Electrochemical reduction of nitrate and nitrite in simulated liquid nuclear wastes.
The electrochemical reduction of nitrate and nitrite in simulated low-level nuclear wastes containing 1.8 M NaNO(3)+0.55 M NaNO(2)+1.16 M NaOH was studied under galvanostatic polarization on tin and bismuth cathodes. The rate of the reduction of nitrate was about the same on both metals. The selectivity (%S) to ammonia was similar on the two metals (12% at 450 mA/cm(2)) and that to nitrogen 82% on Sn and 72% on Bi. On the other hand, the %S to nitrous oxide was lower on Sn (8%) than that on Bi (18%) under the same conditions. The current efficiency (%CE) on both metals was 80% when the 99% of the initial nitrogen was removed. The %CE gradually decreases as the concentration of the nitrogen containing species in the solution decreases during the electrolysis. The energy consumption for the removal of 1g of N was 100 Wh at 450 mA/cm(2) but it can be significantly reduced by a better design of the electrolysis cell.The presence of chromate in the electrolyte, which is a known inhibitor of the cathodic reduction of nitrate, has no influence on the rate of the reduction and the distribution of the products.
Katsounaros
I
I
Department of Chemical Engineering, Laboratory of Inorganic Chemistry, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece.
Dortsiou
M
M
Kyriacou
G
G
D000641:Ammonia / Q000737:chemistry; D001729:Bismuth / Q000737:chemistry; D002840:Chromates / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods*; D004572:Electrolysis; D004573:Electrolytes / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D008956:Models, Chemical; D009566:Nitrates / Q000737:chemistry*; D009573:Nitrites / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D011850:Radioactive Waste; D014001:Tin / Q000737:chemistry; D014865:Waste Disposal, Fluid; D018508:Water Purification
D002840:Chromates; D004573:Electrolytes; D008670:Metals; D009566:Nitrates; D009573:Nitrites; D011850:Radioactive Waste; D014001:Tin; D000641:Ammonia; D009584:Nitrogen; D001729:Bismuth