A novel method for the separation of zinc and cobalt from hazardous zinc–cobalt slag via an alkaline glycine solution

Abstract

Abstract Zinc–cobalt slag, a hazardous waste from hydrometallurgical zinc smelting, is an important secondary source of cobalt; however, the separation of zinc and cobalt is a serious problem in cobalt recovery. A novel approach was proposed to separate zinc and cobalt via an alkaline glycine solution. This innovative method selectively dissolves zinc and cadmium from the slag with a high yield, leaving most of the cobalt and manganese in the residue. The dissolution ratios of zinc and cadmium are 93.81% and 87.64%, respectively, under optimal conditions (pH 10, 45\xa0°C, glycine concentration of 100\xa0g/L, L/S ratio of 40:1, and a reaction time of 180\xa0min). In contrast, the dissolution ratios of cobalt and manganese are almost negligible. Substantial separation of zinc and cobalt occurred as the separation factor reached a value of 736.8. The recovery of zinc and cadmium from the glycine leachate was accomplished by precipitation with an oxalic acid solution, and the precipitation ratios were 97.7% and 99.0%, respectively. The use of glycine as the leaching agent successfully separated zinc and cobalt, which allowed for the recovery of cobalt, and also enabled the recovery of zinc and cadmium.