CdSe nanoflower as a new near infrared-activated photocatalyst for remediation of pharmaceutical wastewaters

Photocatalysis using Near Infrared (NIR) light is a promising method for a wide range of applications from environmental remediation. For this purpose, a flower-like cadmium selenide (CdSe nanoflower), as a new promising NIR-activated photocatalyst, was synthesized through a hydrothermal process and characterized using various spectroscopic and microscopic analytical techniques. The characterization results indicated that CdSe nanoflower is classified as an n-type semiconductor with a direct band gap of 1.7 eV (i.e., E_CB = −0.7 V and E_VB = 1 V indicated by Mott-Schottky analysis), and crystallite size and strain of 9.17 nm and 2.14, respectively. In the presence of various scavengers, the production of reactive oxygen species decreases, resulting in lower degradation efficiency. To investigate the photocatalytic efficacy, sulfamethoxazole (SMX) was used as a model pollutant drug molecule. The optimization of the process revealed that over 98% of SMX could be degraded under NIR irradiation and optimal conditions (pH = 7, photocatalyst dosage = 0.1 g, SMX concentration = 40 mg/L, time = 60 min), where Lagergren model with a correlation coefficient of 0.9765 was the best kinetic model describing the empirical results. The study indicates that CdSe nanoflower can be reused and regenerated up to 7 times with a 12% decrease in performance and after 60 min of degradation, the TOC concentration decreased by 81% in the best conditions. Additionally, CdSe nanoflower showed photodynamic microbial inactivation efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under NIR light irradiation, where almost 95 and 99 % of bacteria was reduced in 20 min. The results of this work show CdSe nanoflower has great potential as a photocatalytic material with antimicrobial properties in the context of wastewater treatment and the management of microbial infections.