Hydrothermal leaching of nickel, uranium and the remaining vanadium from alkali treated boiler ash residue using citric acid

Abstract

IN this study; the boiler ash was subjected to a digestion process using citric acid solution. Previously the ash was treated with NaCO3-NaHCO3 solution for vanadium leaching. In this step about 85% of the vanadium content was leached while nickel was not dissolved using the carbonate solution. The ash after vanadium dissolution was digested using citric acid for nickel and the remaining vanadium beside uranium dissolutions. Experimental results have shown that maximum metals dissolution obtained using 0.3M citric acid was 81, 85 and 89% respectively. The resultant liquor solution was subjected to successive nickel, vanadium and uranium separations. Firstly; the leach liquor is treated with dimethylglyoxime solution to precipitate Ni species. Secondly; the filtrate after Ni separation is treated with TBP/kerosene solvent for uranium extraction. Finally, the aqueous solution is treated with ammonium chloride to precipitate the vanadium content.