PRECIPITATION OF COLLOIDAL SILICA IN HYDROTHERMAL SOLUTION BY METAL CATIONS (KAMCHATKA, RUSSIA)

摘要

Physical and chemical processes in hydrothermal solution in which colloidal silica took part were researched. The rate of nucleation of orthosilicic acid molecules H_4SiO_4 were calculated with the help of mathematical model. The order and constants of rate of silicic acid polymerization reaction were determined. The sizes and diffusion coefficients of colloidal silica particles were measured. Mechanism of coagulation and precipitation of colloidal silica particles by metal cations was investigated. In the experiments various types of metal cations were added to the solution: Ca~(2+), Mg~(2+), Co~(2+), Cu~(2+), Pb~(2+), Al~(3+), Fe~(3+). Cations were added to the solution with slaked lime, calcium chloride, magnesium sulphate, cobalt sulphate, cupric sulphate, plumbous nitrate, aluminium sulphate, aluminium chloride, ferric chloride, sea water. Also cations were added by electrocoagulation on electrodes with soluble metals such as aluminium, ferric and cupric electrodes. The technological scheme of silica precipitation from the separate of geothermal electric power station was developed.