Effect Of Electrochemical Pretreatment Research Articles

The effects of electrochemical pretreatment and curing environment on strength and leaching of stabilized/solidified contaminated sediment

Stabilization and solidification (S/S) is known to improve the structural properties of sediment and reduce contaminant mobility, enabling the utilization of dredged contaminated sediment. Further reduction of contaminants (e.g., tributyltin (TBT) and metals) can be done using electrochemical treatment prior to S/S and could potentially minimize contaminant leaching. This is the first study on how electrochemical pretreatment affects the strength and leaching properties of stabilized sediments. It also investigates how salinity and organic carbon in the curing liquid affect the stabilized sediment.The results showed that the electrolysis reduced the content of TBT by 22% and zinc by 44% in the sediment. The electrolyzed stabilized samples met the requirements for compression strength and had a reduced surface leaching of zinc. Curing in saline water was beneficial for strength development and reduced the leaching of TBT compared to curing in fresh water. The results indicate that pretreatment prior to stabilization could be beneficial in reducing contaminant leaching and recovering metals from the sediment. The conclusion is that a better understanding of the changes in the sediment caused by electrochemical treatment and how these changes interact with stabilization reactions is needed. In addition, it is recommended to investigate the strength and leaching behavior in environments similar to the intended in situ conditions.

Effect of electrochemical pretreatment on the control of scaling and fouling caused by circulating cooling water on heat exchanger and side-stream reverse osmosis membrane

An environment-friendly electrochemical pretreatment process was used to purify the circulating cooling water (Including salts extraction and organics removal), and the effect of electrochemical pretreatment on scale inhibition and reverse osmosis (RO) was explored. Results showed that the electrochemical pretreatment exhibits a good softening ability for different types of water with hardness from 100 to 500 mg/L (Calculated by CaCO3). Considering the treatment efficiency and energy consumption, 5 V and 7 V were suitable for softening treatment of low hardness water and high hardness water respectively (with 300 mg/L hardness as the limit). After electrochemical pretreatment, CaCO3 scale on heater surface can be effectively inhibited and the maximum scale inhibition rate can reach 73.9% at 7 V. Meanwhile, the CaCO3 scale is loose after electrochemical pretreatment, accompanied by the transformation of crystalline phase from calcite to aragonite. The long-term RO membrane flux experiment shows that the pure inorganic salt solution has the least contribution to RO membrane fouling, followed by the pure organic solution. Notably, when inorganic salt ions coexist with organic matters in water, a complex structure of gel network can be formed, which causes serious pollution to RO membrane and sharp decrease of the specific flux (J/J0). Interestingly, RO membrane fouling can be effectively controlled after electrochemical pretreatment even for actual circulating water. This work provides a simple strategy for the development and application of electrochemical technology in softening and RO membrane fouling control.

Electrocoagulation and electrooxidation pre-treatment effect on fungal treatment of pistachio processing wastewater.

The effect of electrochemical pre-treatment on fungal treatment of pistachio processing wastewater (PPW) was investigated. Electrocoagulation (EC) and electrooxidation (EO) were used as electrochemical pre-treatment step before fungal treatment of PPW. Aluminum (Al/Al), iron (Fe/Fe), and stainless steel (SS/SS) electrode pairs were selected as anode/cathode for EC whereas boron doped diamond (BDD/SS) was preferred as anode/cathode electrode pairs for EO experiments in this study. The impact of current density (50-300 A/m2) and operating time (0-240min) were tested for chemical oxygen demand (COD) and total phenol removal. After pre-treatment of PPW, four different fungus species (Coriolus versicolor, Funalia trogii, Aspergillus carbonarius, and Penicillium glabrum) were tested for further treatment. Penicillium glabrum supplied maximum COD and total phenol removal efficiency compared to other fungus strains. The combined electrochemical-assisted fungal treatment process supplied 90.1% COD and 88.7% total phenol removal efficiency when supported with EO pre-treatment. Pre-treatment of PPW with EO method provided better results than EC method for fungal treatment. Operating cost of the combined process was calculated as 6.12 US$/m3. The results indicated that the proposed combined process supplied higher pollutant removal compared to the individual electrocoagulation, electrooxidation, and fungal treatment process.

Effects of Electrochemical Pretreatments on the Kinetics of FeII-FeIII, VIV-VV and Hydroquinone-Quinone Electrode Reactions on Glassy Carbon

The energy efficiency of batteries is dependent on their voltage efficiency and coulombic efficiency. Voltage inefficiencies arise due to sluggish electrode kinetics and, as a result, large overpotentials at the electrode. Furthermore, the higher the overpotential the greater the number of side reactions such as hydrogen formation1-7 at the negative electrode or degradation of the carbon at the positive electrode. Side reactions at either electrode reduce coulombic efficiency and in turn can cause the battery to become unbalanced (e.g. more VV on the positive side than VII on the negative side, in the case of H2formation at the negative electrode of a vanadium flow battery). Therefore, in order to better understand and improve the performance of batteries, it is important to investigate the electrode kinetics. We have previously shown8-13 that electrochemical treatment of carbon electrodes significantly affects the electrode kinetics of VIV-VV oxidation-reduction reactions. In this study, we investigate the effect of electrochemical treatment of glassy carbon on the electrode kinetics of the oxidation-reduction reactions of FeII-FeIII and hydroquinone-quinone and compare the behaviour of these systems to that of the VIV-VV system. Similar to the VIV-VV system, the electrode kinetics of both FeII-FeIII and hydroquinone-quinone are enhanced by cathodic treatment of the electrode and inhibited by anodic treatment (as shown in Fig. 1 (i) and (ii), respectively). Furthermore, the electrode can be toggled between these activated (reduced) and deactivated (oxidised) states. The effects of treatment potential on both FeII-FeIII and hydroquinone-quinone kinetics were investigated in detail for both anodic treatment of a reduced electrode and cathodic treatment of an oxidised electrode. As can be seen in Fig. 2, although there are significant differences between the behaviour of the electrode in the two systems there are also many similarities. We attribute the observed activation and deactivation effects to meta-stable oxygen-containing functional-groups on the electrode surface. Acknowledgements M. Balandeh, M. Al Hajji Safi and A. Bourke would like to thank the Irish Research Council (IRC) for PhD scholarships and R.P. Lynch acknowledges funding from a IRC - Marie Skłodowska Curie Fellowship under grant no. INSPIRE PCOFUND-GA-2008-229520 to perform this research.

Effect of Electrochemical Pretreatment and Flocculation on the Degradation of Pharmaceutical Wastewater

As it is not suitable for bio-treatment method, pharmaceutical wastewater is treated by physiochemical methods in this study. Besides, potassium permanganate oxidation, electrochemical pretreatment and the addition of FeCl3 and AlCl3 after potassium permanganate oxidation were compared. It is proved that electrochemical pretreatment had a little greater degradation efficiency compared with the other two flocculants. Electrochemical oxidation seems to be more cost-effective due to its ease of operation. Electrochemical pretreatment is expected to be a suitable method to assist the pharmaceutical wastewater treatment.

The effect of electrochemical pretreatment on the catalytic activity of carbon-supported gold nanoparticles for NADH oxidation

The electrochemical oxidation of nicotinamide adenine dinucleotide (NADH) is studied systematically on four types of electrodes, i.e., glassy carbon (GC), carbon (C), Au nanoparticles (AuNP), and C-supported AuNP (AuNP/C) in a 0.05M phosphate buffer solution (pH 7.4) before and after the electrochemical pretreatment carried out by repetitive potential scanning between −0.2V and 1.0V (vs. SCE) for 100 cycles. This simple pretreatment improves the electrocatalytic activity of the AuNP/C toward the NADH oxidation remarkably, suggesting the key role of Au oxide layers in facilitating the NADH electrochemical oxidation.

Nanocrystalline graphite-like pyrolytic carbon films as electrodes for electrochemical sensing application

Pyrolytic carbon films (PCFs) were deposited on graphite substrates by methane pyrolysis at temperature range of 1000–1100°C. The fundamental electrochemical behaviors in relation to the surface microstructural properties were investigated to ascertain the potential use of these carbon film electrodes for electroanalytical applications. Cyclic voltammetry were performed to examine the residual current and capacitance and the kinetics parameters were obtained in the presence of Fe(CN)63-/4- as a model redox system. Beside, the effects of electrochemical pretreatment were examined using cyclic voltammetry and electrochemical impedance spectroscopy. Fe(CN)63-/4-, Co(phen)33+/2+, Fe3+/2+, and hydroquinone were the redox systems employed to evaluate the electrochemical behavior of the PCF electrodes after pretreatment. Raman spectroscopy, scanning electron microscopy (SEM), and polarized light optical microscopy (PLOM) were carried out to explain the microstructural and morphological properties. Low and stable residual currents toward anodic activation and high electron transfer kinetics specifically after anodic activation were the attractive features of those carbon film electrodes prepared at the higher part of the processing temperature range.

The Effect of Electrochemical Pretreatment on the Sensing Performance of Single Walled Carbon Nanotubes

In this paper, we report the effect of subsequent electrochemical anodization and cathodization subjected to single walled carbon nanotubes. The performance of the single walled carbon nanotubes before and after activation was evaluated electrochemically using different charged redox probes and a biologically important neurotransmitter-dopamine. Further, for the first time, the surface of single walled carbon nanotubes before and after electrochemical activation was also evaluated using Raman Spectroscopy. Electrochemical results indicated that the pretreatment method employed in this work greatly enhanced the performance of single walled carbon nanotubes towards the detection of the model analytes employed. The observed enhancement in the signal is attributed to the rupture of the basal plane found on the end caps of carbon nanotubes giving rise to a larger density of edge-plane like defects on the single walled carbon nanotubes surface. A detection limit of 10 nM (based on three times the standard deviation of the slope) was also estimated when dopamine was monitored using electrochemically activated single walled carbon nanotube electrodes. In addition, the electrochemically activated carbon nanotubes exhibited a improved selective and sensitive detection of our model analyte dopamine with a minimal electrode fouling of about 3% +/- 1.2% (N = 4).

Surface composition of ordered intermetallic compounds PtBi and PtPb

The surface composition of bulk electrodes made from the ordered intermetallic phases PtBi and PtPb has been studied by ex-situ X-ray photoelectron spectroscopy (XPS) after being subjected to various electrochemical treatments. Analysis of the freshly polished surfaces showed that in the surface and near surface regions the less-noble metals; Bi and Pb are oxidized to a significant extent (28% and 41%, respectively). Upon cycling to increasingly positive potentials, the fraction of oxidized to metallic forms of Bi and Pb decreased gradually to reach the minimal values of 7% and 6% at +400 mV vs. Ag/AgCl (saturated KCl). The observed decrements are due to leaching of surface oxides; Bi 2O 3 on PtBi and PbCO 3 or Pb(OH) 2 on PtPb. When the potential sweep was extended to more positive values, there was a linear decrease in the surface concentration of the less-noble metal, along with a slight increase in the amount of the species in their oxidized state (Bi 2O 3 for PtBi and PbSO 4 for PtPb). Leaching of Bi from the electrode surface occurs in accordance to the Pourbaix diagram for elemental bismuth, indicating no significant increase in stability arising from the formation of an intermetallic phase with platinum. In the case of PtPb, however, the Pb starts to dissolve away at potentials significantly more positive (+800 mV) than what was anticipated from the Pourbaix diagram. The results obtained here are in accord with our previous observations on the effects of electrochemical pre-treatment on these intermetallic phases for the electrocatalytic oxidation of formic acid and other potential fuel cell fuels.

Effects of Electrochemical Pretreatments on NADH Oxidation at NAD+-Modified Carbon Paste Electrodes

Effects of Electrochemical Pretreatments on NADH Oxidation at NAD+-Modified Carbon Paste Electrodes

Effect of electrochemical pretreatment on SERS and catalytic activity of Cu–Zr amorphous alloys

This paper presents results of electrochemical, microscopic, spectroelectrochemical (SERS) and catalytic investigations of Cu–Zr amorphous alloy ribbons aimed at increasing their catalytic activity for the dehydrogenation reaction of aliphatic alcohols. Rapid dissolution in sulphuric acid/copper sulphate solution of partially devitrified Cu–Zr ribbons resulted in a nearly twofold enhancement of their catalytic activity for dehydrogenation of 2-propanol. However, their local SERS activity on the Cu rich areas was not distinctly altered by this electrochemical pretreatment. Yet, the SERS heterogeneity of the devitrified material vanished: the SERS intensity increased considerably outside the Cu rich areas. A tentative mechanism of the effects of various electrochemical pretreatments on the surface activity is discussed.

Effect of electrochemical pretreatment on catalytic activity of Cu–Zr amorphous alloys

This communication presents the results of electrochemical, microscopic, and catalytic investigations of 60Cu–40Zr amorphous alloy ribbons aimed at increasing their catalytic activity for dehydrogenation reaction of aliphatic alcohols. Rapid dissolution in sulphuric acid/copper sulphate solution of partially devitrified Cu–Zr ribbons, and accompanied processes, resulted in a nearly two-fold enhancement of their catalytic activity for dehydrogenation of 2-propanol.

Randomly oriented graphite electrode. Part 1. Effect of electrochemical pretreatment on the electrochemical behavior and chemical composition of the electrode

Randomly oriented graphite electrodes from Union Carbide (ATJ) and Stackpole (SP2020) have been characterized by classical acid-base titration, weight measurements, cyclic voltammetry and X-ray photoelectron spectroscopy (XPS) before and after various chemical and electrochemical pretreatments. It was found that the concentration of strong and weak acidic groups increases upon electrochemical oxidation of the graphite electrode. The weight increase of a graphite electrode as a result of electrochemical oxidation is attributed to the formation of oxidized graphite and the intercalation of anions and solvent molecules into the graphitic material. The intercalation of sulfate was confirmed by the increase of the sulfur 2s and sulfur 2p peaks of the XPS spectra. The electrochemical oxidative pretreatment also causes an increase of the capacitive envelope of the cyclic voltammogram which is not solely related to an increase of the surface area of the electrode. A set of well-defined anodic and cathodic peaks centered at 0.38 V vs. SCE also develops upon oxidation and is attributed to the presence of quinone/hydroquinone redox species.

Effect of electrochemical pretreatment on protein adsorption at glassy carbon electrodes protein

AbstractThree types of electrochemical, pretreatments (ECPs) were assessed as a means of reducing albumin adsorption at glassy carbon electrodes. The cyclic voltammetric and differential pulse responses of the probe analyte, ferrocenemonocarboxylic acid (FCA), in the absence and presence of 4 g L−1 bovine serum albumin (BSA) were used to monitor protein adsorption at pretreated electrodes. Severe dc pretreatment in acid increased BSA adsorption (compared to that at a polished electrode), whereas square‐wave pretreatment in aqueous NaCl and dc pretreatment in base both reduced the amount of BSA adsorption. The effects of the latter two ECPs on the response of acetaminophen in the presence of BSA were examined. The loss of sensitivity in the presence of BSA was reduced at electrodes which were pretreated. However, our results sugges: that ECP which leads to very strong accumulation of analyte may have a deleterious effect on electrode performance in the presence of protein.

Capillary electrophoresis—electrochemistry of microdialysis samples for pharmacokinetic studies

AbstractElectrochemical detection has been shown to be a sensitive method of detection in capillary electrophoresis (CE). The small sample volume required for CE makes it ideal for the analysis of microdialysis samples. In this paper, capillary electrophoresis with electrochemical detection is utilized in the analysis of samples obtained during continuous monitoring of the pharmacokinetics of L‐dopa in the rat. The detection limit for L‐dopa was 98 attomoles or 3.9 ng/mL. The elimination half‐life was calculated to be 10.3 ± 1.1 minutes. Voltammetric characterization was used to verify the identity of L‐dopa and its metabolites. The effects of electrochemical pretreatment on the detector performance was also investigated.

Potentiometric and voltammetric responses of carbon fibre electrodes

The potentiometric response of several carbon fibres to hydrogen ion concentration (ph) was investigated. The effects of electrochemical pretreatment and the presence of complexes in the sample solution were studied. In solutions free of complexing anions, the response of pristine fibres ranged from 42.0 to 58.0 mV ph −1, with a mean of 48.5 mV ph −1. After electrochemical pretreatment, a mean slope of 52.0 ± 2.0 mV ph −1 was obtained. In the presence of EDTA, Tris, citrate, oxalate and tartrate, slopes of 59.0 mV ph − were obtained with pretreated fibres compared with zero slopes or highly curved plots obtained in the absence of pretreatment. The differential pulse voltammetry of iron (III) in a peroxide-containing electrolyte and of molybdate in nitrate- and chlorate-containing electrolytes was examined. At a conventionally sized glassy carbon electrode, the effect on the peak current of increasing the concentration of these ions was broadly in line with depolarizer/electrolyte systems in which catalytic currents occur. At carbon fibre electrodes, these catalytic currents were either absent (for molybdenum/nitrate and iron (III)/peroxide) or severely diminished (for molybdenum/chlorate).

ChemInform Abstract: Effect of Electrochemical Pretreatment on Catalytic Activity of Bismuth Ruthenate Electrodes for Oxygen Evolution in Alkaline Solution.

AbstractAn improvement of the catalytic activity for O2 evolution has been achieved by electrochemical pretreatment (preanodization at typically 0.7 V vs.

Effect of Electrochemical Pretreatment on Catalytic Activity of Bismuth Ruthenate Electrodes for Oxygen Evolution in Alkaline Solution

Abstract The catalytic activity of a film-type bismuth ruthenate electrode for oxygen evolution was greatly enhanced by the electrochemical pretreatment, including potential holding and cycling. On the other hand, any appreciable enhancement in catalytic activity was not observed for a pellet-type bismuth ruthenate electrode. Such an pretreatment effect was explained on the basis of the participation of higher valence Ru species in the oxygen evolution reaction, rather than the increase of surface area.

Carbon fibre micro-electrodes in the differential pulse voltammetry of copper ions

The analytical performance of micro-electrodes manufactured from several types of carbon fibre is investigated. The reduction of copper(II) in a chloride medium is used to assess this performance. Calibration curves in the 10–50 mg 1 −1 range are linear; the relative standard deviation is 4–7% for measurements of 30 mg l −1 Cu 2+. The effect of electrochemical pretreatment on surface ionizable groups is examined with the aid of pH-stat experiments. This pretreatment increases the sensitivity of the electrodes as well as increasing the number of ionizable groups on the electrode surface. It is suggested that these groups are quinoidal, and that their presence increases the ease with which electrochemical reduction takes place.