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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

聚对苯二酚修饰电极测定多巴胺和L-色氨酸的电化学研究

制备了对苯二酚聚合膜修饰玻碳电极(PHQ/GCE),研究了多巴胺(DA)和L-色氨酸(L-Trp)在该电极上的电化学行为,以及支持电解质、溶液pH、扫描速率等对DA和L-Trp伏安响应的影响.实验发现,在pH 5.5的NaH2PO4-Na2HPO4缓冲溶液中,可用PHQ/GCE测定溶液中的DA和L-Trp,两者氧化峰电流均与浓度在1×10-3～5×10-6 mol/L范围内呈良好线性关系,相关系数分别为0.998 3和0.996 5,检出限分别为1×10-6 mol/L和5×10-7 mol/L,该方法简便快捷.     

Electrochemical coupling reactions of benzyl halides on a powder cathode and cavity cell

Benzyl halides adsorbed on a cathode made of pure or silver-doped graphite powder were reduced in an undivided cell using an aqueous electrolyte and an inert anode, in the absence or presence of benzaldehyde. The product ratio is influenced by the applied potential, the leaving halide group and presence/absence of silver electrocatalyst. The highest yield of bibenzyl was obtained from the electrolysis of benzyl bromide on silver-doped graphite at a constant potential equal to −1.0 V vs Ag/AgCl (sat. KCl). Benzyl chloride is less prone to dimerization, but undergoes efficient carbonyl addition to benzaldehyde, especially in the presence of silver. The results can be interpreted as a competition of radical and anionic processes.     

改性粉煤灰处理奥里油废水的实验研究

初步分析了奥里油废水的水质,研究了用酸改性粉煤灰处理奥里油废水的工艺。奥里油废水是一种含有一定表面活性剂、高COD值(大于6000 mg/L)、难生物降解和难O3氧化降解的炼油废水。利用改酸性粉煤灰可对该废水进行预处理,COD去除率达45%。预处理工艺条件是,室温下灰水质量比15∶50,吸附搅拌时间30 min,pH为2~10。     

Electrochemical detection of acetaminophen on the functionalized MWCNTs modified electrode using layer-by-layer technique

A selective electrochemical method is fabricated via layer-by-layer (LBL) method using both positively and negatively charged multi walled carbon nanotubes (MWCNTs) on poly (diallyldimetheylammonium chloride) (PDDA)/poly styrene sulfonate (PSS) modified graphite electrode, for the determination of acetaminophen (ACT) in the presence of dopamine (DA) and high concentration of ascorbic acid (AA). The modified electrode was characterized by cyclic voltammetry (CV) electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Experimental conditions such as pH, accumulation potential and time, effect of potential sweep rates and interferents were studied. In CV well defined peaks for AA, ACT and DA are obtained at 24, 186 and 374 mV, respectively. The separations of peaks were 210, 188 and 398 mV between AA and DA, DA and ACT and AA and ACT, respectively. The diffusion coefficient was calculated by chronocoulometric. Chronoamperometric studies showed the linear relationship between oxidation peak current and concentration of ACT in the range 25–400 μM (R = 0.9991). The detection limit was 5 × 10⁻⁷ mol/L. The proposed method gave satisfactory results in the determination of ACT in pharmaceutical and human serum samples.     

The effect of pH on bioremediation potential for the removal of direct violet textile dye by Aspergillus niger

Alkaline and acidic media have been used in the textile dye industry, depending on the fabric nature. The bioremoval of textile direct violet dye by Aspergillus niger fungal strain was studied. The effect of pH on dye bioremoval was investigated at a pH range from 2 to 11. The direct violet dye bioremoval reached maximum with 92.4%, 64.0%, 91.4%, and 62.3 % at pH values of 2, 3, 8, and 9, respectively, at 24 h of incubation. The percentages of removal rate after 72 h incubation were 98.9, 97.3, 94.0, 95.0, 97.0, and 97.3 at pH 2, 3, 6, 7, 8, and 9, respectively. The optimum pH values were 2, 3, 8, and 9 for direct dye removal. At the end of the experiments, the treatment with fungal strain could reduce COD value of synthetic dye solution by 76-91%. Pseudo first and second order kinetic models were applied to evaluate differences in the biosorption rates and uptakes of textile dye. Pre-equilibrium biosorption of direct violet dye onto fungus under different dye concentrations followed a pseudo second order kinetic model with a high degree of correlation coefficients (R² > 0.99), and the calculated values of q_e nearly matched the experimental values of textile dye during the biotreatment process.     

Preparation and characterization of the dopamine film electrochemically deposited on a gold template and its applications for dopamine sensing in aqueous solution

A dopamine polymer film was electrogenerated on the bare gold template from a 5 × 10⁻³ M dopamine solution in phosphate buffer at pH 7 and next subjected to overoxidation in 0.1 M sodium hydroxide solution. The overoxidized dopamine polymer film obtained shows good permeability to cationic species and was used for quantitative determination of dopamine. A linear relationship between dopamine concentration and current response was obtained in the range of 1 × 10⁻⁶ M to 6 × 10⁻⁴ M with the detection limit 2 × 10⁻⁷ M. The results have shown that using the overoxidized dopamine film it is possible to perform electrochemical analysis of dopamine without interference of ascorbic and uric acids, which is the major limitation in dopamine determination. The modified electrode shows good selectivity, sensitivity, reproducibility and high stability.     

黄磷生产中电极单耗高的原因及对策

从控制电极消耗入手探索工艺管理、电流密度、责任考核,把好原料关,从而降低电极消耗,为黄磷生产节能途径提供一些借鉴。