Application of nanocomposites based on TiO2 and clay minerals for the photocatalytic degradation of low-density polyethylene microplastics

The widespread pollution of microplastics, particularly low-density polyethylene, in various ecosystems has raised substantial environmental and health concerns. The urgent need to mitigate microplastic pollution has led to extensive research, with photocatalysis emerging as one of the most effective methods for microplastic degradation. This study investigates the efficacy of nanocomposites based on TiO2 and clay minerals as photocatalysts in the photocatalytic degradation of low-density polyethylene microplastics under UV-A light irradiation, in aqueous solution. The incorporation of TiO2 within clay layers improved optical properties and photocatalytic performance, reducing the band gap from 3.10 eV for bare TiO2 to 2.95 eV and 2.88 eV for TiO2-MMT and TiO2-Kao, respectively. After 480 min, the mass loss of microplastics showed 14.90% with TiO2, 21.25% with TiO2-MMT, and 28.36% with TiO2-Kao. µ-FTIR analysis confirmed carbonyl group formation in low-density polyethylene, with the highest carbonyl index value of 1.41 observed using TiO2-Kao. The effects of operating variables, including irradiation time, the LDPE-to-catalyst ratio, pH, and ionic strength, were also investigated. The highest mass loss using TiO2-Kao was 30.96% in 60 min under strongly acidic conditions. Doubling the TiO2-Kao amount in the reaction system increased the mass loss of LDPE by up to 10%. On the contrary, at high ionic strength values, LDPE experienced twice the lower mass loss compared to values at distilled water. This study highlights the potential of using nanocomposites based on TiO2 and clay minerals for the photocatalytic degradation of LDPE, emphasizing the importance of optimization of reaction parameters.