Complete electrolysis using a microflow cell with an oil/water interface

A novel microflow cell with a nitrobenzene (NB)/water (W) interface was developed. A poly(tetrafluoroethylene) membrane filter was employed to prepare the NB/W interface which was formed over a thin channel (0.1 mm thick, 48 cm long) on a silver plate. The silver plate was electrolyzed in advance and served as an Ag/AgCl electrode for controlling the Galvani potential difference across the NB/W interface as well as detecting the current flowing through the interface. Using the microflow cell, complete electrolysis was accomplished for the interfacial transfer of a representative ion (i.e., tetramethylammonium ion). Thus, the present microflow cell was shown to be promising for coulometric (i.e., absolute quantitative) analysis of ions. Also, the microflow cell was shown to be useful for determination of the number of electrons for complicated charge-transfer processes at the oil/water interface.     

Reducing sugars production from sugarcane bagasse wastes by hydrolysis in sub-critical water

Biomass is an important renewable and sustainable source of energy. The rational utilization of biomass wastes is important not only for the prevention of environmental issues, but also for the effective utilization of natural resources. Reducing sugar, as a biomass energy precursor, can be further transformed to fuel alcohol in a fermentation process. Sub-critical water is an environmentally friendly solvent and attractive reaction medium. This study deals with the production of reducing sugar from sugarcane bagasse by hydrolysis in sub-critical water and the hydrolysis kinetics of sugarcane bagasse. Kinetics was conducted in a temperature range of 200–240°C using a 200-ml stainless steel batch reactor. A simplified kinetic model based on a parallel and consecutive reaction was proposed. The differential equations resulting from the model were fit to experimental data to obtain kinetic rate constants. The activation energy and the pre-exponential factor were determined. A good agreement between the simplified model and the experimental data was obtained. The experimental results show that the best hydrolysis technology involves a reaction temperature of 240°C, and a reaction time of 120 s. Under these conditions, the reducing sugar yield reaches 61.5%.     

Photocatalytic degradation of Orange G on nitrogen-doped TiO2 catalysts under visible light and sunlight irradiation

In this paper, the degradation of an azo dye Orange G (OG) on nitrogen-doped TiO₂ photocatalysts has been investigated under visible light and sunlight irradiation. Under visible light irradiation, the doped TiO₂ nanocatalysts demonstrated higher activity than the commercial Dugussa P25 TiO₂, allowing more efficient utilization of solar light, while under sunlight, P25 showed higher photocatalytic activity. According to the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectra analyses, it was found that both the nanosized anatase structure and the appearance of new absorption band in the visible region caused by nitrogen doping were responsible for the significant enhancement of OG degradation under visible light. In addition, the photosensitized oxidation mechanism originated from OG itself was also considered contributing to the higher visible-light-induced degradation efficiency. The effect of the initial pH of the solution and the dosage of hydrogen peroxide under different light sources was also investigated. Under visible light and sunlight, the optimal solution pH was both 2.0, while the optimal dosage of H₂O₂ was 5.0 and 15.0 mmol/l, respectively.     

Studies on degradation of Methyl Orange wastewater by combined electrochemical process

The combined process of electro-catalytic oxidation and de-colorization of wastewater contained Methyl Orange (MO) in a double-anode system, with iron plate and graphite plate as anodes and graphite plate as cathode assisted by Co2O3-CuO-PO4(3-) modified kaolin, was investigated systematically. The effects of pH, current density and electrolyte on de-colorization efficiency were also studied. Chemical oxygen demand (COD) was selected as another parameter to evaluate the efficiency of this combined degradation method on treatment of MO wastewater and the results revealed that when initial pH was 5.0, current density was 30 mA cm(-2), NaCl as electrolyte and its concentration was 2.5 g dm(-3), the color removal efficiency and COD removal can reach 100% and 89.7%, respectively. Meanwhile, the kinetics and the possible mechanism were also discussed.     

Oxidative degradation of acridine orange induced by plasma with contact glow discharge electrolysis

Contact glow discharge electrolysis (CGDE) of acridine orange (AO) was investigated under different mediums, pH, and voltages. The results showed that 500 V was the optimum voltage for CGDE of AO under experimental conditions. The concentration and pH had no appreciable effect on the degradation of AO. Fe²⁺ had a remarkable catalytic effect on it. From the variation of AO concentration with the reaction time, it was demonstrated that the oxidation would be a first-order reaction. On the grounds of UV spectra of solution in the degradation process, we speculated the intermediate states. The rate constants and relevant coefficiencies were displayed under different conditions.     

Ultrasonic wave field effects on hydrogen production by water electrolysis

In this paper, Electrochemical impedance spectroscopy (EIS) was used to examine polarization impedance phenomena in ultrasonic water electrolysis. The method has been used previously for electrochemical analysis of fuel cells, corrosion, electroplating, etc. However, the EIS method and curvilinear regression have never been used before to analyze the electrochemical reactions which take place during water electrolysis. This study found that when a 2?V potential was applied, the ultrasonic wave field improved activity impedances and concentration impedances and accelerated the rising of hydrogen bubbles during water electrolysis. Ultrasonic power, electrode gap, and electrolyte concentration were the key parameters that affected water electrolysis. At normal temperature, when the electrode gap was 2?mm, the potential 4?V, and electrolyte concentration 40 wt%, the difference in current density between electrolysis without ultrasonic power and electrolysis with ultrasonic power of 225?W was 240?mA/cm². Deducting the power needed for the ultrasonic wave showed an power savings of 3.5?kW and an economical power efficiency of 15%.     

Colorimetric response of fluorescein-modified multilayer thin films induced by electrolysis of water

The surface of an indium–tin oxide (ITO) electrode was coated with layer-by-layer (LbL) thin films composed of fluorescein-modified poly(allylamine) (F-PAH) and poly(styrenesulfonic acid) (PSS) and their UV–visible absorption spectra were recorded under the influence of electrode potential. The LbL films were prepared by an alternate deposition of F-PAH and PSS on the surface of ITO electrode through an electrostatic force of attraction. The intensity of the absorption band around 500 nm originating from fluorescein residues in the LbL film depended on the pH of the solution in which the LbL film is immersed. The intensity of the absorption band decreased when the electrode potential higher than + 1.2 V was applied, while virtually no response was observed at lower electrode potential. The spectral change was suppressed in solutions with higher buffer capacity. The results were discussed in terms of the changes in local pH in the vicinity of the electrode surface, which in turn was induced by electrolysis of H₂O on the electrode surface.     

氮杂酞菁钴光电催化降解水环境中聚丙烯酰胺

针对水环境中聚丙烯酰胺(HPAM)难以被快速去除的问题,以导电炭黑(CB)为载体,制备了负载型氮杂酞菁钴(NCoPc/CB)和甲基取代氮杂酞菁钴(MeNCoPc/CB)复合材料,并对其光电催化降解HPAM的性能进行了研究.搭建分体式光电协同催化体系,选取50 mg/LHPAM水溶液为目标污染物,以Na2SO4为电解质,...     

Oxidized rare earth-iron compounds in photoassisted electrolysis of water

Anodes for use in a photoelectrolysis cell can be prepared by heating rare earth (R) iron compounds (RFe₂, RFe₃, R₂Fe₁₇ and R₆Fe₂₃) in air using the flame of a Fisher burner. For comparison, iron oxide and titanium oxide were also prepared by heating iron and titanium metal in air. The current-voltage (I–V) properties of these materials were measured in aqueous solution of 1 M NaOH. The flatband potentials (V_fb) were determined with respect to a fixed potential (SCE) by extrapolating the I–V curves to zero current. Anodic photocurrents were generated by light with energy exceeding the band gap of the photoanode material. Photoelectrolysis of water occurred, as evidenced by the evolution of oxygen from the RFeO_x electrodes and hydrogen from the Pt electrode. Most of these electrodes were found to be stable under experimental conditions.     

Stability of hydraulic fall and sub-critical cnoidal waves in water flows over a bump

A forced Korteweg–de Vries (fKdV) equation can be used to model the surface wave of a two-dimensional water flow over a bump when the upstream Froude number is near one. The fKdV model typically has four types of solutions: sub-critical cnoidal waves, sub-critical hydraulic fall, transcritical upstream soliton radiation, and supercritical multiple solitary waves. This paper provides a numerical demonstration of the stability of the hydraulic falls and cnoidal waves solutions.     

Oxalate enhanced mechanism of hydroxyl-Fe-pillared bentonite during the degradation of Orange II by UV-Fenton process

An enhanced method of hydroxyl-Fe-pillared bentonite (H-Fe-P-B) during the degradation of Orange II was studied to provide novel insight to interactions of degradation intermediates with heterogeneous catalyst in UV-Fenton system. Based on the degradation mechanism of Orange II, oxalate enhanced mechanism of H-Fe-P-B in heterogeneous UV-Fenton system was developed. The results showed that additional oxalate could increase the Fe leaching of H-Fe-P-B during heterogeneous UV-Fenton process, which led to higher mineralization efficiency of Orange II and lower energy consumption of treatment. When the concentrations of additional sodium oxalate increased up to 0.1 mmol L(-1), 0.2 mmol L(-1) and 0.4 mmol L(-1), the rate of Orange II degradation could increase 30%, 46% and 63%, respectively. The iron ions leached from catalyst could be adsorbed back to the catalyst again after the organic intermediates were mineralized completely. Then the catalyst of H-Fe-P-B could be reused and additional pollution caused by iron ions could be avoided.     

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.     

Mechanical studies of single glass fibres recycled from hydrolysis process using sub-critical water

The study reports mechanical performance of the recycled glass fibres produced from a water-based solvolysis technology, known as the hydrolysis process. The chemical reaction was carried out using sub-critical water to dissolve polyester resin and recover the glass fibres from composites. The effect of temperatures, times, catalyst and water amount on mechanical properties of the recovered glass fibres were investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and time-of flight secondary ion mass spectroscopy (ToF-SIMS) analyses were also employed to examine the fibre surface associated with the polyester resin eliminated level after the hydrolysis reaction. The results revealed that by carefully adjusting the hydrolysis parameters the tensile strength and failure strain of the recycled fibres decrease by approximately 40-70% in comparison with virgin fibres while Young’s moduli remain similar. The relationship between the hydrolysis conditions, recovered fibres and mechanical performance was discussed in this study.     

Kinetics and mechanism of degradation of p-chloronitrobenzene in water by ozonation

The kinetics and mechanism of p-chloronitrobenzene (pCNB) degradation by ozone were investigated. With reference compounds, nitrobenzene (NB) and chlorobenzene (CB), reaction rate constants of pCNB with O3 and OH were measured by means of competition kinetics (mixtures of pCNB and NB, or pCNB and CB), with the rate constants being, 1.6 L mol(-1) s(-1), 2.6 x 10(9) L mol(-1) s(-1), respectively. During the ozonation process of pCNB, an increase of chloride and nitrate ions in the water sample solution was observed, which is consistent with the decrease in pCNB concentration. But the total organic carbon (TOC) removal rate is not consistent with the pCNB elimination rate indicating only part of pCNB was mineralized and thus presumably some intermediate products were formed. The pCNB degradation intermediate products were analyzed by gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), high performance liquid chromatography (HPLC) and ion chromatography (IC). The main intermediate products were phenol, p-chlorophenol, p-nitrophenol, 2-chloro-5-nitrophenol, 5-chloro-2-nitrophenol, 5-nitro-catechol, para-benzoquinone, 5-nitro-1,2,3-trihydroxy phenol, trihydroxy semiquinone, glycolic acid, oxalic acid, hydroxybutanoic acid, mesoxalic acid, tartrouic acid, malonic acid, maleic acid, hydroxymalonic acid, tartaric acid, malic acid, ketoglutaric acid and muconic acid. From the identified reaction products, a possible degradation pathway for the ozonation of pCNB has been proposed.     

Photoassisted electrolysis of water using a BaTiO3 electrode

We have observed photoinduced currents at BaTiO₃ semiconductor electrodes for incident radiation greater than the band gap energy (Eg = 3.3 eV). Collection efficiencies of 30% were obtained with an applied potential and no apparent electrode degradation was observed. Photoinduced currents were examined at several wave-lengths for five solutions in the pH range from 1.1 to 13.6. Mott-Schottky plots of the functional dependence of the differential capacitance upon applied potential show linear behavior allowing estimation of the flat band potential and carrier concentration. Results for the BaTiO₃ electrodes are compared to those for SrTiO₃, TiO₂ and preliminary investigations on Pb_0.92La_0.08Ti_0.98O₃ and Pb_0.86La_0.14 (Zr_0.10Ti_0.90)_0.965O₃.     

超声波降解水中甲基橙的实验研究

为开发利用超声降解染料废水技术,建立了以甲基橙为模型化合物的超声降解模拟实验。考察了pH值、甲基橙初始浓度、氧化剂过氧化氢的投加浓度以及超声设备声能密度等实验条件对超声氧化降解甲基橙效果的影响。当甲基橙溶液初始浓度为2 mg.L-1、pH值为2时,按0.01 mL/100 mL浓度投加过氧化氢,在300 W声能密度条件下仅需20 min,甲基橙的降解率可达到91.79%。实验结果表明,超声降解染料废水技术操作简单、高效快速,具有广阔的应用前景。     

金橙G为电化学探针测定DNA的研究

在pH5.0的Britton-Robinson(B-R)缓冲溶液中,用电化学方法研究了金橙G(OG)与脱氧核糖核酸(DNA)的结合反应。OG在-0.62V处有一个灵敏的示差脉冲伏安还原峰;当在溶液中加入DNA后,随着DNA浓度的增大,OG的峰电流减小而峰电位不发生变化。峰电流的减小主要是由于溶液中DNA与OG相互结合生成了生物超分子复合物。在最佳条件下,峰电流的降低与DNA的浓度在1.0-15.0mg/L范围内呈良好的线性关系,检出限为0.35mg/L。该方法用于合成样品中DNA的测定,具有较好的回收率和选择性。