ADVANCEMENT OF SOLAR-POWERED PHOTOCATALYTIC COMPOSITES FOR THE REMOVAL OF PHARMACEUTICAL CONTAMINANTS FROM WATER
Abstract:
The presence of pharmaceutical contaminants in water has become a growing concern due to their negative impacts on aquatic ecosystems and the development of antibiotic resistance. Existing techniques for removing these contaminants are often expensive, slow, or produce toxic by-products. Photocatalysis has emerged as a promising method for water treatment due to its efficiency, low mass transfer limitation, and environmental compatibility. In this study, solar-active composites were synthesized using waste biomass from Carica papaya seeds and Musa paradisiaca peels, combined with abundant clay, to degrade four pharmaceutical compounds (Acetaminophen, Ampicillin, Arthemether, and Sulfamethoxazole) in water.
The composites were prepared in two forms: TiO2-modified composites and metal-doped composites, with tungstate and kaolinite as common components. X-ray diffraction analysis confirmed the presence of semiconductor materials (ZnWO4, CuWO4, FeWO4, and TiO2) responsible for the photocatalytic activity of the composites. Photoluminescence and Electron Paramagnetic Resonance (EPR) spectroscopy revealed the presence of defect states induced by carbon and kaolinite, enhancing the photocatalytic performance.
Evaluation of the TiO2-modified composites under sunlight showed that TiO2@ZnWO4 composite exhibited the highest efficiency, achieving complete photodegradation of the target pharmaceutical compounds within 30 minutes, with mineralization rates of 80% and approximately 50% for Ampicillin and Sulfamethoxazole, respectively. The metal-doped composites demonstrated even better photodegradation efficiency, particularly the Cu@ZnWO4 composite, which achieved 100% efficiency for Ampicillin and 68% efficiency for Sulfamethoxazole. The photocatalytic process resulted in the formation of inorganic by-products (NO3-, NO2-, and SO42-) within permissible limits for drinking water according to WHO standards.
The efficiency of both types of composites was minimally affected by changes in electrolyte concentrations, except for Cu@ZnWO4, which exhibited increased efficiency for Sulfamethoxazole with higher electrolyte concentrations. The composites displayed a slight decrease in efficiency (approximately 6%) after five cycles of reusing for Ampicillin removal, while Cu@ZnWO4 consistently lost efficiency when reusing for Sulfamethoxazole removal. Electron Paramagnetic Resonance (EPR) studies indicated that surface oxygen vacancies and defects in the crystal lattices of the composites contributed to their enhanced photocatalytic activity.
Furthermore, the composites effectively removed Ampicillin and Sulfamethoxazole from more complex water matrices, including raw wastewater from an abattoir, a river, and a hand-dug well used for drinking water. These findings highlight the potential of the composites for the development of point-of-use water treatment devices, enabling the effective treatment of drinking water contaminated with pharmaceutical compounds.
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