Degradation of Anionic Dye Eosin by Glow Discharge Electrolysis Plasma

This paper describes a novel method for the degradation of eosin by using glow discharge electrolysis （GDE）. The effects of various parameters on the removal efficiency were studied. It was found that the eosin degradation could be raised considerably by increasing the applied voltage and the initial concentration, or by decreasing pH of the aqueous solution. Fe^2＋ ion had an evident accelerating effect on the eosin degradation. The degradation process of eosin obeyed a pseudo-first-order reaction. The relationship between the degradation rate constant k and the reaction temperature T could be expressed by Arrhenius equation with which the apparent activation energy Ea of 14.110 kJ· mol^-1 and the pre-exponential factor k0 of 2.065× 10^-1 min^-1 were obtained, too. The determination of hydroxyl radical was carried out by using N, N-dimethyl -p-nitrosoaniline （RNO） as a scavenger. The results showed that the hydroxyl radical plays an important role in the degradation process.

Analysis of Energetic Species Caused by Contact Glow Discharge Electrolysis in Aqueous Solution

Contact glow discharge electrolysis is a non-Faradaic electrochemical process with an abnormal relationship between the current and voltage. Hydroxyl radicals, hydrogen radicals and hydrogen peroxide can be produced under the glow discharge, which are often used to degrade organic contaminants in aqueous solution. In this study, with 4-nitrophenol taken as an example of contaminants and tert-butanol as a scavenger of hydroxyl radicals, the role of energetic species in degrading organic compounds was examined in detail. Moreover, the effects of the applied voltage, solution conductivity and pH on the formation of three energetic species were also observed. The formation rate constants of the three energetic species were calculated based on the experimental data.

Synthesis of Poly (Butyl Methacrylate/Butyl Acrylate) Highly Absorptive Resin Using Glow Discharge Electrolysis

A highly absorptive resin poly （butyl methacrylate （BMA）-co-butyl acrylate （BA）） was prepared by emulsion polymerization, which was initiated by glow discharge electrolysis plasma （GDEP）. The effects of discharge voltage, discharge time, monomer ratio and the amounts of cross- linking agent were examined and discussed in detaiI. The chemical structure of the obtained resin was characterized by means of attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The optimal conditions were ob- tained as： discharge voltage was 600 V, discharge time was 8 min, the ratios of BMA：BA being 2：1 for chloroform and 3：1 for xylene, with 2% N, N＇-methylenebis. Under optimal conditions, the oil absorbency was 70 g/g for chloroform and 46 g/g for xylene. Moreover, the absorptive dynamical behavior of the resulting resin was also investigated.

Degradation of Chloroanilines in Aqueous Solution by Contact Glow Discharge Electrolysis

Contact glow discharge electrolysis of some chloroanilines in sodium sulfate was investigated in different initial concentrations. Each of them underwent the dechlorination, deam-ination through oxidative degradation, and were eventually decomposed into hydrogen carbonate and carbon dioxide. It was testified that the chlorine atom and amidogen could be transformed into chloride ion and nitrite ion, respectively. Fe2+ has a remarkable catalytic effect on the degradation of them. On the basis of the detailed analysis of the intermediate products and kinetic behaviors, the reaction pathway was proposed, in which the attack of hydroxyl radical on the benzene ring of starting material might be a key step.

The Role of Fe(Ⅱ)in the Contact Glow Discharge Electrolysis

In this paper, we use methyl violet as a model organic substrate in wastewater to study the effect of Fe（Ⅱ） ion on the contact glow discharge electrolysis （CGDE）. The decoloration rate and the COD （Chemical Oxygen Demand） value have been examined. It is found that the presence of Fe（Ⅱ） ion can accelerate obviously the degradation of methyl violet, because it reacts with H2O2 in the CGDE process to yield hydroxyl radical, just acting as a Fenton-like reagent. Moreover, the optimal conditions for decoloring methyl violet were obtained, by means of an orthogonal experiment, to be [Fe^2＋] =1×10^-3 mol/L, applied voltage of 700 V of and pH = 9.0.

Abatement of Arsenite from Water by Glow Discharge Electrolysis

Glow discharge electrolysis provides an alternative method for the removal of arsenite from water. Glow discharge electrolysis of aqueous solution containing arsenite is studied under altemating current altemating current （50 Hz） discharge. It is found that arsenite [As（III）] get converted to arsenate [As（V）]. The yield is studied with various parameters such as discharge current, duration of discharge and pH （2-10）. The results are interpreted on the basis of interaction of the OH and eaq （produced consequent to the interaction of H2O＋ and e with water at the surface of the solution） with arsenite [As（III）] through the intermediate oxidation state, namely [As（IV）].

Oxidative Degradation of 4-chlorophenol in Aqueous Induced by Plasma with Submersed Glow Discharge Electrolysis

The oxidative degradation of 4-chlorophenol （4-CP） in aqueous solution induced by plasma with submersed glow discharge has been investigated. The concentration of 4-CP and the reaction intermediates were determined by high performance liquid chromatography （HPLC）. Various influencing factors such as the initial pH, the concentration of 4-CP and the catalytic action of Fe^2＋ were examined. The results indicate that 4-CP is eventually degraded into inorganic ion, dioxide carbon and water. The attack of hydroxyl radicals on the benzene rings of 4-CP in the initial stage of oxidative reactions is presumed to be a key step. They also suggest that the reaction is of a pseudo-first order kinetic reaction and the proposed method is an efficient way for the 4-CP degradation,

Mineralization of aqueous pentachlorophenolate by anodic contact glow discharge electrolysis

Exhaustive mineralization of pentachlorophenolate ion（PCP） in phosphate buffer was carried out using anodic contact glow discharge electrolysis（CGDE）,in which plasma was sustained between the electrolyte and anode.During CGDE,PCP degraded smoothly.The amount of total organic carbon decreased significantly,indicating the eventual conversion of the carbon atoms of benzene nucleus to inorganic carbons.Furthermore,chlorine atoms in PCP were liberated as chloride ions.As a primary intermediate product,2,3,5,6tetrachloro-1,4-benzoquinone was detected,and oxalate and formate as byproducts were also found.It was revealed that disappearance of PCP obeyed first-order kinetics.The reaction rate was generally unaffected by both O2 and inert gases in the cell,although it decreased by raising initial pH of solution.In addition,a plausible reaction pathway involving hydroxyl radical was proposed.

Destruction of 4-phenolsulfonic acid in water by anodic contact glow discharge electrolysis

Destruction of 4-phenolsulfonic acid （4-PSA） in water was carded out using anodic contact glow discharge electrolysis. Accompanying the decay of 4-PSA, the amount of total organic carbon （TOC） in water correspondingly decreased, while the sulfonate group of 4- PSA was released as sulfate ion. Oxalate and formate were obtained as minor by-products. Additionally, phenol, 1,4-hydroquinone, hydroxyquinol and 1,4-benzoquinone were detected as primary intermediates in the initial stages of decomposition of 4-PSA. A reaction pathway involving successive attacks of hydroxyl and hydrogen radicals was assumed on the basis of the observed products and kinetics. It was revealed that the decay of both 4-PSA and TOC obeyed a first-order rate law. The effects of different Fe ions and initial concentrations of 4-PSA on the degradation rate were investigated. It was found that the presence of Fe ions could increase the degradation rate of 4-PSA, while initial concentrations lower than 80 mmol/L had no significant effect on kinetic behaviour. The disappearance rate of 4-PSA was significantly affected by pH.

Glow Discharge Induced Hydroxyl Radical Degradation of 2-Naphthylamine

In an aqueous solution, normal electrolysis at high voltages switches over spontaneously to glow discharge electrolysis and gives rise to hydroxyl radical, hydrogen peroxide, and aqueous electron, as well as several other active species. Hydroxyl radical directly attacks organic contaminants to make them oxidized. In the present paper, 2-naphthylamine is eventually degraded into hydrogen carbonate and carbon dioxide. The degradation process is analyzed by using an Ultraviolet (UV) absorption spectrum, high-performance liquid chromatography (HPLC) and chemical oxygen demand (COD). It is demonstrated that 2-naphthylamine (co =30 mg·1-1) is completely converted within 2h at 30℃ and 600 V by glow discharge electrolysis, and the degradation is strongly dependent upon the presence of ferrous ions. COD is ascended in the absence of ferrous ions and descended in the presence of them.

Oxidative Degradation of o-Chlorophenol with Contact Glow Discharges in Aqueous Solution

Contact glow discharge electrolysis (CGDE) of o-chlorophenol (2-CP) was investigated under different pH, voltages and initial concentrations. And the mechanism of the oxidation was explored. The results suggested that the degradation followed the first order kinetic law; Fe2+ had a remarkable catalytic effect on the removal rate of o-chloropenol. In the presence of Fe2+, 2-CP underwent an exhaustive degradation, from which the major intermediates included o-dihydroxybenze, p-hydroxybenze, p-benzoquione and carboxlic acids.

Experimental Study of Plasma Under-liquid Electrolysis in Hydrogen Generation

The application and characteristics of relatively big volume plasma produced with cathodic glow discharges taking place across a gaseous envelope over the cathode which was dipped into electrolyte in hydrogen generation were studied. A critical investigation of the influence of methanol concentration and voltage across the circuit on the composition and power consumption per cubic meter of cathode liberating gas was carried out. The course of plasma under-liquid electrolysis has the typical characteristics of glow discharge electrolysis. The cathode liberating gas was in substantial excess of the Faraday law value. When the voltage across the circuit was equal to 550 V,the volume of cathodic gas with sodium carbonate solution was equal to 16.97 times the Faraday law value. The study showed that methanol molecules are more active than water molecules. The methanol molecules were decomposed at the plasma-catholyte interface by the radicals coming out the plasma mantle. Energy consumption per cubic meter of cathodic gases (WV) decreased while methanol concentration of the electrolytes increased. When methanol concentration equaled 5% (-),WV was 10.381×103 kJ/m3,less than the corresponding theoretic value of conventional water electrolysis method. The cathodic liberating gas was a mixture of hydrogen,carbon dioxide and carbon monoxide with over 95% hydrogen,if methanol concentration was more than 15% (-). The present research work revealed an innovative application of glow discharge and a new highly efficient hydrogen generation method,which depleted less resource and energy than normal electrolysis and is environmentally friendly.