Preformed particle gel: evaluation and optimization of salinity and pH on equilibrium swelling ratio

In this study, preformed particle gel was prepared from a hydrogel crosslinking of an aqueous solution containing chromium acetate (III) and the co-polymer of 2-acrylamido-2-methyl-propanesulfonic-acid sodium salt (AMPS) and acrylamide (PAMPS). The effects of CaCl2 concentration and pH were investigated on swelling behavior. To determine the significant factors that affect the equilibrium swelling ratio (ESR) and also to develop the quadratic mathematical models, central composite design, the most popular form of response surface methodology, was applied. Therefore, the main purpose was to establish functional relationship between the two factors and the ESR using a statistical technique. The results of analysis of variance of the developed models illustrated that the fitted models were significant with a 99 % confidence limit. The results were also shown that the ESRs depended more on CaCl2 concentration than pH and in the range of 22,500–30,000 ppm concentration of CaCl2 there was also an interaction between these two factors. The optimum ESRs with the purpose of maximizing it based on the model prediction with respect to the selected factors were presented in the absence of CaCl2 concentration and the presence of pH in the range of 5–8.