Incorporation of ultrathin porous metal-free graphite carbon nitride nanosheets in polyvinyl chloride for efficient photodegradation

Solid-phase photocatalytic degradation of waste plastics is one of the promising approaches to solve the "white pollution" problem. In this work, a low cost, metal-free, environmentally friendly organic photocatalyst, graphite carbon nitride (g-C₃N₄), was used for the first time to successfully enhance the photodegradation of polyvinyl chloride (PVC) under simulated sunlight from its visible light photocatalytic capability, while its organic nature and abundant surface functional groups were beneficial for its good dispersion in plastics. It was found that the ultrathin porous g-C₃N₄ nanosheet synthesized from urea (the UCN sample) had much stronger photodegradation effect in PVC/g-C₃N₄ composite films than its thick block counterpart synthesized with melamine (the MCN sample) due to its larger specific surface area, higher pore volume, and enhanced photogenerated charge carrier separation. With the incorporation of only 1 wt% UCN sample into PVC, its mechanical properties were largely enhanced with the tensile strength increase of ∼ 45% and the elongation at break increase of ∼ 72%, and its weight loss increased ∼ 58% after 120 h irradiation in the weather resistance test chamber. ^·O₂^- and h⁺ produced by the UCN sample were found as the main active species in the photocatalytic degradation of PVC to dechlorinate PVC and decompose its long-chain molecules into short-chain small molecules until its final degradation into CO₂ and H₂O under ideal conditions.

Photocatalytic Degradation of Plastic Waste: A Mini Review

Plastic waste becomes an immediate threat to our society with ever-increasing negative impacts on our environment and health by entering our food chain. Sunlight is known to be the natural energy source that degrades plastic waste at a very slow rate. Mimicking the role of sunlight, the photocatalytic degradation process could significantly accelerate the degradation rate thanks to the photocatalyst that drastically facilitates the photochemical reactions involved in the degradation process. This mini review begins with an introduction to the chemical compositions of the common plastic waste. The mechanisms of photodegradation of polymers in general were then revisited. Afterwards, a few photocatalysts were introduced with an emphasis on titanium dioxide (TiO2), which is the most frequently used photocatalyst. The roles of TiO2 photocatalyst in the photodegradation process were then elaborated, followed by the recent advances of photocatalytic degradation of various plastic waste. Lastly, our perspectives on the future research directions of photocatalytic plastic degradation are present. Herein, the importance of catalytic photodegradation is emphasized to inspire research on developing new photocatalysts and new processes for decomposition of plastic waste, and then to increase its recycling rate particularly in the current pandemic with the ever-increasing generation of plastic waste.

Recent advancements in supporting materials for immobilised photocatalytic applications in waste water treatment

The aim of this paper is to provide a review on the usage of different anchoring media (supports) for immobilising commonly employed photocatalysts for degradation of organic pollutants. The immobilisation of nano-sized photocatalysts can eliminate costly and impractical post-treatment recovery of spent photocatalysts in largescale operations. Some commonly employed immobilisation aids such as glass, carbonaceous substances, zeolites, clay and ceramics, polymers, cellulosic materials and metallic agents that have been previously discussed by various research groups have been reviewed. The study revealed that factors such as high durability, ease of availability, low density, chemical inertness and mechanical stability are primary factors responsible for the selection of suitable supports for catalysts. Common techniques for immobilisation namely, dip coating, cold plasma discharge, polymer assisted hydrothermal decomposition, RF magnetron sputtering, photoetching, solvent casting, electrophoretic deposition and spray pyrolysis have been discussed in detail. Finally, some common techniques adopted for the characterisation of the catalyst particles and their uses are also discussed.