Since the late 60's DIAMO, in the Czech Republic, has mined uranium via in-situ acid leaching. Sulfuric acid is injected into underground uranium deposits, dissolving the ore. The solution is then pumped to the surface where the uranium is separated from the acid. The spent acid is injected into underground caverns. Over the years this subterranean acid waste lake has grown and now threatens the local drinking water supply. Researchers at ELTECH Systems Corporation have developed an electrochemical process for Ionics Incorporated rated and their Resources Conservation Division as part of a system that will clean up 2.7 million gallons (10.2 X 10(3) M(3)/day) of sulfuric acid waste a day, recover 936 tons per day (850 mT/day) of ammonium aluminum sulfate crystals and reclaim 2 million gallons a day (7.6 x 10(3) m(3)/day) of water. The electrochemical portion of the process will convert Fe+3 in a solution of raw ammonium aluminum sulfate crystal to Fe+2, so pure ammonium alum can be crystallized. This paper discusses the engineering fundamentals used to develop the electrochemical iron reduction system for the DIAMO application. Initial work included cyclic voltammetry to characterize cathode candidates, identify significant reactions, and show feasibility. This was followed by tests at the bench scale, the intermediate scale, and finally at the Pilot scale using commercial size electrodes. The cell design evolved concurrently with the bench and pilot work, culminating in a commercial, skid-mounted unit for the full size plant.
