Enhanced biodegradation of non-biodegradable plastics by UV radiation: Part 1

Abstract

Optimum UV pretreatment of polystyrene (PS), polyethylene (PE) and polyethylene terephthalate (PET) plastics for their efficient biodegradation were evaluated in this study. It was found that a longer incubation time and shorter distance to UV source (t2d2 condition) (UV dose of 7.02 × 1012 μW·cm-2·s) resulted in a higher roughness, hydrophilicity, microbial viability, biofilm formation, surface degradation, and a more significant physical and molecular weight reduction. The highest biodegradation within 45 days happened to PE and PS with respective 7.8 and 5.13% physical weight loss, and 4.71 and 2.1 fold molecular weight reduction compared to the “un-pretreated & strain-free bio-treated” (control-3). The hydrophilicity of PS and PE were increased to the “UV-pretreated & bio-treated” samples with a reduction in water contact angle from 105° to 5° in PS and 102° to 60° in PE. Microscopic analysis indicated significant surface property changes or degradation (cracks and holes) on “UV-pretreated & bio-treated” samples. The thermal gravimetric analysis also showed 73, 25 and 20 °C reductions in degradation temperature of “UV-pretreated & bio-treated” PE, PS and PET, respectively. Chemical transformation revealed new peaks in “UV-pretreated & bio-treated” samples, indicating the positive role of UV in biodegradation efficiency. Statistics analysis showed that 45 days was adequate to obtain optimum biodegradation efficiency (p < 0.05).