PbO2 Anode Research Articles

Simultaneous application of copper and PbO2 anodes for electrochemical treatment of olive oil mill wastewater

Olive oil mill wastewater (OOMW) is a complex effluent that must be treated before discharge into the environment. In this study, a combination of various mechanisms was conducted in an electrochemical cell. Copper and PbO2 anodes were used, while hydrogen peroxide was electro-generated at an activated carbon fiber cathode. Fenton-like reaction and electrooxidation occurred during electrolysis for organic compounds degradation in OOMW. The effects of pH, dilution of OOMW, and electrical current on COD and phenol removals were investigated. The results showed that 78.5% phenol and 60% COD removals were obtained at optimum conditions of 300 mA electrical current, 150 min electrolysis, and pH 3–3.5 (regulated). The regulation of pH during electrolysis significantly developed the treatment efficiency of electrochemical process. Phenol and COD removal kinetics were likely to follow second-order model and first-order model, respectively. Simultaneous application of two anodes had synergic effect on removal efficiency of electrochemical process. Biodegradability (BOD5/COD) was dramatically improved from 0.18 to 0.468 after electrochemical oxidation. It was concluded that the two mechanisms of production of active oxygen and chlorine had synergic effect on electrochemical degradation.

Insights into electrodegradation mechanism of tebuconazole pesticide on Bi-doped PbO2 electrodes

The effect of the Bi doping of PbO2 coatings on the electrochemical degradation of the pesticide tebuconazole (TBC) was investigated. The insertion of 8% Bi (relative to the amount of Pb) in the PbO2 structure afforded a well-defined texturing in the direction of the (200) plane to the PbO2 coatings, as well as, a decrease in the size of the coherent domain of the crystal, an increase in the electrochemical roughness and in the oxidation power of the Bi-doped PbO2 compared with PbO2. Through ultraviolet-visible spectrometry and total organic carbon (TOC) analyses for TCB electrodegradation was possible to chose the current density of 40mAcm−2 as optimized one, with 68% of TOC removed by the Bi-doped electrode and 56% removed by the PbO2 electrode. High resolution liquid chromatography coupled with electrospray ionisation high resolution mass spectrometry helped to propose an oxidation pathway for the electrochemical degradation of TBC. Nine electrooxidation products were identified; which were produced by hydroxylation of the TBC phenyl group and its consequent oxidation to a ketone (including both mono- and dihydroxylated products), by dechlorination (two different products), and by multiple oxidative steps with ring opening (two different products). It was possible to conclude that the electrooxidation of TBC using Bi-doped PbO2 anodes generated products that were less harmful than TBC itself, thus recommending this electrode as an alternative material for wastewater decontamination.

Investigation on electro-catalytic oxidation properties of carbon nanotube–Ce-modified PbO2 electrode and its application for degradation of m-nitrophenol

In this work a carbon nanotube–Ce-modified PbO2 (CNT–Ce–PbO2) electrode was prepared by electrodeposition method, and compared with pure PbO2, Ce–PbO2, and CNT–PbO2 electrodes. The direct and indirect oxidation capacities of prepared electrodes in electro-catalytic oxidation processes were investigated by cyclic voltammetry and hydroxyl radical production tests, respectively. The electro-catalytic activity of electrodes was examined by electro-catalytic oxidation of a model pollutant of m-nitrophenol (m-NP). Besides, high-performance liquid chromatography (HPLC) was also employed to identify the products resulting from the electro-catalytic oxidation of m-NP and the degradation mechanism of m-NP was proposed. Results show that the CNT–Ce–PbO2 anode has higher direct and indirect oxidation capacities than pure PbO2, Ce–PbO2, and CNT–PbO2 anodes. In the electro-catalytic oxidation of m-NP, the m-NP can be oxidized and degraded at all anodes, and the oxidation reactions of m-NP follow first-order kinetics. m-NP and TOC removal efficiencies are about 0.987 and 0.622 after electrolysis of 120min and a maximum first-order rate constant of 0.036min−1 is achieved at the CNT–Ce–PbO2 anode, which are obviously higher than those of the other three kinds of anodes.

Electrochemical degradation of N,N-diethyl-m-toluamide on a boron-doped diamond electrode

This study investigates the electrochemical oxidation of N,N-diethyl-m-toluamide (DEET) on a boron-doped diamond (BDD) anode under different temperatures, current densities, and sample matrixes. For comparison, a commercial Pt electrode and a lab-prepared PbO2 anode were also tested. The oxidation of DEET on BDD was found to be electrochemically irreversible. The degradation of DEET increased with the increase of current density, but was slightly influenced by temperature (25–75°C). Furthermore, the BDD anode was superior to the Pt and PbO2 electrodes with regard to DEET abatement and total organic carbon (TOC) removal. At 0.75A/cm2 and 50°C, the pseudo-first-order rate constants of DEET oxidation were 5.00×10−3–8.98×10−3s−1 in DEET-spiked 1M Na2SO4 solution, municipal wastewater treatment plant secondary effluent (MWTPSE), groundwater (GW), and river water (RW), significantly greater than that (4.73×10−4s−1) in DEET-spiked industrial wastewater (IW). The TOC removal in the real environmental matrixes followed the order MWTPSE>GW≈RW≫IW. Through electrochemical oxidation, DEET was completely mineralized in the DEET-spiked MWTPSE.

PbO2 anodes modified by cerium ions

Lead dioxide coatings deposited from methanesulfonate electrolytes that also contain Ce3+ ions have been investigated. It has been shown that, during the deposition, are formed lead dioxide electrodes micromodified by cerium, which have different physicochemical properties than do traditional PbO2 anodes. The electrocatalytic activity of materials involved in respect to oxygen evolution and oxidation of p-nitroaniline has been investigated.

Theoretical calculation and experimental study on the conductivity and stability of Bi-doped SnO2 electrode

In this study, Ti/SnO2-Sb2O4-Bi2O3/PbO2 anodes are prepared by electrodeposition method, and formation energy and band structure are analysed using first-principles calculations. The phase structure and valence states of the electrode are analysed using X-ray diffraction and X-ray photoelectron spectroscopy, respectively. Furthermore, the accelerated service life of the electrode is evaluated to be 4 A cm−2. The results show that the lattice parameters of Bi-doped SnO2 system increase approximately linearly with increasing Bi doping concentration. For the Bi-doped SnO2 system, the minimum value of formation energy is −10.28eV, and the most stable structure is obtained when the Bi doping ratio is 0.0625. The formation energy gradually increases and the stability decreases with increasing doping ratio. Moreover, the conductivity of the anode reaches the maximum value and the accelerated service life increases up to 52h when the doping ratio is 0.0625. On the basis of our experiment and theoretical calculations, the Bi-doped SnO2 electrode is shown to be a good acid-proof anode.

Effect of matrix on the electrochemical characteristics of TiO2 nanotube array-based PbO2 electrode for pollutant degradation

A series of lead dioxide electrodes developed on titania nanotube arrays with different matrix were fabricated by electrodeposition. Before the deposition of PbO₂, the matrix of this anode was electrochemically reduced in (NH₄)₂SO₄ solution and/or pre-deposited with certain amounts of copper. To gain insight into these pretreatments, the PbO₂ electrodes were characterized by SEM, LSV, and XRD, and their electrocatalytic activities for pollutant degradation were compared using p-nitrophenol (p-NP) as a model. It was confirmed that the electrochemical reduction with (NH4)₂SO₄ resulted in the partial conversion of TiO₂ into Ti₄O₇ and Ti₅O₉, which increased the conductivity of PbO₂ anode, but decreased its electrochemical activity, while the Ti/TNTs*-Cu/PbO₂ electrode with both pretreatments possessed the highest oxygen evolution overpotential of 2.5 V (vs. SCE) and low substrate resistance. After a 180-min treatment on this electrode, the removal efficiency of p-NP reached 82.5% and the COD removal achieved 42.5% with the energy consumption of 9.45 kWh m(-3), demonstrating the best performance among these electrodes with different matrices. Therefore, this titania nanotube array-based PbO₂ electrode has a promising application in the industrial wastewater treatment.

Metal oxide-coated anodes in wastewater treatment

Electrochemical oxidation is an effective wastewater treatment method. Metal oxide-coated substrates are commonly used as anodes in this process. This article compiles the developments in the fabrication, application, and performance of metal oxide anodes in wastewater treatment. It summarizes the preparative methods and mechanism of oxidation of organics on the metal oxide anodes. The discussion is focused on the application of SnO2, PbO2, IrO2, and RuO2 metal oxide anodes and their effectiveness in wastewater treatment process.

Physicochemical characterisation of electrosynthesized lead dioxide coatings on Ti/SnO2-Sb substrates

Abstract SnO2, as an undercoat, has been recently applied on Ti substrate to prepare PbO2 anodes to improve the stability and electro-catalytic activity. In this work, we explored the electro-deposition of PbO2 on the Ti substrate with a Sb-doped SnO2 undercoat, from a traditional acidic nitrate solution. The morphology and microstructure of the PbO2 coatings were investigated by varying electro-deposition temperature and time. It is found that the Sb-doped SnO2 undercoat significantly promotes the electro-deposition process of PbO2. At a low electro-deposition temperature, a preferential crystallographic orientation is usually observed in the coatings, which exhibit a caterpillar-like morphology. At a higher deposition temperature, the PbO2 coatings display a more tightly packed pyramid-like morphology. The crystallite size increases with deposition temperature. Electrochemical performance of the deposited PbO2 largely depends on their morphologies and microstructures. It is suggested that deep reaction path, high porosity and good connectivity between crystallites play a synergic role in determining the electrochemical performance of the PbO2 coatings.

Production of formic acid from biomass-based compounds using a filter press type electrolyzer

There has been a growing interest for the sustainable production of formic acid (FA) in recent years considering its potential use as a hydrogen storage compound. In this context, the electrochemical transformation of carbohydrate-based biomass into formic acid in aqueous media was investigated using a filter-press type electrochemical cell. Therefore the oxidation of mono and disaccharides was carried out at NiOOH, RuO2/Ti (DSA) and PbO2 anodes, in FM01-LC (ICI) electrolyzer. The effect of carbon number of biomass compound, anode material and pH on product distribution was determined. Between the readily available carbohydrates studied in this work at NiOOH anode, in alkaline medium, d-xylose provides the highest selectivity towards formate anion, i.e. 42%. The transformation of d-glucose into formic acid, with 38% selectivity, was achieved at RuO2/Ti (DSA) in 0.5M NaOH medium, applying a current density of 80Am−2. The production of formate anion is mostly accompanied by the formation of oxalate anion and carbonates which constitute the by-products of the reaction. Considering that after acidification of carbonates the resulting CO2 can be easily removed and trapped by the growing plants which provide new biomass-based material, the transformation of oxalate anion (OA) into CO32− is of major importance. For this reason the oxidation of OA at DSA in 0.1M NaOH medium was also studied. In these conditions 60% of the initial oxalate anion was transformed to CO32− at 2.5V vs. SCE.

Bismuth Doped PbO<sub>2</sub> Coatings: Morphology and Electrocatalytic Properties

Modified PbO2 anodes doped with bismuth were prepared by means of electrodeposition in methanesulfonate solutions. The influence of bismuth ions on morphological and electrocatalytic properties of obtained coatings was studied. Both XRD patterns and SEM micrographs demonstrated that incorporation of bismuth diminishes the size of crystal particles. It is shown, that oxygen overpotential on micromodified electrodes is sensibly higher than on non-modified PbO2-electrode. According to obtained results a hypothesis of a mechanism which include transfer of an increased number oxygen radical intermediates to Bi(III) to produce a sensible amount of Bi(IV) and Bi(V) that can participate in the O2 evolution process was proposed.

Performance of Chloride Ions on Electrocatalytic Oxidation Process Using Ti-Nanotubes/PDDA-PbO2 Anode for Phenol Removal

AbstractThe performance of the electrocatalytic oxidation of phenol on poly(diallyldimethylammonium chloride) (PDDA)–modified PbO2 anodes in the presence of chloride ions was studied. The objective was to elucidate the influence of NaCl dosage, current density, initial phenol concentration, and initial pH on this catalysis process in the presence of Cl−. The results revealed that at low current densities, the presence of Cl− could greatly enhance the current efficiency by electrogenerating active chlorine, and the current density increased, but if competitive adsorption of ·OH radicals occurred, the removal efficiency did not improve significantly and the current efficiency decreased. This indicated that the pH value had a major impact on phenol, with optimal removal observed at approximately pH 6–7. In both acidic and alkaline solutions outside this optimal pH window, the removal efficiency deteriorated. The modified anode performs well for phenol degradation for a wide range of phenol concentrations und...

Electrocatalytic performance of PbO<sub>2</sub> films in the degradation of dimethoate insecticide

This study was performed to find the best experimental conditions for the electrochemical removal of the insecticide dimethoate (C 5 H 12 NO 3 PS 2 ) from aqueous solutions using a lead dioxide niobium anode. The process was studied under galvanostatic polarisation mode. The influence of applied current density (10–50 mA·cm–2), initial chemical oxygen demand COD0 (100–550 mg·l –1 ), temperature (30–70°C) and pH (3–11) on COD and instantaneous current efficiency (ICE) was studied. The results showed that almost 90% of COD removal was achieved under optimal experimental conditions, indicating that electrochemical oxidation on a PbO2 anode is a suitable method for treatment of water polluted with dimethoate. It was found that the decay of COD generally followed a pseudo first-order kinetic and the oxidation rate was favoured by increasing the applied current density, temperature, pH and initial COD. The greatest COD removal (90%) was obtained when using an applied current density of 50 mA·cm –2 , COD0 = 320 mg·l –1 , pH = 11, T = 70°C and electrolysis time = 8 h. Keywords: Electrochemical degradation; hydroxyl radicals; organic pollutants; lead dioxide; wastewater

Synthesis of 3-O-methylgallic acid a powerful antioxidant by electrochemical conversion of syringic acid

BackgroundA kinetic study of the electrochemical oxidation of syringic acid (3,5-dimethoxy-4-hydroxybenzoic acid) by cyclic voltammetry at treated gold disk was combined with results of electrolyses at Ta/PbO2 anode in order to convert it into potentially high-added-value product. MethodsThe electrochemical oxidation of syringic acid was carried out in order to convert this compound to 3-O-methylgallic acid. This latter was identified by mass spectrophotometry using LC-MS/MS apparatus. The 3-O-methylgallic acid synthesis was controlled by cyclic volammetry, Ortho-diphenolicdeterminations and DPPH radical-scavenging activity. ResultsThe proposed mechanism is based on the hypothesis of a bielectronic discharge of syringic acid molecule under free and adsorbed form involving two intermediate cation mesomers. Hydrolysis of the more stable of this last one leads to the formation of the 3,4-dihydroxy-5-methoxybenzoic acid (3-O-methylgallic acid) as a major product. The latter aromatic compound was synthesized by anodic oxidation of syringic acid at PbO2 electrode. The cyclic voltammogram of the electrolysis bath of syringic acid shows that the anodic peak potential of 3-O-methylgallic acid was lower (Epa=128mV) than that of SA (Epa=320mV). And the strongest antiradical activity was detected when the 3-O-methylgallic acid concentration was higher". ConclusionThe electrochemical oxidation using PbO2 anode is a rapid, simple and efficient method tool for a conversion of SA into 3-O-methylgallic acid, a potent antioxidant derivative General SignificanceThe electrochemical process consists in a simple transformation of the syringic acid into 3-O-methylgallic acid having a better antioxidant capacity. This result has been justified by cyclic voltametry which shows that anodic peak of 3-O-methylgallic acid is reversible. Furthermore, its potential is lower than that of the irreversible anodic peak of syringic acid to 3-O-methylgallic acid.

Electrochemical degradation of ethidium bromide using boron-doped diamond electrode

Ethidium bromide (EtBr), a DNA intercalating pollutant, is widely disposed in aqueous solutions by most biomedical laboratories. The release of EtBr in the ecosystem may cause serious environmental problems like water pollution, eutrophication and perturbation in aquatic life. In this study, the degradation behavior of EtBr on boron-doped diamond (BDD) electrode was investigated under galvanostatic conditions. The electro-oxidation behavior of EtBr at BDD electrode was firstly examined by means of cyclic voltammetric technique. Such operating parameters as applied current density, types of electrolyte, temperature and initial concentration of EtBr were then varied in order to determine their effects on this oxidation process. The degradation of EtBr was mainly monitored by UV–vis spectrophotometer. The experimental results revealed the suitability of electrochemical processes employing BDD electrode for removing EtBr completely from the solution. The kinetics for EtBr degradation followed a pesudo-first order reaction in most cases, indicating the process was under mass transport control. Moreover, the better performance of BDD anode was proved on a comparative study with PbO2 anode under similar experimental conditions. As a result, the BDD technology could be considered as a nice solution to the treatment of EtBr-polluted wastewater.

Fabrication and Characteristics of a Nanostructure PbO2 Anode and its Application for Degradation of Phenol

In this study, a novel double-walled structure of PbO2 electrodeposited into TiO2 nanotube arrays was successfully fabricated by a pulse electrodeposition (PED) method. TiO2 nanotubes (NT) were prepared by electrochemical anodization and used as a substrate to electrodeposit PbO2. Then the major work focused on the investigation of the morphology and chemical composition of the Ti/TiO2NT/PbO2 anode. The electrochemical measurements were applied to analyze the electrochemical properties of the Ti/TiO2NT/PbO2 anode. The results of field emission-scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) revealed that lead dioxide nanoparticles have been successfully electrodeposited into TiO2NT walls without blocking the tubes. The electrochemical measurements indicated the electrodeposition time of PbO2 have an obvious impact on anode electrochemical activity, because of its influence on the active areas of the anode. The bulk electrolysis demonstrated that the Ti/TiO2NT/PbO2 anode presented excellent electrocatalytic performance for degradation of phenol which containing 17.53 g·L−1 NaCl at the current density of 30 mA·cm−2.

Electrochemical degradation of phenol in aqueous solution using PbO2 anode

The PbO2 electrode was prepared by electrodeposition method in this paper. The electrode was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV). The electrochemical oxidation of phenol in aqueous solution was studied by galvanostatic electrolysis using PbO2 electrode as anode. UV spectroscopy, total organic carbon (TOC) and chemical oxygen demand (COD) measurements were conducted to study the kinetics of phenol electrochemical degradation and the mineralization efficiency under different current densities. The experimental results showed that the applied current density had a positive influence on the degradation of phenol and removal of TOC, but a higher current density led to lower current efficiency and higher energy consumption. The phenol degradation always followed a pseudo-first-order kinetics. In addition, aromatic intermediates and general carboxylic acids generated in the degradation of phenol have been indentified using high-performance liquid chromatography (HPLC) and a general pathway for the electrochemical degradation of phenol on PbO2 anode was proposed.

Role of electrode materials for the anodic oxidation of a real landfill leachate – Comparison between Ti–Ru–Sn ternary oxide, PbO2 and boron-doped diamond anode

In this paper the electrocatalytic properties of Ti–Ru–Sn ternary oxide (TiRuSnO2), PbO2 and boron-doped diamond (BDD) anodes have been compared for the electrochemical oxidation of a real landfill leachate from an old municipal solid waste landfill (average values of COD 780mgdm−3 and NH4+-N266mgdm-3). The experiments have been performed using an undivided flow cell equipped with a stainless steel cathode, under constant current of 2A and flow-rate of 420dm3h−1. The performance of the electrodes has been compared measuring the time evolution of aromatic compounds, COD, ammonium, colour removal, current efficiency and energy consumption. The experimental results indicated that after 8h of electrolyses TiRuSnO2 anode yields only 35% COD, 52% colour and 65% ammonium removal. Using PbO2 ammonium and colour were completely removed but a residual COD (i.e. 115mgdm−3) was present.On the contrary BDD enables complete COD, colour and ammonium removal due to the electrogeneration of hydroxyl radicals from water discharge and active chlorine from chloride ions oxidation. BDD also exhibits greater current efficiency along with a significantly lower energy cost than other electrodes. These results indicated that the electrochemical oxidation with BDD anode is an effective process for the treatment of landfill leachate.

Electrochemical Degradation of Anthraquinone Dye Alizarin Red: Role of the Electrode Material

Anodic oxidation is a promising process for degrading toxic and biologically refractory organic pollutants present in wastewater. Proper selection of electrodes is the key to reach effective and economic treatment. In this study, the electrochemical oxidation of Alizarin Red has been studied in neutral media using lead dioxide (PbO2), boron-doped diamond (BDD) and platinum (Pt) anodes in bulk electrolysis experiments under same conditions. Obtained results have clearly shown that the electrode material is an important parameter for the optimization of such process. Kinetics analysis showed that Alizarin Red is readily oxidized on PbO2 and BDD anodes, Pt anode having a moderate ability to oxidize it. Different current efficiencies were obtained for PbO2 and BDD, depending on the applied current density in the range from 33 to 150 mA cm-2. The effect of the initial Alizarin Red concentration on the performance of PbO2, BDD and Pt anodes, as well as, their comparative oxidation ability was studied. Faster Alizarin Red elimination and TOC removal were obtained using BDD anode with current density of 33 mA cm-2. Bulk electrolysis showed that the complete TOC and color removal were achieved using PbO2 and BDD anodes while Pt anode performed only a partial oxidation of Alizarin Red. Keywords: Alizarin, Degradation kinetics, Anodic oxidation, BDD anode, Hydroxyl radical, TOC removal, triphenyl methyl, physico-chemical, discoloration, microbiological degradation

Unprecedented total mineralization of atrazine and cyanuric acid by anodic oxidation and electro-Fenton with a boron-doped diamond anode

This article reports the complete mineralization of atrazine. Atrazine has been the most widely used s-triazine herbicide. Atrazine occurs in natural waters and presents a potential danger for public health because atrazine is considered as an endocrine disruptor. The use of chemical, photochemical and photocatalytic advanced oxidation processes (AOPs) to decontaminate waters containing atrazine only allowed its conversion into the cyanuric acid as ultimate end products, since it cannot be completely degraded by hydroxyl radicals (•OH) produced by these techniques. The same behavior was previously reported for anodic oxidation and electro-Fenton with Pt anode, although better performances were found using boron-doped diamond (BDD) anode but without explaining the role of generated •OH. Here, the oxidative action of these radicals in such electrochemical AOPs has been clarified by studying the mineralization process and decay kinetics of atrazine and cyanuric acid in separated solutions by anodic oxidation with BDD and electro-Fenton with Pt or BDD anode using an undivided cell with a carbon-felt cathode under galvanostatic conditions. Results showed that electro-Fenton with BDD anode was the more powerful treatment to degrade both compounds. Almost total mineralization, 97% total organic carbon (COT) removal, of atrazine was only feasible by this method with a faster removal of its oxidation intermediates by •OH formed at the BDD surface than that formed in the bulk from Fenton reaction, although the latter process caused a more rapid decay of the herbicide. Cyanuric acid was much slowly mineralized mainly with •OH produced at the BDD surface, and it was not degraded by electro-Fenton with Pt anode. These results highlight that electrochemical advanced oxidation processes (EAOPs) using a BDD anode are more powerful than the classical electro-Fenton process with Pt or PbO2 anodes.