Chung-Shin Lu

Synthesis of bismuth oxyiodides and their composites: characterization, photocatalytic activity, and degradation mechanisms

Bismuth oxyiodides have been prepared using controlled hydrothermal methods. The products are characterized by SEM-EDS, XRD, XPS, FTIR, PL, EPR, and DRS. It is illustrated that BiOI, Bi4O5I2, Bi7O9I3, Bi5O7I, and BiOxIy/BiOpIq composites can be selectively synthesized through a facile solution-based hydrothermal method. UV-Vis spectra display the bismuth oxyiodide materials as indirect semiconductors with an optical bandgap of 1.86–3.316 eV. The photocatalytic efficiency of the powder suspension is evaluated by measuring the Crystal Violet (CV) concentration. This is the first study to demonstrate the superior activities of BiOI, Bi4O5I2, Bi7O9I3, Bi5O7I, and BiOxIy/BiOpIq composites as promising visible-light-responsive photocatalysts. The quenching effects of various scavengers and EPR indicate that the reactive O2˙− plays a major role and ˙OH and h+ play a minor role. The Bi7O9I3/Bi5O7I composite shows the highest photocatalytic activity reaching a maximum rate constant of 0.2225 h−1, which is 6 times higher than that of BiOI and Bi7O9I3 and 4 times higher than that of Bi5O7I.

Mechanistic pathways differences between P25-TiO2 and Pt-TiO2 mediated CV photodegradation

The Crystal Violet (CV) dye represented one of the major triphenylmethane dyes used in textile-processing and some other industrial processes. Various metals doped titanium dioxide (TiO(2)) photocatalysts have been studied intensively for the photodegradation of dye in wastewater treatment. In order to understand the mechanistic detail of the metal dosage on the activities enhancement of the TiO(2) based photocatalyst, this study investigated the CV photodegradation reactions under UV light irradiation using a Pt modified TiO(2) photocatalyst. The results showed that Pt-TiO(2) with 5.8% (W/W) Pt dosage yielded optimum photocatalytic activity. Also the effect of pH value on the CV degradation was well assessed for their product distributions. The degradation products and intermediates were separated and characterized by HPLC-ESI-MS and GC-MS techniques. The results indicated that both the N-de-methylation reaction and the oxidative cleavage reaction of conjugated chromophore structure occurred, but with significantly different intermediates distribution implying that Pt doped TiO(2) facilitate different degradation pathways compared to the P25-TiO(2) system.

Determining the degradation efficiency and mechanisms of ethyl violet using HPLC-PDA-ESI-MS and GC-MS.

BackgroundThe discharge of wastewater that contains high concentrations of reactive dyes is a well-known problem associated with dyestuff activities. In recent years, semiconductor photocatalysis has become more and more attractive and important since it has a great potential to contribute to such environmental problems. One of the most important aspects of environmental photocatalysis is in the selection of semiconductor materials like ZnO and TiO2, which are close to being two of the ideal photocatalysts in several respects. For example, they are relatively inexpensive, and they provide photo-generated holes with high oxidizing power due to their wide band gap energy. In this work, nanostructural ZnO film on the Zn foil of the Alkaline-Manganese Dioxide-Zinc Cell was fabricated to degrade EV dye. The major innovation of this paper is to obtain the degradation mechanism of ethyl violet dyes resulting from the HPLC-PDA-ESI-MS analyses.ResultsThe fabrication of ZnO nanostructures on zinc foils with a simple solution-based corrosion strategy and the synthesis, characterization, application, and implication of Zn would be reported in this study. Other objectives of this research are to identify the reaction intermediates and to understand the detailed degradation mechanism of EV dye, as model compound of triphenylmethane dye, with active Zn metal, by HPLC-ESI-MS and GC-MS.ConclusionsZnO nanostructure/Zn-foils had an excellent potential for future applications on the photocatalytic degradation of the organic dye in the environmental remediation. The intermediates of the degradation process were separated and characterized by the HPLC-PDA-ESI-MS and GC-MS, and twenty-six intermediates were characterized in this study. Based on the variation of the amount of intermediates, possible degradation pathways for the decolorization of dyes are also proposed and discussed.

Silver Vanadium Oxide Nanomaterials: Controlled Synthesis by Hydrothermal Method and Efficient Photocatalytic Degradation of Atrazine and CV Dye

Silver vanadium oxides have received remarkable attention in recent years because of their stability, suitable band gaps, and relatively superior photocatalytic abilities. This study synthesizes silver vanadates by the hydrothermal method and investigates their photocatalytic abilities for removing crystal violet (CV) and atrazine pollutants under visible-light irradiation. The as-prepared silver vanadates are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). Crystal violet and atrazine could be successfully degraded in the presence of silver vanadate catalyst under visiblelight irradiation. The obtained results show complete degradation of crystal violet after 24 h, and over 97% of atrazine was degraded after 72 h of treatment. Moreover, the as-prepared silver vanadate materials show extremely high catalytic stability and maintain stable activity after three catalytic cycles. The scavenger study indicates that •O2− radicals are the main active species, while •OH and h+ play an assistant role in the degradation of CV and atrazine. Liquid chromatography coupled with electrospray ionization mass spectrometry is applied to the analysis of the samples coming from the photocatalytic degradation of CV and atrazine. Potential degradation pathways for atrazine are evaluated exhibiting two different degradation pathways including dechlorination-hydroxylation, alkylic-oxidationde- alkylation. The N-de-methylation of the CV dye takes place in a stepwise manner with the various N-de-methylated intermediate CV species. The excellent activity and photostability reveal that silver vanadate is a promising visiblelight- responsive photocatalyst for water and wastewater treatment.

Erratum to: Determining the degradation efficiency and mechanisms of ethyl violet using HPLC-PDA-ESI-MS and GC-MS

This is a correction to the following paper: Determining the degradation efficiency and mechanisms of ethyl violet using HPLC-PDA-ESI-MS and GC-MS, Wen-Hsin Chung, Chung-Shin Lu, Wan-Yu Lin, Jian-Xun Wang, Chia-Wei Wu, Chiing-Chang Chen, Chemistry Central Journal 2012, 6:63 (30 June 2012).