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

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. FIIR 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 125.90 degrees to the lowest value of 120.04 degrees and 123.8 degrees 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.

Automated summary

This study examined the effects of ozone and UV on the surface alterations of polyethylene microplastics in aquatic environments. The results showed that regardless of the ozone dosage, O-3 +UV was more effective in oxidizing the surface of the microplastic particles.