Highly selective removal of Hg(II) ions from aqueous solution using thiol-modified porous polyaminal-networked polymer

Abstract An efficient porous organic polymer (POP)-based adsorbent (4AS-MBP), synthesized from melamine, 4-allyloxy benzaldehyde and ethanedithiol (EDT) via a Schiff-base reaction and thiol–ene addition in a straightforward strategy, was prepared to remove Hg(II) ions from water. The chemical structure and morphology of 4AS-MBP were investigated by FT-IR, solid-state 13C NMR, EA, SEM, TEM and BET analysis. Adsorption experiments were conducted by varying the Hg(II) concentration, contact time and pH to study the adsorption kinetics and equilibrium. Mesoporous 4AS-MBP exhibited a maximum adsorption capacity of 312 mg g−1. The results indicated that Hg(II) adsorbed onto the adsorbent through monolayer chemisorption. Interestingly, 4AS-MBP was highly stable, even in the presence of 2 M NaOH or HCl, and displayed similar adsorption capacities over a wide pH range. Furthermore, the adsorbents could be reused at least five times without a loss of adsorption capacity. More importantly, the relative selectivity coefficients of 4AS-MBP for Hg()/Pb(II), Hg(II)/Cd(II), Hg(II)/Cu(II), Hg(II)/Zn(II) and Hg(II)/Mg(II) were 54.3, 221, 243, 468 and 823, respectively.