Depolymerızatıon of waste PET wıth NaOH usıng mıcrowave reactor

Environmental pollution is one of the major problems facing current and future urban life, and it also poses a major threat to the world's natural environment. Therefore, one of the most pressing concerns is the need for efficient waste management. One of the most important environmental pollutants is plastic, including polyethylene terephthalate (PET) containers, which constitute a large percentage of plastic. Polyethylene terephthalate is the main material from which plastic bottles are made. It is most common in water bottles, where packaging materials (food and beverages) are common. The main methods used to dispose of plastic waste are burial and incineration. These methods may cause environmental problems, such as the leakage of waste into riverbeds or the generation of gases that are harmful to the environment. Due to the thermo-physical properties of the plastic, it is converted into low-value products, resulting in an economic loss. Therefore, chemical recycling is the ideal alternative for recovering raw materials (PET). The focus of this study was on the chemical depolymerization and production of terephthalic acid (TPA) using alkaline hydrolysis in the presence of titanium dioxide as a catalyst and using a microwave (MW) irradiation reactor for heating and controlling the reaction conditions in terms of temperature and time. For our design experiments, the TAGUCHI DESIGN method and analysis of variance (ANOVA) were used to analyze the product, which is terephthalic acid (TPA), where the temperatures were (165, 180, 195)C, the time was (10, 20, 30) minutes, and the amount of catalyst (0.01, 0.02, 0.03) g, base concentration NaOH% (12, 8, and 4) to conduct PET depolymerization experiments. Statistically, the most influential variable on depolymerization was identified, as the F value for temperature was (92.88), followed by the base concentration, which reached an F value of (46.95), while time and the amount of the catalyst TiO2 showed similar proportions, with their (F) values reaching (30.07) and (32.70). Respectively, the (p) value was found for all variables, as it reached zero(0), meaning that the probability of an error occurring is very small. The effect of the factors among them on the remaining PET was demonstrated through graphics, where contour plots were drawn using the Mini Tab program, which showed that temperature is the largest influence on the depolymerization of PET. Through other drawings, the relationship was explained in detail between the variables and the amount of remaining PET, and a linear regression equation was also created to find the effect of each variable separately on the amount of remaining PET. TPA was produced with high productivity, reaching 99.9% during laboratory experiments. The results were examined by FTIR, HNMR, and microscopy. The results showed a high degree of purity in the product resulting from the experiments. Therefore, this study not only presents an innovative solution to the pressing challenge of PET waste but also underscores the critical role of chemical recycling in the pursuit of environmental sustainability. Beyond merely recovering materials, our proposed approach represents a significant stride toward resource conservation, promising to impart substantial economic value to the realm of plastic sustainability. As we navigate the complex landscape of environmental stewardship, this research contributes a comprehensive and forward-thinking perspective to the evolving field of waste management and sustainable material recovery.