Decolorization of colored poly(ethylene terephthalate) bottle flakes using hydrogen peroxide

A novel process for the oxidative decolorization of green and blue colored poly(ethylene terephthalate) (PET) bottle flakes, using an aqueous solution of hydrogen peroxide (H 2 O 2 ) has been developed. A strong dependence of H 2 O 2 concentration and temperature on decolorization rate has been found. The decolorized flakes were characterized for color and intrinsic viscosity (IV) values; decolorized flakes exhibit color values similar to those of colorless recycled PET. The IV of peroxide bleached PET flakes indicated a decrease in PET molecular weight, which correlated with the severity of decolorization conditions. Despite decreases in PET IV values, the bleached flake still exhibited useful PET molecular weights. The consumption of H 2 O 2 during the bleaching process was quantified titrating residual peroxide with a standardized potassium permanganate solution. H 2 O 2 consumption rates of 0.3–0.9 g per gram of green PET flake were measured, depending on the specific bleaching conditions used.