays revealed stronger bacterial inhibition by CCB. These results highlight the potential of CBTM for efficient dye removal and underscore the multifunctional capabilities of biochar-based adsorbents.

Unveiling the critical role of functional groups in pristine biochar for photocatalytic Cr(VI) remediation under visible light

This study fabricated an activated bentonite–rapeseed straw biochar composite (AC-RSB120-4:3) via hydrothermal carbonization, followed by FeCl3 impregnation and NaOH treatment to enhance methylene blue adsorption. Characterization by BET analysis, XRD, SEM, and FTIR revealed a porous structure and abundant functional groups. The composite showed superior adsorption capacity (425.65 mg/g at neutral pH) compared to pristine biochar. The optimal adsorption performance was achieved when the solution pH was around 10. Kinetics obeyed the pseudo-second-order model (chemisorption control), yet thermodynamics (ΔH = −15.856 kJ/mol) simultaneously indicate prominent physisorption. Multilayer adsorption (Freundlich isotherm) arises from combined pore filling, electrostatic attraction, ion exchange and surface complexation, with physical interactions dominating the initial stage and chemical bonds progressively taking over. Overall, the composite exhibits high efficiency and stability for dye wastewater treatment.

ABSTRACT This study aims to investigate the effects of salt treatment and steam activation on chars derived from biomass wastes (manure, food, and kenaf) and spent tires. Batch sorption experiments were used to evaluate the absorption performance of these chars for benzene, phenol, trichloroethylene (TCE), and arsenate. Steam activation of biochars at 900°C increased their specific surface area, enhancing the sorption of all contaminants. Steam-activated chars exhibited sorption capacities of 25–125 mg/g and 15–70 mg/g for benzene and phenol, respectively, one order of magnitude higher than those of pristine biochars. Further treatment with CaCO3 and CaSO4 decreased the sorption capacity of manure biochar for benzene by 10–30%. In contrast, treatment with CaCO3 and CaSO4 enhanced the sorption capacity of manure biochar for TCE and phenol by approximately 10% and 5–10%, respectively, due to reduced hydrophobicity and the formation of surface functional groups. Similarly, the salt treatment following steam activation slightly increased the sorption capacity for arsenate, reaching up to 1.6 mg/g. These findings suggest that steam activation and surface treatment with CaCO3 and CaSO4 selectively enhance the sorption of various contaminants in natural and engineered systems. Implications: Pyrolysis is widely explored as a final disposal process for various types of organic waste, including agricultural, food, biomass, and thermoplastic wastes, due to its ability to produce valuable by-products, bio-oil, biochar, and syngas as energy sources. Compared to direct combustion with excess air, biochar production may be less cost-effective due to the additional energy required for the pyrolysis process. To overcome this economic disadvantage, improving the properties of biochar via various processes has been proposed to provide additional value to biochar. It has been reported that chemical activation of biochar with salt treatment could enhance the porosity and surface area by facilitating carbonization and preventing structural collapse, and that the steam activation could develop micro- and mesopores in carbonized material by gasification of carbon at high temperature using steam. Compared to acid and oxidants, salt treatment is less toxic, easier to remove, and more sustainable. In this study, we investigated the effects of salt treatment (CaCO3 and CaSO4) and steam activation (900 oC) on chars derived from biomass wastes (manure, food, and kenaf) and spent tires.

The effects and underlying mechanisms of modified biochar combined with nitrification inhibitors on nitrous oxide mitigation in acidic soils.

Cadmium induces toxicity to both flora and fauna, even when it is present in trace amounts. Electroplating, pigments, smelting, mining, alloy production, plastic, cadmium-nickel batteries, fertilizers, pesticides, paint, synthesis of dye, textile operations, and refining sectors all release cadmium into the aquatic environment. "Solvent extraction, adsorption, ion exchange, and precipitation" are a few strategies for removing cadmium. Biochar is an inexpensive and sustainable adsorbent that has proven to be an efficacious adsorbent for the recovery of Cd(ii) from water. This study discusses the toxicity of cadmium as well as some recent developments of pristine biochar and modified biochar for the elimination of cadmium (Cd) from aqueous solution.

BackgroundAntimony (Sb), with low biodegradability and high bioavailability in plants, poses significant health risks via the food chain due to its chronic toxicity and carcinogenicity. Modified biochar represents a promising amendment for ecological remediation of metal-contaminated croplands, yet the efficacy and mechanisms of its application in mitigating Sb accumulation and improving plant growth in Sb-polluted agricultural systems remain inadequately elucidated and require systematic investigation.ResultsIn this study, pristine biochar (BC) and iron-modified biochar (FeBC) were prepared from pomelo peel flesh (PPF; Citrus maxima), and their effects on rice root growth, Sb content, and metabolism under 30 mg/L Sb stress were evaluated. Treatment with 5 g/L BC and 5 g/L FeBC increased root length by 35.04% and 84.60%, respectively, while reducing Sb accumulation in roots by 25.79% and 28.03%, respectively. Root metabolite analysis showed that, compared to BC, FeBC significantly decreased levels of p-coumaroylagmatine, silibinin, and osmanthuside A by 75%, 37%, and 37%, respectively. Conversely, FeBC elevated levels of (S)-actinidine, phaeophorbide A, and 2-keto-6-acetamidocaproate by 187%, 156%, and 122%, respectively. These altered metabolites were enriched in five key metabolic pathways: phenylalanine, tyrosine, and tryptophan biosynthesis; phenylalanine biosynthesis; lysine degradation; tryptophan metabolism; and pantothenate and CoA biosynthesis. Correlation analysis demonstrated significant interrelationships among biochar-induced metabolites, root growth, and Sb accumulation dynamics under Sb stress.ConclusionsThe findings provided the insights that FeBC enhanced rice root metabolism and growth while reducing root Sb accumulation. This study provided a methodological foundation for developing eco-friendly remediation technologies in Sb-contaminated soils to enable safer and more sustainable rice production.Graphical abstractSupplementary InformationThe online version contains supplementary material available at 10.1186/s12870-025-07071-y.

Cadmium immobilization in river sediments using nano-chlorapatite modified biochars: Effects on prokaryotic communities.

Biochar has demonstrated effectiveness in environmental remediation. However, the physicochemical properties of biochar change with natural aging, which potentially impacts its efficacy. This study was designed to evaluate the effects of aged biochar (at 1% and 5% rates) on the growth of Chinese cabbage, greenhouse gas emission, and Cd remediation in soils. Canada goldenrod (Solidago canadensis L.) feedstock biochar was subjected to three artificial aging processes (freeze–thaw cycle, dry–wet cycle, and hydrogen peroxide oxidation) to prepare aged biochar. Results showed that aging significantly altered properties and structure of biochar. Biochar addition had no effect on CH4 emissions, but it decreased cumulative N2O emission (all treatments) and increased cumulative CO2 emission (only the pristine biochar at 5% application rate). Aged biochar showed no effect on microbial life strategy and Shannon index. However, PB-5% application shifted the life history strategies of A-strategists (resource acquisition microbe) towards Y-strategists (high-yield microbe) such as Proteobacteria, Gemmatimonadota, Bacteroidota, Firmicutes and Actinobacteriota, which partially attributed to the enhanced soil CO2 emission. Aged biochar reduced plant uptake Cd and soil available Cd concentrations by up to 36.6% and 34.0%, respectively, ascribing to improved soil physicochemical properties and functional bacterial abundance.