The article presents the results of silicon dioxide leaching from quarry waste dumps with silicon content of 50% and more. NaOH solution was used as a leaching agent and H2SO4 solution as a precipitant. The influence of basic parameters on the leaching process (concentration of leaching agent, operating temperature, ratio of liquid phase to solid phase, stirring speed) and on the precipitation process (concentration of the precipitant and temperature) was investigated. As a result of using the optimal parameters a high efficiency of silica powder production of 98.7 % was achieved. The powder is presented mainly in the form of particle agglomerates. The average particle size is 300-700 nm, the size of agglomerates is more than 700 nm. The structure is predominantly porous.

The paper presents the results of studies of the main parameters of synthesis of silicon dioxide powder from Balaklava deposit sludge with silicon dioxide content of 24%. During the study caustic soda solution is used as a leaching agent and sulfuric acid was used as a precipitant. At the leaching stage the concentration of leaching agent, the ratio of liquid phase to solid phase, the optimum temperature of leaching as well as the mode of pulp agitation are investigated. At the precipitation stage, the following parameters are considered: concentration of precipitating agent and temperature of the precipitation process. As a result of using the optimal parameters the high efficiency of obtaining silica powder of 98.56% is achieved. Average particle size is 200-800 nm, and agglomerate size is more than 800 nm.