A statistical model for determination of metastable zone width for anti-solvent precipitation of tar balls

In this study, the supersaturation of tar balls collecting from Caspian Sea beaches has been investigated by using anti-solvent addition precipitation method. Supersaturation was measured for tar ball particles in a hexane-methanol mixture. The supersaturation, the difference between the solution and saturation concentrations of tar balls, is the main driving force for both nucleation and growth process in precipitation. The focus of this study is to investigate the metastable zone width limit and its influences on supersaturation. Determination of metastability range is vital to find the appropriate amount of solvent and anti-solvent for solving or precipitating tar balls.Response Surface Methodology (RSM) has been employed to determine effect of parameters such as the anti-solvent addition rate, mixing regime, initial solute concentration, the metastable zone on supersaturation. Response surface model is a simple predictive tool works fairly well to predict supersaturation.Analysis of variance (ANOVA) technique was used to evaluate the efficiency of the proposed model. The results show the metastability zone width has the major effect on supersaturation