Electrooxidation Of Phenol Research Articles

Electrocatalytic effect of NiO supported onto activated carbon in oxidizing phenol at graphite electrode: Application in tap water and olive oil samples

The activated carbon doped by nickel oxide (NiO/AC) was prepared using solid reaction. The obtained powder was characterized using X-ray diffraction (XRD) and infrared spectroscopy (IR). The NiO/AC was also used to catalyze the electro-oxidation of phenol at carbon paste electrode (CPE) using electrochemical approaches. Kinetic parameters of phenol oxidation (as the electron transfer coefficient, diffusion coefficient and heterogeneous rate constant) were investigated. The results confirm that phenol oxidation is catalyzed by nickel oxide, due to resonance, steric and aggregation effects.The experimental conditions were optimized by varying chemical and electrochemical parameters, which involve the oxidation of phenol. The electrode NiO/AC–CPE exhibits a good linear range from 1.0×10−6molL−1 to 8.0×10−5molL−1 and 1.0×10−4molL−1 to 1.0×10−3molL−1 with a limit of detection of 7.09×10–7molL–1 (signal (S) to noise (N) ratio, S/N=3). This modified electrode NiO/AC-CPE offers a considerable improvement in voltammetric sensitivity toward phenol determination, compared to the unmodified electrode (CPE). The selectivity of the NiO/AC–CPE in detecting phenol was investigated for a number of ions (Cu2+, Cd+2, Ag+, Pb2+, Zn2+, Fe3+, Ni2+, Al3+, Mg2+, Ag2+ and Cr3+) and biomolecules (4-nitrophenol, dopamine, 2-nitrophenol, paracetamol, hydroquinone, catechol, resorcinol, 4-aminophenol and 3-aminophenol). The proposed method was successfully applied to phenol determination in tap water and olive oil.

Electro-oxidation of phenol over electrodeposited MnOx nanostructures and the role of a TiO2 nanotubes interlayer

More and more attention has recently been paid to the electrochemical treatment of wastewater for the degradation of refractory organics, such as phenol and its derivatives. The electrodeposition of different types of manganese oxides (MnOx) over two substrates, namely metallic titanium and titania nanotubes (TiO2-NTs), is reported herein. X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS) analyses have confirmed the formation of different oxidation states of the manganese, while Field Emission Scanning Electronic Microscopy (FESEM) analysis has helped to point out the evolutions in the morphology of the samples, which depends on the electrodeposition parameters and calcination conditions. Moreover, cross section FESEM images have demonstrated the penetration of manganese oxides inside the NTs for anodically deposited samples. The electrochemical properties of the electrodes have been investigated by means of cyclic voltammetry (CV) and linear sweep voltammetry (LSV), both of which have shown that both calcination and electrodeposition over TiO2-NTs lead to more stable electrodes that exhibited a marked increase in the current density. The activity of the proposed nanostructured samples toward phenol degradation has been investigated. The cathodically electrodeposited manganese oxides (α-MnO2) have been found to be the most active phase, with a phenol conversion of 26.8%. The anodically electrodeposited manganese oxides (α-Mn2O3), instead, have shown higher stability, with a final working potential of 2.9V vs. RHE. The TiO2-NTs interlayer has contributed, in all cases, to a decrease of about 1–1.5V in the final (reached) potential, after a reaction time of 5h. Electrochemical impedance spectroscopy (EIS) and accelerated life time tests have confirmed the beneficial effect of TiO2-NTs, which contributes by improving both the charge transfer properties (kinetics of reaction) and the adhesion of MnOx films.

Simultaneous removal of phenol and dichromate from aqueous solution through a phenol-Cr(VI) coupled redox fuel cell reactor

To eliminate contaminants like phenol and dichromate from aqueous solutions is still a hot research interest. In contrast to a traditional method within high intensity of energy input, both dichromate and phenol were removed within self-powered process through a phenol-Cr(VI) coupled redox fuel cell reactor, which was uniquely assembled on Ni/C anode the electro-oxidation of phenol takes place to give electrons and then go through the external circuit reducing Cr(VI) to Cr(III) on the cathode. Taking an example of 0.94 g L−1 phenol in 0.2 M phosphate buffer solution (PBS) serving as the anolyte and 0.15 g L−1 Cr(VI) in 0.5 M H2SO4 serving as the catholyte, a net power density of 0.184 W m−2 at 0.61 V can be gained. A removal efficiency of 98.6% for 0.94 g L−1 phenol within 132 h and 99.8% for 0.30 g L−1 Cr(VI) within 60 h can be readily achieved in the system. This confirmed in the fed-batch mode that either the contaminants of phenol and Cr(VI) in solutions is effectively removed or the energy contained in chemicals as the form of electricity has been exactly retrieved.

Simultaneous electro-oxidation of phenol, CN−, S2− and NH4+ in synthetic wastewater using boron doped diamond anode

Electrochemical decontamination of phenolic synthetic wastewater containing CN−, S2− and NH4+ using a boron-doped diamond (BDD) electrode was investigated. The removal of phenol, its oxidation byproducts, total organic carbon (TOC), chemical oxygen demand (COD), and the inorganic species were evaluated in relation to specific energy consumption (SEC) and average current efficiencies (ACE) in single, binary, ternary and quaternary matrices of the inorganic species cohabiting phenol in solution. The total amount of COD removal, ACE and SEC were found to depend on the nature of ions in solution and were also proportional to the degree of inorganic species in the matrix. The decay kinetics of phenol as well as the inorganic species in different matrices mainly follow first order kinetics. ACE for binary and higher matrices values of 44.3–58.8% and 58.9–79.3%, respectively, indicate 132–207% and 208–315% increase in ACE, respectively, as compared to the 19.1% ACE when phenol was present alone. The SEC of 57.0 kWh/kg-COD estimated for the single phenol matrix dropped from 57kWh/kg-COD to between 15.1–20.6 and 7.83–15.2kWh/kg-COD for the multicomponent matrices which corresponds to a percent decrease of 63.2–73.5% and 73.3–86.3%, respectively. Presence of the inorganic species insignificantly affected phenol oxidation, though they delayed the attainment of steady state of complete decontamination depending on the species in the matrix. This study demonstrates the viability of oxidation at BDD anodes as an alternative treatment means for effective decontamination of phenolic wastewater containing inorganic species.

Smectite-chitosan-based electrodes in electrochemical detection of phenol and its derivatives

In this paper smectite-chitosan bionanocomposite (SМ-C) based on smectite (SM) from Crni Timok (Black Timok) basin, Serbia, was synthesized and characterized using chemical analysis, XRD and FTIR. The SM-C obtained was used for the modification of a glassy carbon electrode (GCE). The modified electrode (GCE/SM-C) was tested in the electrooxidation of phenol and different nitrophenols in acidic and alkaline solutions. Cyclic voltammograms (CV) obtained for GCE/SM-C, contrary to that obtained for the bare glassy carbon electrode, exhibited multiple oxidative peaks. The cathodic limit set to allow encompassing of nitro group reduction increased sensitivity for 4-nitrophenol detection. It also led to the appearance of additional peaks of 2-nitrophenol and decrease of the electrode passivation rate. The first-order derivative linear sweep voltammetry improved the sensitivity of the detection of different phenolic compounds from their mixed solution. The application of GCE/SM-C in alkaline environment led to increased current response while lowering the passivation rate. The quantitative determination of phenol and nitrophenols in a mixture, based on electrooxidation, had some disadvantages in both acidic and alkaline solution. Nevertheless, the concept of electrooxidation as a method for the detection and distinction of phenol and its nitro derivatives from water solution was proven.

Kinetics of electrooxidation of phenol on polycrystalline platinum

Abstract This work reports on kinetics of phenol electrooxidation reaction (PhER), examined at polycrystalline Pt electrode in 0.5 M H2SO4 and 0.1 M NaOH supporting solutions. Important aspects of PhER kinetics were analysed based on potential-dependent, a.c. impedance-derived values of charge-transfer resistance and capacitance parameters. Special attention was also given to the influence of supporting electrolyte ions on the process of phenol oxidation (pH dependence of the PhER), in relation to an important role of anion adsorption on the Pt catalyst surface.

An electrochemical mechanisms study on steel/IrO2–Sb2O3 electrodes for oxidation of phenol in water

Phenol, a known water pollutant, was electrochemically oxidized on a steel/IrO2–Sb2O3 novel anode. Since the oxidation mechanisms vary based on the anode material, a mechanisms study of electrooxidation of phenol on it was conducted. The phenol oxidation was carried out at 20 mA/cm2 constant current density with a pH 11.00 Na2SO4 medium at room temperature. During 6 h of electrolysis, samples were tested for chemical oxygen demand removal efficiency of the anode. The steel/IrO2–Sb2O3anode showed 76.3% chemical oxygen demand removal efficiency. Both 4-nitroso-N,N-dimethylaniline and the HCO3–/CO32– radical scavenger tests confirmed the formation and presence of the hydroxyl radicals in the system. Therefore, it was concluded that the hydroxyl radicals that are generated on the anode surface are the main cause for the oxidation mechanism. Moreover, ICE, HPLC, and UV-vis absorbance and cyclic voltammetry results confirmed the presence of catechol and benzoquinone as intermediates and the reaction mechanism.

Electrooxidation of Phenol on PtRh and PtRu Alloys in 0.1 M NaOH Solution

Electrooxidation of Phenol on PtRh and PtRu Alloys in 0.1 M NaOH Solution

Electrooxidation of Phenol at Palladium-Based Catalyst Materials in Alkaline Solution

Electrooxidation of Phenol at Palladium-Based Catalyst Materials in Alkaline Solution

Beneficial effect of Ni in pillared bentonite based electrodes on the electrochemical oxidation of phenol

The influence of Ni on the electrochemical performance of Fe containing bentonite-based electrode materials was investigated in the electrochemical oxidation of phenol in acidic solution. Clay originated from Mečji Do, Serbia, was submitted to pillaring. Mixed pillaring solutions containing Al3+ and Fe3+ or Al3+, Fe3+ and Ni2+ were used for this purpose. The XRD, chemical and FTIR analysis and nitrogen physisorption at -196°C were used for sample characterization. The electrochemical behavior of the pillared clay-based electrodes was tested by cyclic voltammetry. The results confirmed that the pillaring was successful. The presence of Ni in the electrode material enhanced the electrode stability. It is possible that the presence of Ni restricted the electrode fouling caused by the formation of polymeric products during the electrooxidation of phenol.

Effect of Ru Dopant Amount on the Electrocatalytic Capability of Ti/SnO2-Sb-Gd-Ru Electrodes in the Phenol Oxidation

SnO2 electrodes doped with Sb have been used in the process of anodic oxidation of contaminants organic due to its electrochemical properties, high performance and its low cost [1]. Recent studies have found that by introducing elements of rare earths, especially Gd in Ti/SnO2-Sb electrodes, favors a be tter performance in the catalytic activity for the electrooxidation of phenol [2], however, the main problem presented by this type of electrode is its short life time which limits its applications to industrial wastewater treatment. Therefore, increase the active life time of these anodes has a significant importance to develop treatment technologies of organic contaminants in wastewater. Different investigations have been directed to extend the useful life of SnO2-Sb anodes incorporating dopants metallic, as platinum, ruthenium [3] and Iridium or by the introduction of a interlayer of IrO2, RuO2 [4] between the surface of Ti and the SnO2-Sb film. The results reported indicate that the life time is increased, although decreases the electrocatalytic activity for pollutant elimination due to that reduces the potential of the oxygen evolution reaction (OER). This paper reports the study of influence of the Ru content on the electrocatalytic capability of Ti/SnO2-Sb(5%)-Gd(1%) electrodes in the electrooxidation of phenol.The electrodes were synthesized using the Pechini method [5] and calcined at 600° C. The relationship molar acid ethylene glycol/citric/metals was 3/14/1, respectively. The molar relations of Sn/Sb(5%) and Sn/Gd(1%) were constants and Ru amount was variable: Sn/Ru(0, 0.25, 0.5, 0.75%). The obtained electrodes were characterized by X-ray, microscopy electron scanning (SEM), photoelectron spectroscopy (XPS). The electrochemical characterization of electrodes was carried out by cyclic voltammetry, determination of Tafel slope with respect to the oxygen evolution reaction, the roughness factor and accelerated life tests. The electrocatalytic activity of electrodes was evaluated with respect to the electrooxidation of a phenol solution (100 ppm) to constant current (60 mA). The phenol solution was analyzed during the electrolysis by UV-Vis spectroscopy, liquid chromatography high efficiency (HPLC) and total organic carbon (TOC).The results indicate that the incorporation of Ru in the system Ti/SnO2-Sb-Gd, induces changes in crystallinity and morphology of the material, also modifies the antimony content and the oxygen content in the SnO2 network on the surface of the film. The percentages of Sb+5 were much higher on the surface for Sn/Ru(0.25%) in comparison to others electrode materials. The presence of Ru slightly modifies the potential onset of the oxygen evolution reaction (OER). Therefore, with regard to the system Ti/SnO2-Sb(5%)-Gd(1%), the addition of small amounts of Ru does not produce a substantial effect on variation in phenol degradation and TOC removal as shown in Fig. 1, in addition, the presence of Ru increases the life time of the electrodes. ReferencesYuan Liu, Huiling Liu, Jun Ma and Junjing Li. J. of Hazardous Materials. 213– 214 (2012), 222– 229.Yu-Hong Cui, Yu-Jie Feng, Zheng-Qian Liua, Electrochimica Acta. 54 (2009), 4903-4909.R. Berenguer, C. Quijada, E. Morallon. Electrochimica Acta. 54 (2009), 5230–5238Christos Comninellis and G. Chen (eds.). Electrochemistry for the Environment, chapter 2. 2010, Springer.M.P. Pechini, US Patent 3330697, 1967.

Nanoscale Solid-State Separator/Electrolyte for3D All-Solid-State Batteries

Nanoscale Solid-State Separator/Electrolyte for3D All-Solid-State Batteries

Synthesis of SnO2-Sb(5%)-Gd(2%) Anodes at Different Calcination Temperatures and Its Effect On Phenol Electrooxidation Process

Ti/SnO2-Sb(5%)-Gd(2%) anodes were synthesized by the Pechini method with different calcination temperatures (specifically, 500, 600 or 700°C). The anodes obtained were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and cyclic voltammetry (CV). The electrocatalytic property of the anodes as a function of the calcination temperature was evaluated by assessing the electrooxidation of phenol at a constant potential. The phenol degradation was followed by UV-Vis spectroscopy in relation to the time of electrolysis. The results show that the applied calcination temperatures induce variations in the morphology (the surface roughness), the Tafel slope for the oxygen evolution reaction and the electrocatalytic activity of the examined anodes. In particular, Ti/SnO2-Sb(5%)-Gd(2%) anodes that were calcined at temperatures below 700°C are more effective for the degradation of phenol, whereas calcination temperature of 700°C produce anodes with low performance for the removal of phenol.

Direct electrochemistry of Penicillium chrysogenum catalase adsorbed on spectroscopic graphite

The voltammetric studies of Penicillium chrysogenum catalase (PcCAT) adsorbed on spectroscopic graphite, showed direct electron transfer (DET) between its active site and the electrode surface. Analogous tests performed with the commercially available bovine catalase revealed that mammalian enzyme is much less efficient in the DET process. Both catalases were found capable to catalyse the electrooxidation of phenol, but differed in the specifics of catalytic action. At an applied potential of 0.45V the non-linear regression showed the kinetics of the bioelectrochemical oxidation catalysed by the PcCAT obeyed the Hill equation with a binding constant K=0.034±0.002M2 (Hill's coefficient n=2.097±0.083, R2=0.997), whilst the catalytic action of the bovine catalase was described by the Michaelis–Menten kinetic model with the following parameters: Vmax,app=7.780±0.509μA, and KM,app=0.068±0.070molL−1. The performance of the electrode reaction was affected by the electrode potential, the pH, and temperature. Based on the effect of pH and temperature on the electrode response in presence of phenol a tentative reaction pathway of its bioelectrocatalytic oxidation has been hypothesised. The possible application of these findings in biosensing phenol up to concentration 30mM at pHs below 7 and in absence of oxidising agents (oxygen or H2O2) was considered.

Phenol electrooxidation on Fe–Co 3O 4 thin film electrodes in alkaline medium

Fe–Co 3O 4 thin film with different amounts of Fe have been used for the electro-oxidation of phenol in alkaline medium at room temperature. The electrodes were prepared by coating stainless steel supports with successive layers of the oxides, obtained by thermal decomposition at 673 K. The electrolysis was carried out at constant potential and the phenol disappearance, during the electrolysis, was monitored by UV–Vis absorbance measurements between 250 and 500 nm. After 3 h of electrolysis, the intermediates were identified by comparing the HPLC data and UV–Vis spectra to those from pure standards. The results indicate that the same oxidation products are formed on the different prepared electrodes, namely the decomposition products of phenol such as benzoquinone, hydroquinone and cathecol in basic medium. Simulated results show clearly the decrease of the amount of phenolic species with the electrolysis time. An enhancement of the phenol removal is observed with the presence of iron in the oxide. Under the operating conditions, around 30% of the initial phenol has been removed at ca. 3 h and the complete degradation is obtained after 54 h of electrolysis, when Fe–Co 3O 4 thin film with 10% of Fe is used as anode.

Phenol determination on HDTMA-bentonite-based electrodes

The partial and complete substitution of cations in the interlayer region of clay with different amounts of hexadecyl trimethylammonium bromide (HDTMABr) was performed. The aim was to synthesize organo-bentonites to be used as constituents of porous electrodes for the electrooxidation of phenol. Domestic clay from Bogovina was subjected to a common procedure of the production of organo-bentonites. It included the following steps: grinding, sieving, Na-exchange, cation exchange and drying. The samples were characterized by X-ray diffraction (XRD) analysis, while the textural properties were evaluated by nitrogen physisorption. The multisweep cyclic voltammetry was applied to analyze the behavior of the clay modified glassy carbon electrode. The influences of the surfactant loading and pH of the support electrolyte were investigated. Rapid deactivation of electrodes occurred in an acidic environment, while good stability of the investigated electrodes was obtained in alkaline medium.

Electrooxidation of Phenol on a Ti/RuO2 anode: effect of some electrolysis parameters

The influences of electrolysis time, anodic area, current density and supporting electrolyte on phenol and its byproducts degradation on a Ti/RuO2 anode were investigated. It was observed that phenol and its byproducts were rapidly broken down in the presence of chloride ions. Gas chromatography/mass spectrometry (GC/MS) data have shown that the presence of chloride ions lead to chlorophenols formation, due to reactions with Cl2 and/or OCl¯ generated during electrolysis. However, these intermediate products were also degraded later by the oxidizing agents. The standards established by the CONAMA (Brazilian National Council for the Environment) for phenols and chlorophenols in effluents were achieved after 360 min of electrolysis with a current density of 10 mA cm-2. Cyclic voltammograms obtained with the anodes before and after 436 h of electrolysis under severe salinity conditions (2 mol L-1) and current density (800 mA cm-2) showed that Ti/RuO2 did not lose its electrocatalytic properties. This fact indicates that Ti/RuO2 can be used for the treatment of effluents containing phenols in a chloride environment

Electrooxidation of phenol on different organo bentonite-based electrodes

Bentonite was modified by the exchange of inorganic cations with hexadecyl trimethylammonium, dodecyl trimethylammonium or tetramethylammonium cation. The obtained materials were characterized by physisorption of nitrogen and X-ray diffraction analysis. Multisweep cyclic voltammetry was applied to analyze phenol response on different organo bentonite-based electrodes. The aim of the investigation was to determine the influence of the type of modifying agent on the electrochemical performance of the investigated electrodes. All electrodes exhibited similar electrochemical behavior but with different intensities of the electrochemical response and Tafel slopes. The difference in Tafel slopes reflected different level of involvement of pores in the phenol electrooxidation.

Behavior of a Ti/RuO 2 anode in concentrated chloride medium for phenol and their chlorinated intermediates electrooxidation

The electrooxidation of phenol and its intermediate compounds in concentrated sodium chloride solutions on a Ti/RuO 2 anode was studied with electrochemical techniques allied to UV–vis spectrometry, Gas Chromatography/Mass Spectroscopy (GC/MS) and chemical oxygen demand (COD) analysis. Results have shown that although the increase of chloride ion concentration favors initially the chlorophenols formation, it also favors both the phenol and chlorophenols degradation through an indirect oxidation mechanism. Increasing amounts of chloride ion led to a decrease in the specific energy consumption for both phenol and COD removal from solution. CG/MS analysis indicated that after a 30-min electrolysis in the presence of 20 g L −1 NaCl, with a current density of 10 mA cm −2, the treated solution contained less than 0.002% of the initial phenol concentration (100 mg L −1). A substantial reduction in the chlorophenols concentration was also achieved under the same electrolysis conditions.

Mixed pillared bentonite for electrooxidation of phenol

Bentonite was pillared with Al, Al-Cu, Al-Fe or Al-Co poly(hydroxo metal) cations for electrochemical oxidation of phenol in acidic solution. Multisweep cyclic voltammetry was applied to analyze the behavior of the bentonite modified glassy carbon electrode. The influence of pillaring on the electrocatalytic properties was investigated. Reactivation of the electrodes after prolonged phenol oxidation was performed by cathodisation at -2 V.