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Electrochemical Treatment (electrochemical + treatment)
Selected AbstractsAnalysis of electrochemical degradation products of sulphonated azo dyes using high-performance liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2006Dana Van, rková Electrochemical treatment of wastewaters containing azo dyes in the textile industry is a promising approach for their degradation. The monitoring of the course of the decomposition of azo dyes in wastewaters is essential due to the environmental impact of their degradation products. In this work, aqueous solutions of a simple azo dye with a low molecular weight (C.I. Acid Yellow 9) and more complex commercial dye (C.I. Reactive Black 5) were electrochemically treated in a laboratory-scale electrolytic cell in sodium chloride or ammonium acetate as supporting electrolytes. Ion-pairing reversed-phase high-performance liquid chromatography coupled with negative-ion electrospray ionization mass spectrometry is applied for the identification of electrochemical degradation products. In addition to simple inorganic salts, the formation of aromatic degradation products obtained due to the cleavage of azo bonds and further degradation reactions is shown, as well as chlorination where sodium chloride is the supporting electrolyte. Degradation mechanisms are suggested for the treatment with sodium chloride as the supporting electrolyte. Copyright © 2006 John Wiley & Sons, Ltd. [source] Treatment of Process Water Containing Heavy Metals with a Two-Stage Electrolysis Procedure in a Membrane Electrolysis CellENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2005R. Fischer Abstract The capability of a two-stage electrochemical treatment for the regeneration of acidic heavy-metal containing process water was examined. The process water came from sediment bioleaching and was characterized by a wide spectrum of dissolved metals, a high sulfate content, and a pH of about 3. In the modular laboratory model cell used, the anode chamber and the cathode chamber were separated by a central chamber fitted with an ion exchanger membrane on either side. The experiments were carried out applying a platinum anode and a graphite cathode at a current density of 0.1,A/cm2. The circulation flow of the process water in the batch process amounted to 35,L/h, the electrolysis duration was 5.5,h at maximum and the total electrolysis current was about 1,A. In the first stage, the acidic process water containing metals passed through the cathode chamber. In the second stage, the cathodically pretreated process water was electrolyzed anodically. In the cathode chamber the main load of dissolved Cu, Zn, Cr and Pb was eliminated. The sulfuric acid surplus of 3,4,g/L decreased to about 1,g/L, the pH rose from initially 3.0 to 4,5, but the desired pH of 9,10 was not achieved. Precipitation in the proximity to the cathode evidently takes place at a higher pH than farther away. The dominant process in the anode chamber was the precipitation of amorphous MnO2 owing to the oxidation of dissolved Mn(II). The further depletion of the remaining heavy metals in the cathodically pretreated process water by subsequent anodic treatment was nearly exhaustive, more than 99,% of Cd, Cr, Cu, Mn, Ni, Pb, and Zn were removed from the leachate. The high depletion of heavy metals might be due to both the sorption on MnO2 precipitates and/or basic ferrous sulfate formed anodically, and the migration of metal ions through the cation exchanger membrane via the middle chamber into the cathode chamber. In the anode chamber, the sulfuric acid content increased to 6,7,g/L and the pH sank to 1.7. All heavy metals contained, with the exception of Zn, were removed to levels below the German limits for discharging industrial wastewaters into the receiving water. Moreover, the metal-depleted and acid-enriched process waters could be returned to the leaching process, hence reducing the output of wastewater. The results indicated that heavy metals could be removed from acidic process waters by two-stage electrochemical treatment to a large extent. However, to improve the efficiency of metal removal and to establish the electrochemical treatment in practice, further work is necessary to optimize the operation of the process with respect to current density, energy consumption, discharging of metal precipitates deposited in the electrode chambers and preventing membrane clogging. [source] The effect of solids on the electrochemical treatment of olive mill effluentsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2007Efi Kotta Abstract The electrochemical oxidation of an olive mill effluent over Ti,Pt anodes was studied. The effluent had an average total chemical oxygen demand (COD) value of 234 g L,1, soluble COD of 61 g L,1, soluble phenolic content 3.4 g L,1, total solids of 80 g L,1 and pH = 5.1. Experiments were conducted in a 10 L vessel with the effluent recirculating at 1 L s,1. The applied current was varied between 5 and 20 A, the salinity between 1 and 4% NaCl, and experiments were performed with the effluent diluted with water to achieve the desired initial concentration. Emphasis was given to the effect of the presence of solids as well as of varying operating conditions on process performance as assessed in terms of COD, color and phenols removal. In general, degradation of phenols occurred relatively fast with conversion increasing with increasing applied current and decreasing initial organic loading and this was accompanied by low COD removal levels and moderate decolorization. The presence of solids had practically no effect on phenols removal, which, in most cases, was complete in less than about 180 min of reaction. However, oxidation in the presence of solids resulted in a substantial solid fraction being dissolved and this consequently increased sample color and the soluble COD content. The solid content typically found in olive mill effluents may partially impede its treatment by electrochemical oxidation, thus requiring more severe operating conditions and greater energy consumption. Copyright © 2007 Society of Chemical Industry [source] Initiating electropolymerization on graphene sheets in graphite oxide structureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2010Ali Eftekhari Abstract Because of its special chemical composition, graphite oxide has peculiar influences on electrochemical processes. The existence of various functional groups significantly affects electropolymerization processes and the formation of conductive polymers. Electrochemical synthesis of polyaniline (as a prototype of conductive polymers) on a paste-based substrate of graphite oxide was investigated. In this case, the electropolymerization is significantly different from conventional cases, and the polymer is generated just during the first potential cycle. This can be attributed to the fact that graphite oxide can assist the monomer oxidation. Alternatively, electropolymerization was successfully performed inside the graphite oxide layers via electrochemical treatment of aniline-intercalated graphite oxide in the supporting electrolyte. Although these phenomena are related to the chemical composition of graphite oxide, the graphite prepared by the reduction of graphite oxide also displayed some advantages for the electropolymerization (over natural graphite). There is an emphasis on the morphological investigations throughout this study, because novel morphologies were observed in the system under investigation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2204,2213, 2010 [source] Sulphur passivation of GaSb, InGaAsSb and AlGaAsSb surfacesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2007E. Papis Abstract The effects of electrochemical treatment in either 21%(NH4)2S-H2O or 16%Na2S-C3H7OH solutions on the surface properties of GaSb, In0.23Ga77As0.18Sb0.82 and Al0.34Ga0.66As0.025Sb0.975 have been investigated by complementary use of Variable Angle Spectroscopic Ellipsometry (VASE) and X-ray Photoelectron Spectroscopy (XPS). We have shown that electrochemical sulphuration enables to produce 94,350 nm thick insulating overcoats with good surface morphology. The main components of the passivating layers are Ga2S3 and Sb2S5when formed on GaSb, while additional components of In2S3, admixture of Al2O3 and appearance of Al-As bond were observed on InGaAsSb and AlGaAsSb, respectively. The main feature distinguishing the effect of electrochemical treatment in Na2S,C3H7OH when comparing to those in (NH4)2S-H2O is that passivating layers contain additional components of Na2SO3 and/or Na2SO4. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thirty-five years in bioelectromagnetics researchBIOELECTROMAGNETICS, Issue 1 2007C-K. Chou Abstract For 35 years, I have been involved in various bioelectromagnetics research projects including acute and long-term radiofrequency (RF) bioeffects studies, dosimetry, exposure systems, MRI safety, cancer studies involving hyperthermia and electrochemical treatment, development of RF exposure and measurement standards, and product compliance. My first study demonstrated that effects on isolated nerve and muscle preparations were due to thermal effects of RF exposure. The recording of cochlear microphonics in animals shows the mechanical nature of the microwave auditory effect. In 1992, we published the results of a large-scale lifetime study in which 100 rats were sham-exposed and 100 rats were exposed for 21 h/day for 25 months to a pulsed RF signal. In dosimetry studies, human models were employed as well as many animal species including mice, rats, rabbits, monkeys, and birds of many sizes. Cancer hyperthermia studies demonstrated that knowledge of temperature distribution was crucial for successful treatment. Research on electrochemical treatment of tumors with direct current involved cellular, animal, and clinical studies. Over the past few decades, there has been rather extensive investigation of the public health impact of RF exposure. In my opinion, future research in bioelectromagnetics should place greater emphasis on medical applications. Bioelectromagnetics © 2006 Wiley-Liss, Inc. [source] Biomimetic Approach to Confer Redox Activity to Thin Chitosan FilmsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Eunkyoung Kim Abstract Electron transfer in biology occurs with individual or pairs of electrons, and is often mediated by catechol/o -quinone redox couples. Here, a biomimetic polysaccharide-catecholic film is fabricated in two steps. First, the stimuli-responsive polysaccharide chitosan is electrodeposited as a permeable film. Next, the chitosan-coated electrode is immersed in a solution containing catechol and the electrode is biased to anodically-oxidize the catechol. The oxidation products covalently graft to the chitosan films as evidenced by electrochemical quartz crystal microbalance (EQCM) studies. Cyclic voltammetry (CV) measurements demonstrate that the catechol-modified chitosan films are redox-active although they are non-conducting and cannot directly transfer electrons to the underlying electrode. The catechol-modified chitosan films serve as a localized source or sink of electrons that can be transferred to soluble mediators (e.g., ferrocene dimethanol and Ru(NH3) 6Cl3). This electron source/sink is finite, can be depleted, but can be repeatedly regenerated by brief (30 s) electrochemical treatments. Further, the catechol-modified chitosan films can i) amplify currents associated with the soluble mediators, ii) partially-rectify these currents in either oxidative or reductive directions (depending on the mediator), and iii) switch between regenerated-ON and depleted-OFF states. Physical models are proposed to explain these novel redox properties and possible precedents from nature are discussed. [source] | ||||||||||||||||