Fe–Mn–Y oxide-modified biochar composites for efficient Tl(I) removal from water: Adsorption performance and mechanisms

Porous biochar derived from discarded corn stalks was developed as a regenerable adsorbent for treating Tl-containing wastewater. The Tl adsorption capacity of Fe–Mn–Y doped biochar (FMYBC) was significantly enhanced compared to unmodified biochar. The IPD model accurately described Tl(I) adsorption on FMYBC, indicating that intraparticle diffusion is a key controlling step. Removal efficiency remained largely stable over a broad initial pH range of 3–13. Doping with rare earth elements markedly improved the adsorption performance of Fe Mn modified biochar under acidic conditions. However, the presence of coexisting ions (Na + , Mg 2+ , Ca 2+ ) reduced FMYBC's Tl + adsorption capacity. After two adsorption–desorption cycles, MFYBC retained 86.4% of its initial Tl removal capacity, demonstrating good stability and regeneration potential. Based on XPS and FTIR analyses, the primary Tl(I) removal mechanisms include ion exchange, surface complexation, and oxidation.