Effect of Thermo-Photocatalytic Process Using Zinc Oxide on Degradation of Macro/Micro-Plastic in Aqueous Environment

Abstract

More than 320 million tons of plastics are produced annually, and the rate of plastic waste generation steadily increases by 3.9% per year. Introduction of plastic waste into water bodies may lead to many adverse environmental impacts as the plastic debris is very stable and generally requires a longer time to degrade. Over a period of time, bulk plastic debris will slowly degrade into small fragments known as macroplastics (particles size >5mm) and microplastics (particles size <5mm). Accumulation of this newly emerging class of pollutants potentially decreases the efficiency of the existing water treatment system. Therefore, improvement on the existing water treatment technique is required. This study aimed at investigating the effect of using the UV-assisted thermo-photocatalytic reaction on the degradation of polypropylene (PP) macro- and microplastics in an aqueous environment for 6 hours. ZnO nanoparticles (<50 nm) were employed as the photocatalyst. 23 Full Factorial design was carried out in order to identify the correlation between the reaction temperature (35-50 o C), size of PP plastic (25-100 mm2 ) and the catalyst dosage (1–3 g/L) factors and their influences on the weight loss of macro/micro-plastics. Maximum plastic weight loss of 7.8 wt% was achieved at 50°C, 1 g/L ZnO and 25 mm2 of PP plastic. The interaction between temperature and size must be taken into consideration.

The Role of the Reactive Species Involved in the Photocatalytic Degradation of HDPE Microplastics Using C,N-TiO2 Powders

“…Photocatalysis has recently been proven to degrade low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), and polypropylene (PP) MPs in aqueous solutions [ 10 , 11 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. However, complete degradation of any of these plastics has not been reported yet.…”

Advanced oxidation processes for the degradation of microplastics from the environment: A review

“…The effects of ZnO nanoparticles (50 nm) catalyst in a UV‐assisted thermo‐photocatalytic process to accelerate the degradation of PP MPs showed the maximum weight loss of 7.8% of PP plastic at 50°C and 1 g/L of catalyst (Razali, Abdullah, & Zikir, 2020). The polymeric chains on PP were vigorously attacked and oxidized by photo‐generated • OH and O 2 •‐ radicals on the surface of ZnO.…”

“…The presence of longer rods and increased catalyst surface area created a higher number of radicals on photolysis resulting in higher degradation of the LDPE film. UVC/H 2 O 2 oxidation of polyester microfibre MP resulted in a mass loss of 52.7% after 48 h using a dosage of 500 mg L À1 H 2 O 2 under 4.0 mW cm À2 UVC irradiation(Easton, Koutsos, & Chatzisymeon, 2023).The effects of ZnO nanoparticles (50 nm) catalyst in a UVassisted thermo-photocatalytic process to accelerate the degradation of PP MPs showed the maximum weight loss of 7.8% of PP plastic at 50 C and 1 g/L of catalyst(Razali, Abdullah, & Zikir, 2020). The polymeric chains on PP were vigorously attacked and oxidized by photogenerated • OH and O 2 •radicals on the surface of ZnO.…”

An urgent call to think globally and act locally on landfill disposable plastics under and after covid-19 pandemic: Pollution prevention and technological (Bio) remediation solutions

“…Other possibilities include microplastics photocatalytic degradation (e.g., with zinc oxide), which stands out as a viable and energy-efficient method (which also removes plastics at a nanoscale) [111]. However, some end products from photocatalytic degradation may impose a risk to both animal and human health.…”