-Tang Chang

Assessment upon azo dye decolorization and bioelectricity generation by Proteus hauseri.

This study explored dye decolorization and bioelectricity generation of indigenous Proteus hauseri ZMd44 for dye-bearing wastewater treatment. Chemical structures of azo dyes apparently affected the performance of dye biodecolorization. Additions of diazo dye C.I. reactive blue 160 (RBu160) stimulated simultaneous dye decolorization and bioelectricity generation of ZMd44 in single chamber microbial fuel cells (MFCs). However, high-level additions of RBu160 repressed capabilities of power production in MFC due to competition of electrons used for reductive decolorization. Decolorized intermediates of RBu160-phenyl methadiamine and 5-sulfoanthranilic acid as electron shuttles might mediate electron transport for current generation in MFC.

Comparative study on characteristics of azo dye decolorization by indigenous decolorizers.

This study provides a first attempt to explore indigenous strains with excellent decolorization capability from the most biodiverse region in Taiwan for dye-bearing wastewater treatment. Bacterial isolates were obtained via serial selections under selection pressure of the fungicide nystatin and model textile dye(s). According to profiles of protein expression and PCR-augmented 16S rRNA gene analyses for strain identification, >99% of nucleotide sequences in isolated strains were identical to type strains Aeromonas hydrophila, Klebsiella pneumoniae, Enterobacter cancerogenus, Proteus hauseri, Acinetobacter johnsonii. This first-attempt study not only explored most abundant decolorizers in Taiwan, but also compared their color removal performance for further applications.

Deciphering characteristics of bicyclic aromatics--mediators for reductive decolorization and bioelectricity generation.

This first-attempt study quantitatively assessed electron-mediating characteristics of bicyclic aromatics - 1-amino-2-naphthol, 4-amino-1-naphthol (i.e., decolorized intermediates of azo dyes - orange I and II) for color removal and power generation in MFCs. According to cyclic-voltammetric profiles, the presence of reduction and oxidation peak potentials clearly suggested a crucial role of these intermediates as electron-shuttling mediators. Shake-flask cultures also showed that appropriate accumulation of 1A2N, 4A1N apparently enhanced color-removal efficiencies of bacterial decolorization. This study clearly suggested that suitable supplementation of electrochemically active electron shuttle(s) to dye-bearing MFCs is a promising strategy to stimulate reductive decolorization and bioelectricity generation.

Exploring characteristics of bioelectricity generation and dye decolorization of mixed and pure bacterial cultures from wine-bearing wastewater treatment

This study uncovered microbial characteristics of bioelectricity generation and dye decolorization in single-chamber microbial fuel cells (MFCs) using activated sludge for wine-containing wastewater treatment. Phylogenetic tree analysis on 16S rRNA gene fragments indicated that the predominant strains on anodic biofilm in acclimatized MFCs were Gamma-Proteobacteria Aeromonas punctata NIU-P9, Pseudomonas plecoglossicida NIU-Y3, Pseudomonas koreensis NIU-X8, Acinetobacter junii NIU-Y8, Stenotrophomonas maltophila NIU-X2. Our findings showed that the current production capabilities of these pure strains were only ca. 10% of those of their mother activated sludge, indicating that synergistic interactions among microbes might be the most influential factor to maximize power generation in MFCs. Plus, these electrochemically active strains also performed reductive decolorization of C.I. reactive blue 160, suggesting that bioelectricity generation might be directly associated to azo dye decolorization to deal with electron transfer on anodic biofilm in MFCs.

Assessment of the strategies for reducing volatile organic compound emissions in the automotive industry in Taiwan

Automotive coating processes must adhere to consumer preferences, such as anti-rust, weatherproof and overall appearance of coatings. Some solvents are added as thinners and additives to avoid excessive viscosity of the coating materials and to increase facility in painting. In addition, solvents use in the automotive industry in Taiwan is estimated at 7200 ton/year in major coating processes, including electrodeposition coating, primer coating, top coating, and bar coating. Volatile organic compounds (VOCs) are not easily controlled. It is important to know the VOC-pollution sources and emission characteristics before treating the VOCs in automobile industry. In this study, 80 stacks in five factories were tested to evaluate emission characteristics in each VOC-source. After examining the flue gases, the amount of solvents used for washing spray gun and base coating are estimated at 3350 ton/year, and about 1700 ton/year for primer coat and clear coat. The organic solvents include toluene, xylene, ethyl acetate, n-butyl acetate, and ketone. VOC emission factors from each plant ranges between 500 and 650 g-VOC/l coating. To reduce the amount of coating and waste liquor, recommended methods include increasing gun spray efficiency, lengthening the same color-painting period, reducing the solvent content in painting and adding treatment equipment. The high-solid content painting, waterborne coat, and powder coat should be used for traditional painting. Moreover, carbon adsorption bed and zeolite rotator recovery system can replace scrubbers, since they can be used as solvent recovery equipment.

Study of Various Nanostructures Titania with Graphene Composites: The Preparation and Photocatalytic Activities

Different kinds of graphene (GN)/titania nanocomposites using graphene and P25 or Titanium (IV) n-butoxide (TBOT) as precursors were prepared with hydrothermal method. To investigate the differences of the photocatalytic properties of composites with various shapes of titanium dioxide (TiO2), three types of TiO2, including titanium nanotubes (TNT), titanium nanosheets (TNS) and titanium nanoparticles (TNP) were successfully prepared and combined with GN to form the composites. The prepared composites were confirmed by Ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), and transmission electron microscopy (TEM), etc. Photocatalytic activities of composites were carried out by the degradation of Reactive Black 5 (RBk5) and Norfloxacin (NFXC) under the radiation of UV lamp. Results indicate that the differences in the TiO2 morphology of the composites greatly influence the catalytic properties. In addition, the heterojunction between graphene and TiO2 also play an important role in the photocatalytic abilities of composites. In this study, it can be seen that the prepared composites exhibit higher photocatalytic activity including excellent adsorption capacity and photo-degradation ability than P25. The photocatalytic activity of GN–TNS is higher than that of GN–TiO2 and GN–TNT.

Photocatalytic degradation of malathion by TiO2 and Pt-TiO2 nanotube photocatalyst and kinetic study

Photocatalytic degradation of malathion, is investigated using Titanium Nanotubes (TNT) and Pt modified TNT (Pt-TNT) photocatalyst in an aqueous solution under 365 nm UV lamp irradiation. The TNT photocatalyst is prepared on pretreated strong alkaline solution via the hydrothermal method. The Pt-TNT was prepared by light deposition. The variations in morphology, formation mechanism, phase structure, and pore structure of TNT and Pt-TNT are characterized using UV-Vis, transmission electron microscopy (TEM), and N2 adsorption/desorption isotherm analyzer, respectively. The effect of the initial malathion concentration, reaction temperature, catalyst loading, solution pH value, irradiation time and Pt loading are studied and the optimized values are obtained. Moreover, the photodegradation performance and kinetics of malathion onto TNT and Pt-TNT are also examined with the aid of model analysis by kinetic data. The results show that under acid conditions, the performance of photocatalysts for treating malathion is high. The time of complete degradation increases with an increase in the initial malathion concentration. The degradation rate decreases with increasing initial malathion concentration. The degradation efficiency can reach 100% under acid conditions for any initial malathion concentration when the reaction time is 70 min. In addition, experimental decoloration kinetics data follow the pseudo-first-order reaction model.

Photocatalytic Degradation of Oxytetracycline by Ternary Mixed Catalyst and Toxicity Assessment Using Boar Sperm

Response surface methodology was adopted to obtain ternary mixed catalysts of TiO2-loaded ZSM-5 zeolite and graphene. Oxytetracycline was used as challenged toxicant to evaluate the photocatalytic degradation efficiency of the composites. The optimal weight ratio of graphene, TiO2, and ZSM-5 was 1:8:1. The composites were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, fourier transform infrared, N2 adsorption-desorption isotherms, and transmission electron microscope with an energy-dispersive spectroscopy system, etc. Synthesized samples showed high stability and strong visible-light absorption efficiency. The optimal operating conditions of oxytetracycline photocatalytic degradation were achieved over a wide range of pH and temperature. With 0.1 g/L of optimal ternary mixed composite, the photocatalytic degradation of oxytetracycline was nearly reached completion within 150 min at all treatment temperatures at pH 7. Toxicity of degraded oxytetracycline solution was assayed by a boar sperm quality model using fluorescent staining and flow cytometry. During 180 min of photocatalytic treatment, the degraded oxytetracycline solution showed increasing biotoxicity and changed the morphology and function of boar sperm, despite not killing them.

Carbon dioxide adsorption on amine-impregnated mesoporous materials prepared from spent quartz sand

Mesoporous MCM-41 was synthesized using cetyltrimethyl ammonium bromide (CTAB) as a cationic surfactant and spent quartz sand as the silica source. Modification of the mesoporous structure to create an absorbent was then completed using 3-aminopropyltrimethoxysilane. Amine-Quartz-MCM (The A-Q-MCM) adsorbents were then characterized by N2 adsorption/desorption, elemental analysis (EA), X-ray fluorescence (XRF), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), as well as the carbon dioxide (CO2) adsorption/desorption performance. In this study, spent quartz sand was utilized to synthesize Quartz-MCM (Q-MCM) and the amine functionalized material, A-Q-MCM, which exhibited a higher uptake of CO2 at room temperature compared with the nongrafted material. The results showed that Q-MCM is similar to MCM-41 synthesized using commercial methods. The surface area, pore volume, and pore diameter were found to be as high as 1028 m2/g, 0.907 cm3/g, and 3.04 nm, respectively. Under the condition of CO2 concentration of 5000 ppm, retention time of 50 cc/min, and the dosage of 1 g/cm3, the mean adsorption capacity of CO2 onto A-Q-MCM was about 89 mg/g, and the nitrogen content of A-Q-MCM was 2.74%. The adsorption equilibrium was modeled well using a Freundlich isotherm. Implications: In this study, spent quartz sand was utilized to synthesize Q-MCM. The amine functionalized material exhibited a higher uptake of CO2 at room temperature compared with the nongrafted material. The results showed that Q-MCM is similar to MCM-41 synthesized using commercial methods. The adsorption equilibrium was modeled well using a Freundlich isotherm.

Catalytic decomposition of CF4 over iron promoted mesoporous catalysts.

A series of mesoporous catalysts (MCM-41) promoted by iron nanoparticles were prepared by the co-precipitation method and tested for the decomposition of carbon tetrafluoride (CF4). The addition of iron oxide nanoparticles to MCM-41 led to an improvement in the catalytic activity for CF4 decomposition. The catalyst was the most active around 5 wt% iron added to MCM-41. Methods of X-ray Powder Diffractometer, Scanning Electron Microscope-Energy Dispersive Spectrometer, BET, and high resolution transmission electron microscopy were used to characterize the MCM-41 catalysts. The analytical results indicated that the addition of over 2 wt% iron nanoparticles increased the surface area of MCM-41, which was the rate-determining factor of CF4 decomposition over MCM-41 catalyst. In conclusion, the addition of iron was responsible for the enhancement of catalytic activity of MCM-41.