Renewable and efficient removal of arsenic from contaminated water by modified biochars derived from As-enriched plant

Multifunctional Sites for Enhanced Adsorption of Arsenic Using Sulfydryl-Modified Biochar/MgFe-Layered Double Hydroxides

Arsenic contamination in water poses a significant threat to the environment and human health due to the high toxicity of arsenic. Therefore, the development of functionalized materials with an enhanced adsorption capacity for arsenic remains a key research focus in water purification. In this study, straw powder was hydrothermally pretreated and subsequently pyrolyzed with zinc chloride at 700 °C to produce hydrothermal biochar with tailored pores. The hydrothermal biochar was then modified with sulfhydryl groups, and Sulfhydryl-Modified Biochar/MgFe-Layered Double Hydroxides (SH@HB/MgFe-LDH) composites were synthesized using the coprecipitation method. By utilizing HB with a high surface area, a composite material with a high specific surface area of 479.3677 m2/g was prepared. The experimental results indicated that the SH@HB/MgFe-LDH composites exhibited excellent arsenic adsorption performance across a wide pH range, achieving an arsenic adsorption capacity as high as 388.01 mg/g. The adsorption process and mechanism of the SH@HB/MgFe-LDH composites were investigated through adsorption kinetics, adsorption isotherms, thermodynamic analysis, and X-ray photoelectron spectroscopy. Additionally, recycling studies demonstrated that the composites maintained stable performance over three reuse cycles, showing good potential for practical applications. Overall, the SH@HB/MgFe-LDH composites offer an effective solution for arsenic pollution control in water while promoting the high-value utilization of agricultural and forestry waste.

Modeling the removal of Cd(II) and Pb(II) from aqueous solutions by biochar derived from arsenic hyperaccumulator Pteris vittata

This study explored the feasibility of utilizing biochar derived from Pteris vittata, an arsenic (As)-hyperaccumulating plant, for cadmium (Cd) and lead (Pb) adsorption. Biochars were produced from P. vittata with high and low As accumulation and compared with biochar derived from uncontaminated corn straw. The results demonstrated that P. vittata biochar exhibited superior adsorption capacity, reaching 98.4 mg/g for Cd(II) and 176 mg/g for Pb(II). Pb(II) adsorption was 38.2 % higher than that of Cd(II), primarily due to Pb(II)'s lower hydration energy and stronger affinity to biochar surfaces. Mechanistic analysis revealed that surface complexation was the dominant adsorption pathway, while As release from P. vittata biochar facilitated additional adsorption sites, creating a synergistic effect that enhanced metal uptake. By integrating geochemical modeling, this study provides novel insights into the interactions between biochar-derived As and heavy metal adsorption. Its findings highlight the potential of P. vittata biochar as an innovative and sustainable material for controlling heavy metal pollution.

Bimetallic Zinc-Iron-Modified Sugarcane Bagasse Biochar for Simultaneous Adsorption of Arsenic and Oxytetracycline from Wastewater

Arsenic (As), a highly toxic and carcinogenic heavy metal, poses significant risks to soil and water quality, while oxytetracycline (OTC), a widely used antibiotic, contributes to environmental pollution due to excessive human usage. Addressing the coexistence of multiple pollutants in the environment, this study investigates the simultaneous adsorption of As(III) and OTC using a novel bimetallic zinc-iron-modified biochar (1Zn-1Fe-1SBC). The developed adsorbent demonstrates enhanced recovery, improved adsorption efficiency, and cost-effective operation. Characterization results revealed a high carbon-to-hydrogen ratio (C/H) and a specific surface area of 1137 m2 g-1 for 1Zn-1Fe-1SBC. Isotherm modeling indicated maximum adsorption capacities of 34.7 mg g-1 for As(III) and 172.4 mg g-1 for OTC. Thermodynamic analysis confirmed that the adsorption processes for both pollutants were spontaneous (ΔG < 0), endothermic (ΔH > 0), and driven by chemical adsorption (ΔH > 80 kJ mol-1), with increased system disorder (ΔS > 0). The adsorption mechanisms involved multiple interactions, including pore filling, hydrogen bonding, electrostatic attraction, complexation, and π-π interactions. These findings underscore the potential of 1Zn-1Fe-1SBC as a promising adsorbent for the remediation of wastewater containing coexisting pollutants.

Potential in treating arsenic-contaminated water of the biochars produced from hyperaccumulator Pteris vittata and its environmental safety

In this study, biochar derived from pyrolyzed aboveground parts of Pteris vittata (P. vittata) was modified with iron(Fe) and applied to aqueous solutions containing arsenite (As[III]) or arsenate (As[V]) for remediation purposes. The adsorption efficiency, biochar characteristics pre- and post-adsorption, microscopic As distribution, and As morphology were analyzed. Additionally, the potential and leaching safety of P. vittata biochar for As-contaminated water remediation were evaluated. Results indicated that P. vittata biochar contained oxygen-containing functional groups and aromatic structures. Modification with Fe increased specific surface area and total pore volume. Unmodified P. vittata biochar displayed low adsorption of As(III) and As(V), while Fe modification significantly enhanced As adsorption capacity and reduced As leaching by 69%-89%. Maximum adsorption capacities of Fe-modified P. vittata biochar for As(III) and As(V) were 7.64 and 10.2 mg/g, respectively, as determined by Langmuir fitting. The superior adsorption efficiency of As(V) over As(III) by Fe-modified biochar was attributed to better electrostatic interaction with the adsorbent. Analysis revealed similar As species in P. vittata biochar before and after adsorption, with a significant presence of As(III). Remarkably, As in P. vittata remained highly stable during pyrolysis and adsorption, possibly due to strong Fe-As binding. Fe-modified P. vittata biochar shows promise for application, but further pretreatment may be necessary to achieve optimal results.

The effects of iron-based nanomaterials (Fe NMs) on plants under stressful environments: Machine learning-assisted meta-analysis

Mitigating the adverse effects of stressful environments on crops and promoting plant recovery in contaminated sites are critical to agricultural development and environmental remediation. Iron-based nanomaterials (Fe NMs) can be used as environmentally friendly nano-fertilizer and as a means of ecological remediation. A meta-analysis was conducted on 58 independent studies from around the world to evaluate the effects of Fe NMs on plant development and antioxidant defense systems in stressful environments. The application of Fe NMs significantly enhanced plant biomass (mean = 25%, CI = 20%-30%), while promoting antioxidant enzyme activity (mean = 14%, CI = 10%-18%) and increasing antioxidant metabolite content (mean = 10%, CI = 6%-14%), reducing plant oxidative stress (mean = -15%, CI = -20%∼-10%), and alleviating the toxic effects of stressful environments. The observed response was dependent on a number of factors, which were ranked in terms of a Random Forest Importance Analysis. Plant species was the most significant factor, followed by Fe NM particle size, duration of application, dose level, and Fe NM type. The meta-analysis has demonstrated the potential of Fe NMs in achieving sustainable agriculture and the future development of phytoremediation.

Biochar loaded with ferrihydrite and Bacillus pseudomycoides enhances remediation of co-existed Cd(II) and As(III) in solution

Bioremediation is one of the effective ways for heavy metal remediation. Iron-modified biochar (F@BC) loaded with Bacillus pseudomycoides (BF@BC) was synthesized to remove the coexistence of cadmium (Cd) and arsenic (As) in solutions. The results showed that B. pseudomycoides significantly increased the removal rate of Cd(II) by enhancing the specific surface area and Si-containing functional groups of biochar (BC). The surface of F@BC was enriched with Fe-containing functional groups, significantly improving As(III) adsorption. The combination of ferrihydrite and strains on BF@BC enhanced the removal of Cd(II) and As(III). It also promoted the oxidation of As(III) by producing an abundance of hydroxyl radicals (·OH). The maximum saturated adsorption capacity of BF@BC for Cd(II) and As(III) increased by 52.47% and 2.99 folds compared with BC, respectively. This study suggests that biochar loaded with Fe and bacteria could be sustainable for the remediation of the coexistence of Cd(II) and As(III) in solutions.