湿式亜鉛製錬工程におけるシリカの基礎的挙動について Behavior of Silica in the Zinc Refinery Process

In recent year, it is necessary to treat imported ore in zinc hydrometallurgy because of stable demand of material and depletion of domestic mine. However, the imported ore often contains a lot of impurities. Among them, SiO<SUB>2</SUB> complicates solid-liquid separation after leaching process. The cause of this degradation is understood that Zn<SUB>2</SUB>SiO<SUB>4</SUB> produced in roasting process is leached in leaching process, and then supersaturated silica solves in solution. In previous research, it was reported that solid-liquid separation was improved by increasing of pH and temperature, and seed method was effective for reducing SiO<SUB>2</SUB> concentration. However, mechanism of the solid-liquid separation improvement hasn't been well understood. The purpose of this paper is to obtain the knowledge for the effects of temperature, pH and impurities on silica polymerization.<BR>(1) Solution temperature influences the colloidal silica polymerization, and the polymerization is promoted as the temperature is elevated.<BR>(2) In the solution of pH range from 1 to 3, the polymerization rate is almost the same. When pH is raised to 4, the polymerization rate has been promted.<BR>(3) Hydrolysis reaction of Fe and Al influences the decreasing of SiO<SUB>2</SUB> concentration by rising pH in field test.<BR>(4) Addition of silica seed has greatly reduced the ionic and colloidal silica in the solution.