Highly efficient capacitive removal of Cd2+ over MoS2-Carbon framework composite material in desulphurisation wastewater from coal-fired power plants

Abstract

Cadmium (Cd2+) is the main toxic heavy metal in desulphurisation wastewater for coal-fired power plants. Here, a novel carbon skeleton/molybdenum disulphide composite material (MoS2/AC) with expanded layer spacing was synthetized in one step for Cd2+ removal through the capacitive deionization method. As the results showed, the Cd2+ removal capacity of the MoS2/AC cell was 22.15 mg g−1, and the concentration of Cd2+ in the simulated wastewater was effectively reduced from 10 ppm to <0.1 ppm. According to the characterisation, the layer spacing of MoS2 nanosheets in MoS2/AC increased by 58.06% compared with the original commercial MoS2, which could provide more active sites for Cd2+ adsorption. Moreover, the XPS results showed that electrosorption and complexation on the surface of MoS2/AC were the main routes for Cd2+ removal, especially the complexation between Cd2+ and metal-sulphur. In addition, the selective adsorption efficiency of MoS2/AC was more than 98% under the coexistence of other ions, such as Na+, Mg2+, and Ca2+. The regenerated MoS2/AC also had a high adsorption capacity for Cd2+ even after 5 cycles. The MoS2/AC material also exhibited excellent removal capability for heavy metal ions in the actual desulphurisation wastewater from coal-fired power plants (<1 ppb). The results indicated that MoS2/AC may be a prospective material for heavy metal ion removal from wastewater.