Effect of precipitation conditions on the growth of cobalt oxalate grains during recycling of cemented carbide scrap

Abstract

Electrolysis process was used to recover WC particles from scrap cemented carbide WC-25%Co and the cobalt oxalate precursors were prepared simultaneously. The effects of precipitation conditions including pH and CTAB on the growth of cobalt oxalate crystal were investigated. The experimental results indicate that the precipitation conditions have significant effect on the surface morphology, particle size and agglomerative circumstances of cobalt oxalate precursors during the recycling process of cobalt from cemented carbide scrap. The original hydrogen bonds could gradually transform into amino coordination bonds with increasing pH level leading to optimized crystallinity degree of cobalt oxalate. However, the recovery rate decreased with pH over 5.0 due to the decreased deposition efficiency of cobalt oxalate. The addition of surfactant CTAB can prevent the agglomeration of cobalt oxalate with the effect of hydrophilic group and hydrophobic group of CTAB. The optimum parameters to prepare WC and cobalt oxalate are: current density = 95 mA cm−2, pH = 5.0 and CTAB = 0.75 wt%. Under this condition, the recovery rate of WC and Co reached 98.25% and 92.81%, respectively.