COMPARISON OF THE EFFECTS OF ANIONIC AND CATIONIC SURFACTANT ON THE PRECIPITATION OF CALCIUM OXALATES

Influence of anionic, sodium dodecyl sulfate (SDS) and cationic, dodecylammonium chloride (DDACI) surfactant, on spontaneous batch precipitation of calcium oxalate is investigated. A combination of particle number and size analysis, thermogravimetric analysis, X-ray diffraction, optical microscopy, electrophoretic and adsorption measurements is used to characterize the processes involved. SDS and DDACl affect the precipitation process at different stages. SDS acts as a nucleation modifier. The action of both surfactants at the stage of primary particle formation exhibits a complex dependence of the rates and mechanisms of crystal growth and aggregation on the structure of aqueous surfactant solutions. Both surfactants inhibit crystal growth and aggregation by adsorption due to the charge and hydrophobic effects. Preferential DDACI sorption on oxalic faces changes the habit of calcium oxalate monohydrate crystals.