The use of electro-electrodialysis for the removal of sulphuric acid from decontamination effluents

The decontamination of reactor compounds and the treatment of the decontamination effluents are an inherent part of reactor-dismantling studies. In this context we investigated the recovery of sulphuric acid from decontamination effluents by means electro-electrodialysis (EED). To use EED, we needed to fmd out, at the highest suitable temperature, (1) which is the limiting membrane current density and maximum cathode current density for the separation, and (2) how the choice of the membrane influences these values, and the electric yield. Using a laboratory-scale EED set-up, we compared four anionic membranes: Neosepta AMH and ACM, Selemion AAV, and Solvay's AW. The limiting current density at 323 K for each membrane varied between i(m,lim) = [0.16 A cm(-2) and 0.17 A cm(-2)], the maximum cathode current density i(c,max) = 0.08 A cm(-2). For AMH, AAV and AW at a membrane current density of i(m) = 0.14A cm(-2), average proton leaks varied between 17% and 25%, and the specific energy necessary for 90% displacement of the acid varied between E = [22.6 and 25.3] x 10(5) J L-1. For the ACM membrane, a negligible apparent proton leak resulted in a specific energy of only 16.8 x 10(5) J L-1. Yet for this particular separation, in our laboratory-scale experiments, AMH possessed the best combination of electrochemical and mechanical properties.