Polyacrylamide Gel Polymerization: Ascorbic Acid-ferrous Sulfate-ammonium Persulfate Initiator for Acid System

A new initiator system for polyacrylamide gel polymerization at low pH is developed. The system consists of ascorbic acid, ferrous sulfate and ammonium persulfate (AP). It is effective under acid conditions even if the concentration of the initiators is very low. To get high incorporation efficiency of acrylamide, the ratio of the AP, ascorbic acid and ferrous sulfate must be in a suitable range. The conversion efficiency has been assessed as a function of the pH of the gelling solution, in pH2.0--6.58 range. New system is able to guarantee>98% conversion in the pH 2.0--5.0 range. In contrast to the hydrogen peroxide-ascorbic acid-ferrous sulfate system widely used under acid conditions, new system gives a much higher incorporation efficiency of acrylamide, lower gel pore size at the same concentration and cross linkage and better gel mechanical property that made the gel easy handle for general purpose. The recommended concentrations of the initiators are: AP, 2.2-3.3 mmol/L, ascorbic acid, 0.91-1.82mmol/L, FeSO(4), 0.046-0.092 mmol/L.