Removal of Acid Orange 7 from water by electrochemically generated Fenton's reagent

The removal of azo dye Acid Orange 7 (AO7) from water was investigated by the electro-Fenton technology using electrogenerated hydroxyl radicals (OH) which leads to the oxidative degradation of AO7 up to its complete mineralization. H(2)O(2) and Fe (II) ions are electrogenerated in a catalytic way at the carbon-felt cathode. AO7 decay kinetics and evolution of its oxidation intermediates were monitored by high-performance liquid chromatography. The absolute rate constant of AO7 hydroxylation reaction has been determined as (1.20+/-0.17)x10(10)M(-1)s(-1). The optimal current value for the degradation of AO7 was found as 300 mA. AO7 degradation rate was found to decrease by increase in Fe(3+) concentration beyond 0.1mM. Mineralization of AO7 aqueous solutions was followed by total organic carbon (TOC) measurements and found to be 92%. Based on TOC evolution and identification of aromatic intermediates, short-chain carboxylic acids and inorganic ions released during treatment, a plausible mineralization pathway was proposed.     

The effect of magnetic field on domain electroluminescence in barium titanate crystals near the ferroelectric phase transition

By measuring electroluminescence (EL) in barium titanate crystals exposed to a pulsed electric field in combination with a magnetic field, we have studied the dependence of a shift in the temperature of maximum EL on the magnetic field strength and on the mutual orientation of the electric and magnetic fields. The possible mechanisms of the observed effects are discussed.     

Oxidative decomposition of azo dye C.I. Acid Orange 7 (AO7) under microwave electrodeless lamp irradiation in the presence of H2O2

A novel microwave electrodeless lamp (MWL) rather than traditional electrode lamp (TEL) was used in a H(2)O(2)/MWL system as light source. This technique provided a new way to study the simultaneous effect of both UV-vis light and microwave irradiations. This study showed that H(2)O(2)/MWL process was 32% more effective than H(2)O(2)/TEL process in degrading azo dye Acid Orange 7 (AO7). Further study found that the degradation of AO7 by the H(2)O(2)/MWL process was initiated by the attack of HO* radicals generated by the photolysis of H(2)O(2). However, the direct photolysis of AO7 by MWL irradiation was not negligible. Effect of operation parameters, such as the initial concentrations of AO7 and H(2)O(2) and pH, were investigated. A kinetic model of degradation of AO7 by H(2)O(2)/MWL process was found, in which not only the HO* oxidation but also direct photolysis were considered. The kinetic model was consistent with the experiment results. The degradation of AO7 by H(2)O(2)/MWL corresponded to a pseudo-first order reaction. The apparent reaction constant (k(ap)) was a function of initial concentrations of H(2)O(2) and AO7 and pH of the solution.     

Decolorization of orange II by catalytic oxidation using iron (III) phthalocyanine-tetrasulfonic acid

Orange II, C.I. Acid Orange 7 (AO7), is oxidatively decolorized via catalytic oxidation by iron(III) phthalocyanine-tetrasulfonic acid (Fe(III)-PcTS) as a biomimetic catalyst and KHSO(5) as an oxygen donor. The nature of the decolorization of AO7 was investigated in the catalyst concentration range of 10-50 microM, in which the initial concentration of AO7 was 417 mg l(-1). A 99.6% decolorization was observed at [KHSO(5)] = 2.5 mM and [Fe(III)-PcTS] = 20 microM after a 3-h reaction period. However, the fact that only 4.9% of the TOC was removed indicated that the conversion to CO(2) was incomplete. The results of a total organic nitrogen analysis of the reaction mixture showed that the nitrogen in the azo chain was mainly converted to N(2) gas. In addition, 38.6% of the AO7 was converted to 1,2-dihydroxynaphthalene, and 21.4% to p-phenolsulfonic acid. These results indicate that the degradation via this catalytic system involves the conversion of AO7 to phenolic compounds, followed by N(2) production. In addition, a Microtox test showed that toxicity of the solution increased as a result of AO7 oxidation using this catalytic system.     

Photooxidation processes for an azo dye in aqueous media: modeling of degradation kinetic and ecological parameters evaluation

Three photooxidation processes, UV/H(2)O(2), UV/S(2)O(8)(2-) and UV/O(3) were applied to the treatment of model wastewater containing non-biodegradable organic pollutant, azo dye Acid Orange 7 (AO7). Dye degradation was monitored using UV/VIS and total organic carbon (TOC) analysis, determining decolorization, the degradation/formation of naphthalene and benzene structured AO7 by-products, and the mineralization of model wastewater. The water quality during the treatment was evaluated on the bases of ecological parameters: chemical (COD) and biochemical (BOD(5)) oxygen demand and toxicity on Vibrio fischeri determining the EC(50) value. The main goals of the study were to develop an appropriate mathematic model (MM) predicting the behavior of the systems under investigation, and to evaluate the toxicity and biodegradability of the model wastewater during treatments. MM developed showed a high accuracy in predicting the degradation of AO7 when considering the following observed parameters: decolorization, formation/degradation of by-products and mineralization. Good agreement of the data predicted and the empirically obtained was confirmed by calculated standard deviations. The biodegradability of model wastewater was significantly improved by three processes after mineralizing a half of the initially present organic content. The toxicity AO7 model wastewater was decreased as well. The differences in monitored ecological parameters during the treatment indicated the formation of different by-products of dye degradation regarding the oxidant type applied.     

Adsorption of acid dyes from aqueous solutions by the ethylenediamine-modified magnetic chitosan nanoparticles

The adsorption characteristics of Acid Orange 7(AO7) and Acid Orange 10 (AO10) from aqueous solutions onto the ethylenediamine-modified magnetic chitosan nanoparticles (EMCN) have been investigated. The EMCN were essentially monodispersed and had a main particle size distribution of 15-40 nm and saturated magnetization of 25.6 emu/g. The adsorption experiments indicated that the maximum adsorption capacity occurred at pH 4.0 for AO7 and pH 3.0 for AO10, respectively. Due to the small diameter and the high surface reactivity, the adsorption equilibrium of AO7 and AO10 onto the EMCN reached very quickly. Equilibrium experiments fitted well with the Langmuir isotherm model, and the maximum adsorption capacity of the EMCN at 298K was determined to be 3.47 mmol/g for AO7 and 2.25 mmol/g for AO10, respectively. Thermodynamic parameters such as enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were estimated and the results indicated that the adsorption process was spontaneous and exothermic. Furthermore, the EMCN could be regenerated through the desorption of the dyes in NH(4)OH/NH(4)Cl solution (pH 10.0) and could be reused to adsorb the dyes again.     

Removal of C.I. Acid Orange 7 from aqueous solution by UV irradiation in the presence of ZnO nanopowder

The removal of C.I. Acid Orange 7 (AO7) from aqueous solution under UV irradiation in the presence of ZnO nanopowder has been studied. The average crystallite size of ZnO powder was determined from XRD pattern using the Scherrer equation in the range of 33 nm. The experiments showed that ZnO nanopowder and UV light had a negligible effect when they were used on their own. The effects of some operational parameters such as pH, the amount of ZnO nanopowder and initial dye concentration were also examined. The photodegradation of AO7 was enhanced by the addition of proper amount of hydrogen peroxide, but it was inhibited by ethanol. From the inhibitive effect of ethanol, it was deducted that hydroxyl radicals played a significant role in the photodegradation of the dye. The kinetic of the removal of AO7 can be explained in terms of the Langmuir-Hinshelwood model. The values of the adsorption equilibrium constant, K(AO7), and the kinetic rate constant of surface reaction, k(c), were 0.354(mg l(-1))(-1) and 1.99 mg l(-1)min(-1), respectively. The electrical energy consumption per order of magnitude for photocatalytic degradation of AO7 was lower in the UV/ZnO/H(2)O(2) process than that in the UV/ZnO process. Accordingly, it could be stated that the complete removal of color, after selecting desired operational parameters could be achieved in a relatively short time, about 60 min.     

The effect of Fe0/Fe2+/Fe3+ on nitrobenzene degradation in the anaerobic sludge

The influence of Fe(0)/Fe(2+)/Fe(3+) on the nitrobenzene (NB) degradation in the anaerobic granular sludge was studied and the results demonstrated that: adding iron powder into the anaerobic sludge could exert an accelerative effect on the NB degradation and the degradation rate was faster than that by using iron or the anaerobic sludge alone. The external addition of Fe(2+)/Fe(3+) exhibited different influences on the NB degradation depending on the concentrations of Fe(2+)/Fe(3+) and the solution's pH. When Fe(2+)/Fe(3+) are less than 100 mg/L at pH 6, Fe(2+)/Fe(3+) inhibited the NB degradation slightly, and when Fe(2+)/Fe(3+) was 100-200 mg/L, the NB degradation was enhanced. When pH was shifted to 9, Fe(2+) of lower than 100 mg/L promoted the NB degradation, and 200 mg/L Fe(2+) inhibit the NB degradation. The synergism of combined use of iron and the anaerobic sludge in treating NB wastewater was proposed, and adjusting the concentrations of Fe(2+)/Fe(3+) in the anaerobic sludge according to the pH of the wastewater could be an effective method to obtain a high removal rate of NB.     

Photodegradation of nitrobenzene using 172 nm excimer UV lamp

Photodegradation of nitrobenzene (NB) using an excimer UV lamp at a wavelength of 172 nm is investigated. Experimental results show that high concentration nitrobenzene can be efficiently degraded with irradiation by excimer UV lamp, and confirm that degradation of nitrobenzene is more efficient by UV/H(2)O(2) combination than UV only. In the case of using UV only, 60 min of treatment was found to be sufficient to degrade the major part of NB solution with a concentration of less than 4mM. In the case of using the combination of UV/H(2)O(2) with a H(2)O(2) concentration of 7:1 molar ratio to NB, 4.07 mM NB solution drastically decreased to 0.41 mM after treatment for only 20 min. Degradation intermediate products are identified by analyzing the degradation products with GC/HRMS and possible degradation pathways of nitrobenzene are suggested.     

Amorphous TiOBCN—A new solar photocatalyst

Amorphous photocatalyst TiOBCN was prepared for the first time. The TiOBCN showed obvious absorption in the visible light region up to 520 nm and 783 nm. The degradation rate of AO7 in TiOBCN solution increased quickly from 0% to 99.46% in 150 min after undergoing solar simulating irradiation. For TiO₂ the degradation rate of AO7 is just 57.2%.The experimental results also revealed that the degradation rate of AO7 first increases, and then decreases to a range concentration falling within 5 to 35 mg/L. The optimum catalyst loading for the degradation of AO7 is 400 mg/L.     

硼硅酸盐生物活性玻璃在直流电场下的体外矿化性能

硼硅酸盐生物活性玻璃具有良好的生物活性和骨传导性, 但大多数生物活性玻璃表现出非线性降解和矿化行为, 矿化性能会随着时间而减缓。电场作为一种外场辅助调节的方法, 能够干预玻璃的离子交换和扩散。本研究利用直流电场干预硼硅酸盐生物活性玻璃的体外矿化, 加快降解较慢阶段中硼硅酸盐生物玻璃的生物活性。将熔融法制备的成分为18SiO₂-6Na₂O-8K₂O-8MgO-22CaO-2P₂O₅-36B₂O₃的硼硅酸盐生物活性玻璃浸泡在SBF生理模拟液中, 施加0~90 mA的电流, 研究直流电场对硼硅酸盐生物玻璃降解及体外矿化性能的影响。研究结果表明, 施加电场不仅可以提高硼硅酸盐生物活性玻璃的降解率和离子释放量, 而且有利于玻璃网络水解和表面羟基化, 加速羟基磷灰石的生成。其中失重率比对照组提高了3%~5%, 硼和钙的离子释放量分别较对照组提高了2.3~2.9倍和1.9~2.3倍。对硼硅酸盐生物活性玻璃表面结构分析得出, 暴露在电场下的样品表面生成了磷灰石层。应用直流电场可以提高生物活性玻璃的降解及体外矿化性能, 为提升骨修复效果提供了一种新思路。     

原子氧对航天材料表面的作用与防护 I原子氧与航天材料的作用

综述了低地球轨道环境下原子氧与航天材料的相互作用及其机制，介绍了原子氧敏感性材料以及它们在低地球轨道环境下的降解情况。     

Large-area uniform dust-free plasma CVD

In the weak magnetic field perpendicular to the discharge electric field, both the electrons and positive ions are transported in the direction of E×B drift by the space charge electric field produced by the preceded electrons. As a result, radicals are generated uniformly outside of discharge space between the electrodes in the direction of E×B drift. On the other hand, negatively charged heavy particles such as dust particles can be removed from discharge space in the direction opposite to E×B drift of plasmas. The authors have studied the transport mechanisms of magnetized dusty plasmas and its applications for the large-area uniform a-Si:H thin film deposition in plasma CVD methods. This paper reviews the transport phenomena and the transport mechanisms of dust particles and the results of film preparation under particle-free process conditions.     

Current understanding of the origin of equiaxed grains in pure metals during ultrasonic solidification and a comparison of grain formation processes with low frequency vibration,pulsed magnetic and electric-current pulse techniques

The formation of fine,non-dendritic equiaxed grains throughout a casting without the addition of refiners(i.e.independent of alloy chemistry),is made possible by using ultrasonic,magnetic or pulsed magnetic and electric current pulse techniques.The dominant mechanisms proposed for the grain refinement produced during the application of an external field are cavitation phenomena assisted nucleation or fragmentation of dendrites(ultrasonic field),wall crystals arising from the cold surface of the mould(electric current pulse,magnetic and pulsed magnetic fields).In all these cases fluid flow provides an additional contribution(e.g.reduced temperature gradients,growth rate and remelting of dendrites)to maintaining an equiaxed grain structure.The origin of equiaxed grains under an external field also depends on the casting conditions(volume and shape of casting)and the type of alloy other than the mechanisms specific to a particular technique.The current work aims to provide a detailed understanding of the various factors and mechanisms that influence the grain refinement achieved during the solidification of pure metals(magnesium and zinc)subjected to Ultra Sonic Treatment(UST).The role of the temperature range of UST application,time duration and an unpreheated sonotrode are examined with respect to the origin,evolution of equiaxed grain structure,morphology and the columnar to equiaxed transition.The origin of grains was analysed from three fundamental aspects that contribute to refinement(i)heterogeneous nucleation(ii)fragmentation of existing dendrites and(iii)grains produced from the colder surfaces(arising from mould walls or vibrating surfaces as wall crystals).A comparison of UST refinement with mechanical,low-frequency vibration,electric current pulse and magnetic field solidification of pure metals has also been provided to highlight the importance of the cold surfaces(sonotrode and mould wall)in influencing grain refinement.     

Electric-field-assisted switching in magnetic tunnel junctions

The advent of spin transfer torque effect accommodates site-specific switching of magnetic nanostructures by current alone without magnetic field. However, the critical current density required for usual spin torque switching remains stubbornly high around 10(6)-10(7) A cm(-2). It would be fundamentally transformative if an electric field through a voltage could assist or accomplish the switching of ferromagnets. Here we report electric-field-assisted reversible switching in CoFeB/MgO/CoFeB magnetic tunnel junctions with interfacial perpendicular magnetic anisotropy, where the coercivity, the magnetic configuration and the tunnelling magnetoresistance can be manipulated by voltage pulses associated with much smaller current densities. These results represent a crucial step towards ultralow energy switching in magnetic tunnel junctions, and open a new avenue for exploring other voltage-controlled spintronic devices.     

The effect of applied magnetic field on the growth mechanisms of liquid phase electroepitaxy

Binary (GaAs) and ternary (InGaAs) single crystals were grown by the growth process of liquid phase electroepitaxial (LPEE) under an applied static magnetic field. The effect of the applied magnetic field on two main growth mechanisms of the LPEE growth process, namely the “electromigration” and “natural convection” in the liquid zone, were examined numerically and experimentally. Numerical results show that the flow and concentration patterns exhibit three distinct stability characteristics: stable structures up to the magnetic field level of 2.0 kG, transitional structures between 2.0 and 3.0 kG, and unstable structures above 3.0 kG. In the stable region, the applied magnetic field suppresses the flow structures, and the intensities decrease with the increasing magnetic field level. In the transitional region, the flow intensity increases dramatically with the magnetic field strength, and concentrations show very different patterns leading to a wavy growth interface. Under strong magnetic field levels, the flows cells are confined to the vicinity of the vertical wall and exhibit significant non-uniformity near the growth interface.Experiments performed under various magnetic field levels show that the growth process at the 4.5 kG field level yields satisfactory growths. However, the growth experiments at higher field levels were unsatisfactory and unstable. Although the crystals were still grown, large wholes were observed in the grown crystals. This observation was attributed to the strong interaction of the applied electric and magnetic fields, making the convective flow in the solution very strong and unstable. However, lower magnetic field and electric current levels had very beneficial effects, namely flat growth interfaces and prolonged growth due to weak convection in the liquid zone, and a substantial increase in the growth rate (about 5–10 times higher) due to the effect of magnetic field on the mechanisms of “electromigration”. Such positive developments give the LPEE growth process the potential of becoming a commercial technique.     

Degradation of gas-liquid gliding arc discharge on Acid Orange II

The effects of pH value, initial concentration of dye solution and temperature on the degradation efficiency of Acid Orange II (AO7) using gas-liquid gliding arc discharge were investigated. The influences of pH value and temperature on degradation efficiency were not apparent. Increasing initial solution concentration caused the decrease of degradation rate and the increase of absolute degradation quantity. Considering energy efficiency and absolute degradation quantity, the gas-liquid gliding arc discharge is fit for treating high concentration organic wastewater. A possible mineralization pathway was proposed through the analysis of intermediate products detected by gas chromatograph coupled with mass spectrophotometer (GC-MS) and ion chromatograph (IC). Hydroxyl radicals reacted with the azo linkage-bearing carbon of a hydroxy-substituted ring, leading to the cleavage of -C-N- and degradation of AO7. The solution biodegradability was significantly improved (BOD(5)/COD from 0.02 to 0.43). The toxicity of intermediate products was lower than that of the initial Acid Orange II.     

Spin Dynamics and Spin Transport

Spin-orbit (SO) interaction critically influences electron spin dynamics and spin transport in bulk semiconductors and semiconductor microstructures. This interaction couples electron spin to dc and ac electric fields. Spin coupling to ac electric fields allows efficient spin manipulating by the electric component of electromagnetic field through the electric dipole spin resonance (EDSR) mechanism. Usually, it is much more efficient than the magnetic manipulation due to a larger coupling constant and the easier access to spins at a nanometer scale. The dependence of the EDSR intensity on the magnetic field direction allows measuring the relative strengths of the competing SO coupling mechanisms in quantum wells. Spin coupling to an in-plane electric field is much stronger than to a perpendicular field. Because electron bands in microstructures are spin split by SO interaction, electron spin is not conserved and spin transport in them is controlled by a number of competing parameters, hence, it is rather nontrivial. The relation between spin transport, spin currents, and spin populations is critically discussed. Importance of transients and sharp gradients for generating spin magnetization by electric fields and for ballistic spin transport is clarified.     

Spin Dynamics and Spin Transport

Spin-orbit (SO) interaction critically influences electron spin dynamics and spin transport in bulk semiconductors and semiconductor microstructures. This interaction couples electron spin to dc and ac electric fields. Spin coupling to ac electric fields allows efficient spin manipulating by the electric component of electromagnetic field through the electric dipole spin resonance (EDSR) mechanism. Usually, it is much more efficient than the magnetic manipulation due to a larger coupling constant and the easier access to spins at a nanometer scale. The dependence of the EDSR intensity on the magnetic field direction allows measuring the relative strengths of the competing SO coupling mechanisms in quantum wells. Spin coupling to an in-plane electric field is much stronger than to a perpendicular field. Because electron bands in microstructures are spin split by SO interaction, electron spin is not conserved and spin transport in them is controlled by a number of competing parameters, hence, it is rather nontrivial. The relation between spin transport, spin currents, and spin populations is critically discussed. Importance of transients and sharp gradients for generating spin magnetization by electric fields and for ballistic spin transport is clarified.