Removal of polyester fibre microplastics from wastewater using a UV/H2O2 oxidation process

Plastic microfibres originating from laundry wastewater are released in significant numbers to the environment due to a current lack of suitable removal technology. Advanced oxidation processes could offer a promising option to mitigate the problem due to their ability to destruct organic pollutants rather than transferring them to other forms. In this study, the effect of UV irradiation and hydrogen peroxide treatment on the removal of microplastics (MPs) was determined. MPs mass loss, carbonyl index (CI) change, and physical changes on their surface, as characterised by Fourier transform infra-red spectroscopy, scanning electron microscopy and atomic force microscopy were monitored. Additionally, the chemical oxygen demand (COD) of the water was monitored to examine the release and degradation of soluble organic material from MPs. The effect of varied UVC dose and H2O2 concentration was investigated. A dose of 500 mg L-1 H2O2 under 4.0 mW cm-2 UVC irradiation resulted in mass loss of 52.7% after 48 h (with a calculated half life of 45.3 h). Also, it was observed that degradation of fibres occurred through the formation of shallow holes, pits and cracks across their surface as well as changes in the relative abundance of oxygen containing functional groups. This chemical change was evidenced by the CI of treated MPs, which was increased up to 10.6% compared to untreated fibres. Moreover, the proposed UVC/H2O2 treatment could degrade 15.2% MPs and completely remove COD in real hospital laundry wastewater matrix within 9 h and 3 h of treatment, respectively.