Development of ZnO-TiO2 photocatalyst for lldpe degradation
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Date
2016-06
Authors
Leong Qiao Lin
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Abstract
The photodegradation of commodity plastic waste using metal oxide nanoparticle has received great attention because of cost effectiveness and eco-friendly nature of this technology to treat waste. Titanium dioxide (TiO2) is one the most commonly used photocatalyst for commodity plastic degradation. However, the photocatalytic efficiency of TiO2 incorporated polymer composite is very poor because of recombination of electron-holes (e-h) of the photocatalyst, poor water adsorption characteristic of polymer matrix with hydrophobic nature and severe agglomeration of photocatalyst in polymer matrix. Therefore, in this work ZnO/TiO2 (ZT) photocatalyst composite made of ZnO and TiO2 via sol gel process with different solvent such as ethanol (Et) and isopropanol (IPA) and mixture (mix) of those solvent was investigated. ZT photocatalyst using ethanol (ZT-Et) and subsequently calcined at 500oC for 2 h was found to have the highest photocatalytic activity for methylene blue solution degradation compared to bare ZnO or bare TiO2; indicating coupling of pure oxides can overcome the recombination of e-h. The efficacy of ZT-Et were 88.20% under solar radiation after 45 minutes while 87.86% under UV radiation after 5 hour. ZT-Et were then surface modified with 3-trimethoxysilyl propyl methacrylate (MPS) and polyacrylamide (PAM) prior to LLDPE composite fabrication to avoid agglomeration and improve water absorption property of LLDPE. The mechanical and degradation properties of LLDPE/PAM-MPS-ZT-Et composite was evaluated and compared to pure LLDPE. The mechanical property such as tensile strength and modulus of elastic of LLDPE/PAM-MPS-ZT-Et composite were improved by 0.08% and 0.48%, respectively. Upon exposure of UV light for 144 h, the LLDPE/PAM-MPS-ZT-Et (2.0 wt%) had the excellent degradation by 114 fold as compared to pure LLDPE. Therefore, based on the findings, 2.0 wt% ZT-Et photocatalyst that has been modified with PAM-MPS for fabrication of LLDPE composite is recommended to accelerate degradation of LLDPE waste.