Novel visible-driven Ag2O/Fe2O3/TiO2 nano sized hetero-structured photocatalyst: Synthesis, characterization and photo-degradation of tetracycline

Bimetallic Ag/Fe-MOG derived flake-like Ag2O/Fe2O3 p-n heterojunction for efficient photodegradation organic pollutants within a wide pH range

In this paper, we reported a facile and clean strategy to prepare the flake-like Ag2O/Fe2O3 bimetallic p-n heterojunction composites for photodegradation organic pollutants. The surface morphology, crystal structure, chemical composition and optical properties of Ag2O/Fe2O3 were characterized by SEM, high-resolution TEM images with EDX spectra, XRD, XPS, FT-IR and UV-vis DRS spectra respectively. The formation of Ag2O/Fe2O3 p-n heterojunction facilitated the interfacial transfer of electrons as well as the separation of charge carries. Hence, the as-synthesized Ag2O/Fe2O3-3 composites exhibited ultra-high photocatalytic activity. Under the experimental conditions of catalyst dosage of 0.4 mg mL-1 and irradiation time of 60 min, the degradation conversion rate of rhodamine B reached 96.1 %, which was 5.0 and 2.8 times of pure phase Ag2O and Fe2O3, respectively. Meanwhile, the degradation performance of Ag2O/Fe2O3-3 was not limited by pH, and it can achieve high degradation efficiency under 3-11. In addition, Ag2O/Fe2O3-3 also showed superb degradation ability for other common anionic dyes, cationic dyes and antibiotics. XPS and FT-IR spectra showed that Ag2O/Fe2O3-3 retained a carbon skeleton that facilitated electron transport and light absorption conversion. And the analyses of quenching experiment and EPR demonstrated •O2-, •OH and h+ were crucial reactive oxidant species contributing to the rapid organic pollutant degradation. This work provides new insights into obtaining p-n photocatalysts heterojunction with excellent catalytic activity for removing organic pollutants from wastewater.

Floating Carbon-Doped TiO2 Photocatalyst with Metallic Underlayers Investigation for Polluted Water Treatment under Visible-Light Irradiation

In the current study, we analysed the influence of metallic underlayers on carbon-doped TiO2 films for RhB decomposition and Salmonella typhimurium inactivation under visible-light irradiation. All the experiments were divided into two parts. First, layered M/C-doped-TiO2 film structures (M = Ni, Nb, Cu) were prepared by magnetron sputtering technique on borosilicate glass substrates in the two-step deposition process. The influence of metal underlayer on the formation of the carbon-doped TiO2 films was characterised by X-ray diffractometer, scanning electron microscope, and atomic force microscope. The comparison between the visible-light assisted photocatalytic activity of M/C-doped TiO2 structures was performed by the photocatalytic bleaching tests of Rhodamine B dye aqueous solution. The best photocatalytic performance was observed for Ni/C-doped-TiO2 film combination. During the second part of the study, the Ni/C-doped-TiO2 film combination was deposited on high-density polyethylene beads which were selected as a floating substrate. The morphology and surface chemical analyses of the floating photocatalyst were performed. The viability and membrane permeability of Salmonella typhimurium were tested in cycling experiments under UV-B and visible-light irradiation. Three consecutive photocatalytic treatments of fresh bacteria suspensions with the same set of floating photocatalyst showed promising results, as after the third 1 h-long treatment bacteria viability was still reduced by 90% and 50% for UV-B and visible-light irradiation, respectively. The membrane permeability and ethidium fluorescence results suggest that Ni underlayer might have direct and indirect effect on the bacteria inactivation process. Additionally, relatively low loss of the photocatalyst efficiency suggests that floating C-doped TiO2 photocatalyst with the Ni underlayer might be seen as the possible solution for the used photocatalyst recovery issue.