Highly efficient removal of trace thallium from surface water by Co@Fe Prussian blue analogue coated membrane

• We develop an adsorptive membrane for highly efficient Tl + removal; • The new membrane has superior removal efficiency for ultralow concentration of Tl + ; • Mechanisms on the superior Tl + removal efficiency of the membrane are explored; • Ion exchange and intercalation contribute to the highly efficient Tl + removal; • This study offers a solution for remedying ultralow Tl + contaminated surface water. Super trace thallium(I) (Tl + ) is still highly toxic and its removal from surface water is challenging. Here, we developed a new adsorptive membrane by immobilizing bimetal (cobalt and iron) Prussian blue analogues (Co@Fe-PBAs) on a polytetrafluoroethylene microporous membrane (Co@Fe-PBAs-M). The prepared membrane displayed precise adsorption of trace Tl + (50 μg/L) from complex water. A variety of interfering factors, such as water pH, competitive adsorption of positive ions (Na + and K + ) and negative ions (CO 3 2– and PO 4 3- ), natural organic matters (e.g., fulvic acid and bovine serum albumin) were evaluated during Tl removal. The composite membrane showed high removal efficiency (over 80 %) during long-term dynamic membrane separation of surface water containing super trace Tl + (<2.0 μg/L), breaking through the adsorption limitation in ultralow concentration of Tl + . The unique bimetal electron transfer of Co@Fe-PBAs-M reinforced the adsorptive performance to Tl + through dual ion exchange and intercalation. In the treatment of real Pearl River water containing 0.5 μg/L of Tl + , our membrane effectively reduced the Tl + concentration to 0.04 μg/L during 6-h continuous separation, which was far below the required level for drinking water (i.e., 0.1 μg/L). This work offers a promising solution for safe drinking water by remedying ultralow Tl + contaminated surface water.