Highly selective removal of thallous ions from wastewater using Prussian Blue biochar composite

Thallium, a highly toxic pollutant, shows greater toxicity to human than other common heavy metals such as mercury, lead, cadmium and its effective removal from wastewater gains great attention. The main restriction for the Tl⁺ removal is the interference of a high concentration of co-existing ions in wastewater. Therefore, the goal of the current work was to synthesis adsorbent with high selectivity for the Tl⁺ removal. Herein, the pore size sieving strategy was proposed and Prussian blue-impregnated biochar (BC@PB) particles was synthesized. More than 95% Tl⁺ can be removed even the concentrations of the coexistence ions (Na⁺, Cd²⁺, and Zn²⁺) 1,000 higher than the initial concentration of Tl⁺ (500 μg/L). BC@PB also showed large adsorption capacity (9365 μg/g) and more than 99% Tl⁺ (initial concentration, 500 μg/L) were removed in just 1 min. The BC@PB had excellent and stable Tl⁺ removal ability (> 99%) over a range of pH from 3 to 9, which covered the pH range of common thallium-containing wastewater. The density functional theory (DFT) calculation confirmed that not only hydrated volume but also the hydration free energy of ions, which governed the energy barrier for ions entering into narrow channels of BC@PB, played essential roles on the selectivity removal of Tl⁺. Overall, due to its high selectivity, high adsorption capacity and easy preparation process, the synthesized BC@PB particles based on the pore sizing sieving strategy, can be a promising candidate for the removal of thallium from wastewater.