Temperature dependence of precipitate redissolution: a calcium adsorption model

Long-chain alkyl and alkylaryl sulfonates used in micellar flooding systems were found in previous studies to precipitate upon addition to inorganic electrolytes and in some cases to redissolve and reprecipitate in excess sulfonate solutions. These studies also revealed that the major mechanism responsible for redissolution in micellar solubilization. To further test the validity of this mechanism, data for the dependence of precipitation/redissolution on temperature in the sulfonate/CaCl₂ system are used to obtain various thermodynamic parameters such as heats of dissolution, micellization, solubilization and calcium adsorption on micelles. Also a sequence of molecular processes leading to precipitate redissolution is proposed and tested using temperature data. The temperature dependence predicted by the model is found to agree with experimental data.