Synergistic enhancement in ultra-trace thallium(I) removal using the titanium dioxide/biochar composite

• Published in: Journal of environmental management Vol. 375; p. 124274
• Main Authors: Huang, Juanxi, Mo, Jianying, Deng, Ziyi, Deng, Yirong, Mai, Shenglin, Xie, Yuan, Zhong, Canbin, Long, Jianyou, Zhang, Gaosheng, Zhang, Ling, Xiao, Tangfu, Li, Huosheng
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2025
• Subjects: Adsorption; Biochar; cation exchange; Charcoal - chemistry; Drinking water; environmental management; potassium; Remediation; river water; surface area; Thallium; Thallium - chemistry; titanium; Titanium - chemistry; titanium dioxide; toxicity; wastewater; Wastewater - chemistry; Water Pollutants, Chemical - chemistry; Water Purification - methods; Thallium; Drinking water; Remediation; Adsorption; Biochar
• ISSN: 0301-4797; 1095-8630; 1095-8630
• DOI: 10.1016/j.jenvman.2025.124274

Thallium (Tl), recognized for its high toxicity, is subject to stringent international regulations regarding its permissible concentrations at ultra-trace levels. In this study, titanium dioxide (TiO2) was integrated with potassium (K)-rich biochar to create TiO2/biochar (TiO2/BC) composites for synergistic enhancement in ultra-trace Tl(I) removal, focusing on achieving concentration below the rigorous local threshold of 0.1 μg/L for drinking water. The Tl(I) adsorption behavior of TiO2/BC was thoroughly investigated, along with characterizing the mechanisms behind Tl(I) removal. The material prepared at a TiO2/BC mass ratio of 1:2 demonstrated high efficiency in lowering Tl(I) concentrations, showing resilience against interference from coexisting ions at concentrations ranging from 1 to 100 mM. Actual wastewater from polluted river water containing Tl was successfully treated to meet regulatory limits, highlighting the practical applicability of the composites. The composites displayed a remarkable maximum adsorption capacity of 1152 mg/g at a material dosage of 0.1 g/L, surpassing most materials reported. The underlying Tl(I) removal mechanisms include inner-sphere surface complexation, cation exchange between K+ and Tl+, and electrostatic adsorption. Superior to individual components, the TiO2/BC composite benefits from an enlarged specific surface area and K⁺-based ion-exchange interactions. Tl capture was also found to have a linearly positive correlation with the K release from the composites. Overall, this study contributes to a better understanding of the interaction between titanium oxides and K-rich biochar, offering a promising approach for remediating water sources contaminated with ultra-trace levels of Tl. [Display omitted] •Efficient Tl(I) removal by TiO2/biochar composite: maximum capacity = 1152 mg/g•Effluent Tl(I) concentration <0.1 μg/L in both synthetic and actual wastewater•The TiO2/biochar composite has good resistance to coexisting matrix•Synergism between K-rich biochar and TiO2 enhances ultra-trace Tl(I) removal•Main mechanisms include surface complexation and K+-Tl+-based ion exchange