Self-templated formation and characterization of polyhedral CoS hollow nanocage (HNC) for heavy metal ions (Ag+, Cd2+, Cu2+, Pb2+ and Zn2+) removal in aqueous solutions

The contamination of water by heavy metal ions can easily cause serious environmental problems and damage to the human body hands down. Using zeolitic imidazolate framework-67 (ZIF-67) as a sacrificial template, polyhedral CoS hollow nanocages (HNC) were successfully synthesized by self-template approach as adsorbents for heavy metal ions removal. The CoS HNCs suggested good chemical stability and extremely efficient heavy metal ions removal of Ag + , Cd 2+ , Cu 2+ , Pb 2+ and Zn 2+ , which can be ranked in the order of Ni 2+ ≪ Zn 2+ , Cd 2+  < Pb 2+ , Cu 2+ , Ag + . The saturation adsorption for Ag + reached 2147.944 mg g −1 and exhibited high distribution coefficients (K d ) > 107 mL g −1 . The CoS HNCs can rapidly reduce the Ag  +  concentration from ppm level to trace level of 1 ppb. It has been proved that the rapid and selective adsorption was achieved via the hierarchical pore structure of the CoS HNCs can better disperse these metal vacancies with super affinity and the S 2− , reduce the mass transfer distance and accelerate mass transfer. It is expected that such a CoS HNCs could be a promising alternative to conventional materials for the adsorption of heavy metal ions.