Removal of arsenic from drinking water by the electrocoagulation using Fe and Al electrodes

A novel technique of electrocoagulation (EC) was attempted in the present investigation to remove arsenic from drinking waters. Experiments were carried out in a batch electrochemical reactor using Al and Fe electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as pH (4–9), current density (2.5–7.5 A m⁻²), initial concentration (75–500 μg L⁻¹) and operating time (0–15 min) were examined. Optimum operating conditions were determined as an operating time of 12.5 min and pH 6.5 for Fe electrode (93.5%) and 15 min and pH 7 for Al electrode (95.7%) at 2.5 A m⁻², respectively. Arsenic removal obtained was highest with Al electrodes. Operating costs at the optimum conditions were calculated as 0.020 € m⁻³ for Fe and 0.017 € m⁻³ for Al electrodes. EC was able to bring down aqueous phase arsenic concentration to less than 10 μg L⁻¹ with Fe and Al electrodes. The adsorption of arsenic over electrochemically produced hydroxides and metal oxide complexes was found to follow pseudo second-order adsorption model. Scanning electron microscopy was also used to analyze surface topography of the solid particles at Fe/Al electrodes during the EC process.     

Glassy carbon electrodes coated with poly(allylamine hydrochloride), PAH: Characterization studies and application to ion-exchange voltammetry of trace lead(II) at combined PAH/mercury film electrodes

Glassy carbon electrodes coated with adsorbed single layers of the cationic polyelectrolyte poly(allylamine hydrochloride), PAH, were produced by solvent evaporation for subsequent development of PAH modified thin mercury film electrodes (PAH/TMFE). The present work describes the preparation, incorporation features towards lead(II) species, as well as the morphological characterization of PAH coatings of different molar loadings, prepared from polyelectrolyte solutions of different composition. The present PAH films revealed interesting morphologic features, related to the process of solvent evaporation and to the specific structural properties of the PAH polyelectrolyte in the assembling medium.The novel PAH-thin mercury film electrodes, developed for the determination of trace lead(II) as its anionic forms in chloride medium, were found to be stable, sensitive and reproducible. Concentrations in the ppb concentration region could be easily assessed using 20 s accumulation time (detection limit 1.2 ppb, i.e. 6 nM, 3σ) with low relative standard deviations (<2.5%). The sensitivity of the SWASV determination of lead(II) increased 20% compared to the uncoated TMFE. The linearity range reached at least two orders of magnitude. Additionally, the PAH-coated mercury film electrodes presented an improved resistance to fouling by common surfactants.     

Lithographically fabricated disposable bismuth-film electrodes for the trace determination of Pb(II) and Cd(II) by anodic stripping voltammetry

This work reports the photolithographic fabrication of disposable bismuth-film electrodes (BiFEs) using a thin-film deposition approach. The deposition of the bismuth layer was carried out by sputtering of metallic bismuth on a silicon substrate while the exact geometry of the BiFEs was produced by photolithography. The utility of these sensors was tested for the simultaneous trace determination of Cd(II) and Pb(II) by square wave anodic stripping voltammetry (SWASV). Using the selected conditions, the limits of detection were 0.5 μg l⁻¹ for Pb(II) and 1 μg l⁻¹ for Cd(II) at a preconcentration time of 4 min. The interference caused by Cu(II) was alleviated by the addition of ferrocyanide in the sample solution. Finally, the proposed BiFEs were successfully applied to the determination of Cd and Pb in a phosphate fertilizer and a river water sample. These sensors offer wide scope for trace metal analysis in terms of mass-production of mercury-free disposable sensors with performance comparable to their mercury counterparts.     

Nanomolar detection of rutin based on adsorptive stripping analysis at single-sided heated graphite cylindrical electrodes with direct current heating

A single-sided heated graphite cylindrical electrode (ss-HGCE) was designed. Compared to previous alternative current (AC) heating, much simpler and cheaper direct current (DC) heating supplier was adopted for the first time to perform adsorptive accumulation of rutin at ss-HGCE at elevated electrode temperature. This offers great promise for low cost, miniaturization and high compatibility with portability. The square wave voltammetry (SWV) stripping peak current was enhanced with increasing the electrode temperature only during preconcentration step. This enhancement was contributed to the forced thermal convection induced by heating the electrode rather than the bulk solution, which is able to improve mass transfer and facilitate adsorption hence enhance stripping response. A detection limit of 1.0 × 10⁻⁹ M (S/N = 3) could be obtained at an electrode temperature of 48 °C during 5 min accumulation, one magnitude lower than that at 28 °C (room temperature). This is the lowest value at carbon-based electrodes for rutin determination as we know. Such novel method was also successfully used to determine rutin in pharmaceutical tablets.     

Study on the treatment of waste metal cutting fluids using electrocoagulation

Electrocoagulation (EC) technique is applied for the treatment of waste metal cutting fluids (WMCFs) characterized by high COD and TOC concentration, discharged from metal manufacturing facilities including automotive engine, transmission, and stamping plants. The effects of initial pH, current density and operating time on the performance of EC are investigated by using sacrificial Al and Fe electrodes. Upon treatment by EC, the COD of WMCF is reduced by 93% and the TOC is reduced by 78% for Al electrode at pH 5.0, current density of 60 A/m² and operating time of 25 min. For Fe electrode, the reduction in COD is 92% and reduction in TOC is 82% at pH 7.0, current density of 60 A/m² and operating time of 25 min. Under optimal operating conditions, the operating costs are calculated as 0.497 $/m³ (0.023 $/kg removed COD or 0.144 $/kg removed TOC) for Fe electrode, and 0.768 $/m³ (0.036 $/kg removed COD or 0.228 $/kg removed TOC) for Al electrode. Fe electrode is found to be more efficient than Al electrode in terms of parameters such as COD and TOC removal efficiencies and operating costs.     

Optimization of atrazine removal from synthetic groundwater by electrooxidation process using titanium dioxide and graphite electrodes

ABSTRACT

Atrazine is used in agriculture and is known for its high toxicity. It therefore poses a risk to surface and ground waters, and human life. In this study, an electrochemical method was optimized for atrazine removal from SGW using TiO₂ and graphite electrodes. A comparison between one factor at a time period optimization and Box-Behnken design (BBD) optimization using RSM was carried out to select the optimum conditions. The results show excellent atrazine removal efficiency (99.70%) and close optimum conditions for both applied methods (pH 7 and 7.4; current 2.5 and 2 A and time 14 and 12.12 min, respectively).     

废碳钢电极处理活性艳红染料的实验研究

本文研究了铁电极处理活性艳红染料X-3B.选取不同电流、电导率、pH、电解质和浊度作为影响脱色率的因素,初步探讨了铁电极脱色的机理和反应动力学.结果表明:电流为1A,KCI浓度为2g/L,电解时间为12min时,脱色率高达99.5%,反应机理主要为协同沉淀和吸附作用.     

甘氨酸基于表面活性效应在石墨电极上的伏安行为研究

研究了甘氨酸在表面活性剂存在下于石墨电极上的电化学行为,发现表面活性剂能显著提高甘氨酸的氧化峰电流,在此基础上,建立了一种直接测定甘氨酸的电化学方法。优化了测定条件,即介质的pH、富集电位、富集时间等。氧化峰电流与甘氨酸在1.00×10-7~1.00×10-4mol·L-1之间呈良好的线性关系,检出限为8.24×10-9 mol·L-1。应用于实际样品分析,回收率为96%~104%。     

DL-精氨酸/石墨烯修饰电极测定铅

用循环伏安法制备DL-精氨酸/石墨烯修饰玻碳电极,研究金属铅在修饰电极上的电化学行为。在0.1 mol/L pH=4.5的NaAc-HAc缓冲液中,以DL-精氨酸/石墨烯修饰电极作为工作电极,用循环伏安法测定-1.0~1.0 V处的溶出峰电流。实验结果显示:铅的浓度与溶出峰电流具有良好的线性关系,范围是3.0×10-9~9.0×10-7mol/L,检测限为1.0×10-10mol/L,用于测定金属结果满意。     

On the adsorption and kinetics of phase transients of adenosine at the different carbon electrodes modified with a mercury layer

Optical roughness of a pyrolytic graphite electrode with basal (PGEb) and edge orientation (PGEe), a glassy carbon electrode (GCE), and the same electrodes modified with mercury (MFE) was studied by an optical diffractive element (DOE) based sensor. Electrochemical characterisation of these electrodes used was performed by cyclic voltammetry (CV) and capacitance measurements (C-E curves and electrochemical impedance spectroscopy, EIS). The kinetics of phase transients of adenosine adsorbed on PGEb, and GCE modified with mercury layer of different thicknesses (thickness was changed from 0.02 to 2 μm) was studied by chronoamperometry (j-t curves) and capacitance measurements (C-E curves). In acidic (pH 5) solution adenosine forms two different two-dimensional (2D) physisorbed condensed layers on the MFE. The first of these (region I) is located at more positive potential; the centre of this adlayer is situated around −0.4 V. The second 2D physisorbed film (region III) is formed at more negative potentials; the centre of the region III is around −1.3 V. The 2D condensed films (adlayer I and III) of adenosine still exist on the PGEb substrate modified by 0.02 μm thick mercury layer. Adlayers III and I of adenosine exist on the GCE modified with mercury layer down to 0.02 and 0.2 μm, respectively. The kinetics of phase transients of the adenosine films taking place by a potential jump from dilute adsorption region (state II and IV) to the 2D physisorbed film (region I and III) at the PGEb and GCE substrates modified with mercury (Hg-PGEb and Hg-GCE) were studied, respectively. During both of the phase transients of IV→III and II→III of adenosine a polynucleation and growth process on both the Hg-PGEb and Hg-GCE was detected. The phase transients of II→I are characterised by an exponential decay of the current without the current maximum (the adsorption process took place only). It was observed that the phase transients of IV→III are the fastest at the HMDE and gradually slow down on 2 μm Hg-GCE and 2 μm Hg-PGEb, respectively.     

Phosphorus Removal from Continuous Phosphate-Contaminated Water by Electrocoagulation using Aluminum and Iron Plates Alternately as Electrodes

The objective of this study was to investigate the effects of the main parameters on phosphate removal from continuous phosphate-contaminated water by electrocoagulation based on removal rate and system energy consumption. In the experiment, aluminum and iron plates were used as alternate electrodes and experiment parameters included initial phosphate concentration, current density, flow rate, and initial pH. The results indicated that increases of initial phosphate concentration and flow rate had reduced removal rate and energy consumption. Removal rate and system energy consumption increased by increasing current density. The maximum removal efficiency of 90% was obtained at flow rate 40 mL/min. The minimum energy consumption was 0.165 kWh/m³ at flow rate 100 mL/min. With the increase of initial pH from 4 to 8, the removal rate increased and energy consumption decreased. When the pH was above 8, the removal rate decreased and energy consumption increased. The maximum removal efficiency of 92% and minimum energy consumption of 0.191 kWh/m³ were obtained at pH 8.     

汞膜电极阳极溶出伏安法测定痕量锗的研究

提出了一种以铂基汞膜电极阳极溶出伏安法测定痕量锗的方法,发现在pH 7的酒 石酸缓冲溶液中于-1.20 V和-0.50 V左右出现两个溶出峰。锗的浓度在0.01～1 mg/L范围内 与第一个峰(-1.20 V)有良好的线性关系,检出下限为1×10-9。     

Cr(III) oxidation with lead dioxide-based anodes

A procedure for preparing PbO₂-based electrodes with a titanium substrate is proposed. A platinum underlayer is first deposited on Ti by metal organic chemical vapor deposition (MOCVD), followed by the electrodeposition of the PbO₂ layer. The prepared Ti/Pt/PbO₂ anodes were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) before being used for oxidation of Cr(III) in sulphuric acid. The current efficiency was determined for that electrodes and the results were compared with those obtained with Pb/PbO₂ and Ebonex^®/PbO₂ electrodes with different pH conditions. The Ti/Pt/PbO₂ were found to have a very good electrochemical behaviour (current efficiency: φ=0.93 for pH 2), and may be used as dimensionally stable anodes for the oxidation of Cr(III).     

铋膜电极阳极溶出伏安法测食盐中锌含量

用铋膜电极代替汞膜电极可避免环境污染。采用玻碳电极同位镀铋在酸性的KSCN介质中测定食盐中锌,结果峰形好、灵敏度高、峰电流值大,检测限为7．8×10^-8mol／L,线性范围为2．0×10^-6mol／L～1．3×10^-5mol／L,加标回收率为92．2％-102．2％。     

离子液体修饰碳糊电极测定海红果中的槲皮素

用离子液体1-甲基-3-丁基咪唑六氟磷酸盐([bmim]PF6)作修饰剂制备了离子液体修饰碳糊电极(IL/CPE)。在0.2 mol/L B-R(p H 3.2±0.1)缓冲溶液中,采用循环伏安法研究了槲皮素在该修饰电极上的电化学行为,建立了测定槲皮素的新方法。研究表明,槲皮素在IL/CPE电极上的氧化、还原峰电位差比在裸碳糊电极(CPE)上的小,而峰电流却显著增加,说明IL/CPE对槲皮素有电催化作用;在循环伏安曲线上,槲皮素的峰电流与其浓度在0.1~50μmol/L呈良好的线性关系,其线性方程为ip(μA)=3.941 3+0.211 9 c(μmol/L),线性相关系数为0.999 4,检出限为3.0×10-8mol/L。该法用于测定海红果中的槲皮素取得了较好的结果。     

Pt/laponite clay-modified gold electrode for direct methanol fuel cells

This work employs a novel technique in which laponite clay-modified gold electrodes are used as the anode for direct methanol fuel cells. The platinum/laponite clay (Pt/Clay) films on indium tin oxide electrode were characterized by using scanning electron microscope and energy-dispersive X-ray spectroscopy. Various contents of laponite clay (0.1, 0.5, 1.0, and 2.0?wt%) with constant platinum (Pt) catalyst content on modified gold electrodes were studied as an anode catalyst for methanol oxidation. The catalyst poisoning was observed as a function of time. The 1.0?wt% Pt/Clay-modified gold electrode shows the highest activity for methanol oxidation, 27.73?% higher than Pt only modified gold electrode at 2.5?min. The peak current of 1?% Pt/Clay-modified gold electrode is 3.50?% higher than the peak current of Pt only modified gold electrode at 57.5?min. The higher content of Pt/Clay-modified gold electrode shows strong resistance to catalyst poisoning. The Pt/Clay-modified gold electrode is a new and promising electrode for a direct methanol fuel cell and can replace existing commercial catalysts.     

三维电极电解阴离子表面活性剂废水的研究

采用三维电极电解法对含阴离子表面活性剂（LAS）废水的处理进行了研究，考察了不同电极组合、槽电压、停留时间、电极间距及废水的pH值对降解效果的影响，并对电解机理作了初步探讨.实验表明：LAS废水处理的最佳工艺为：极间距2cm，槽压为8V，电解时间为40min.LAS、COD、TOC的去除率分别在94.5%、66.2%和58.7%以上.电极材料对去除率有很大影响.     

复合电沉积制备镍-石墨烯电极及其电催化析氢性能研究

以紫铜为基体,电沉积制备了镍还原氧化石墨烯(Ni-RGO)复合电极,研究了石墨烯质量浓度、电流密度、pH、温度和时间对Ni RGO复合电极的电催化析氢性能。得到最佳配方和工艺条件为:Ni(NH2SO3)2·4H2O 350 g/L,NiCl2·6H2O 10 g/L,C6H8O7·H2O 5 g/L,H3BO320 g/L,十二烷基苯磺酸钠0.12 g/L,RGO 0.16 g/L,pH 3.5,温度40°C,电流密度5 A/dm^2,时间10 min。该条件下所得Ni-RGO复合电极的电催化析氢性能最佳。     

Electroreduction of hexachlorobenzene in protic solvent at Hg cathodes

The electrochemical reduction of hexachlorobenzene (HCB) to lower chlorinated benzenes has been studied in methanol solution. Differential pulse voltammetry at a sessile mercury drop cathode showed four reduction waves at E=–1.13, –1.33, –1.57 and –1.84V vs the standard hydrogen electrode, corresponding to sequential reduction to penta-, tetra-, tri- and dichlorobenzenes, respectively. The formation of these products was followed with time using a recirculating flow-through cell; the isomer distributions of the lower chlorinated benzenes were as predicted from a mechanism involving chloride elimination from radical anion intermediates. A maximum current efficiency of 60% was achieved in single-pass experiments in which the potential was controlled near the peak of the first reduction peak (–1.2V) and the initial concentration of HCB was 1mm.     

竹炭对汞、铅混合液中Hg^2＋和Pb^2＋的吸附研究

研究竹炭对汞、铅混合溶液中的Hg^2＋和Pb^2＋的吸附行为。结果表明竹炭能同时吸附混合溶液中的Hg^2＋、Pb^2＋在pH值3．2—6．2的范围内,竹炭对溶液中的汞和铅均有较大的吸附能力,最佳的吸附pH值为5．9;吸附平衡时间为270min;在一定的实验条件下,随着混合溶液中被吸附离子的浓度增大,吸附量增大,但吸附率减小;随着竹炭投放量的增大,吸附量减小,但去除率增大。合适的吸附剂用量,能完全有效的除去混合溶液中的汞和铅。竹炭对混合溶液中汞和铅的吸附行为分别遵守Freundlich等温方程。