Removal of silicon in acid leaching and flocculation processes during zirconium oxychloride octahydrate production

The efficiency of silicon removal technology by acid leaching and flocculation during zirconium oxychloride octahydrate (ZrOCl2⋅8 H2O) production has been improved. The optimum conditions of acid leaching were found to be as follows: transiton material, 300 g; HCl (6 mol/L), 600 mL; leaching time, 4 h; and leaching temperature, 100 °C. The nonionic polyoxyethylene lauryl ether (AEO9) was adopted as the flocculant. The optimum flocculation conditions were found to be as follows: temperature, 40 °C; flocculant amount, 10 ml (concentration 1%); time, 1 h. The zirconium oxychloride solution after purification contained 36 ppm SiO2 and 160 g/L ZrOCl2. The polymerization and flocculation mechanisms of silicic acid were analyzed. Results of Fourier-transform infrared, scanning electron microscopy, nuclear magnetic resonance, and Brunauer–Emmett–Teller analyses showed the main transformation and properties of the products in the acid leaching and flocculation processes.