Synthetic polymer delivery system.: Sustained release of persulfate during the photo-oxidation of an azo-dye

Abstract

A synthetic delivery system based on the copolymer ethylene vinyl-acetate (from now on EVA-polymer) and the carrier, bovine serum albumin (from now on BSA) were prepared by polymer dissolution in the presence of persulfate. This system acted as a long-term polymer release device, cleaning aqueous solutions containing Orange II under visible light irradiation. The polymer and the carrier used were found to be inert and the observed oxidation was only due to persulfate. As expected, the higher initial loadings of persulfate deliver a higher amount of oxidant, leading to a faster photo-degradation of Orange II. The decoloration of Orange II by persulfate only occurred under visible light irradiation suggesting a dye sensitized process. The persulfate release during the reaction was sufficient to decolore amounts of Orange II, usually found in large water bodies (∼50mg C/l). Disks of EVA-persulfate were used in conjunction with light increasing the release performance of the synthetic delivery system. The addition of BSA can be selective in order to regulate the release of persulfate in the delivery system. The synthetic polymer delivery system was reused over many cycles, since, the polymer delivery system could be retrieved after each cycle. The repetitive use of the persulfate based disks have implications for the long-term detoxification of contaminated water, opening the way for new applications that are not possible by simple addition of persulfate-ions in homogeneous solutions.