A two-step zircon decomposition method to produce zirconium oxychloride: alkali fusion and water leaching

Abstract

In this work, a two-step zircon method to produce zirconium oxychloride was introduced, and the alkali fusion technique with NaOH and water leaching process were investigated. The effects of the operating conditions on the decomposition of zircon were determined, and the optimal conditions are as follows: alkali/zircon mass ratio of 0.7 at the first step and 0.6 at the second step (0.7 + 0.6), fusion temperature of 700 °C and fusion time of 0.5 h at the first step and 0.5 h at the second step (0.5 + 0.5 h). Under these conditions, the decomposition alloy of zircon sand can reach 97.25 %. In the fusion process of zircon sand, the products of first step are mainly Na2ZrO3 and ZrSiO4, the products of second step are Na2ZrO3 and Na2SiO3, and the diffraction peaks of Na2ZrSiO5 are not observed. The conditions of water leaching process were investigated as well, and the optimal conditions are as follows: liquid–solid ratio of 5:1, leaching time of 0.5 h, leaching temperature of 50 °C and leaching three times. Under these conditions, the contents of leaching products SiO2 and Na2O are 3.51 % (40 % ZrO2) and 4.46 % (40 % ZrO2), respectively. The crystal phase structures of Na2ZrO3 and Na2SiO3 are formed in water leaching process.