Primary study of KOH alkali fusion – nitric acid leaching process in extraction of West Kalimantan zircon concentrate

Abstract

Abstract This paper aims to prepare the primary study of zirconia concentrate using KOH alkali fusion, nitric acid leaching and coprecipitation method. Alkali fusion with KOH was done with stoichiometric ratio ZrSiO4/KOH of 1:1.5 at 700 °C and 180 min. Variation of water leaching temperature at 25 °C, 95 °C and concentration in nitric acid at 4M and 6M were investigated to determine the optimal parameter to form zirconia. Phase in raw material, residue of water leaching, and product of calcination were investigated by using XRD. High composition of zirconia at 52.12 % and silica 9.64 % in zircon concentrate corresponded to the intensity peak of XRD pattern. Alkali fusion with KOH changed the visual and microstructure into irregular and porous structure in the strong caustic environment. Temperature of water leaching at 25 °C was the optimal condition to produce the highest intensity peak of zirconate and the zirconia formation. Nitric acid at 4M was preferable to form the lower of silica gel formation and produce the highest zirconia.