Treatment of wastewater from synthetic textile industry by electrocoagulation–electrooxidation

Treatment of wastewater from a textile industry that produces synthetic polyester cloths was studied employing electrochemical techniques. The sample was initially subjected to electrocoagulation to remove suspended solids. Mild steel and aluminum electrodes were tried as anodes; and aluminum was found to be effective for the removal of suspended solids. Using aluminum as anode, the chemical oxygen demand (COD) concentration of the effluent which was initially at the level of 1316 mg L⁻¹ could be reduced to 429 mg L⁻¹ by electrocoagulation. After electrocoagulation, the effluent was further subjected to electrooxidation using graphite and RuO₂/IrO₂/TaO₂ coated titanium as anodes. During the electrooxidation tests, both COD and chloride ion were simultaneously estimated; and the effect of Cl⁻ ion is discussed. The measurements have revealed the depletion of Cl⁻ ion concentration implying the generation of free chlorine during electrooxidation. The depletion of Cl⁻ ion concentration and the COD removal were observed to be comparatively high in the presence of graphite electrode. The effects of electrode materials and current density on COD removal are discussed. The instantaneous current efficiency (ICE), mass transfer coefficient and energy consumption were estimated.     

Electrochemical removal of cadmium using a batch undivided reactor with a rotating cylinder electrode

The performance of an undivided electrochemical batch reactor with a rotating cylinder electrode under potentiostatic control is examined for the removal of cadmium from a sodium sulfate solution containing 500 ppm Cd(II) at pH ? 7. The effect of hydrogen evolution as a side cathodic reaction on the figures of merit of the reactor is analysed. The best results were obtained for a cathode potential of ?0.9 V against the saturated calomel electrode. With an angular velocity of 1500 rpm the space time yield and the normalized space velocity were 0.66 mol m^?3 s^?1 and 3.9 h^?1 respectively, while the fractional conversion was 67.3% with a current efficiency of 66.7%. The surface morphology of the deposits as a function of the applied potential is also reported. © 2001 Society of Chemical Industry     

Studies on electrochemical treatment of dairy wastewater using aluminum electrode

This study reports results of electrochemical treatment to the synthetic dairy wastewater using aluminum electrode. Response surface methodology with four factors and five level full factorial central composite design has been used to design the experiments. Four operational parameters, namely current density (J): 61.73–308.64 A/m²; dosage of sodium chloride (NaCl) (m): 0–2 g/l; electrolysis time (t): 10–90 min and initial pH (pH_o): 5–11, have been taken as input parameters and percentage chemical oxygen demand (COD) removal (Y₁) and the specific energy consumed (kWh per Kg of COD removed, Y₂) have been taken as responses of the system. Multiresponse optimization technique has been applied to find values of operational parameters which maximize the Y₁ and simultaneously minimize Y₂. The optimum values of operational parameters were found to be J = 123.46 A/m², m = 2.0 g/l, t = 74 min, and pH_o = 6.5. Optimum Y₁ and Y₂ were found to be 70.91% and 1.32 kWh/kg COD removed. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

石墨电极对接试验旋合度及其加工控制的探讨

介绍了石墨电极对接试验旋合度的概念及加工时对其进行检测控制的重要性和必要性,提出了简便可行的测量计算方法并对检测控制要求进行了分析探讨,对加工过程对接试验所测旋合度的检测控制情况进行了简要统计分析.     

不同阴离子的四丁基季铵盐对草酸在铅电极上电解还原的影响

用恒电流电解法研究了四丁基氢氧化铵和不同的阴离子在草酸电解还原过程中的作用。四丁基铵阳离子可以提高电流效率,但电流效率的增加值不受浓度变化的影响。阴离子对电流效率的作用可以忽略。通过测量电极溶液界面的电容值,发现电流效率和季铵盐在电极表面的吸附相关。     

紫外光预处理与预氯化强化除藻的作用比较

采用紫外光C波段对含藻原水进行预处理,并与预氯化工艺进行了对比,结果表明:4支40W的紫外灯预处理6min后,气浮出水除藻率为87.6%,浊度为1.85NTU,CODMn去除率为38.7%;预氯化后,气浮出水除藻率为88%,浊度为2.44NTU,CODMn去除率为38.2%。气浮出水再经过滤、加氯消毒,发现紫外光预处理可减少消毒出水中的三氯甲烷生成量。紫外光预处理的运行成本为0.09元/m3,预氯化的运行成本为0.01元/m3。     

Comparison study of dyestuff wastewater treatment by the coupled photocatalytic oxidation and biofilm process

Degradation of Rhodamine B (RhB) and COD by means of the coupled photocatalytic oxidation (PCO) and biofilm systems has been studied. The coupled PCO-biofilm systems were divided into two operation systems. The one (R1) consisted of a pre-PCO and a post-biofilm reactor system and the other (R2) was a pre-biofilm and a post-PCO reactor system. In a batch experiment, the order of initial decolorization rate was photocatalytic oxidation > adsorption > photolysis. The color removal rate of RhB was decreased with an increase of the initial COD concentration. In a continuous experimental study, almost all color was removed in the PCO reactor. During 180 days, the color and COD removal efficiencies in the R2 (pre-biofilm + post-PCO) system were higher than those in the R1 (pre-PCO + post-biofilm) system. In our experimental ranges, the PCO process was superior to Fenton oxidation in the color and COD removal.     

电吸附技术及吸附电极材料研究进展

电吸附技术得益于环保、清洁、简单和节能的技术优势,在海水脱盐淡化及污染物吸附处理领域具有重要的应用潜力。如何构建高电荷容量的吸附电极是构建高效电吸附装置、提高吸附效率的关键所在。本文从电吸附技术原理出发,介绍了电吸附技术吸附储存离子的双电层理论模型,并对电吸附技术的研究进展进行了总结。随后从吸附电极材料制备角度对碳吸附电极、层状金属氧化物吸附电极、复合型吸附电极分别进行综述,对每一类电极材料特点及不足进行了总结,归纳分析了针对各类材料不足之处的解决方案,并基于高效电吸附技术实际应用目标,对吸附电极材料的设计制备进行了展望。     

Ozone treatment of textile effluents and dyes: effect of applied ozone dose,pH and dye concentration

The ozonation of wastewater supplied from a treatment plant (Samples A and B) and dye‐bath effluent (Sample C) from a dyeing and finishing mill and acid dye solutions in a semi‐batch reactor has been examined to explore the impact of ozone dose, pH, and initial dye concentration. Results revealed that the apparent rate constants were raised with increases in applied ozone dose and pH, and decreases in initial dye concentration. While the color removal efficiencies of both wastewater Samples A and C for 15 min ozonation at high ozone dosage were 95 and 97%, respectively, these were 81 and 87%, respectively at low ozone dosage. The chemical oxygen demand (COD) and dissolved organic carbon (DOC) removal efficiencies at several ozone dose applications for a 15 min ozonation time were in the ranges of 15–46% and 10–20%, respectively for Sample A and 15–33% and 9–19% respectively for Sample C. Ozone consumption per unit color, COD and DOC removal at any time was found to be almost the same while the applied ozone dose was different. Ozonation could improve the BOD₅ (biological oxygen demand) COD ratio of Sample A by 1.6 times with 300 mg dm^?3 ozone consumption. Ozonation of acid dyes was a pseudo‐first order reaction with respect to dye. Increases in dye concentration increased specific ozone consumption. Specific ozone consumption for Acid Red 183 (AR‐183) dye solution with a concentration of 50 mg dm^?3 rose from 0.32 to 0.72 mg‐O₃ per mg dye decomposed as the dye concentration was increased to 500 mg dm^?3. © 2002 Society of Chemical Industry     

Electrochemical removal of phenol in alkaline solution. Contribution of the anodic polymerization on different electrode materials

The removal of organic pollutants based on electropolymerization on an anode was performed in the case of phenol in alkaline solution. The polymer formed by a process involving less than two electrons per molecule of phenol, is then precipitated by decreasing the pH and finally filtered and disposed. The electrochemical polymerization of phenol (C₀ = 0.105 M) in alkaline solution (pH = 13) at 86 °C has been studied by galvanostatic electrolysis, using a range of anode materials characterized by different O₂-overpotentials (IrO₂, Pt and β-PbO₂). Measurements of total organic carbon and HPLC have been used to follow phenol oxidation; the morphology of the polymer deposited on the electrode surface has been examined by SEM. Experimental data indicate that phenol concentration decreases by oxidation according to a first order reaction suggesting a mass transport limitation process. Polymeric films formed in alkaline solution did not cause the complete deactivation of the anodes. SEM results show that the polymeric films formed on Ti/IrO₂ and Pt anodes cannot be mineralized. On the other hand, complex oxidation reactions leading to the partial incineration of polymeric materials can take place on the Ta/β-PbO₂ surface due to electrogenerated HO radicals which have an oxidizing power much higher than that of intermediaries formed respectively on IrO₂ and Pt. It is assumed that the polymer films formed on these anodes have different permeability characteristics which determine the rate of mass transfer of the phenol. The fractions of phenol converted in polymers were 25, 32 and 39% respectively with Ti/IrO₂, Pt and Ta/β-PbO₂, a series of materials in which the O₂-overvoltage increases.     

Novel electrochemical surface modification method of carbon fiber and its utilization to the preparation of functional electrode

The electrooxidative and -reductive methods for the surface modification of carbon fiber were developed. The carbon fiber surface was first oxidized under anodic conditions to introduce phenolic hydroxyl groups on the carbon fiber, and then the resulting oxidized carbon fiber was treated under cathodic conditions in the presence of various kinds of electrophiles such as alkyl halides and alkyl tosylates introducing the alkyl groups on the carbon fiber. The changes of the functional groups on the carbon fibers were confirmed by the X-ray photoelectron spectroscopy (XPS) study and the observation of the hydrophilicity. The functional carbon fiber electrode introduced β-cyclodextrin (β-CD) was then prepared by this electrochemical method. The electroreduction of acetophenone (1) was carried out using the resulting carbon fibers as cathodes. The use of the carbon fiber modified with β-CD gave relatively high dl selectivity of the reductive coupling products 2 (the dl/meso ratio: 5.2), while the dl/meso ratio using the untreated carbon fiber was 3.0, and the formation of 1-phenyl ethanol (3) was observed only by using the β-CD-modified carbon fiber. The observed products selectivity is discussed from the viewpoints of the interaction between the electrogenerated species and the functional groups on the carbon fibers.     

Effect of chloride concentration on the electrochemical treatment of a synthetic tannery wastewater

The electrochemical treatment of a synthetic tannery wastewater prepared with 30 compounds used in animal skin processing was studied. Electrolyses were performed in a one-compartment flow cell at a current density of 20 mA cm⁻², using a dimensionally stable anode (DSA^®) of composition Ti/Ir_0.10Sn_0.90O₂ as the working electrode. Effects of chloride concentration and presence of sulfate were evaluated. Variation in the concentration of phenolic compounds as a function of electrolysis time revealed a first-order exponential decay; faster phenol removals were obtained with increasing chloride concentration in the wastewater. Lower phenol removals were obtained in the presence of sulfate. Higher chloride concentrations led to a faster decrease in total organic carbon (TOC), chemical oxygen demand (COD), and absorbance values at 228 nm. Faster wastewater color removal, higher current efficiency and lower energy consumption were also obtained. This electrochemical treatment was also able to reduce the wastewater toxicity for Daphnia similis.     

Application of elimination voltammetry in the study of electroplating processes on the graphite electrode

The electrode reaction mechanism of electrolytical coating by nickel on paraffin impregnated graphite electrode (PIGE) was investigated by cyclic voltammetry (CV) and elimination voltammetry with linear scan (EVLS). The EVLS, a relatively new method of processing electrochemical signals obtained by voltammetry, is able to eliminate some individual chosen currents from total voltammetric currents measured at different scan rates. During the electrodeposition of metals on the graphite electrode, hydrogen evolved from aqueous acidic solutions interferes with the plating process. The elimination of kinetic current arising due to hydrogen evolution enables one to study other processes proceeding at the electrode. Cyclic voltammograms for metal coating deposition/dissolution on the graphite electrode were measured at three scan rates (12.5, 25 and 50 mV/s) and the EVLS functions were calculated for one or two eliminated currents. The results indicate the occurrence of surface reactions with the adsorption of intermediates on graphite. The application of EVLS provides deeper insight into the mechanism of electrode reaction during metal deposition.     

环己醇与环己酮在疏水性复合电极上的电化学转化

将自制的2种疏水性复合电极(M-PTFE,M=Ni、Zn)分别应用于环己醇的电化学氧化和环己酮的电化学还原,测定了不同条件下的循环伏安曲线和电极稳定性,结果表明环己醇电化学氧化的转化率达92.5%和环己酮电化学还原的转化率达94.6%。     

Electrochemical behavior of acetaminophen and its detection on the PANI-MWCNTs composite modified electrode

A polyaniline-multi-walled carbon nanotubes (PANI-MWCNTs) composite modified electrode was fabricated and the electrochemical behaviors of acetaminophen on the PANI-MWCNTs composite modified electrode were investigated by using cyclic voltammetry (CV), single-potential step chronocoulometry and square-wave voltammetry (SWV). The results showed that this electrode exhibited excellent electrocatalytic effects on the redox of acetaminophen. Consequently, a simple and sensitive electroanalytical method was developed for the determination of acetaminophen. The oxidation peak current was proportional to the concentration of acetaminophen from 1.0 × 10⁻⁶ to 1.0 × 10⁻⁴ mol/L and 2.5 × 10⁻⁴ to 2.0 × 10⁻³ mol/L, respectively. The detection limit was 2.5 × 10⁻⁷ mol/L. The proposed method was used to detect acetaminophen in Composite Chlorzoxazone Tablets and the results were satisfying.     

The effect of solids on the electrochemical treatment of olive mill effluents

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     

A novel perspective on the formation of the solid electrolyte interphase on the graphite electrode for lithium-ion batteries

In this paper, we describe how the mechanism of formation of a protective film [the solid electrolyte interphase (or interface) (SEI)] on a graphite electrode for Li-ion batteries was investigated from the novel perspective of precipitation of the final decomposition products that arise from the reduction of a nonaqueous electrolyte solution in contact with the graphite electrode. Within the framework of this new perspective, we can elegantly account for the compositional and structural differences between the basal-plane and edge-plane SEIs and for the origins of the multi-layer structure and the parabolic growth law of the SEIs on both the edge-plane and basal-plane surfaces of the graphite electrode.     

Electrochemical and nanoelectrogravimetric studies of the nucleation and growth mechanisms of rhenium on polycrystalline gold electrode

The nucleation and growth mechanisms for rhenium on polycrystalline gold electrodes from an electrolytic bath containing 0.75 mM HReO₄+0.1 M Na₂SO₄ (pH 2) have been studied. The potentiostatic step technique was simultaneously employed with measurements of mass changes in an electrochemical quartz crystal microbalance. Scanning electronic microscopy of rhenium electrodeposits were obtained. The mass–time transients were fitted with equations deduced from the current–time relationships of the conventional nucleation and growth models. The global equation that fitted the Δm/t transients indicated that the electrodeposition process of rhenium started with a two-dimensional progressive nucleation (PN2D), followed by another two contributions. The first of them corresponds to a progressive nucleation growing under diffusion control (PN3D_dif) and the second contribution, which is observed at longer times, corresponds to a progressive nucleation under charge transfer control (PN3D_CT). From these three contributions, the PN2D corresponds to the charge of a monolayer and was attributed to 2D nuclei produced by the reduction of adsorbed perrhenate. The PN3D_dif was the most important contribution and represented 70–80% of the mass increase. The faradic efficiency for the electrodeposition process was in the range of 12–18% for the experimental conditions of this study.     

Electrochemical and morphological characterization of gold nanoparticles deposited on boron-doped diamond electrode

A novel two-step method was employed to synthesize gold nanoparticles dispersed on boron-doped diamond (BDD) electrode. It consisted of sputter deposition at ambient temperature of maximum 15 equivalent monolayers of gold, followed by a heat treatment in air at 600 °C. Gold nanoparticles with an average diameter between 7 and 30 nm could be prepared by this method on polycrystalline BDD film electrode. The obtained Au/BDD composite electrode appeared stable under conditions of electrochemical characterization performed using ferri-/ferrocyanide and benzoquinone/hydroquinone redox couples in acidic medium. The electrochemical behavior of Au/BDD was compared to that of bulk Au and BDD electrodes. Finally, the Au/BDD composite electrode was regarded as an array of Au microelectrodes dispersed on BDD substrate.