Abstract
Heterogeneous photocatalysts for water decontamination were obtained by the optimized synthesis of bismuth-functionalized reduced graphene oxide (rGO/Bi) using the Hummer method and microwave treatment. Sulfamethazine (SMZ) was used as model pollutant to evaluate the photocatalytic efficacy. Photocatalysts were characterized by VP-SEM, HRTEM, XDR, XPS, RAMAN, and FTIR analyses, which confirmed the effective reduction of GO to rGO and the presence of bismuth as a crystalline phase of Bi2O3 polydispersed on the surface. Their performance was influenced by the rGO/Bi ratio, microwave temperature, and treatment time. The as-obtained 5%rGO/Bi composite had the highest photocatalytic activity for SMZ degradation under visible light irradiation (λ > 400 nm), achieving 100% degradation after only 2 h of treatment. The degradation yield decreased with higher percentages of rGO. Accordingly, the rGO/Bi catalysts efficiently removed SMZ, showing a high photocatalytic activity, and remained unchanged after three treatment cycles; furthermore, cytotoxicity tests demonstrated the nontoxicity of the aqueous medium after SMZ degradation. These findings support the potential value of these novel composites as photocatalysts to selectively remove pollutants in water treatment plants.
Highlights
Sulfamethazine (SMZ) is an anti-infective agent used as antibiotic in human and veterinary medicine against bacteria responsible for bronchitis and prostatic and urinary tract infections, among others
Analyses demonstrated that Graphene oxide (GO) is efficaciously reduced to reduced graphene oxide (rGO) and bismuth is polydispersed on the surface as a crystalline phase of Bi2 O3
Diffuse reflectance analysis showed an increase in band gap energy with lower percentages of rGO, making the rGO/Bi hybrid material more sensitive to visible light irradiation (λ > 400 nm), with a positive effect on SMZ degradation
Summary
Sulfamethazine (SMZ) is an anti-infective agent used as antibiotic in human and veterinary medicine against bacteria responsible for bronchitis and prostatic and urinary tract infections, among others. The strong antimicrobial activity, stable chemical properties, and low cost of SMZ have led to its widespread utilization [1,2]. Prolonged exposure to low concentrations of antibiotics in water can be cytotoxic or promote resistance to bacterial strains, posing a major public health challenge [3]. Advanced oxidation processes (AOPs) have proven effective to oxidize compounds resistant to conventional biological treatments, minimizing the discharge of these contaminants into the environment [4,5]. Heterogeneous photocatalysis is an AOP that benefits from the easy preparation of photocatalysts, their reusability, and their selectivity against contaminants. Photocatalysis induced by visible light offers further advantages, given the hazard-free and sustainable nature of sunlight and its inexhaustible supply
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