Abstract
It is significant to develop functional materials with high selectivity, high adsorption capacity and easy separation to reduce thallium (Tl) pollution caused by human activities. Polysaccharide-based cyanide-bridged bimetallic coordination polymers (PCBPs) were developed for the removal of Tl(I) and Tl(Ⅲ) simultaneously, and the effects of lists of conditions on the removal of Tl showed that the maximum adsorption rate of Tl reached 98.3 % after 180 min. Meanwhile, the stable adsorption efficiency of Tl could be maintained in a wide range of pH. Moreover, even in the interfering system where high-intensity cations and total organic matter coexist, PCBPs still showed excellent Tl removal efficiency. Notably, the amphoteric structure of PCBPs provided many chemical chelation sites, significantly improving the adsorption capacity of PCBPs for Tl. Importantly, XRD, SEM, TEM, BET, and magnetization tests show that PCBP has a large pore and specific surface area, stable structure, and recyclable magnetic characteristics conducive to the adsorption of thallium. More importantly, the π-π conjugation and chelation of the above functional groups with Tl(I) and Tl(Ⅲ) were well confirmed by FT-IR and XPS for their adsorption mechanism. What is more, the adsorption isotherm and kinetics agreed with the Freundlich model and the pseudo-second-order model, respectively, indicating that the adsorption of Tl was a multi-layer chemical adsorption process. Besides, the Gibbs free energy was negative, indicating that the adsorption process of Tl was spontaneous. Therefore, the polysaccharide-loaded ferric ferrocyanide coordination polymer exhibited high-efficiency and selectivity removal of Tl(I) and Tl(Ⅲ), which would provide technical support and theoretical guidance for the treatment of thallium-containing wastewater.
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