Rapid Degradation of Superabsorbent Poly(Potassium Acrylate) and its Acrylamide Copolymer Via Thermo-Oxidation by Hydrogen Peroxide

Abstract

Superabsorbent poly(potassium acrylate) (P(KA)) and poly[acrylamide-co-(potassium acrylate)] (P(Am-co-KA)) were synthesized and their effective degradation via chemical and biological processes were pursued. Significant reductions in dry mass and water absorbency were observed after P(KA) (53% and 54%, respectively) and P(Am-co-KA) (43% and 40%, respectively) were buried in the soil for ten weeks, indicating their partial biodegradation. Although the living fungal culture failed to degrade the polymers, digestion by its crude peroxidase (20 U/g, 16 h) significantly decreased the dry mass (15%; 15.0 ± 0.3 g) and water absorbency (13%; 16.0 ± 1.0 g/g) of P(KA). Chemical oxidation using H2O2 at high temperature with/without peroxidase efficiently liquidized both polymers specifying significant changes of their structures. The maximum degradation of P(KA) (99.84% weight loss) was obtained when incubated with 12.8% (v/w) H2O2 at 65 °C for 7.3 h while 98.43% weight loss was achieved after P(Am-co-KA) was incubated with 14.8% (v/w) H2O2 at 68 °C for 9.2 h. To assess the phytotoxicity of the degraded products, their effect on seed germination was determined. No significant inhibition was observed in mung bean germinating on both the untreated polymers and their oxidized products. On sweet corn, the degraded products were apparently less inhibitory than did the untreated polymers. These results suggested that the rapid and efficient degradation of polyacrylate and its copolymer by the thermo-oxidation of H2O2 could be applied for a larger scale of superabsorbent waste management.