Electrochemical oxidation of an acid dye by active chlorine generated using Ti/Sn<Subscript>(1−<Emphasis Type="Italic">x</Emphasis>)</Subscript>Ir<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> electrodes

The generation of active chlorine on Ti/Sn_(1−x)Ir _x O₂ anodes, with different compositions of Ir (x = 0.01, 0.05, 0.10 and 0.30 ), was investigated by controlled current density electrolysis. Using a low concentration of chloride ions (0.05 mol L⁻¹) and a low current density (5 mA cm⁻²) it was possible to produce up to 60 mg L⁻¹ of active chlorine on a Ti/Sn_0.99Ir_0.01O₂ anode. The feasibility of the discoloration of a textile acid azo dye, acid red 29 dye (C.I. 16570), was also investigated with in situ electrogenerated active chlorine on Ti/Sn_(1−x)Ir _x O₂ anodes. The best conditions for 100% discoloration and maximum degradation (70% TOC reduction) were found to be: NaCl pH 4, 25 mA cm⁻² and 6 h of electrolysis. It is suggested that active chlorine generation and/or powerful oxidants such as chlorine radicals and hydroxyl radicals are responsible for promoting faster dye degradation. Rate constants calculated from color decay versus time reveal a zero order reaction at dye concentrations up to 1.0 × 10⁻⁴ mol L⁻¹. Effects of other electrolytes, dye concentration and applied density currents also have been investigated and are discussed.     

Simultaneous removal of organic and inorganic pollutants in tannery wastewater using electrocoagulation technique

Tannery wastewater can cause severe environmental problems related to its high chemical oxygen demand, high biochemical oxygen demand, high total suspended solids, high oil and grease contents together with the elevated chromium concentration and objectionable color. The one-step electrocoagulation process was carried out to simultaneously remove chromium and various pollutants from tannery wastewater at ambient temperature in the laboratory scale. Low-cost commercial iron plates were employed in this study as anodes and cathode materials. Effects of various parameters were investigated including types of electrode configuration, initial pH of wastewater (7–9), current density (15.7–24.6 Am⁻²) and circulating flow rate of wastewater (0–3.67 lmin⁻¹). The optimum condition was found by applying the mono-polar electrode in a parallel connection at the current density of 22.4 Am⁻², flow rate of wastewater of 3.67 lmin⁻¹ and 20 min electrolysis time. The initial pH of wastewater ranging from 7–9 provided the similar removal efficiency. At optimum condition, more than 95% of chromium and pollutants except TKN and TDS were eliminated from the wastewater and the properties of the treated wastewater met the standard and permitted to discharge into the environment. The required energy consumption at optimum condition was less than 0.13 kWhm⁻³ wastewater. In addition, the COD reduction was fit very well with the first-order kinetics model.     

Electrochemical treatment of pharmaceutical azo dye amaranth from waste water

The electrochemical behavior of pharmaceutical azo dye amaranth has been investigated in distilled water and Britton–Robinson buffer. One well-defined irreversible cathodic peak is observed. This may be attributed to the reduction of the –N=N– group. Calculation of the number of electrons transferred in the reduction process has been performed and a reduction mechanism proposed. Results indicate that the electrode process is diffusion controlled. The cathodic peak in the case of controlled potential electrolysis is found to reduce substantially with a decrease in color and absorbance. The reaction has first order kinetics with k value 5.75 × 10⁻² abs min⁻¹. The efficiency of different electrode materials (platinum and steel) for decolorisation is compared. Chemical oxygen demand (COD) decreases substantially from 2,680 to 96 ppm at platinum and to 142 ppm at steel. This translates to 97% COD removal at platinum and 95% at steel.     

In situ active chlorine generation for the treatment of dye-containing effluents

This study examined the possibility to remove colour causing-compounds from synthetic effluent by indirect electrochemical oxidation using iridium oxide anode electrodes. Using a high concentration of chloride ions (17.1 mM) and various current densities, it was possible to produce high concentration of active chlorine with a specific production rate of 2.8 mg min⁻¹ A⁻¹. The best performance for acid methyl violet 2B dye (MV2B) decomposition was obtained using Ti/IrO₂ anodes operated at a current density of 15 mA cm⁻² during 40 min of treatment in the presence of 3.42 mM of chloride ions. Under these conditions, more than 99% of MV2B was removed (with a reaction rate apparent constant of 0.20 min⁻¹), whereas COD and TOC removal were 51% and 75%, respectively. The electrolytic cell was then used for the degradation of three other synthetic dye solutions: Eosin yellowish (EOY), Trypan Blue (TRB), Acridine Orange (ACO). TRB was the most difficult dye to remove from solution with a value reaction rate constant of 0.12 min⁻¹, compared to 0.19 min⁻¹ and 0.24 min⁻¹ recorded for ACO and EOY dyes, respectively. More than 99% of these dyes were removed by electrochemical oxidation.     

Preparation and evaluation of RuO2–IrO2, IrO2–Pt and IrO2–Ta2O5 catalysts for the oxygen evolution reaction in an SPE electrolyzer

IrO₂–RuO₂, IrO₂–Pt and IrO₂–Ta₂O₅ electrocatalysts were synthesized and characterized for the oxygen evolution in a Solid Polymer Electrolyte (SPE) electrolyzer. These mixtures were characterized by XRD and SEM. The anode catalyst powders were sprayed onto Nafion 117 membrane (catalyst coated membrane, CCM), using Pt catalyst at the cathode. The CCM procedure was extended to different in-house prepared catalyst formulations to evaluate if such a method could be applied to electrolyzers containing durable titanium backings. The catalyst loading at the anode was about 6 mg cm⁻², whereas 1 mg cm⁻² Pt was used at the cathode. The electrochemical activity for water electrolysis was investigated in a single cell SPE electrolyzer at 80 °C. It was found that the terminal voltage obtained with Ir–Ta oxide was slightly lower than that obtained with IrO₂–Pt and IrO₂–RuO₂ at low current density (lower than 0.15 A cm⁻²). At higher current density, the IrO₂–Pt and IrO₂–RuO₂ catalysts performed better than Ir–Ta oxide.     

DSA electrochemical treatment of olive mill wastewater on Ti/RuO<Subscript>2</Subscript> anode

The electrochemical oxidation of olive mill wastewater (OMW) over a Ti/RuO₂ anode was studied by means of cyclic voltammetry and bulk electrolysis and compared with previous results over a Ti/IrO₂ anode. Experiments were conducted at 300–1,220 mg L⁻¹ initial chemical oxygen demand (COD) concentrations, 0.05–1.35 V versus SHE and 1.39–1.48 V versus SHE potential windows, 15–50 mA cm⁻² current densities, 0–20 mM NaCl, Na₂SO₄, or FeCl₃ concentrations, 80 °C temperature, and acidic conditions. Partial and total oxidation reactions occur with the overall rate being near first-order kinetics with respect to COD. Oxidation at 28 Ah L⁻¹ and 50 mA cm⁻² leads to quite high color and phenols removal (86 and 84%, respectively), elimination of ecotoxicity, and a satisfactory COD and total organic carbon reduction (52 and 38%, respectively). Similar performance can be achieved at the same charge (28 Ah L⁻¹) using lower current densities (15 mA cm⁻²) but in the presence of various salts. For example, COD removal is less than 7% at 28 Ah L⁻¹ in a salt-free sample, while addition of 20 mM NaCl results in 54% COD reduction. Decolorization of OMW using Ti/RuO₂ anode seems to be independent of the presence of salts in contrast with Ti/IrO₂ where addition of NaCl has a beneficial effect on decolorization.     

The Biodegradabilities of Different Oil-Based Fatliquors

The biodegradabilities of different oil-based fatliquors derived from rape oil, fish oil, castor oil or mineral oil variants were investigated by evaluating the respiration curves, BOD₅/COD values, COD (chemical oxygen demand) and TOC (total organic carbon) removal ratios. Simultaneously, degradation kinetics of the fatliquors were also studied. The results indicated that the BOD₅/COD values and the COD and TOC removal ratios of all the natural oil based products are higher than 0.45 and 85%, respectively, implying that all of them are biodegradable. The mineral oil based fatliquors have lower than 0.2 and 10% values, showing unbiodegradable characteristics and were used as the control. The biodegradability order is castor oil > fish oil > rape oil > mineral oil product. Further study indicated that the differences in biodegradability result from the varying fatty acid composition (such as ricinoleic acid and polyunsaturated fatty acids). The higher the active group content, the more beneficial for modification reactions and result in a higher biodegradation rate. The degradation kinetics studies revealed that the degradation rate constants (k) of castor oil, fish oil and rape oil products are 0.87, 0.84 and 0.81 d⁻¹ for the sulfated fatliquor, and 0.95, 0.93, 0.85 d⁻¹ for the oxidized–sulfited fatliquors, respectively; indicating that the overall degradation rate followed the same trend as the biodegradability order where castor oil > fish oil > rape oil, whether the fatliquors underwent modification as sulfated or oxidized–sulfited.     

Effects of temperature and current density on zinc electrodeposition from acidic sulfate electrolyte with [BMIM]HSO<Subscript>4</Subscript> as additive

The effects of temperature and current density on cathodic current efficiency, specific energy consumption, and zinc deposit morphology during zinc electrodeposition from sulfate electrolyte in the presence of 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO₄) as additive were investigated. The highest current efficiency (93.7%) and lowest specific energy consumption (2,486 kWh t⁻¹) were achieved at 400 A m⁻² and 313 K with addition of 5 mg dm⁻³ [BMIM]HSO₄. In addition, the temperature dependence of some kinetic parameters for the zinc electrodeposition reaction was experimentally determined. Potentiodynamic polarization sweeps were carried out to obtain the expression for each parameter as a function of temperature. In the condition studied, the exchange current density depended on temperature as ln(i ₀) = −a/T + b and the charge transfer coefficient was constant. Moreover, the adsorption of the additive on cathodic surface obeyed the Langmuir adsorption isotherm. The associated thermodynamic parameters indicated the adsorption to be chemical.     

Electrochemical degradation of the Acid Blue 62 dye on a β-PbO<Subscript>2</Subscript> anode assessed by the response surface methodology

The electrochemical degradation of the anthraquinonic dye Acid Blue 62 in a filter-press reactor on a Ti/Pt/β-PbO₂ anode was investigated using the response surface methodology with the variables: current density, pH, [NaCl], and temperature. The system’s modeling was carried out with the charge required for 90% decolorization (Q ⁹⁰) and the chemical oxygen demand removal percentage after a 30 min electrolysis (COD ³⁰), with good correlations between predicted and observed values. Best conditions for decolorization were attained in acidic solutions (pH = 4) with medium to high [NaCl] (1.0–2.0 g L⁻¹) and lower temperature due to the prevalent oxidant species HOCl and Cl₂. Optimal conditions for COD ³⁰ removal were attained at high current densities in pH > 5 solutions with high [NaCl], when the prevalent oxidant species are HOCl and OCl⁻. The lowest charge per unit volume of the electrolyzed solution necessary for total mineralization was attained at pH 11.     

High temperature water electrolysis using metal supported solid oxide electrolyser cells (SOEC)

Metal supported cells as developed according to the DLR SOFC concept by applying plasma deposition technologies were investigated for use as solid oxide electrolyser cells (SOEC) for high temperature steam electrolysis. Cells consisting of a porous ferritic steel support, a diffusion barrier layer, a Ni/YSZ hydrogen electrode, a YSZ electrolyte and a LSCF oxygen electrode were electrochemically characterised by means of i-V characteristics and electrochemical impedance spectroscopy measurements including a long-term test over 2000 h. The cell voltage during electrolysis operation at a current density of −1.0 A cm⁻² was 1.28 V at an operating temperature of 850 °C and 1.4 V at 800 °C. A long-term test run over 2000 h with a steam content of 43% at 800 °C and a current density of −0.3 A cm⁻² showed a degradation rate of 3.2% per 1000 h. The impedance spectra revealed a significantly enhanced polarisation resistance during electrolysis operation compared to fuel cell operation which was mainly attributed to the hydrogen electrode.     

Reaction between Hydrosulfide and Iron/cerium (hydr)oxide: Hydrosulfide Oxidation and Iron Dissolution Kinetics

Hydrosulfide oxidation and iron dissolution kinetics were studied at normal pressure, under inert (N₂) atmosphere, in a liquid–solid mechanically-stirred slurry reactor. The kinetic variables undergoing variations were: hydrosulfide initial concentration (0.90–3.30 mmol/L), oxide initial surface area (16–143 m²/L) and pH (8.0–11.0). The hydrosulfide consumption and products (thiosulfate and polysulfide) formation were quantified by means of capillary electrophoresis, while iron dissolution was monitored through atomic absorption spectroscopy. Most of Fe(II) produced at pH = 9.5 remained associated with the oxide surface in the time-scale of the experiments. The hydrosulfide oxidation by the iron/cerium (hydr)oxide was found to be surface-controlled, with rates (R_i) of both sulfide oxidation and Fe(II) dissolution expressed in terms of an empirical rate equation: R_i = k_i[HS⁻]_t=0^−0.5[A]_t=0[H⁺]_t=0^−0.5 , where k_i represents the apparent rate constants for the oxidation of HS⁻ (k_HS) or the dissolution of Fe(II) (k_Fe), [HS⁻]_{t = 0} is the initial hydrosulfide concentration, [A]_{t = 0} is the initial Fe/Ce (hydr)oxide surface area and [H⁺]_{t = 0} is the initial proton concentration. The rate constant, k_HS, for the oxidation of hydrosulfide at pH = 9.5 was (3.4219 ± 0.65) × 10⁻⁴ mol² L⁻¹ m⁻² min⁻¹, with the rate of hydrosulfide oxidation being ca. 10 times faster than the rate of Fe(II) dissolution (assuming a 1:2 stoichiometric ratio between HS⁻ oxidized and Fe(II) produced; k_Fe = (3.9116 ± 0.41) × 10⁻⁵ mol² L⁻¹ m⁻² min⁻¹).     

Using electrocoagulation-electroflotation technology to treat synthetic solution and textile wastewater, two case studies

The purpose of this study was to investigate the effects of the operating parameters, such as pH, initial concentration (C_i), duration of treatment (t), current density (j), interelectrode distance (d) and conductivity (κ) on the treatment of a synthetic wastewater in the batch electrocoagulation (EC)-electroflotation (EF) process. The optimal operating conditions were determined and applied to a textile wastewater. Initially a batch-type EC-EF reactor was operated at various current densities ranging from 11.55 to 91.5 mA/cm² and various electrode gaps (1, 2 and 3 cm). For solutions with 300 mg/L of silica gel, good turbidity removal (89.6%) was obtained without any coagulant when the current density was 11.55 mA/cm², and with initial pH at 7.6, conductivity at 2.1 mS/cm: the treatment time was hold for 10 min and the electrode gap was 1 cm. Application of the optimal operating parameters on a textile wastewater showed a high removal efficiency for the following variables: suspended solid (SS) 85.5%, turbidity 76.2%, biological oxygen demand (BOD₅) 88.9%, chemical oxygen demand (COD) 79.7%, and color over 93%.     

Zn<Superscript>2+</Superscript>-exchange kinetics and antimicrobial properties of synthetic zirconium umbite (K<Subscript>2</Subscript>ZrSi<Subscript>3</Subscript>O<Subscript>9</Subscript>·H<Subscript>2</Subscript>O)

Zirconium umbite, K₂ZrSi₃O₉·H₂O, is a microporous framework ion exchanger whose potential as a carrier for Zn²⁺ ions in antimicrobial formulations has not yet been investigated. Accordingly, batch Zn²⁺-exchange kinetics of synthetic zirconium umbite (K-UM) and the subsequent antimicrobial action of the zinc-bearing phase (Zn-UM) against Staphylococcus aureus and Escherichia coli are reported. Nonstoicheiometric over-exchange of Zn²⁺ for K⁺ was observed and attributed to hydrolysis and complexation reactions of Zn²⁺ within the umbite framework. The exchange process, which was described by a simple pseudo-first-order model (k ₁ = 2.69 × 10⁻⁴ min⁻¹, R ² = 0.992), did not achieve equilibrium within 120 h at 25 °C, by which time the uptake of zinc was found to be 1.04 mmol g⁻¹. The minimal bactericidal concentrations of Zn-UM for E. coli and S. aureus were found to be >10 g cm³ and <1.0 g cm³, respectively.     

Electrochemical process for the treatment of landfill leachate

In this paper, the anodic oxidation of a real leachate from an old municipal solid waste landfill has been studied using an electrolytic flow cell equipped with a lead dioxide (PbO₂) anode and stainless steel as the cathode. The influence of several operation parameters such as (i) the applied current (from 0.5 to 3 A), (ii) liquid flow rate (from 50 to 420 L h⁻¹), (iii) temperature (from 25 to 50 °C), and (iv) pH (from 3.5 to 8.2) on the COD removal rate, current efficiency, and energy consumption has been evaluated. The galvanostatic electrolyses always yielded COD values below the discharge limit (COD <160 mg L⁻¹); the COD removal rate increased with rising applied current, solution pH, and temperature, whereas it remained almost unaffected by the recirculation flow rate. These results indicate that the organic compounds were mainly removed by their indirect oxidation by the active chlorine generated from chlorides oxidation. The specific energy consumption necessary to reduce the organic load to below the disposal limit was 90 kWh m⁻³.     

Synthesis and characterization of Ni–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite coatings containing different forms of alumina

Electrodeposited Ni–Al₂O₃ composite coatings were prepared using alumina powders synthesized from solution combustion method, precipitation method and a commercial source. Solution combustion synthesized alumina powder yielded α-phase; precipitation method yielded purely γ-phase; commercial alumina powder was a mixture of α-, δ- and γ-phases. A nickel sulfamate bath was used for electro-codeposition. The current densities (0.23 A dm⁻² for 20 h, 0.77 A dm⁻² for 6 h, 1.55 A dm⁻² for 3 h and 3.1 A dm⁻² for 1.5 h) and bath agitation speeds (100, 200, 600 and 1000 rpm) were varied. The pH variations of the bath were higher during the electrodeposition of combustion synthesized alumina. The effect of different forms of alumina particles on the microhardness and microstructure of the nickel composite coating was studied. Composite coating containing combustion synthesized alumina particles was found to have higher microhardness (550 HK). It was found that at lower agitation speed (100 rpm), bigger particles were incorporated and at higher agitation speed (1000 rpm), smaller particles were incorporated. The area fraction of alumina particles incorporated in nickel matrix was highest for commercial alumina (24%). This study shows that it is not suffice to take just the current density and stirring speeds into account to explain the properties of the coatings but also to take into account the source of particles and their properties.     

Electrochemical treatment of water containing chlorides under non-ideal flow conditions with BDD anodes

In this work a undivided parallel plate cell equipped with boron doped diamond (BDD) anode was tested as electrochemical reactor for disinfection of water. Two configurations were adopted: a single pass configuration (SPC) and a recirculated configuration (RC) in which also a reservoir was inserted in the hydraulic circuit. In both the experimental configurations the system worked in continuous mode with a flow rate ranging from 0.05 to 0.42 dm³ min⁻¹; in the RC the recirculating flow rate ranged from 0.45 to 6 dm³ min⁻¹. Thermostated (25 °C) galvanostatic electrolyses were carried out with aqueous solutions containing 100 mg dm⁻³ of chloride ions: values of current density from 2.5 to 5.0 mA cm⁻² were used. Steady state data revealed that active chlorine and chlorate ions were the main oxidation products. Particular attention was paid to the hydrodynamics both for SPC and RC: pulse-response curves were experimentally obtained with an inert tracer, and the behaviour of the system was interpreted by models based on a combination of ideal flow reactors, bypass flow elements, and dead zones. The hydrodynamic models were utilized to predict the outlet concentration of the electrolysis products. A good agreement between model predicted and experimental data was obtained for a wide range of experimental conditions. Preliminary disinfection tests were then performed using Escherichia coli as model microorganism. Results were discussed in terms of both disinfection efficiency and by-products formation.     

Fabrication and electroanalytical characterization of label-free DNA sensor based on direct electropolymerization of pyrrole on p-type porous silicon substrates

Label-free DNA sensors based on porous silicon (PS) substrate were fabricated and electrochemically characterized. p-type silicon wafer was electrochemically anodized in an ethanolic hydrofluoric (HF) solution to construct a PS layer on which polypyrrole (PPy) film was directly electropolymerized. To achieve direct electropolymerization of PPy on PS substrate without pre-deposition of any metallic thin-film underlayer, a low resistivity wafer (0.01–0.02 Ω cm) was used. The rough surface of the PS layer allowed for a strong adsorption of the PPy film. Intrinsic negative charge of the DNA backbone was exploited to electrostatically adsorb 26 base pairs of probe DNA (pDNA) into the PPy film by applying positive bias. The pDNA was designed to hybridize with the target DNA (tDNA) which is the insertion element (Iel) gene of Salmonella enterica serovar Enteritidis. Dependence of peak current (i _p ) around 0.2 V vs Ag/AgCl on tDNA concentration and incubation time were shown from the cyclic voltammograms of PS/PPy + pDNA + tDNA substrates in a 0.01 M potassium perchlorate solution. Plot of i _p vs incubation time showed a reduction in current density (J) by ca. 29 μA cm⁻² every hour. Sensitivity obtained from a plot of i _p vs tDNA concentration was −166.6 μA cm⁻² μM⁻¹. Scanning electron microscopy (SEM) image of the cross-section of a PS/PPy + pDNA + tDNA multilayered film showed successful direct electropolymerization of PPy for a nano-PS DNA biosensor.     

Kinetic Study of the Prooxidant Effect of α-Tocopherol. Hydrogen Abstraction from Lipids by α-Tocopheroxyl Radical

A kinetic study of the prooxidant effect of α-tocopherol was performed. The rates of allylic hydrogen abstraction from various unsaturated fatty acid esters (ethyl stearate 1, ethyl oleate 2, ethyl linoleate 3, ethyl linolenate 4, and ethyl arachidonate 5) by α-tocopheroxyl radical in toluene were determined, using a double-mixing stopped-flow spectrophotometer. The second-order rate constants (k _p) obtained are <1 × 10⁻² M⁻¹ s⁻¹ for 1, 1.90 × 10⁻² M⁻¹ s⁻¹ for 2, 8.33 × 10⁻² M⁻¹ s⁻¹ for 3, 1.92 × 10⁻¹ M⁻¹ s⁻¹ for 4, and 2.43 × 10⁻¹ M⁻¹ s⁻¹ for 5 at 25.0 °C. Fatty acid esters 3, 4, and 5 contain two, four, and six –CH₂– hydrogen atoms activated by two π-electron systems (–C=C–CH₂–C=C–). On the other hand, fatty acid ester 2 has four –CH₂– hydrogen atoms activated by a single π-electron system (–CH₂–C=C–CH₂–). Thus, the rate constants, k _abstr/H, given on an available hydrogen basis are k _p/4 = 4.75 × 10⁻³ M⁻¹ s⁻¹ for 2, k _p/2 = 4.16 × 10⁻² M⁻¹ s⁻¹ for 3, k _p/4 = 4.79 × 10⁻² M⁻¹ s⁻¹ for 4, and k _p/6 = 4.05 × 10⁻² M⁻¹ s⁻¹ for 5. The k _abstr/H values obtained for 3, 4, and 5 are similar to each other, and are by about one order of magnitude higher than that for 2. From these results, it is suggested that the prooxidant effect of α-tocopherol in edible oils, fats, and low-density lipoproteins may be induced by the above hydrogen abstraction reaction.     

Electrochemical study of the codeposition of Mg–Li–Al alloys from LiCl–KCl–MgCl<Subscript>2</Subscript>–AlCl<Subscript>3</Subscript> melts

This work presents a novel electrochemical study on the codeposition of Mg, Li and Al on a molybdenum electrode in LiCl–KCl–MgCl₂–AlCl₃ melts at 943 K to form Mg–Li–Al alloys. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of magnesium on pre-deposited aluminum leads to the formation of a liquid Mg–Al solution, and the succeeding underpotential deposition of lithium on pre-deposited Mg–Al leads to the formation of a liquid Mg–Li–Al solution. Chronopotentiometric measurements indicated that the codeposition of Mg, Li and Al occurs at current densities lower than −0.47 A cm⁻² in LiCl–KCl–MgCl₂ (0.525 mol kg⁻¹) melts containing 0.075 mol kg⁻¹ AlCl₃. Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li and Al is −2.100 V, and the codeposition of Mg, Li and Al is formed when the applied potentials are more negative than −2.100 V. The diffusion coefficient of aluminum ions in the melts was determined by different electrochemical techniques. X-ray diffraction and inductively coupled plasma analysis indicated that α, α + β and β Mg–Li–Al alloys with different lithium and aluminum contents were obtained via potentiostatic and galvanostatic electrolysis.     

Electrochemical treatment of methyl parathion based on the implementation of a factorial design

Commercial methyl parathion was treated by an electrochemical method using Ti/Pt as anode, Stainless Steel 304 as cathode and sodium chloride as electrolyte. Based on a number of preliminary experiments, a factorial experimental procedure was designed in order to optimize the electrolysis efficiency, in terms of removed COD and energy consumed kW h per kg of removed COD. The parameters examined were the temperature, the stirring rate of the brine solution, the input rate of the organic material, the current density, the electrolyte concentration and the concentration of Fe ²⁺ ions added. In the experimental range studied, the lower energy consumption measured was 6.61 kW h ( kg COD _r) ^–1 and the higher COD reduction measured was 86.3. From a mathematical model, the optimum conditions for the electrochemical treatment of MeP for 2.03 kW h ( kg COD _r) ^–1 were found to be Input rate of MeP 4300 mg COD min^–1, NaCl concentration 4.5, 4 g l^–1 of added FeSO₄, current density 0.47 A cm^–2, temperature 45 °C and stirring rate 400 rpm. An experiment was conducted under these optimum conditions which resulted in a satisfactory removal of the organic load (in terms of COD, BOD ₅). Furthermore, a significant improvement in the COD/BOD₅ ratio was achieved, rendering the effluent amenable to further biological treatment.