Insight into selective removal of trace thallium (Tl(Ι)) by novel chitosan adsorbents encapsulating low-cost silicate...

Recently, thallium (Tl) contamination at trace levels has gained worldwide attention, particularly in the remote ore-smelting regions of China. To effectively eliminate the residual target Tl(I) ions, one of the best strategies is to develop novel adsorbents with high selectivity. In this study, we selected silicate mineral waste (SMW) and chitosan (CTS) to synthesize a low-cost composite adsorbent for the removal of trace Tl(I). The results show that a mass ratio for SMW to CTS was optimized as 3:1 (denoted as SMW@CTS), and the preferred SMW@CTS exhibited a 37% higher removal efficiency compared to pure CTS beads (19%), underscoring the critical role of SMW in enhancing trace-level adsorption of Tl(I). Under the optimal conditions of 25 °C, pH = 5, and 6 g/L dosage, SMW@CTS achieved a Tl(I) removal efficiency of approx. 89% for an initial concentration of 100 μg/L. Moreover, the thermodynamics for the adsorption of Tl(I) onto SMW@CTS were investigated, and the structural characteristics of SMW@CTS were also characterized in detail. Furthermore, the mechanism for the high selectivity of Tl(I) onto SMW@CTS has been explored in the presence of humic acid and a series of competing ions. These findings highlight the novel SMW@CTS as a promising candidate for eliminating trace-level Tl(I) contamination from co-existing substances.