Valorisation of metal-contaminated microplastic waste in the synthesis of porous metal-modified TiO2 semiconductors

Microplastics (MP), plastic debris under 5 mm in size, pose significant environmental and societal risks. These MP, found globally in various environments, are ingested by marine and terrestrial life, causing health problems and contaminating food sources such as seafood. MP have also been detected in human placentas and breast milk. Tackling MP pollution is challenging due to the need for global management practices. The circular economy presents a viable solution to MP pollution. After recovering MP through adsorption, filtration, or coagulation, we can use them as secondary raw materials (SRM) for producing high-value products. For instance, polyethylene (PE) MP can be converted into biodegradable polymers, and polyethylene terephthalate (PET) MP can be transformed into hydrogen and organics through photocatalysis. These products can find applications as biodegradable packaging or for energy production. However, these methods often use pure polymers, not real-world MP, that may contain adsorbed pollutants like heavy metals (HM). Our proposed method addresses this issue, offering a way to repurpose HM-contaminated MP and potentially reduce their environmental impact. We used HM-contaminated MP as porogenic agents and metal sources in the sol-gel synthesis of TiO2-based semiconductors. Ni, Zn, Cd and Cu contaminated PE MP were mixed with a titanium alkoxide in an acid medium (to promote the release of metals) to produce the sol, which was aged into a gel and then subjected to calcination to produce porous Ni-, Zn-, Cd-, and Cu-TiO2 semiconductors. The obtained materials demonstrated photocatalytic activity against pollutants like dyes from the textile industry and fatty acids. As the CO2 derived from the calcination of MP can be captured and transformed into valuable products, this approach provides a viable method for repurposing HM-contaminated MP collected through remediation strategies, avoiding the accidental release of the recovered MP in other environmental compartments. Also see: https://micro2024.sciencesconf.org/558454/document