High efficient and continuous recovery of iodine in saline wastewater by flow-electrode capacitive deionization

Abstract

Iodine (I) is a non-renewable and important scarce resource and an essential trace element for human body. Meanwhile, the low concentration radioactive iodine produced by the nuclear industry can cause serious harm to the environment and human beings. The purpose of this study is to investigate the removal and recovery of low-concentration iodine in wastewater by flow-electrode capacitive deionization (FCDI) technology to achieve sustainable utilization of iodine. We systematically investigate the effect of FCDI on iodine enrichment performance under different operating parameters. The results indicate that compared with Cl−, I− is preferentially removed. Cl− and I− have different removal behaviors from brackish water to brine concentration, but I− show a better removal behavior and has a higher selectivity. The iodine removal efficiency remains above 96% after continuous100 cycles under the optimal operating parameters of the FCDI unit with high charge utilization efficiency. Long-term batch experiments show that the low-concentration feed iodine solution (100 mg/L) can be effectively concentrated to 18 times after 24 h operation, with the final iodine concentration dropping to 8.2 mg/L in the feed water chamber and rising to 1818.5 mg/L in the concentration chamber. Overall, the excellent concentration effect, high removal efficiency, and low-energy consumption of the FCDI system in the iodine removal and recovery make it a promising method for the treatment of iodine-containing wastewater.