Synthesis of a high-purity zircon powder with variations of HCI concentration and heating temperature

This work described an experimental investigation of the synthesis in high-purity zircon (ZrSi0₄) powders from zircon sand by varying the processing procedure. The zircon powder was obtained from natural zircon sand taken from Kereng Pangi, Central Kalimantan. The sand was subjected to sieving (mesh 40) and planetary ball milling for 2h. Impurities in the sand were reacted using HCl or NaOH and removed from the precipitate. The purification process was carried out by firstly optimizing the HCl concentration (0.5-2.0 M) and heating temperature (60-100 °C) during stirring of the mixture of the sand and HCl to remove the Fe, Ti, and Ca-based substances. The samples were precipitated and washed with distilled water to achieve a neutral pH. To remove excessive silica, the distilled powders were reacted with NaOH and again washed with distilled water until neutral. The products were powders which were then subjected to X-ray diffraction characterization where the data were qualitatively and quantitatively analyzed using Match! and Rietica softwares. It was found that 0.8 M HCl concentration and heating at 80 °C was the most effective condition to produce a single phase of zircon. A lower reaction temperature required higher HCl concentration, while a higher temperature of 90 °C might give pure zircon powder but applying 100 °C produced some impurities which were possibly due to more rapid evaporation of HCl.