Sulfide-occluded zeolites: Cooperative adsorption-precipitation system for near perfect decontamination of aqueous Hg species

Abstract

Sulfide-occluded zeolites could allow both adsorption reaction of zeolites and precipitation reaction of sulfides to operate within one system, which leads to synergic effects on removal of toxic cationic heavy metals from aqueous systems. Here we proved that near complete decontamination of aqueous Hg cations bellow WHO guideline level of 1 ppb could be accomplished with sulfide-occluded zeolites. Interestingly, adsorption of cationic Hg species resulted in the formation of discrete HgS crusts on the surfaces of the zeolite crystals. TEM and Hg removal isotherms strongly indicated that the HgS crust played a crucial role not only in preventing the back-release of adsorbed Hg species but also in scavenging residual aqueous Hg species. Therefore, in-situ cooperation of adsorption and precipitation reactions performed by sulfide-occluded zeolites could be applied to reliable and safe Hg decontamination of aqueous systems.