A study on fenton technology for polypropylene waste degradation and recovery of high-value chemicals

Plastic waste management and handling are critical issues, and the development of breakthrough technology for these purposes is a challenging task. In this chapter, it will explore the feasibility of waste degradation and hopefully provide some insights and fundamental information for scientists and chemical engineers to address the issues of degradation and mineralization of inert plastic wastes, with polypropylene (PP) as an example, through effective chemical processes including surface activation and Fenton and photo-Fenton technology. To achieve a greener reaction process for practical use, commercially available hydrogen peroxide (H₂O₂) has been widely used as an oxidant. The Fenton reaction under ambient dark conditions was successful in converting the activated PP materials into water-soluble organic matter and carbon dioxide (CO₂) within 40 min, while the photo-Fenton reaction under UV-vis illumination was able to achieve complete mineralization within 80 min as determined by the analysis of the reaction solutions. In addition, the dissolved organic matter generated from the Fenton reaction was identified as belonging to three main classes: monocarboxylic acids, dicarboxylic acids, and diols. The study revealed that the concentration of H₂O₂ used in the Fenton reaction significantly affects the amount of diols and carboxylic acids recovered from the PP degradation, where the ratio could be tuned from 37.2 to 2.1% for diols and from 55.9 to 93.1% for carboxylic acids, under dark conditions. Moreover, under photo-Fenton degradation conditions, due to rapid decomposition, a positive pressure was observed (CO₂ gas: 550 kPa/g of material) from complete degradation of the activated PP. The gas pressure could potentially be converted into mechanical energy for further applications. Copyright © 2019 Springer Nature Singapore Pte Ltd.