Electrodeposition of Nickel from Sulfamate Effluents

Abstract

Nickel sulfamate (amidosulfonate) solutions are widely used for industrial nickel plating, when bright electrodeposits with low stress are required. Partial decomposition of sulfamate with decreasing pH below ca. 2.5 degrades the properties of nickel electrodeposits, decreases charge yields and results in spent solutions, from which nickel must be recovered before they could be discharged to sewers. Results are reported for charge yields for nickel recovery from industrial sulfamate effluent, using an electrochemical reactor operating at constant current in batch recycle mode, and incorporating a nickel mesh cathode, platinised titanium anode and cation-permeable membrane to prevent anodic oxidation of sulfamate. The decrease in the charge yield from 0.99 after 3 hours to ca. 0.5 after 14 hours, resulted primarily from time-dependent catholyte pH, due to anodic oxygen evolution causing the ratio of proton to sodium ion transport through the membrane to increase with time.