Remediation of marine microlitter: proposing photocatalysis technology for the removal of HDPE and PS microplastics from polluted water before its arrival to the oceans

, Cedillo-González Erika, Cristina Siligardi.

Currently, our seas are polluted by marine litter. Marine litter is principally composed of plastic. Big items such as nets, bags, and bottles are causing entanglement and asphyxia of marine fauna. Their smaller equivalents, known as microplastics (MPs), are defined by the United Nations as small plastic particles of diameter ≤ 5 mm. A full gamma of marine species is consuming MPs. Of more significant concern is that, due to their small size and high surface area, microplastics can adsorb persistent organic pollutants (POPs), transferring them throughout the tropic chain. The solutions to microplastics environmental problem that has been already proposed include plastic recycling, environmental education and implementation of politics for reducing plastic waste generation. However, none of these proposals represents a sustainable solution for microplastic marine pollution. In this work, we propose visible light photocatalysis using N-TiO2, C,N-TiO2 and C,N-TiO2/SiO2 semiconductors for the chemical removal of primary high-density polyethylene (HDPE) and polystyrene (PS) MPs from polluted water. The photocatalysts were characterized by XRD, DRS, FTIR, BET, and FEG-SEM. The HDPE microplastics were characterized by FTIR and optical and electron microscopy. Photocatalysis was performed in aqueous media in order to facilitate the future scaling of the process into wastewater treatment plants. The influence of pH, temperature, semiconductor's form and MPs' size on the photocatalytic removal of MPs was tested. The removal process was monitored by mass loss, FTIR, carbonyl index and optical microscopy. Photolysis was also performed at the same conditions, without semiconductors. From the obtained results, it was found that at the best conditions, removal of up to 70% of the original MPs is possible. Thus, it was demonstrated that photocatalysis of MPs in an aqueous medium is possible, providing an alternative solution to marine microlitter.

View online