Comparison of surficial modification of micro-sized polyethylene in between by UV/O3 and UVO submerged system

Abstract

This study examined the effects of ozonation and UV applied in series (O 3 +UV) or simultaneously (UVO) under four different ozone dosages from 4 to 7 mg/min to understand the surface alterations on polyethylene microplastics in aquatic environments via the photochemical oxidation process. The plastic samples were analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. FTIR spectroscopy showed that the levels of carbonyl (ketone and esters) and vinyl groups increased gradually with increasing ozone dose injected; the highest was observed at 6 mg/min of ozone. On the other hand, the levels at 7 mg/min of ozone were slightly lower than those at 4 to 6 mg/min. This could be related to the deeper penetration into the crystalline bulk polymeric chain. The contact angle changed from 125.90º to the lowest value of 120.04º and 123.8º for O 3 +UV and UVO, respectively. Furthermore, XPS showed that C-O was only presented in the 7 mg/min sample, whereas C-O, OH, C=O, and C-C=O remained for 4 to 6 mg/min. Overall, O 3 +UV can oxidize the surface of the polyethylene microplastic particles more effectively than those of UVO, irrespective of the ozone dosages.

Insights into the removal of microplastics and microfibres by Advanced Oxidation Processes

“…PE degradation by ozone-based processes was recently evaluated applying UV irradiation (under ozone dosages of 4-7 mg/min during 180 min). The increase of O 3 dose was up to 6 mg/min and it showed a gradual increase of the levels of carbonyl (ketone and esters) and vinyl groups (Zafar et al, 2021). PE has single carbon bonds in its structure, which are quite resistant to photo-oxidative degradation due to the lack of UV-visible chromophores.…”