Abstract
In recent years, high quality zinc ore in hydrometallurgy is decreasing because of stable demand of material, depletion of domestic mine and increased usage of recycling waste material. Therefore the impurity contained in the ore rose to the inexperienced level. Especially, SiO2 in zinc concentrate produced Zn2SiO4 in roasting process and Zn2SiO4 is easily leached in leaching process to form the supersaturated silica in the solution. As a result, silica turns into a gel to make complicates the solid-liquid separation difficult after leaching process. Several methods was proposed to solve this problem. However the factors affecting the silica polymerization have not been clearly understood. In previous paper, authors classified silica into three forms, and investigated the influence of several factors. The purpose of this paper is to obtain the knowledge for the effects of organic condense agents and inorganic compounds on the silica polymerization of colloidal silica.
(1) The colloidal silica in the solution was charged negatively and could be removed by addition of cationic condensing agents.
(2) The inorganic additives such as MnO2, PbSO4, ZnS,CaSO4 and ZnFe2O4 had no effect on the form of Silica existing in the solution. In the case of the addition of Al (OH) 3 and Fe (OH) 3, the concentration of colloidal silica decreased and the concentration of solid silica increased.
(3) In the case of addition of solid silica, the concentration of colloidal silica decreased and the concentration of solid silica increased. This effect was promoted with increasing solid silica loading.
(4) At high sulfuric acid concentration, the colloidal silica was stable. The solid silica added in the solution efficiently removed the colloidal silica also at high sulfuric acid concentration.
