Novel sulfhydryl functionalized covalent organic frameworks for ultra-trace Hg2+ removal from aqueous solution

Abstract

• Two novel sulfhydryl functionalized covalent organic frameworks was prepared. • The sulfhydryl groups on COFs skeleton behave as effective sites for Hg 2+ removal. • Two environment-friendly sulfhydryl modifiers have been successfully applied. • COFs adsorbents have the advantages of moderate adsorption capacity and low-cost. • COFs adsorbents have potential for Hg 2+ removal in real wastewater treatment. Two kinds of novel sulfhydryl functionalized covalent organic frameworks were fabricated as adsorbents for the removal of ultra-trace concentrations of Hg 2+ from water. The two kinds of sulfhydryl functionalized covalent organic frameworks were obtained via a thiol-ene click reaction between the thiol groups of trithiocyanuric acid (TTC) or bismuththiol (BMT) and vinyl groups on the surface of covalent organic frameworks. The material structure was characterized by XRD, SEM, EDS, FT-IR, BET, and TG analysis. Due to their rich sulfur content, both adsorbents (COF-SH-1 and COF-SH-2) exhibited a high level of selective Hg 2+ removal from aqueous solution with maximum adsorption capacities of 763.4 mg g −1 and 526.3 mg g −1 , respectively. Furthermore, in the presence of ultra-low concentrations of Hg 2+ both materials exhibited excellent performance, achieving rapid Hg 2+ removal at concentrations from 10 μg L −1 to less than 0.02 ng L −1 . Analysis of the adsorption mechanism indicates that the sulfur containing chelating groups exhibit a strong binding capacity for Hg 2+ . Results show that the structure determines the performance, with the amount of adsorption sites being related to the adsorption capacity. Therefore, as sulfhydryl functionalized covalent organic frameworks contain an abundance of adsorption sites, these materials can effectively achieve the removal of ultra-low trace Hg 2+ concentrations and have promising future application potential for the environmental detection of heavy metals.