The effect of Ozonation on the chemical structure of microplastics

Abstract Microplastics are not susceptible to microbial degradation, thus often end up in aquatic ecosystem. Moreover, microplastics cause danger to aquatic biota and human. Effective technological solutions to degrade microplastics in wastewater treatment plants are desirable. Biodegradation is one of the most applied techniques, but takes a long time. This study evaluates the ozonation as pre-treatment to transform the chemical structure of polyethylene microplastics into more susceptible to biodegradation. The process was done by using a corona-discharge ozonator and batch reactor, varied pH value (6, 7, 8, 10, 12), ozone flowrate (1, 3, 5 L/min), and contact duration (1, 2, 3 hours). The study was begun by quantification of OH radicals and dissolved ozone, ozonation of microplastics, evaluation of ozonation by gravimetric weight loss including the change of microplastics chemical structure through FT-IR (Fourier Transform Infrared). The results revealed chemical structure changes of polyethylene after ozonation confirmed by the appearance of carbonyl bonds and the loss of weight. The optimum operating condition appeared at pH 12 with 5 L/min ozone flowrate, resulted in 0.0482% weight loss and carbonyl bond intensity reached 104.556% after 3 hours ozonation.