Effect of tartrates with various counterions on the precipitation of calcium oxalate in vesicle solutions

The effect of tartrates with various counterions on the crystallization of CaOxa in vesicles was investigated in the concentration range from 0.3 to 66.7 mM in lecithin vesicle solutions using X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. Various tartrates with hydrogen, sodium, potassium, and a mixture of sodium and potassium cations were considered. For K2tart and NaKtart, only calcium oxalate monohydrate (COM) and calcium oxalate trihydrate (COT) were obtained depending on the concentrations. However, for H2tart and Na2tart, calcium oxalate dihydrate (COD) was first induced in the debt of COM, then COT was induced in the debt of COM and COD. The maximum percentages of COD were about 55% and 35% for H2tart and Na2tart in the concentration ranges from 6.7 to 13.3 and 1.67 to 10 mM, respectively. Linear relationships were obtained between the decrease of the mole percent (mol%) of COM crystals, or the increase of mol% of COD or COT crystals and the increase of the logarithm of the molar concentration of the tartrates. The different results are discussed in terms of the reduction in the degree of freedom associated with the adsorption process at the membrane–water interface, the ionic radii of the counterions, the solubility and the molecular structures of the hydrates, and the different adsorption of the counterions at the crystals of the calcium oxalate hydrates.