Triazine-based N-rich porous covalent organic polymer for the effective detection and removal of Hg (II) from an aqueous solution

Abstract

Triazine-based N-rich covalent organic polymer (TBN-1) was prepared for effective removal and selective detection of Hg2+ from model solutions. The π-π conjugated structure formed by alternating electron-deficient triazine group and electron-rich benzene group promotes the electron transfer and strong fluorescence. The ultra-high specific surface area and abundant metal complex groups provide excellent adsorption sites for heavy metals. The TBN-1 suspension has obvious fluorescence quenching effect when encountering Hg2+ even when the solutions are treated with co-ions and humic acid. The merits of TBN-1 are unreservedly manifested when further testing the adsorption kinetics of TBN-1 for Hg2+ removal. With the maximum adsorption capacity of 1630 mg g−1, 99.99% of Hg2+ can be removed within 20 min from a 10 ppm solution using TBN-1. The covalent organic polymer (COP) also exhibits a high stability in a wide range of pH and a significant selectivity for Hg2+. About 99.9% Hg2+ can be adsorbed in acidic, co-ions competitive and humic acid contaminated solutions. The TBN-1 can be also reused for at least 5 cycles with acceptable Hg2+ adsorption capacity retention. The mechanism for the excellent Hg2+ adsorption performance of TBN-1 is revealed by coupling physico-chemical model fitting, chemical computation, and experimental characterization, which indicates the coordination and cation-π effects and high electron density of the material to facilitate its complexation with Hg2+. This work offers new prospects for the application of triazine-based COPs for environmental remediation.