Electrocatalytic Degradation Research Articles

A simple degradation method for sulfur mustard at ambient conditions using nickelphthalocyanine incorporated polypyrrole modified electrode

Electrocatalytic degradation of sulfur mustard (SM) was studied using a gold electrode modified with nickelphthalocyanine and polypyrrole (NiPc/pPy/Au) in the presence of a cationic surfactant cetyltrimethyl ammonium bromide. Several techniques such as cyclic voltammetry, scanning electron microscopy, electrochemical impedance spectroscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy have been employed for the characterization of modified electrodes. NiPc/pPy/Au modified electrode exhibited excellent electrochemical sensing and degradation ability towards SM. The present modification indicated two electron involvements in the electrocatalytic degradation of SM in addition to being an irreversible adsorption controlled process. Degraded products were identified by gas chromatography-mass spectrometry. Moreover, electrochemical parameters of oxidation of SM such as heterogeneous rate constant (0.436 s−1), transfer coefficient (0.47) and the number of electrons involved (2) were deduced from cyclic voltammetry results. The NiPc/pPy/Au modified electrode showed excellent electrocatalytic degradation towards SM when compared to bare gold, pPy/Au and NiPc/Au modified electrode at ambient conditions.

TiO2-NTs/SnO2-Sb anode for efficient electrocatalytic degradation of organic pollutants: Effect of TiO2-NTs architecture

There are growing interests in the TiO2 nanotubes (TiO2-NTs) based Sb-doped SnO2 anode (TiO2-NTs/SnO2-Sb) for organic pollutants degradation due to its high oxygen evolution potential and enhanced degradation performance. However, whether and how the TiO2-NTs substrate architecture of the electrodes affects the electrocatalytic capability for organic pollutant degradation has not been reported yet. This work addressed this issue, investigating the effect of the pore diameter and length of TiO2-NTs on the electrocatalytic capability of TiO2-NTs/SnO2-Sb electrode, which was fabricated by Sb-doped SnO2 coating electrodeposition on different TiO2-NTs architecture substrates by successfully adjusting the Ti substrate anodization time and voltage. The characterizations of morphology, crystal structures and composition as well as the electrochemical characteristics were comparably studied. It confirmed the modification of TiO2-NTs substrate greatly improved the electrocatalytic degradation of organic pollutant, using phenol as the target contaminant. The pore diameter and length of TiO2-NTs substrates of the TiO2-NTs/SnO2-Sb electrode were verified to be crucial to the pollutant degradation efficiency, and the one with TiO2-NTs of 85nm pore diameter and 5μm length performed the best.

Electrocatalytic hydrodehalogenation of 2,4-dichlorophenol in aqueous solution on palladium–nickel bimetallic electrode synthesized with surfactant assistance

Hydrodehalogenation (HDH) of 2,4-dichlorophenol (2,4-DCP) on a palladium–nickel (Pd–Ni) bimetallic electrode was investigated in this paper. The Pd–Ni bimetallic electrode was prepared on meshed titanium (Ti) substrate by electrochemical deposition with assistance of sodium dodecyl benzene sulfonate (SDBS). Cyclic voltammetry (CV) results revealed that the hydrogen adsorption peak current value of electrode became larger when SDBS was added in electrode preparation process. The structure and composition of the electrode were characterized by scanning electron microscopy (SEM), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and X-ray diffraction (XRD). Dechlorination experiment was conducted on the Pd–Ni(SDBS)/Ti electrode in the presence of 100 mg L−1 (0.61 mmol L−1) 2,4-DCP. The removal efficiency of 2,4-DCP reached 100% with dechlorination current of 5 mA within 70 min in aqueous solution, meanwhile the current efficiency was 33.9%. The Pd–Ni(SDBS)/Ti electrode exhibits a good application prospect for electrocatalytic degradation of 2,4-DCP.

Advanced oxidation process for the removal of ionic liquids from water: The influence of functionalized side chains on the electrochemical degradability of imidazolium cations

Advanced oxidation processes can assist in the elimination of imidazolium-based ionic liquids (ILs) from water. With the aid of electrocatalytic degradation at a lead dioxide anode, it was shown that the degradation rate of these ILs from aqueous solutions was dependent on a change in the nature of the side chains in the cation. All the ionic liquids were efficiently oxidized within 240min. Even the mineralization of ILs was high up to 97% depending on structure. Cyclic voltammetry indicated that ILs were oxidized indirectly by radicals generated on the anode surface. HPLC-UV and electrospray mass spectroscopy analysis suggest that ILs undergo degradation along a pathway involving intermediates produced as a result of hydroxyl radical substitution to side chain and by oxidative cleavage of the imidazolium ring. The probability of imidazolium core attack by OH radicals increased with decreasing length of the substituted side chain.

Comparison of various organic compounds destruction on rare earths doped Ti/Sb-SnO2 electrodes

Ti/Sb-SnO2 and three kinds of rare earths (REs), namely Ce, Gd, and Eu doped Ti/Sb-SnO2 electrodes were prepared and tested for their capacity on electrocatalytic degradation of three kinds of basal aromatic compounds (benzoquinone, hydroquinone and catechol) and six kinds of aliphatic acids (maleic acid, fumaric acid, succinic acid, malonic acid, oxalic acid and acetic acid). The elimination of selected organics as well as their TOC removal with different doped Ti/Sb-SnO2 electrodes was described by first-order kinetics. Compared with Ti/Sb-SnO2, the Gd and Eu doped electrodes show better performance on the degradation of most of the selected organics, while Ce doped electrode shows either closely or lower efficiency on the degradation of these selected organics. Besides electrode material, the molecular structure of organic compound has obvious effect on its degradation in the electrocatalytic process. Catechol is more resistant to the electrophilic attack by hydroxyl radicals than benzoquinone and hydroquinone. The compound with more complicate molecular structure or longer carbon chain is more difficult to be mineralized. The aliphatic acid with higher oxygen content or more double bonds is more readily to be oxidized in the electrocatalytic process.

Properties of PbO<sub>2</sub> Electrode Modified by AEO-7 for Electrocatalytic Degradation of Crystal Violet

In order to improve the performance of PbO2electrode, A kind of surface active agent – AEO-7 was added into nitric acid bath and modified PbO2electrode was prepared on stainless steel substrate by anodic oxidation. The modified variations on surface morphology of the electrodes were examined by Scanning Electron Microscopy(SEM); The polarization curves, Tafel curves and Cyclic voltammograms of modified and unmodified PbO2electrodes were compared in Crystal violet solution; The electrocatalytic activities were inspected by electrocatalytic degradation of crystal violet. It was found that the modified electrode showed higher oxygen evolution potential, better corrosion resistance, and more excellent electrocatalytic activity than the unmodified electrode.

Preparation of Sb2O3‐loaded Activated Carbon Particle Electrode and Its Electrocatalytic Degradation of Methyl Orange in a Three‐dimensional Electrode Cell

AbstractElectrocatalysis on the degradation of methyl orange is investigated using Sb2O3‐loaded activated carbon (Sb2O3/AC), a new particle electrode. The electrode was prepared by an impregnation method. An orthogonal array with four factors and three levels was selected to carry out the experiment. Electrocatalysis on the degradation of methyl orange through Sb2O3/AC was characterized by a series of parameters, including the amount of the particle electrode, the concentration of Na2SO4, the cell voltage, and the electrolysis time, and the results were compared with those of a conventional AC particle electrode. The results indicate that calcination temperature has the greatest impact on the catalytic activity of the particle electrode. The optimal conditions for preparing the Sb2O3/AC electrode include an 8 mL SbCl3 solution, 90 min hydrolysis time, 400 °C calcination temperature, and 180 min calcination time. As well, the degradation efficiency of the Sb2O3/AC electrode is consistently higher than that of the AC electrode under the same electrolysis conditions. The electrochemical oxidation of methyl orange of both electrodes conformed to pseudo first‐order kinetics, but the rate constant of the Sb2O3/AC electrode was 2.29 times that of the AC electrode; this is likely due to the high electrocatalytic activity of the experimental electrode. The electrocatalysis results exhibited the synergetic effects of AC and Sb2O3 in the new particle electrode.

Effect of Univalent Cations Fluoride in F-Sb Codoped SnO<sub>2</sub> Electrode on Electro-Catalytic Degradation of Methyl Orange

In this work, F-Sb codoped SnO2film electrode material has been prepared and used as an anode on titanium (Ti) substrate for degradation of methyl orange. The emphasis is laid on the effect of univalent cations fluoride doped during preparation of F-Sn codoped SnO2composites by sol gel method. The facts show that univalent cations fluoride could affects the electro-catalytic degradation rate of methyl orange by F-Sb codoped composite film on the Ti electrode. A promotion to the degradation rates of methyl orange could be observed when KF or NH4F was used as codopant but other fluoride codopant such as LiF, NaF or HF could slow the methyl orange degradation. X-ray diffraction (XRD) and x-ray photo-electron spectroscopy (XPS) were used to study structures and composition of the anode surface.

Electrocatalytic Degradation of p-Nitrophenol Affected by the Synergsic Effect of Cathode and Anode

Electrocatalytic Degradation of p-Nitrophenol Affected by the Synergsic Effect of Cathode and Anode

Electrocatalytic degradation of bisphenol A in water on a Ti-based PbO 2–ionic liquids (ILs) electrode

This study presents an electrocatalytic method for the degradation of bisphenol A (BPA) in water based on a novel Ti-based PbO 2–ionic liquids (ILs) electrode. The electrode showed a high stability and reusability due to the better electroconductivity and reusability of ILs. Besides, the influence factors on BPA degradation were investigated in detail, and under the optimal conditions the degradation efficiency of BPA could reach 100% within 150 min. What's more, over 75% chemical oxygen demand (COD) removal was achieved on PbO 2–ILs(10%)/Ti electrode. The mechanism of the degradation reaction was proposed based on the results of high performance liquid chromatography coupled with mass spectrometry (LC/MS). It was deduced that hydroxyl radicals ( OH) generated in the electrocatalytic process played a key role in oxidizing BPA to form CO 2 and H 2O, which could be determined by fluorescence methods. All these results illustrated that PbO 2–ILs/Ti electrode was effective for pollutants degradation and had a great potential application.

Fabrication, characterization and electrocatalytic properties of a solid modified electrode based on PW 11O 39Fe(III)(H 2O) 4− and chitosan

A solid modified electrode based on PW 11O 39Fe(III)(H 2O) 4− (PW 11Fe) and chitosan (CS) was fabricated by sol–gel process via immobilization of PW 11Fe, adsorbed on CS, onto the surface of a glassy carbon (GC) or a graphite (C) electrode with methyltrimethoxysilane as a cross-linking agent. After characterization by scanning electron microscope (SEM) and transmission electron microscope (TEM), the electrochemical characteristics of the PW 11Fe/CS/C system and its electrocatalytic activity towards H 2O 2 reduction were investigated using electrochemical methods such as cyclic voltammetry and alternating current impedance. It was found that the PW 11Fe/CS/C system still retained the electrochemical properties of the PW 11Fe and its eletrocatalytic activity towards H 2O 2 reduction in homogeneous solution. Application of the PW 11Fe/CS/C system in electrocatalytic degradation of nitrobenzene (NB) revealed that 100% of NB degradation was obtained at 120 min in 0.1 M Na 2SO 4 + NaHSO 4 (pH 3.5) solution containing 1 mM NB.

Preparation and Application of Iron-Loaded Activated Carbon for Catalytic Oxidation of Phenol Wastewater

The catalyst was prepared by using activated carbon as the carrier and loading with iron oxide as the active component, the main factors affecting the preparation of this catalyst were further analyzed. When this catalyst was applied to the electrocatalytic oxidation degradation of phenol simulation wastewater, the affecting factors on the removing rate of phenol were studied. Under the optimized preparation conditions of soaking in 2mol/L HCl and 5%NaOH for 12 h, respectively, and then in FeCl3 with the concentration of 10% for 24h, calcination temperature 240°C for 2.5 h, the optimum catalytic activity could be obtained.

Electrocatalytic Degradation of Cellulose Using Lead Dioxide Anode

A novel method of cellulose degradation is investigated in this paper. In this work, a three-electrode system, which contains a Pb/PbO2 anode, two copper cathodes and a reference saturated calomel electrode (SCE), is applied to electrocatalytic degradation of cellulose. The composition of the products in filtrate is characterized by phenol-sulfuric acid method, NMR and GC-MS. In addition, the solid sample is analyzed via Ubbelohde capillary viscometer and FT-IR spectra. The results suggest that it is effective to convert cellulose to soluble sugar, 5-hydroxymethylfurfural (5-HMF) and other products by electrocatalytic method. The reaction mechanism of cellulose degradation is also discussed.

Indirect Electrocatalytic Degradation of Cyanide at Nitrogen-Doped Carbon Nanotube Electrodes

Nitrogen-doped carbon nanotube (N-CNT) mat electrodes exhibit high catalytic activity toward O(2) reduction, which can be exploited for the remediation of free cyanide (CN(-)). During the electrochemical O(2) reduction process, the hydroperoxide anion (HO(2)(-)) is formed and then reacts to chemically oxidize cyanide (CN(-)) to form cyanate (OCN(-)). The proposed electrochemical-chemical (EC) mechanism for CN(-) remediation at N-CNTs is supported by cyclic voltammetry and bulk electrolysis, and the formation of OCN(-) is confirmed via spectroscopic methods and electrochemical simulations. Our results indicate that by exploiting their catalytic behavior for O(2) reduction, N-CNTs can efficiently convert toxic CN(-) to the nontoxic OCN(-).

Treatment of high explosive production wastewater containing RDX by combined electrocatalytic reaction and anoxic–oxic biodegradation

Treatment of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) wastewater by combined process of electrocatalytic reaction and anoxic–oxic (A/O) activated sludge process was investigated. The degradation intermediates of RDX during the synergistic system of electrochemical reduction and electrochemical oxidation were analyzed by tandem mass spectrometry (MS/MS), and a pathway for electrocatalytic degradation of RDX was proposed. In order to remove RDX from the wastewater, an electrochemical system using TiO 2-NTs/SnO 2-Sb anode was applied to the pretreatment process. The effect of the operating parameters on the electrochemical process performance was studied. The electrocatalytic process removed 39.2% of COD and 97.5% of RDX, and increased biodegradability index from 0.18 to 0.51, which resulted in a great improvement in the biodegradability. The start-up and operation period for the anoxic–oxic activated sludge process were also investigated. As a conclusion, the toxic and refractory organic pollutants were effectively removed in the electrochemical pretreatment and this combined process was successfully employed.

Electrochemical degradation of some organic dyes by electrochemical oxidation on a Pb/PbO2 electrode

This work investigated the electrocatalytic degradation of three types of textile dyes by electrochemical oxidation on lead dioxide anode. The influence of pH, current density, time of electrolysis, temperature, the conductive salt concentration and the initial dye concentrations were critically examined. The results of these influences are expressed in terms of the remaining organic compounds concentrations (color removal) and Chemical Oxygen Demand (COD removal). Also, both of the current efficiency and power consumption values are calculated. In this manuscript we report that, the highest electrocatalytic activity was achieved in the presence of NaCl (3 g/l), 30 mA/cm2, pH of 3 and temperature of 30 °C. The highest electroactivity could be attributed to indirect oxidation of the investigated dyes by the electrogenerated hypochlorite ions formed from the chloride oxidation. In addition, contribution from direct oxidation could also be possible via reaction of these dyes with the electrogenerated hydroxyl radicals adsorbed on the lead dioxide surface.

Electrocatalytic degradation of 2,4-dichlorophenol by granular graphite electrodes

A reactor using granular graphite as an electrode material was used to electrochemically degrade 2,4-dichlorophenol. The degradation efficiency reached more than 95% after 24 h at all experimental conditions. Adsorption of 2,4-dichlorophenol by the granular graphite can be described with the Freundlich isotherm. The degradation kinetics are pseudo-first-order. The degradation rate increased linearly with both applied current density and flow rate. The pseudo-first-order surface reaction rate constants, ka, at a flow rate of 5 mL/min increased from 0.0015 L/h m 2 at an applied current density of 0.41 mA/m 2 to 0.0028 L/h m 2 at an applied current density of 2.21 mA/m 2. The ka values at a current density of 1.14 mA/m 2 increased from 0.0021 L/h m 2 at a flow rate of 5 mL/min to 0.0068 L/h m 2 at a flow rate of 50 mL/min. Charge efficiency, ranging from less than 1 to 60 μg/C, increased with the concentration of 2,4-dichlorophenol and decreased with the applied current density. Hence, using a low applied current density could be more economical than a high applied current density when applying this technique.

The Box-Benkhen experimental design for the optimization of the electrocatalytic treatment of wastewaters with high concentrations of phenol and organic matter

In this work, the Box-Benkhen experimental Design (BBD) was applied for the optimization of the parameters of the electrocatalytic degradation of wastewaters resulting from a phenolic resins industry placed in the suburbs of Medellin (Colombia). The direct and the oxidant assisted electro-oxidation experiments were carried out in a laboratory scale batch cell reactor, with monopolar configuration, and electrodes made of graphite (anode) and titanium (cathode). A multifactorial experimental design was proposed, including the following experimental variables: initial phenol concentration, conductivity, and pH. The direct electro-oxidation process allowed to reach ca. 88% of phenol degradation, 38% of mineralization (TOC), 52% of Chemical Oxygen Demand (COD) degradation, and an increase in water biodegradability of 13%. The synergetic effect of the electro-oxidation process and the respective oxidant agent (Fenton reactant, potassium permanganate, or sodium persulfate) let to a significant increase in the rate of the degradation process. At the optimized variables values, it was possible to reach ca. 99% of phenol degradation, 80% of TOC and 88% of COD degradation. A kinetic study was accomplished, which included the identification of the intermediate compounds generated during the oxidation process.

Electro-catalytic degradation of methylene blue wastewater assisted by Fe 2O 3-modified kaolin

The electrochemical oxidation of methylene blue (MB) wastewater assisted by Fe 2O 3-modified kaolin in a 200 mL electrolytic batch reactor with graphite plate as electrodes was investigated. The catalyst was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of pH, current density and introduction of NaCl on the efficiency of the electrochemical degradation process were also studied. It was found that Fe 2O 3-modified kaolin has higher catalytic activity in the electrochemical degradation of MB wastewater. 96.47% chemical oxygen demand (COD) removal was obtained in 40 min of electrochemical treatment of MB wastewater at pH 3, current density was equal to 69.23 mA cm −2.

Electro-Catalytic Performance of Composite Oxide Sn-Sb-Mn/Ceramic Particle Electrode System

Sn-Sb-Mn/ceramic particle electrodes were prepared by a thermal decomposition technique. The morphology, crystal phase composition, BET surface area and pore size distribution of the electrodes were characterized by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and N(2) physical adsorption techniques, respectively. The properties of oxygen evolution at the three-dimensional electrode system were studied and the electrocatalytic property was investigated by cyclic voltammetry. The electrochemical degradation of artificial phenol wastewater was conducted in a multi-electrode reactor. Results showed that the catalytic layer of as-prepared ceramic particle electrodes had large BET surfaces and abundant micropores, which were beneficial for the electrocatalytic reaction. Results also indicated that the electrocatalytic degradation occurred where oxygen evolution took place. The multi-electrode system was far better at degrading phenol than a two-dimensional electrode system. The removal ratio of phenol and total organic carbon (TOC) were 92.3% and 66.7%, respectively. This study demonstrates that a three-dimensional electrode system exhibits excellent electrocatalytic performance.