A new strategy for selective recovery of low concentration cobalt ions from wastewater: Based on selective chelating precipitation-flotation process

Abstract

BackgroundA significant amount of low-concentration heavy metal ion wastewater is generated daily by the mining and metallurgy industry, endangering human health and the environment. A novel method of selective chelating precipitation–floatation of copper and cobalt ions is proposed for the recovery of cobalt from wastewater. MethodsBased on the chelation of cobalt and copper ions with α-nitroso-β-naphthol (NN), the flotation process is adopted to solve the problem of fine particle separation from solution in low-concentration ions removal. Significant findingsUnder the optimized precipitation flotation conditions, the flotation recovery ratios of the copper, cobalt, and zinc ions were found to be 98.47%, 42.48%, and 9.35%, respectively, and the separation effect of cobalt and zinc showed to be outstanding, as their separation factor reached 598. Industrial wastewater also has a good flotation separation effect. Based on the mechanism studies, Co2+/Co3+ and Cu2+ were selectively chelated by NN to form hydrophobic NN-Co/Cu precipitation particles. Moreover, electrostatic attraction is the main force in the proposed flotation process. Eventually, we tried calcination to recycle the flotation products to verify the potential of the cobalt–copper composite oxides in capacitor materials. The results prove that the precipitation–flotation method has great efficiency and potential for selectively recovering low-concentration metal ions and separating fine particles from solution.