Facile fabrication of Cu-exchanged ZnS nanoadsorbents for highly efficient removal of contaminants

Cu(I)-exchanged ZnS nanoadsorbents having highly efficient adsorption performances toward cationic dyes and heavy metals have been fabricated via facile cation exchange using pristine ZnS nanostructures as templates. Their surface properties such as surface charges and areas have been controlled by adjusting the molar ratio of Cu to Zn(R-Cu/(Zn)). The adsorption efficiency of Cu-exchanged ZnS nanoadsorbents is highest at a R-Cu/(Z)n value of 0.4 because the net surface charges of the nanocomposites resulting from the substitution of Cu(I) ions for Zn(II) ions in the ZnS lattice are electronically most negative. Both the surface areas and the total pore volumes of Cu-exchanged ZnS nanocomposites are also largest at a R-Cu/(Zn) value of 0.4, supporting that Cu-exchanged ZnS (R-Cu/(Zn) = 0.4) nanocomposites have the largest adsorption capacities of cationic dyes. The kinetics and isotherms of adsorption and the effects of various parameters such as concentration, pH, and time on the adsorption process have been also investigated in detail; the adsorption of Cu-exchanged ZnS nanorods shows the Langmuir isotherm model with the maximum capacities of 86.6, 57.0, and 53.1 mg g(-1) for rhodamine B, Co(II), and Ni(II), respectively. The adsorption of cationic dyes to our nanoadsorbents is mainly driven by attractive electrostatic interactions while van der Walls forces also play a role. The composite nanorods have high stability as well in spite of successive reuse. Overall, our prepared Cu-exchanged ZnS nanoadsorbents are suggested to have great potential applicability in the treatment of wastewater containing cationic dyes or heavy metals.