SEMIBATCH PRECIPITATION OF CALCIUM-OXALATE MONOHYDRATE

Calcium oxalate monohydrate (COM) formation on the semi-batch precipitation of CaCl2 and Na2C2O4 solutions in the stoichiometric ratio carried out at pH = 6 and 37 or 70-degrees-C. respectively, was studied. When a certain level of supersaturation in the system is reached. individual COM crystals of a rather uniform size are formed. These crystals then grow and form 'loose' agglomerates that later develop into compact and spherical particles. The particle size distribution (PSD) rapidly shifts during early stages of precipitation towards larger sizes as a result of crystal growth and agglomeration. Later the PSD reaches a shape and position on the size axis that remain virtually constant with progressing precipitation. COM agglomerates consisting of mainly intergrown crystals are formed by mechanism of primary and secondary agglomeration. The primary agglomeration can constitute an important factor in urolithiasis.