The degradation pathway of aminosilicone polymer in aqueous microemulsion by Fenton process

This research systematically studied the degradation pathway of aminosilicone polymers (PDMAS) by Fenton process in aqueous microemulsion. We show that the optimum parameters of Fenton process for degradation of PDMAS and COD reduction in aqueous microemulsion (COD = 4500 mg/L) are pH of 2.5, ferrous iron of 5 mM, and hydrogen peroxide of 10 mM. Under optimal reaction conditions and with pH modified to 8 after Fenton reactions, 42 mg/L NH4+ was produced along with 76.8% COD removal, in which oxidation and coagulation contributed 10.6% and 66.2%, respectively. Yet, COD removal of PDMAS emulsion by same amount of ferric ions at pH 8 was only 5.7%, indicating the major removal of COD was through precipitation of PDMAS and its oxidation intermediates from Fenton reaction due to the destabilization of the microelumsion resulted from surfactant degradation. Comparison of the FTIR spectra before and after treatment by Fenton process revealed the absence of amine groups on side chains, which suggested the complete break down of the C-N bonds by hydroxyl radicals. GPC results further showed that the backbone of PDMAS was likely broken down randomly, resulting in intermediates with lower molecular weights.