Investigation of the conditions for the production of calcium magnesium acetate (CMA) road deicer in an extractive crystallization process

Calcium magnesium acetate (CMA) is considered as the best road deicer to re place the environmentally unacceptable NaCl and CaCl2. However, the high co st of CMA prohibits its widespread use. The present study is dealing with t he investigation of a crystallization method for the production of deicing CMA crystals of desired physical properties and the elucidation of the cond itions under which such a product can be formed. Extractive crystallization is promising for the low cost production of CMA crystals considering that acetic acid is produced by a biochemical method and removed from the fermen tation broth in situ by organic extractant systems. In this method, this or ganic phase, which contains the acetate ions is contacted with an aqueous p hase which is the source of calcium and magnesium ions. The extractive crys tallization process resulted in the production of well-formed, large, and n on-spherical crystals of calcium acetate (CA), magnesium acetate (MA), and calcium magnesium acetate double salt (CMADS). The crystal size was affecte d by the concentration of acetic acid in both the organic and aqueous phase s, whereas the crystal type and hydration level were determined primarily b y the acetic acid concentration in the aqueous phase. The molar ratio of th e precursor salts (CaCO3/MgCO3) in the reaction mixture was found to be the major factor for determining the habit and Ca/Mg content of crystals. Crys tallization of CMADS was favored at high concentrations of acetic acid in t he aqueous phase and at higher temperatures as shown from supplementary eva poration-to-dryness experiments.