High-performance sulfur-rich COF/PTFE composite membrane for the efficient removal of Hg(II) from acidic wastewater

Covalent organic frameworks (COFs) have emerged as advanced materials for addressing heavy metal pollution in acidic environments. However, powdered COF adsorbents face challenges such as poor operability and a tendency to agglomerate, limiting their industrial wastewater treatment applications. In this study, we prepared a sulfur-rich COF-OSH/mPTFE composite membrane through in situ growth and subsequent modification of COFs on the surface of amino-functionalized PTFE porous membranes. The COF-OSH/mPTFE composite exhibits a remarkable adsorption capacity for mercuric cations (Hg2+), reaching 223.5 mg/g. Notably, even at pH 1, the adsorption capacity remains high at 68.9 mg/g. The adsorption process demonstrates excellent resistance to interference from Na+ and Ca2+ ions and shows good reusability. Furthermore, COF-OSH/mPTFE reduced the concentration of Hg2+ in a 100 mL solution (5 mg/L) by over 80 % within 13 min at pH 5, and by over 40 % at pH 2. Even after continuous treatment of 20 L of Hg2+ solution, a significant reduction in Hg2+ concentration in the filtrate was still observed. The COF-OSH/mPTFE composite membrane addresses the cleanliness and recovery issues associated with powdered adsorbents in adsorption environments. The simple, efficient, and low-energy filtration process endows COF-OSH/mPTFE with excellent capability for treating acidic wastewater containing Hg2+.