Direct Electrodeposition of Ga and the Simultaneous Production of NaOH and NaHCO3 from Carbonated Spent Liquor by Membrane Electrolysis

Abstract

The direct electrodeposition of Ga from carbonated spent liquor is proposed by membrane electrolysis with the simultaneous production of NaOH and NaHCO3. The effects of electrolysis time, current density, and mechanical agitation on current efficiency (CE) are studied. Metallic Ga is successfully electrodeposited from synthetic liquor with a very low Ga concentration by using a Ga-coating cathode. The current efficiency for NaOH production decreases with the electrolysis time. After 13 h of electrolysis, the concentration of NaOH rose to 109 g L–1. The current efficiency for NaHCO3 production is almost constant in the first 8 h, and the value is about 74%. Then, the current efficiency decreases rapidly due to the accelerated formation of CO2. The largest concentration of NaHCO3 is about 108 g L–1. Ga electrodeposition is affected obviously by an additive (FC-95), the current density, and mechanical agitation. In carbonated spent liquor, 97.9% of Ga can be electrochemically extracted.