Highly efficient and irreversible removal of cadmium through the formation of a solid solution.

• A novel strategy was proposed to efficiently and irreversibly remove Cd2+. • A new mechanism for the removal of Cd2+ with ZnS was confirmed. • Formation of a solid solution instead of CdS plays a predominant role in the removal process. • Solid solution possesses better thermodynamic stability than CdS. Sulfur-containing materials are very attractive for the efficient decontamination of some heavy metals. However, the effective and irreversible removal of Cd2+, coupled with a high uptake efficiency, remains a great challenge due to the relatively low bond dissociation energy of CdS. Herein, we propose a new strategy to overcome this challenge, by the incorporation of Cd2+ into a stable Zn x Cd 1-x S solid solution, rather than into CdS. This can be realised through the adsorption of Cd2+ by ZnS nanoparticles, which have exhibited a Cd2+ uptake capacity of approximate 400 mg g−1. Through this adsorption mechanism, the Cd2+ concentration in a contaminated solution could effectively be reduced from 50 ppb to <3 ppb, a WHO limit acceptable for drinking water. In addition, ZnS continued to exhibit this noteworthy uptake capacity even in the presence of Cu2+, Pb2+, and Hg2+. ZnS displayed high chemical stability. Particles aged in air for 3 months still retained a> 80% uptake capacity for Cd2+, compared with only 9% uptake capacity for similarly-aged FeS particles. This work reveals a new mechanism for Cd2+ removal with ZnS and establishes a valuable starting point for further studies into the formation of solid solutions for hazardous heavy metal removal applications. [ABSTRACT FROM AUTHOR]