Chlorophyll sensitized and salicylic acid functionalized TiO2 nanoparticles as a stable and efficient catalyst for the photocatalytic degradation of ciprofloxacin with visible light

Photocatalytic degradation of ciprofloxacin from water with waste polystyrene and TiO2 composites

Ciprofloxacin (CIP) is one of the widely used antibiotics with a broad antimicrobial spectrum in the fluoroquinolone type. Its concentration in water bodies has increased over the years due to its frequent use. Since ciprofloxacin in the aquatic ecosystem adversely affects human health as well as other organisms, it must be removed from wastewater. The aim of this study was to develop Polystyrene (PS) and Titanium dioxide (TiO2) composites that can be used as catalysts in CIP removal by photocatalytic process. Waste PS (obtained from disposable cutlery) was used in the synthesis of these composites. In this study, PS-TiO2 composites with different PS content (C20, C50, C80; the numbers in the names indicate the PS percentage in the composite by weight) were synthesized. This is important in terms of the use of one waste in the removal of another waste. This process was optimized using Box-Behnken design, one of the response surface method. Parameters such as the amount of polymer in the composite, pH and initial CIP concentration were studied and their effects on CIP removal were found. The validity and adequacy of the selected model were evaluated according to the relevant statistical data. These are R2 = 0.9751, adjusted R2 = 0.9565, the model's p-value <0.05 and the lack of fit-value 0.246. Optimum conditions for CIP removal were obtained when the C50 was used, with a pH value of 3 and an initial CIP concentration of 5 mg/L. In the process carried out under these conditions, the CIP removal was found to be 95.01 % at the end of 180 min. This value was predicted as 94.37 % in the model. According to these results, C50 composite synthesized with waste PS can be used effectively for CIP removal.

Effluent toxicity study using biomarkers for ciprofloxacin photoelectrocatalytic degradation by bismuth-doped titanium dioxide nanotubes

Ciprofloxacin hydrochloride (CIP) is a broad-spectrum synthetic antibiotic often found in domestic sewage and industrial waste due to the inefficiency of conventional treatments. Given the potential risk of drug accumulation, this study presents coatings of titanium dioxide nanotubes (TiO2) doped with different bismuth (Bi) concentrations to degrade CIP through photocatalytic and photoelectrochemical processes. Characterization studies revealed that bismuth (Bi) doping affected the morphology of the materials, with concentrations of 0.01 and 0.05 mol L-1, resulting in collapsed materials with a smaller active surface area. Photocatalysis tests for all the materials exhibited a similar degree of efficiency to photolysis, approximately 33%. Ecotoxicity tests using the biomarkers Lactuca sativa L., Lemna minor, and Artemia salina indicated that, although they were similar to photolysis in terms of efficiency, the effluents generated when employing the doped catalysts showed lower levels of toxicity, with the best results achieved for the material doped with 0.005 mol L-1 of Bi, with a toxicity level approximately 40% lower. Photoelectrocatalysis proved to be the most efficient CIP degradation technique. The highest degradation rate was observed for materials doped with 0.005 mol L-1 of Bi, with an efficiency of 46%, which is 1.4 times more efficient than photolysis. These results demonstrate that materials doped with low amounts of Bi can be effectively used as photoanodes for drug degradation, as their performance is superior, and the final product generated exhibits low toxicity to living organisms.

Facile aqueous synthesis and comparative evaluation of TiO2-semiconductor and TiO2-metal nanohybrid photocatalysts in antibiotics degradation under visible light

Advanced oxidation processes using TiO2-based nanomaterials are sustainable technologies that hold great promise for the degradation of many types of pollutants including pharmaceutical residues. A wide variety of heterostructures coupling TiO2 with visible-light active nanomaterials have been explored to shift its photocatalytic properties to harness sun irradiation but a systematic comparison between them is lacking in the current literature. Furthermore, the high number of proposed nanostructures with different size, morphology, and surface area, and the often complex synthesis processes hamper the transition of these materials into commercial and effective solutions for environmental remediation. Herein, we have designed a facile and cost-effective method to synthesize two heterostructured photocatalysts representative of two main families of novel structures proposed, hybrids of TiO2 with metal (Au) and semiconductor (CeO2) nanomaterials. The photocatalysts have been extensively characterized to ensure a good comparability in terms of co-catalyst doping characteristics, morphology and surface area. The photocatalytic degradation of ciprofloxacin and sulfamethoxazole as target pollutants, two antibiotics of high concern polluting water sources, has been evaluated and CeO2/TiO2 exhibited the highest activity, achieving complete antibiotic degradation at very low photocatalyst concentrations. Our study provides new insights into the development of inexpensive heterostructured photocatalysts and suggests that the non-stoichiometry and characteristic d and f electronic orbital configuration of CeO2 have a significantly improved role in the enhancement of the photocatalytic reaction.

Synthesis of CuO/GO-DE Catalyst and Its Catalytic Properties and Mechanism on Ciprofloxacin Degradation

A new catalyst, copper oxide/graphene oxide-diatomaceous earth (CuO/GO-DE), was prepared by the ultrasonic impregnation method. The optimal conditions for catalyst preparation were explored, and its structure and morphology were characterized by BET, XRD, SEM, TEM, FTIR, Raman and XPS. By taking ciprofloxacin as the target pollutant, the performance and reusability of CuO/GO-DE to degrade antibiotic wastewater was evaluated, and the optimal operating conditions were obtained. The main oxidizing substances in the catalytic system under different pH conditions were analyzed, as well as the synergistic catalytic oxidation mechanism. The intermediate products of ciprofloxacin degradation were identified by LC-MS, and the possible degradation process of ciprofloxacin was proposed.