Angela Severino

Microplastic (MP) pollution represents a major environmental challenge because of its persistence and widespread accumulation in aquatic and terrestrial ecosystems. This review critically examines current technologies for MP removal and degradation, with particular emphasis on heterogeneous photocatalysis and its integration into photocatalytic membrane reactors (PMRs). Biological, physicochemical and advanced oxidation processes—including adsorption, membrane bioreactors, electrocoagulation, flotation, advanced filtration, sol–gel technologies and photocatalytic systems—are analyzed in terms of mechanisms, advantages, limitations and remediation potential. The literature identifies heterogeneous photocatalysis as one of the most promising approaches for degrading recalcitrant polymers through the generation of reactive oxygen species. Recent advances in photocatalyst engineering have significantly enhanced the performance of TiO₂-, ZnO-, WO₃-, graphene-, CdS- and MOF-based materials. Particular attention is devoted to PMRs, which combine photocatalytic degradation with membrane separation, enabling continuous operation, efficient photocatalyst recovery, improved removal efficiency and reduced membrane fouling. The review also highlights plastic photoreforming as an emerging strategy for simultaneously converting plastic waste into hydrogen and other value-added chemicals. Overall, integrated photocatalytic membrane systems offer a promising and sustainable platform for large-scale MP remediation, although further research is needed to improve long-term stability, energy efficiency and industrial-scale implementation.

Conventional wastewater treatment plants (WWTPs) have limited efficiency in removing emerging pollutants (EPs), meaning these pollutants persist and lead to widespread ecological contamination. In this study, real effluents from a WWTP were characterized using TOC and Py-GC/MS, which indicated the presence of various organic compounds that could be indicative of micro-nanoplastics (MNPs) or plastics additives. To address this challenge, we propose the use of a photocatalytic membrane reactor (PMR) as an advanced treatment system capable of achieving high degradation efficiency under mild operating conditions. Preliminary experimental tests were conducted using various commercial photocatalysts (TiO₂, WO₃, Nb₂O₅), four UV lamps, and oxidants (air, O₂) using added Gemfibrozil (GEM) as a drug model compound. Real effluent samples collected from WWTP were tested with and without pretreatment to remove coarse particles prior to photocatalysis. Mineralization was achieved in both cases, but it occurred at a higher rate for the pretreated effluent. The mineralization of GEM and EPs in real effluent was achieved within five hours under UV irradiation using titanium dioxide (TiO₂) as a low-cost photocatalyst in a PMR. The results highlight the potential of photocatalytic systems, and particularly PMRs, as a promising technology for removing recalcitrant pollutants in real effluents offering a viable solution for improved environmental protection.

The accumulation of microplastics and nanoplastics in aquatic environments has raised significant concerns in recent years, given the potential health risks to both aquatic ecosystems and humans; due to their nanometer size, they enter the food chain of aquatic species and consequently that of humans too. This study presents an efficient plasmonic photocatalyst for degrading polystyrene nanoplastics (PS NPs), while simultaneously generating green hydrogen in the process. Blank controls show that the presence of PS NPs is necessary for H₂ evolution, since under identical conditions, it does not occur in their absence. A series of visible light-responsive plasmonic photocatalysts consisting of TiO₂ nanoparticles (NPs) supporting Pd, Au, Pt, and Ag NPs were prepared via the impregnation method. Among the synthesized nanoparticle photocatalysts, the 3 wt % Pd/TiO₂ NP photocatalyst exhibited superior hydrogen generation, producing 1329.76 μmol_H2 g_cat ^–1 after 2 h of irradiation, while also achieving a reduction in the average PS NP diameter. This study illustrates the potential of solar NP photocatalysis for environmental remediation and simultaneous hydrogen evolution.