Synthesis of photocatalyst composite films from recycled plastics via hot pressing for dye wastewater treatment†

Abstract

The design and synthesis of self-suspended photocatalyst films are vital for environmental protection and resource management. We fabricated plastic-supported Pt/N–TiO₂ (PNT) photocatalyst films from waste plastic via hot pressing. We examined the effects of hot-pressing parameters on visible-light-responsive photocatalyst films made from high-impact polystyrene (HIPS), and the influence of source (virgin vs. recycled) and of other waste plastics (polypropylene and polyethylene terephthalate) on the properties and photocatalytic activity of hot-pressed films. When the temperature was not high enough, the polymer did not melt completely, leading to uneven surfaces and poor photocatalyst dispersion. Excessive pressure caused overcompression, increased film hardness, and hindered photocatalyst loading. The optimal parameters for film preparation using recycled HIPS were 140 °C and 90 kg cm⁻². Recycled HIPS containing hydrophilic additives exhibited better photocatalytic performance than virgin HIPS. Under optimal conditions, all three types of recycled plastic were effectively pressed into film. After 15 cycles of simulated solar irradiation, HIPS(R)/PNT exhibited 73.17% acid red 1 decolorization and 92.82% catalyst retention. The amorphous nature of HIPS facilitates tight photocatalyst loading, highlighting the potential of recycled HIPS as a photocatalyst carrier. We successfully developed a green waste-derived photocatalyst film preparation method for dye wastewater treatment and waste-plastic recycling.