Environmental aspects of impacts of the impurities in the industrial microsilica during its processing
The mechanism of inhibitory effects of microsilica impurities on microsilica dissolution was discovered. The relevance of the work is due to the demand for liquid glass in the enterprises of Central Russia and the lower cost of raw materials, namely sodium silicate, compared with analogues. Waste disposal helps to solve the problems of resource conservation and environmental management. Microslica was studied by differential thermal analysis using a TGA 2 in the temperature range of 20...800 °C with a heating rate of 20 °C/min in air. Modification of microsilica was carried out by mixing with sodium hydroxide with a concentration of 15...25 wt.% at a temperature 20...50 °C with stirring at 600 rpm. The mechanism of formation of by-products with the basis of the obtained data was determined. The greatest contribution to the inhibitory effect on the process of producing liquid glass is made by aluminum ions. The resulting byproduct, hydroalumination sodium is formed in several stages and is catalyzed by sodium silicate. The reduction in the rate of mass transfer and temperature in the modification process of the microsilica reduces the amount of produced byproducts. The mechanism of inhibition of the process of dissolution of microsilica, a byproduct of the production of aluminum fluoride, was determined. The mechanism of the formation byproducts was proposed. The activation energy of the polymerization reaction was obtained. The value of the activation energy is 7.73 kJ/mol, indicates that the synthesis process takes place in the diffuse region. The optimal parameters of physical and chemical modification are determined. Microilica is treated with sodium hydroxide with a concentration of 25 % at a temperature of 20 °C at a speed of 600 rpm.