Photoelectrocatalytic degradation of sulfamethoxazole on g-C3N4/BiOI/EG p-n heterojunction photoanode under visible light irradiation

Abstract

Sulfamethoxazole (SMX) is one of the antibiotics which is used to treat a variety of bacterial infections in both humans and animals. The inflow of this pharmaceutical drug from various sources into the aquatic environment necessitates the development of new and efficient technologies for its removal from water. As such, a stand-alone and robust photoanode made from a p-n heterojunction of BiOI and g-C3N4 anchored on exfoliated graphite was fabricated and used in the photoelectrocatalytic degradation of SMX pollutant. Herein, we report the synthesis, characterization and photoelectrochemical application of graphitic carbon nitride/bismuth oxyiodine/exfoliated graphite (g-C3N4/BiOI/EG) photoanode for removal of SMX as a target pollutant from the water. The g-C3N4/BiOI/EG nanocomposite was synthesized using ultrasonication method and characterized using X-RD, FTIR, Raman spectroscopy, TGA, FESEM coupled with EDS, TEM, UV–Vis DRS and XPS techniques. The results revealed that the BiOI microspheres and irregular g-C3N4 sheets were anchored on the structure of EG sheets. The electrochemical properties of the fabricated photoanodes were studied by CV and EIS using 5 mM [Fe(CN)6]3−/4- contained in 0.1 M KCl solution. The ternary g-C3N4/BiOI/EG photoanode was found to be displaying better electron-hole separation and optical properties due to the formation of p-n heterojunction in the ternary nanocomposite photoanode. The decrease in concentration of SMX was monitored using a UV–Vis spectrophotometer. The optimum current density and pH used were 5 mA cm−2 and 6.23 respectively. At the optimum conditions, the antibiotic removal efficiency was 88% with a rate constant of 7.65 × 10−3 min−1 and correlation coefficient (R2) of 0.997. The results showed that g-C3N4/BiOI/EG photoanodes can be applied in the photoelectrochemical degradation of pharmaceutical pollutants in water.