Enhanced Aqueous Photo-Degradation of Ciprofloxacin and Tetracycline Using Ag-Decorated ZnO Plasmonic Catalyst
Shirley P. Onkani, Samson O. Akpotu, Paul N. Diagboya, Fanyana M. Mtunzi, Emmanuel Osabohien
Abstract
High Resolution Image Download MS PowerPoint Slide One major group of aqueous emerging contaminants is antibiotics. The occurrence in potable water is increasing, and their presence has several unintended consequences, including antibiotic resistance. This has led to over seven hundred thousand deaths annually, a value projected to hit 10 million by 2050, hence the need for their removal. Most current potable water treatment technologies are not well suited to antibiotic elimination. Hence, photocatalytic degradation was studied here. A comparative photo-degradation of two antibiotics, ciprofloxacin (CPF) and tetracycline (TC), was investigated using a ZnO photocatalyst and its Ag-doped (2.5%, 5%, and 7.5%) species. The Ag-doping did not significantly affect the ZnO crystal structure but enhanced the specific surface area and pore size values and lowered the band gap energies. The 2.5 wt % Ag-ZnO expressed the best properties and exhibited up to 50% and 43% enhancement in the degradation of CPF and TC, respectively, compared to the pristine ZnO photocatalysts. It exhibited excellent reusability, retaining ∼82% and 91% of the initial degradation of CPF and TC, respectively, after four cycles. The observed optimum parameters for the effective degradation of both antibiotics are a mass of ∼35 mg at pH 9 (alkaline medium) using a concentration of 12 mg/L in a solution volume of 350 mL over a time range of 120 min. The 2.5 wt % Ag-ZnO is a promising applicable material for potable water treatment.