Corrosion-resistant membrane electrode for the selective capture of Co2+ from Ca2+-rich, acidic wastewater from nuclear decommissioning process

Abstract

During decommission or replacement of nuclear power plants, more than 60% of produced wastes are from surface contaminated or radio-activated concretes. To clean-up these contaminated concrete wastes, acid decommissioning process is widely used to separate radioactive isotopes such as 60Co2+ and 152Eu3+ from crushed concrete particle and then transferred to acidic solutions with plenty amount of Ca2+. To reduce the total amount of radioactive waste, the electrochemical reduction and mineralization process using corrosion-resistive, carbon nanotube based membrane electrode (CR-CME) is investigated in this study for the selective capture of Co2+ from Ca2+-rich acidic leachate. Under the applied voltage of -1.0 V (vs. SCE) and flux of 80 LMH, CR-CME kept its Co2+ removal efficiency higher than 99.7 % in the range of 0.1mM ~ 0.5 mM Co2+ with 0.5 M Ca2+ and pH 2. The maximum Co2+ removal capacity was 69.1 mg/g with 80 LMH of flux until the pores of CR-CME were blocked by the mineralized Co, while CR-CME used with representative electrochemical mineralization condition showed only 27 % and 19.6 mg/g of removal efficiency and capacity, respectively. In addition, the removal capacity of CR-CME was easily restored after the washing of deposited Co by acid such as HNO3. The current results showed that the membrane-type electrode applied electrochemical mineralization system can selectively remove Co2+ from Ca2+-rich acidic leachates generated during decommissioning of radio-activated concrete wastes.