Effect of the chromium ion diffusion in polyacrylamide/chromium acetate gelation system with surrounding water on gelation behavior

The diffusion of Cr3+ from the Cr3+/HPAM system is simulated by quantifying the entrapment ability of the Cr3+ after dialysis analysis through a dialysis bag method to study the Cr3+ diffusion effect on the gelation types. After the gelant is put in the dialysis bag surrounded by the solvents, only the diffusion of the aqueous ions are allowed, which eventually can be detected in the dialysate. By monitoring the gelants with varying initial contents, we find that the Cr3+ dialysis kinetics and total dialyzed amount are changed. In this particular experiment, the gelation types are classified and the classification result differences for the same gelant with or without dialysis process are investigated and compared. In this study, we assess the gelant contents in terms of possible limiting scenarios for successful gelation and discuss their gelation results influenced by the Cr3+ diffusion The results demonstrate that Cr3+ diffusion, in different extent, influences the gelation types and gelation time of the Cr3+/HPAM systems with varying HPAM molecular weight (MW), the Cr3+ initial concentration, the initial HPAM polymer concentration, or the degree of initial HPAM hydrolysis. Along with the gelation types and the accompanying morphological study, determine the relationships between the initial Cr3+ concentration and the true Cr3+ concentration entrapped on the polymers are possible, which are pretty distinct from each other. Neglecting to consider such diffusion effects will lead to overestimating of the crosslinking results. In addition, a sorption model is used to demonstrate the sorption trend changes before and after the gelation time.