Process of chemistry recycling of PET in alkaline medium: effect of concentration of hydroxide ion, color of PET and reaction time

ABSTRACT This work investigated the chemical hydrolysis process of polyethylene terephthalate (PET) in alkaline medium; specifically, colorless and colored post-consume bottles. The chemical recycling of post-consume PET bottles is still very little explored in Brazil, not being so different from what is being practiced in other countries. Among possible variables of investigation, in this work was studied the sodium hydroxide (NaOH) concentration and the PET color. The post-consume PETdepolymerization reaction was performed at the concentrations of 1.0, 3.0, 5.0, 7.5 and 10.0 mol L-1 NaOH, and in 7.5 mol L-1was the one that showed the best results, regarding the extent of the reaction and the purity of the recovered monomer, terephthalic acid (TPA). The reaction was also made for PET of different colors at the concentration of 7.5 mol L-1 NaOH, whose results showed a lower performance when compared to those obtained for non-colored PET. This result suggests that it is due to the presence of dyes, which, due to their same chemical structure, compete for nucleophilic attack of the hydroxyl ion (OH-) during the hydrolysis reactionof of PET. Infrared Spectrophotometry (FTIR), X-ray diffraction (XRD), as well as Thermogravimetric (TGA / DTG) analysis confirmed that the reaction products resulted in TPA, since the spectra were coincident with those of the commercial TPA. The increasing consumption of PET packaging and aleatory environmental disposal need quick solutions; the results of this work are important and corroborate with the advance of the research for reutilization of raw material.