Auxiliary electrodialysis realizes over 50 times concentration of nuclide ions from liquid effluents of nuclear power plants

Rapid and highly effective enrichment of nuclides containing liquid effluent is crucial for online monitoring of radioactive trace elements from nuclear power plants (NPPs). In this study, auxiliary electrodialysis (AED) was proposed for high enrichment of trace ions in the liquid effluents of NPPs. The effects of the auxiliary ion type and concentration and the operating voltage on the AED concentration performance were investigated. When the volume ratio of the solution was 140: 1 with 0.03 mol/L HNO3 as the auxiliary electrolyte, most of the nuclide ions were concentrated more than 50 times after the two-stage electrodialysis experiment. In the first-stage electrodialysis, the concentration of most ions, with the exception of the higher valence ions (Ru3+ and Zr4+), tends to increase with increasing operating voltage. The diluate stream volume could be minimized to 98.8% with a total energy consumption of 9.5 kWh/m3. By considering the impact of boron in the liquid effluents, more than 52 times concentrations could still be achieved by extending the running time of the first-stage ED (increasing the ion removal rate). The transmembrane fluxes of various cations decreased in the order of Cs+ > Sr2+ > Zn2+ > Co2+ ≈ Ni2+ ≈ Mn2+ > Fe3+ > Cr3+ > Ru3+ > Zr4+, which is attributed to the experimental operating parameters and ionic properties. This research provided a viable technique for rapid and highly effective enrichment of nuclides containing liquid effluents for both radioactive element monitoring and wastewater volume reduction.