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

Abstract

Sulfur-containing materials are very attractive for the efficient decontamination of some heavy metals. However, the effective and irreversible removal of Cd 2+ , 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 Cd 2+ into a stable Zn x Cd 1-x S solid solution, rather than into CdS. This can be realised through the adsorption of Cd 2+ by ZnS nanoparticles, which have exhibited a Cd 2+ uptake capacity of approximate 400 mg g −1. Through this adsorption mechanism, the Cd 2+ 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 Cu 2+ , Pb 2+ , and Hg 2+. ZnS displayed high chemical stability. Particles aged in air for 3 months still retained a > 80% uptake capacity for Cd 2+ , compared with only 9% uptake capacity for similarly-aged FeS particles. This work reveals a new mechanism for Cd 2+ removal with ZnS and establishes a valuable starting point for further studies into the formation of solid solutions for hazardous heavy metal removal applications.

Efficient arsenic removal by a bifunctional heterogeneous catalyst through simultaneous hydrogen peroxide (H2O2) catalytic oxidation and adsorption

“…The pseudo-first-order model (Eq. 5) was used to simulate the dynamics of As(III) removal (Wang et al 2020).…”

Aqueous Adsorption of Heavy Metals on Metal Sulfide Nanomaterials: Synthesis and Application

“…ZnS NCs often have a higher adsorption capacity and are more stable than similar FeS NCs. Wang et al [118] investigated Cd 2+ adsorption with FeS and ZnS, observing that FeS and ZnS had adsorption capacities of 116 and 401 mg/g for Cd 2+ , respectively. While ZnS takes longer to reach equilibrium, it has a more effective and stable removal effect.…”

“…The higher capacity of zinc sulfide may be partly because of the ease with which zinc (E 0 = −0.763) can undergo cation exchange and other interactions with HMs via electrons transfer due to it being a more reactive metal than iron (E 0 = −0.440). For practical applications in engineered remediation, a low re-release rate of contaminants and high chemical stability are required [118]. With ZnS, no significant amount of captured Cd 2+ was released after shaking with ultra-pure water for 24 h the and aged ZnS could still achieve >80% removal efficiency of Cd 2+ , significantly greater than those achieved by FeS.…”

Novel and highly efficient functionalized bentonite for elimination of Cu2+ and Cd2+ from aqueous wastes

“…The removal of Cd 2+ , Cu 2+ , Pb 2+ and Hg 2+ by ZnS and FeS nanomaterials was 99% in mixed metal cation solutions in presence of 60 fold concentrations of Ca 2+ and Mg 2+ . Hence the presence of other cations have negligible or no effect on the toxic metal removal using metal-sulfide nanomaterials [69]. In other study, the elimination of Cd 2+ by MnO 2 loaded D301 showed no significant effect in presence of several cations (Na + , K + and Ca 2+ , or Mg +2 ) and anions ( Cl − , NO 3-, SO4 2− and PO 4 presence of EDTA on the sorption of Cd 2+ and Zn 2+ by apatite showed a decrease in the uptake of Cd 2+ and Zn 2+ due to the formation of [CdEDTA] 2and [ZnEDTA] 2complexes [71].…”