Silica Extraction from Hydrothermal Heat Carrier by Membrane Filters

Abstract

The experiments on silica extraction by membrane filters were carried out. Three types of membranes were tested. The first were ceramic membrane filters with diameters of pores 0.1-0.3 ìm and average pores diameter 0.2 ìm. The second type were filters with pores sizes in the range of ultrafiltration – 0.01-0.001 ìm. The third was filter with reverse osmosis membrane with diameters of pores in the range 0.001-0.0001 ìm. Addition of coagulant aluminium sulphate was used in the experiments with ceramic filters. Temperature of solution was varied from 20 to 90 0C, mass rate of filtrate was from 5 to 720 liters per hour. Concentration of Al3+ cation added with coagulant in the experiments with ceramic filters was from 2 to 10 mg/liter. Selectivity of membrane layers with respect to colloidal silica particles and molecules of orthosilicic acid was determined in the experiments. Concentrated solutions with SiO2 content about 27 g/liter were obtained by reverse osmosis filtration. Results of our work can be applied for developing of technology of silica extraction from hydrothermal heat carriers.