SULFURIC ACID BAKING OF PARTIALLY DECOMPOSED RIRUWAI ZIRCON SAND: PROCESS OPTIMIZATION USING RESPONSE SURFACE METHODOLOGY TOWARD FOUNDRY SPECIFICATIONS
Riruwai zircon sand from Nigeria contains exceptionally high concentrations of uranium and thorium (>26,000 ppm), making conventional fine milling undesirable because of the associated generation of radioactive dust. This study investigates sulfuric acid baking as the second stage of a two-stage chemical beneficiation process for upgrading partially decomposed Riruwai zircon sand toward foundry specifications without fine milling. The starting material, obtained from a previous partial decomposition treatment, contained sodium zirconate (Na2ZrO3) as an intermediate phase together with residual zircon and associated impurities. Response Surface Methodology based on a Central Composite Design was employed to optimize the sulfuric acid baking process by evaluating the effects of temperature, baking time, and solid-to-liquid ratio on iron and combined uranium-thorium (U+Th) removal. The solid-to-liquid ratio was identified as the most influential process variable for both responses, followed by temperature. Numerical optimization predicted optimum conditions of 291 °C, 120 min, and a solid-to-liquid ratio of 1.5, which were validated experimentally. Under these conditions, the U+Th concentration decreased from 17,200 ppm in the partially decomposed zircon to 252 ppm, satisfying the foundry specification of
Authors : Mohammed, A., Kareem, S.A. and Saddiq, H.A.
Category : Open Access Volume (Issue) : 12(1) Date Uploaded : 5th August 2026