Catalytic Degradation of the UV-filter Phenylbenzimidazole Sulfonic Acid Lead by Synthesized ZnONPs

Graduate #45
Discipline: Chemistry and Chemical Sciences
Subcategory: Chemistry (not Biochemistry)

Loraine Soto-Vázquez - Turabo University
Co-Author(s): Francisco Márquez, Turabo University, Gurabo, PR

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Water pollution has emerged as a primary concern in environmental issues due to the consumption of pharmaceuticals and personal care products, which are chemical substances resilient to traditional remediation methods. Due to this, photocatalysis has been considered as promising decontamination method because the capability to mineralize the pollutant.

Zinc oxide nanoparticles (ZnONPs) were synthesized, characterized and employed as the catalyst to test the hypothesis that the photodegradation depends on the catalyst loading. Also, a higher catalytic activity depends on the pollutant concentration because at saturation conditions the interaction between the catalyst and the pollutant is diminished. ZnONPs were synthesized via precipitation using zinc acetate, and fully characterized by SEM-EDS, XRD and Raman spectroscopy. This material was used to prove the photocatalytic activity against phenylbenzimidazole sulfonic acid (PBSA), using a homemade photoreactor and varying the catalyst loading and the initial concentration of PBSA to determine the optimal experimental conditions by analyzing aliquots at different times by UV-vis spectroscopy.

Sphere-like particles of 100 nm diameter were identified with a wurtzite crystal structure with an elemental composition of zinc and oxygen. The hypothesis was confirmed and an optimal catalyst loading of 1.0 gL-1 was able to achieve 50% of photodegradation. When the catalyst loading increases, a lower photodegradation activity occurs suggesting that a light screening effect is produced. 90% of photodegradation was achieved at a lower concentration confirming the second hypothesis. These results suggest that when PBSA initial concentration increases, the interaction with the ZnONPs decreases, resulting in a lower photocatalytic activity. By means of control experiments it was determined that the radiation, oxygen sources and the catalyst are necessary, since the degradation of PBSA is negligible under anoxic conditions, or in absence of catalyst or radiation source.

In conclusion, we successfully synthesized and characterized ZnONPs and a high photocatalytic activity was shown with degradation rates of 90% of PBSA in a short period of time, suggesting that this process is a viable option to clean polluted water sources. The next step, with the aim of confirming this process as an environmentally remediation solution, the photoproducts of PBSA will be characterized by UPLC-MS.

Not Submitted

Funder Acknowledgement(s): Financial support provided by the US DoE, through the Massie Chair project at University of Turabo, and US DoD under contract W911NF-14-1-0046 are gratefully acknowledged. Also the authors thank the Molecular Science Research Center at University of Puerto Rico for the Raman characterization.

Faculty Advisor: Francisco Márquez, fmarquez@suagm.edu