Decoloration of waste PET alcoholysis liquid by an electrochemical method

Disperse Red 60 simulated polyester alcoholysis liquid decoloration by electro-Fenton with Fe₃O₄ catalyst was studied. The influences of the main operating parameters such as catalyst dosage (0.3-0.9 g/L), current density (60-120 mA/cm²) and pH (1-7) were optimized by response surface methodology (RSM) based on Box-Behnken surface statistical design (BBD). In optimal conditions, the initial concentration of 25 mg/L disperse red polyester alcoholysis liquid was catalyzed by 0.6 g/L Fe₃O₄, and the decoloration efficiency was 97.18% with the current density of 90 mA/cm² and initial pH of 4.6. There was a relative error of 1.18% with the predicted model when the predictive value was 98.25% under the same conditions. In addition, ultraviolet-visible absorption spectra (UV-Vis), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to study the degradation mechanism during decoloration. The intermediates were identified and the proposed degradation pathways were investigated by liquid chromatography-mass spectrometry (LC-MS) analysis.