Investigation of electrochemical oxidation technology for selective bromine extraction in comprehensive utilization of concentrated seawater

Comprehensive utilization of concentrated seawater is a significant means to promote the development of the desalination industry, and then effectively relieve the freshwater crisis in coastal areas. Bromine exists in (concentrated) seawater as the main element, and is an important basic chemical. Its extraction becomes an important aspect of comprehensive utilization of concentrated seawater. Selective oxidation of bromide using a three-electrode system and an electrolyzer, was applied to extract bromine from concentrated seawater. It was feasibility for selective oxidation of bromide at the anode potential between 1.0 V and 1.5 V (with respect to the standard hydrogen electrode, SHE). Within this potential range, the formation of bromine was favored over that of chlorine and oxygen with the graphite rod electrode used in this study. Chloride was difficult to be oxidized at the selected anode potential (1.350 V vs. SHE) even though its concentration was very high. Both chloride and sulfate as coexisting ions showed a promoting effect on the electro-oxidation of bromide due to their contribution to the total conductivity of the solution. However, hardness ions such as calcium ion and magnesium ion had little effect on selective oxidation of bromide. Taking yield of bromine, current efficiency and energy consumption into overall consideration, operation time from 4 h to 10 h might be optimal in the process of treating concentrated seawater.