It is known that when water are used for technological purposes, in circulating water supply systems of enterprises as a coolant during continuous heating and cooling, the formation of insoluble precipitates, most often calcium carbonates, occurs on the walls of heat exchangers, which leads to a large number of problems, even production can be stopped for cleaning equipment. To prevent the formation of salts, it is necessary to use precipitation inhibitors. Sodium polyacrylate was investigated as a precipitation inhibitor. The composition, morphology and IR spectra of calcium carbonate precipitate obtained in the absence and in the presence of sodium polyacrylate were studied. It was established that the effect of sodium polyacrylate on the mechanism of crystallization of carbonate sediment depends on the pH of the initial solution. The results of IR spectroscopy, X-ray diffraction analysis and images obtained by electron microscopy indicate the participation of polymer molecules in the formation of the crystalline structure of the carbonate precipitate.
The influence of water-soluble organic compounds (adipic, polyaspartic and phosphonic acids) and their compositions on the crystallization of calcium and magnesium salts in dynamic conditions has been studied. It is found that the induction period of phase formation increases in the presence of polyaspartic and phosphonic acids 2.3–5.2 times in the range of their content from 0.05 to 0.2 ppm. The results of XRD and electron microscopic studies confirm the change in the phase composition and morphology of the crystalline precipitate that is formed. The dibasic carboxylic acid influence on the induction period, composition and structure of the precipitate is much less. It is established that the composition of organic acids also increases the induction period of phase formation. The complex inhibitor provides an increase in the critical supersaturation level in the system. The phosphonic and carboxyl groups of the inhibitor interact with calcium and magnesium ions and block the crystallization nuclei. When interacting with the dicarboxylic acid and polyacid adsorption on the surface of the formed crystals, the microcrystals dissolve.
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