Work

Enhanced thallium(I) removal from wastewater utilizing biochar derived from high-potassium fruit peels

Year: 2025

Type: article

Abstract: Biochar derived from fruit peels can effectively remove thallium (Tl) from wastewater, yet the specific role of potassium (K) in this process remains underexplored. This study focuses on K-rich biochars, particularly from banana peels, to elucidate the underlying mechanisms of Tl sequestration. The biochars were found to contain various K species, including loosely bound K in dissolvable compounds, exchangeable K cationic resin-like carbonaceous polymers, and tightly bound K in the biochar matrix. A positive correlation was observed between K release and Tl removal efficiency, indicating that ion exchange involving exchangeable K plays a dominant role in Tl uptake. Adsorption kinetics followed a pseudo-second-order model, while isotherms aligned with the Langmuir model, with a maximum adsorption capacity of 224 mg/g at pH 5.8. When applied to real acidic mine drainage containing 7.0 μg/L of Tl, the biochar reduced Tl concentrations to below 2.0 μg/L, thereby meeting local industrial discharge standards. Characterization techniques confirmed that Tl removal primarily occurred through K(I)-Tl(I) cationic exchange and chloride-mediated precipitation as insoluble thallium chloride. These findings not only highlight the efficacy of K-rich biochars for Tl remediation but also clarify the pivotal role of biochar-derived potassium in facilitating Tl removal from contaminated waters.

Source: Desalination and Water Treatment

DOI: 10.1016/j.dwt.2025.101300