Exploring effects of chemical structure on azo dye decolorization characteristics by Pseudomonas luteola

This follow-up study tended to provide a systematic comparison for how the variation of functional groups and molecular structures present in model azo dyes affects color removal capability of Pseudomonas luteola. As sulfo group at methyl orange (p-MO) or carboxyl group at 4-(4'-dimethylaminophenylazobenzoic acid) sodium salt (denoted p-MR) were both para to azo bond, the ranking of decolorization rate was p-MO>p-MR due to the stronger electron-withdrawing effect of the sulfo group. For isomers, when the functional groups (sulfo group at 2-(4'-dimethylamino-phenylazo) benzenesulfonic acid sodium salt (o-MO) or carboxyl group at methyl red (o-MR)) were ortho to azo bond, the decolorization rate significantly decreased (e.g., p-MO>o-MO or p-MR>o-MR) likely due to steric hindrance near azo linkage(s). Similarly, for phenolic azo dyes the series of decolorization rate was 3-(4'-dimethylaminophenylazo) phenol (m-OH)>2-(4'-dimethylaminophenylazo) phenol (o-OH). Apparently, azo dyes with different properties of substituent on aromatic ring could affect the efficiency of biodecolorization of P. luteola. Moreover, the relative position (e.g., ortho, meta, para) of the substituent to azo bond could also influence the capability of biodecolorization of P. luteola. Regarding the electronic effect, azo dyes with stronger electron-withdrawing group (e.g., sulfo group) at specific positions (e.g., at para) could be more easily biodecolored than those with a carboxyl group.     

An advanced model of designing controlled strain rate dies for axisymmetric extrusion

This paper presents an advanced model for the design of stream-lined axisymmetric extrusion dies based on a prescribed strain rate variation. This is vital to the preparation of the workpieces with mechanical properties that are very sensitive to the strain rate distribution during a manufacturing process. The proposed model, which incorporates Tresca’s yield criterion and velocity field with the die angularity, can give an accurate prediction of the die shape. Influences of the interfacial friction and the ram velocity on the die geometry are also studied. As a verification of the proposed model, an updated Lagrangian formulated, elasto-plastic finite element program was developed to analyze the axisymmetric extrusion process. A clear derivation of the load-correction matrix, which is in dispensable for the surface traction rate equilibrium in the updated Lagrangian formulation, is described for the application of the finite element simulation. A friction-correction matrix based on a constant shear law is used to solve the interfacial friction. From the comparison of the resultant strain rate distribution, it verifies that the advanced model can determine the surface angularity and friction force in the extrusion process.     

A miniature air breathing direct formic acid fuel cell

Small fuel cells are considered likely replacements for batteries in portable power applications. In this paper, the performance of a $\text{2}\text{cm}\text{×2.4}\text{cm}\text{×1.4}$ cm passive miniature air breathing direct formic acid fuel cell (DFAFC) at room temperature is reported. The cell produced current density up to 250 mA/cm² and power density up to 33 mW/cm² at ambient conditions. The fuel cell runs successfully with formic acid concentration ranging from 1.8 and 10 M with little degradation in performance. These results show that passive fuel cells can compete with batteries in portable power applications.     

Reactivity of sorbate and glycerol in some model intermediate moisture systems

Model systems were developed to study the rôle of selected humectants and antimycotics in non-enzymic browning, haemoprotein breakdown and collagen degradation reactions at a_w 0·85 and initial pH 5·5. a_w adjustment was made using sodium chloride and the solutions contained 0·5% glucose, 0·5% sorbate, 0·5% propionate, 30% glycerol or 30% glycerol plus 0·5% sorbate. During aerobic storage at 38°C or 65°C, 10% lysine or glutamate solutions all exhibited increased browning and 0·01% or 0·02% haemoglobin solutions increased loss of haemoprotein from solution in the presence of glycerol and/or sorbate. During anaerobic storage only the glucose-containing solutions exhibited any reactivity.The pH and concentration of reactive carbonyls in the systems were also monitored and the rôle of sorbate and glycerol oxidation products in non-enzymic browning is discussed in the light of these results.Breakdown of the collagen in heat-treated tendon during storage at 38°C under similar conditions was also studied. Although the results were not unequivocal, it was apparent that, at least initially, storage in 30% glycerol caused increased degradation.     

Biological hydrogen production in an anaerobic sequencing batch reactor: pH and cyclic duration effects

An anaerobic sequencing batch reactor (ASBR) was used to evaluate biological hydrogen production from carbohydrate-rich organic wastes. The goal of the proposed project was to investigate the effects of pH (4.9, 5.5, 6.1, and 6.7), and cyclic duration (4, 6, and 8 h) on hydrogen production. With the ASBR operated at 16-h HRT, 25 g COD/L, and 4-h cyclic duration, the results showed that the maximum hydrogen yield of 2.53 mol H₂/mol sucrose_consumed appeared at pH 4.9. The carbohydrate removal efficiency declined to 56% at pH 4.9, which indirectly resulted in the reduction of total volatile fatty acid production. Acetate fermentation was the dominant metabolic pathway at pH 4.9. The concentration of mixed liquor volatile suspended solid (MLVSS) also showed a decrease from nearly 15,000 mg/L between pHs 6.1 and 6.7 to 6000 mg/L at pH 4.9. Investigation of the effect of cyclic duration found that hydrogen yield reached the maximum of 1.86 mol H₂/mol sucrose_consumed at 4-h cyclic duration while ASBR was operating at 16-h HRT, 15 g COD/L, and pH 4.9. The experimental results showed that MLVSS concentration increased from 6200 mg/L at 4-h cyclic duration to 8500 mg/L at 8-h cyclic duration. However, there was no significant change in effluent volatile suspended solid concentration. The results of butyrate to acetate ratio showed that using this ratio to correlate the performance of hydrogen production is not appropriate due to the growth of homoacetogens. In ASBR, the operation is subject to four different phases of each cycle, and only the complete mix condition can be achieved at react phase. The pH and cyclic duration under the unique operations profoundly impact fermentative hydrogen production.     

Cu2O/TiO2 heterostructure nanotube arrays prepared by an electrodeposition method exhibiting enhanced photocatalytic activity for CO2 reduction to methanol

Cu₂O/TiO₂ composite nanotube arrays demonstrating enhanced photocatalytic performance were synthesized using an electrodeposition method to impregnate the p-type Cu₂O into the n-type titanium dioxide nanotube arrays (TNTs). The morphological results confirmed that the TNTs are wrapped by the Cu₂O nanoparticles and the UV–Vis absorption spectra showed that the Cu₂O/TNTs display a better ability for visible light absorption compared to the pure TNTs. CO₂ photocatalytic reduction experiments carried out by using Cu₂O/TNT nanocomposites proved that Cu₂O/TNTs exhibit high photocatalytic activity in conversion of CO₂ to methanol, while pure TNT arrays were almost inactive. Furthermore, Cu₂O/TNTs also exhibited augmented activity in degradation of target organic pollutant like acid orange (AO) under visible light irradiation. The ultra enhanced photocatalytic activity noticed by using Cu₂O/TNTs in CO₂ reduction and degradation of organic pollutant could be attributed to the formation of Cu₂O/TiO₂ heterostructures with higher charge separation efficiency.     

An artificial photosynthesis system based on CeO2 as light harvester and N-doped graphene Cu(II) complex as artificial metalloenzyme for CO2 reduction to methanol fuel

An artificial photosynthesis catalyst composed of CeO₂, N-doped graphene and copper ions (CeO₂–NG–Cu^2 +) was fabricated. The light-harvesting CeO₂–NG was characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic reduction of CO₂ was conducted in an aqueous solution of Na₂SO₃. Results indicated that the reduction rate of CO₂ to methanol approached 507.3 μmol · g⁻¹ cat. · h^− 1 for CeO₂–NG–Cu^2 + artificial photosynthesis system in 80 min, whereas the reduction rate was only 5.8 μmol · g⁻¹ cat. · h^− 1 for bare CeO₂–NG without metalloenzyme. Therefore, artificial metalloenzyme played a vital role in reducing CO₂ to methanol fuel.     

Synthesis and visible catalytic applications of graphene–titania dioxide nanotube composites

A novel photocatalyst of graphene–titania dioxide nanotube (GN–TNT) composites was prepared using a simple hydrothermal reaction with ascorbic acid as a reducing agent. High resolution transmission electron microscope (HR-TEM), fourier transform infrared spectrometer (FT-IR), thermo gravimetric analyzer (TGA) and N₂ adsorption/desorption analyzer (BET) methods were used to assess the morphologies and structures of as-synthesized materials. HR-TEM analysis further confirmed the presences of graphene and titanium (TiO₂) nanotubes in the nanocomposite photocatalyst. The results exhibited that photocatalytic performance of a GN–TNT photocatalyst significantly improved under visible light. In addition, the existence of a competitive effect between As³⁺ and reactive black 5 (RBK5) molecules in the mixed solution was found. The photocatalytic process is also discussed in this paper.     

Facile synthesis of maghemite nanoflakes arrays for supercapacitor application

Electrochemically synthesized maghemite nanoflakes arrays onto stainless steel substrate are used as supercapacitor electrode material. The synthesized thin films are characterized for their structure, surface morphology and electrochemical properties by XRD, SEM and cyclic voltammetry. The X-ray diffraction study revealed that the films are polycrystalline in nature with cubic crystal structure of maghemite (γ-Fe₂O₃). Scanning electron microscopy shows the formation of nanoflakes array of maghemite. Moreover, the hydrophilicity of maghemite nanoflakes arrays enhances the intimate contact at electrode/electrolyte interface. Maghemite thin film shows better capacitive performance in aqueous Na₂SO₃ electrolyte. The relatively maximum specific capacitance of 524 F/g was found in Na₂SO₃ than NaOH electrolyte at scan rate of 5 mV/s. Maghemite nanoflakes arrays exhibited good electrochemical stability in Na₂SO₃ with 76.71% charge storage after 250 cycles.