Selective flotation separation of smithsonite from calcite by using cupferron

Considering that smithsonite has a similar crystal structure to calcite, more selective collectors are required to achieve its flotation separation. In this study, a new collector, cupferron, was used for the selective flotation of smithsonite from calcite. The selective mechanism of the effect of cupferron was investigated by FTIR analysis, zeta potential experiments, adsorption measurements, and DFT studies. Results of the microflotation test showed that the flotation recovery of smithsonite was 90.45 % at pH 8.0 with 10 x 10-4 mol/L of cupferron, whereas the flotation recovery of calcite was lower than 15.00 %. The FTIR results demonstrated that the cupferron was chemisorbed on the surface of smithsonite through a five-membered chelate ring formed with zinc atoms, whereas the adsorption on the surface of calcite was weak. The results of the zeta potential test further indicated that the cupferron was adsorbed selectively on the surface of smithsonite, whereas almost no adsorption was observed on the surface of calcite. In addition, the adsorption amount test results illustrated that the adsorption amount of cupferron on the surface of smithsonite was higher than that on the surface of calcite, which led to the difference in the flotation recovery of smithsonite and calcite under the same conditions. The results of the DFT study proved that the adsorption energy of cupferron acting on the surface of smithsonite is lower than that on the calcite surface. Moreover, the stronger covalent nature of Zn-O2 bonds than Ca-O2 bonds is responsible for the selective collection of smithsonite from calcite by cupferron. Therefore, cupferron can be applied as a potential collector for the flotation separation of smithsonite from calcite. Meanwhile, this study also provides a reference for the development of collectors for the flotation separation of smithsonite and calcite.