Complex character of the influence of polycarboxylic and phosphonic acids on the crystallization of calcium and magnesium salts in dynamic conditions

Abstract

. 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.