Polymeric nanocomposite materials for photocatalytic detoxification of polycyclic aromatic hydrocarbons in aquatic environments-A review

Polycyclic aromatic hydrocarbons (PAHs) are a known class of persistent and ubiquitous contaminants not only found in sediments but also associated with coastal areas and waters of urbanized estuaries. Due to their hy-drophobic nature, PAHs tend to accumulate in the aquatic sediments, leading to bioaccumulation and elevated concentrations over time which is of global concern owing to the serious health risks that they pose to both humans and aquatic life. However, this review highlights various polymeric nanocomposite materials (PNMs) used for the photocatalytic degradation and mechanism of PAHs in aquatic sediments and associated water bodies. It presents the current progress made in the understanding of the toxicological effects of PAHs and mechanisms of their detoxification using photocatalytic processes as an alternative green method for environ-mental pollution, remediation and control. The paper also provides a brief account of the chemistry, origin and photocatalytic transformation of PAHs, highlighting their bioaccumulation in aquatic sediments and marine environments. It finally accentuates the significance of PNMs as a plausible candidate for the effective treatment of PAHs-contaminated aquatic environments. The available literature reveals that a small number of PNMs has been used to photodegrade PAHs in industrial effluents, seawater, aqueous solution and synthetic wastewater samples. Anthracene, phenanthrene, 2-naphthol and naphthalene as low molecular weight-PAHs were photo -degraded using these PNMs under natural light. The findings also show that only chitosan-and graphene oxide -based PNMs have been employed to photodegrade these kinds of PAHs in water matrices. Most of the PNMs found in the literature were based on the iron oxide or magnetite incorporation which generates reactive oxygen species via AOPs. Another finding was no study was conducted on the photodegradation of PAHs in soil and sediments which are their main sink in the environment.