Zinc-doped ferrite nanoparticles as bi-functional catalysts for decolorization of disperse dyes in glycolysis of colored poly(ethylene terephthalate) fabrics

The upgraded poly(ethylene terephthalate) (PET) glycolysis catalyzed by Zinc-doped magnetic ferrite nanoparticles (Zn-MNPs) was applied in recycling of PET textiles colored by different disperse dyes. As bi-functional catalysts, Zn-MNPs acted as Lewis acid in PET glycolysis and dispersion electrodes in dye decolorization. The decomposition of dyes kept pace with PET glycolysis in the presence of Zn-MNPs because of the cleavage of azo chromophores in azo dyes and the loss of substituent groups in anthraquinone dyes, resulting in color removal rates of 71.91% and 54.85%, respectively. In order to improve the recyclability of excessive ethylene glycol (EG) in glycolysis liquid (GL), electro-Fenton process was further applied to eliminate the benzene ring and stubborn additives in residual dyes. The decolorization rate of both azo and anthraquinone dyes can be increased to more than 97.54% in 2 h, with 2.6 vt% of H2O2 concentration, 0.35 wt% of Zn-MNPs dosage, and 0.19 A/cm2 of current density. The discolored GL can be purified by rectification to recover EG and reused in PET glycolysis. The results reveal that simultaneously PET degradation and decolorization can be realized through the upgraded glycolysis combined with electro-Fenton process catalyzed by Zn-MNPs.