Photocatalytic degradation of 5-fluorouracil in an aqueous environment via Bi–B co-doped TiO2 under artificial sunlight

Abstract

The morphology of a series of Bi–B co-doped titanium oxide photocatalysts and its optical properties were characterized. The results suggested that boron and bismuth as co-dopants were incorporated into the framework of titanium matrix. For the B and Bi-doped TiO2 samples, surface area decreased while the Bi content increased. Based on the photoluminescence spectra, a decrease in recombination rate of photogenerated carriers was observed with the increasing amount from 0.5 to 3 mol% of Bi in Bi–B–TiO2 composites. The most active photocatalyst in 5-fluorouracil (5-FU) photodegradation was 3 mol% of Bi in Bi–B–TiO2. The effects of operating parameters: pH, drug concentration and natural organic matter presence (NOM) in the effluent from wastewater treatment plant, were investigated. The highest efficiency of 5-FU photodegradation was observed at neutral pH for the drug concentration equal to 1 mg/L and photocatalyst of 0.05 g/L. While in distilled water solutions, the catalyst showed good removal efficiency of the drug, the process was totally inhibited by NOM in the complex matrix which was the treated sewage, what could be connected with the internal filter and scavenging effect. Based on the identification of organic and inorganic by-products of the photooxidation, the pathway of 5-FU degradation was proposed. The mineralization was poor (5–7%) in the case of both 3Bi–B–TiO2 and pure TiO2 for the drug of 50 mg/L, but photocatalytic oxidation of drug led to non-toxic products toward Lemma minor.