New laterite biochar composite offers sustainable solution for arsenic-contaminated water
Laterite and biochar team up to remove arsenic from contaminated water
image: Optimized synthesis and characterization of laterite biochar composite for arsenic removal: examining colloidal stability and As(III) oxidation
Credit: Prashant Singh & Abhijit Maiti
Arsenic contamination in water remains a serious public health challenge in many parts of the world, especially in regions where groundwater is widely used for drinking and irrigation. A study published in Biochar reports an eco-friendly adsorbent made from biochar and laterite minerals that can efficiently remove both major forms of arsenic from water while remaining regenerable and safe for disposal.
The study, led by Prashant Singh and Abhijit Maiti, developed an optimized laterite biochar composite, known as LBC, by combining carbonized biomass with acid-treated laterite, a naturally abundant iron-rich soil. The composite uses biochar as a stable porous carbon matrix and laterite-derived iron and aluminum oxyhydroxides as active mineral sites for arsenic capture.
“Arsenic contamination is not only a water treatment problem, but also a sustainability challenge,” said corresponding author Dr. Abhijit Maiti. “Our goal was to design an adsorbent that can be made from locally available materials, works effectively for different arsenic species, and can be regenerated after use.”
The researchers focused not only on whether the material could remove arsenic, but also on how to prepare it in the most effective way. They optimized the pyrolysis temperature, the pH at which biochar is added to the laterite solution, the final precipitation pH, and the ratio of laterite to biochar. The best material was obtained by first producing biochar at 400 °C, then incorporating it into acid-leached laterite solution at pH 3, where iron and aluminum hydroxide nucleation begins. The process was terminated near pH 7.4, the point of zero charge, which improved particle settling, washing, and separation.
Compared with pristine biochar and post-pyrolyzed composites, the optimized LBC showed much higher arsenic removal. The Langmuir model estimated maximum adsorption capacities of 21.39 g kg⁻¹ for arsenate, As(V), and 14.01 g kg⁻¹ for arsenite, As(III). The material also showed rapid adsorption, especially for As(V), and maintained strong performance across several biomass sources, including rice straw, wheat straw, mustard straw, wood dust, pineapple leaves, and hemp stem. This suggests that the laterite-derived mineral phase is the main driver of arsenic removal, while biochar provides a useful porous support.
Advanced characterization helped explain how the material works. FTIR and XPS analyses showed that hydroxyl groups and metal oxides on the composite surface play important roles in arsenic binding. Electron paramagnetic resonance and quenching experiments further revealed that hydroxyl radicals contribute to the oxidation of As(III) into As(V), which is then more strongly adsorbed by the composite.
The material also performed reasonably well in more complex water conditions. Most competing ions had limited effects, although phosphate reduced removal efficiency because of its structural similarity to arsenic species. Importantly, the spent adsorbent passed toxicity characteristic leaching procedure tests, suggesting that it can be safely landfilled under the tested conditions. The LBC could also be regenerated using 0.2 M NaOH and retained more than half of its original adsorption capacity after five adsorption and desorption cycles.
Because laterite and biomass are widely available in many arsenic-affected regions, the researchers suggest that this approach could be especially useful for developing countries seeking low-cost and scalable water treatment options.
“Our findings show that careful process optimization can turn simple natural materials into a high-performance adsorbent,” Dr. Maiti said. “This laterite biochar composite offers a promising route toward safer water using sustainable and locally accessible resources.”
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Journal Reference: Singh, P., Maiti, A. Optimized synthesis and characterization of laterite biochar composite for arsenic removal: examining colloidal stability and As(III) oxidation. Biochar 6, 100 (2024).
https://doi.org/10.1007/s42773-024-00389-0
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.