The selective depression effect of dextrin on pyrite during the Zn–Fe sulfides flotation under low alkaline conditions

As an environmentally friendly scale inhibitor, characterized by low cost, high efficiency and no secondary pollution, dextrin was utilized as a depressant in the flotation separation of mixed Zn-S concentrate. The microflotation results clearly demonstrate that dextrin exerted a good inhibitory effect on pyrite and sphalerite could be separated successfully from pyrite in low alkaline environment. The mixed mineral flotation results further indicate that sphalerite could be efficiently separated from its synthetic mixture with pyrite via the use of dextrin as the depressant in the pH range of 7–9. The contact Angle test shows that dextrin can be adsorbed on the surface of Cu-activated pyrite to enhance hydrophobicity, but not on the surface of Cu-activated sphalerite. The results of infrared spectroscopy investigations and XPS analyses indicate that under low alkali conditions, copper ions activate sphalerite, and copper sulfide polysulfide forms on sphalerite surface without Cu(OH)2 formation. Cu(OH)2, Fe(OH)2 and CuS were generated on pyrite surface due to the activation of copper ions. The adsorption between dextrin and metal hydroxyl compounds was the main cause of pyrite inhibition， which is attributed to the hydrophilic hydroxyl group in the dextrin molecule. According to these results, dextrin can be used as a selective depressant for pyrite during sphalerite flotation in low alkaline environment. © 2022 Elsevier B.V.