Indirect Electrochemical Oxidation of Phenol in the Presence of Chloride for Wastewater Treatment (original) (raw)
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Separation and Purification Technology, 2010
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.
Anodic oxidation of phenol on Ti/IrO2 electrode: Experimental studies
Catalysis Today, 2010
The electrochemical oxidation of acidic solutions of phenol on a Ti/IrO 2 anode has been investigated by cyclic voltammetry and bulk electrolysis in a single-compartment cell. In the potential region of oxygen evolution, anodic oxidation resulted in electrode passivation (as evidenced by voltammetric measurements) allegedly due to the formation of a polymeric film on its surface. Phenol degradation increased with increasing temperature in the range investigated 30-80 • C and it was affected by the addition of Cl − and Br − anions in the supporting electrolyte. Complete conversion of 10 mM phenol was achieved after 37 Ah L −1 of charge passed at 80 • C under galvanostatic conditions (50 mA cm −2 ) in absence of Cl − . In contrast only 10 Ah L −1 were needed in the presence of 35 mM Cl − . The presence of chloride can induce reactions involving chlorohydroxyl radicals and electrogenerated oxidants such as free chlorine. On the other hand, addition of Br − slightly inhibited degradation possibly due to bromide scavenging of electrogenerated active species. Phenol degradation proceeded through the formation of three dominant, aromatic intermediates, namely 1,4-benzoquinone, hydroquinone and pyrocatechol, while total oxidation to CO 2 was not significant unless harsh conditions (i.e. high temperatures and charges) were employed.
Anodic oxidation of phenol on Ti/IrO< sub> 2 electrode: Experimental studies
Catalysis Today, 2010
The electrochemical oxidation of acidic solutions of phenol on a Ti/IrO 2 anode has been investigated by cyclic voltammetry and bulk electrolysis in a single-compartment cell. In the potential region of oxygen evolution, anodic oxidation resulted in electrode passivation (as evidenced by voltammetric measurements) allegedly due to the formation of a polymeric film on its surface. Phenol degradation increased with increasing temperature in the range investigated 30-80 • C and it was affected by the addition of Cl − and Br − anions in the supporting electrolyte. Complete conversion of 10 mM phenol was achieved after 37 Ah L −1 of charge passed at 80 • C under galvanostatic conditions (50 mA cm −2 ) in absence of Cl − . In contrast only 10 Ah L −1 were needed in the presence of 35 mM Cl − . The presence of chloride can induce reactions involving chlorohydroxyl radicals and electrogenerated oxidants such as free chlorine. On the other hand, addition of Br − slightly inhibited degradation possibly due to bromide scavenging of electrogenerated active species. Phenol degradation proceeded through the formation of three dominant, aromatic intermediates, namely 1,4-benzoquinone, hydroquinone and pyrocatechol, while total oxidation to CO 2 was not significant unless harsh conditions (i.e. high temperatures and charges) were employed.
Journal of The Electrochemical Society, 2007
In this work, we investigated the elimination of phenol from aqueous acidic solutions by electrochemical oxidation at Ti/Ru 0.3 Pb ͑0.7−x͒ Ti x O y oxide electrodes. The process was studied by carrying cyclic voltammetry ͑CV͒ and electrolysis experiments in acidic media ͑HClO 4 0.1 mol L −1 ͒ as a function of the electrode composition. CV in the presence of phenol showed that the electrocatalytic response of the electrode increases with increasing the Pb content. Large phenol degradation was obtained with the introduction of PbO x. The Pb-free composition ͑Ti/Ru 0.3 Ti 0.7 O 2 ͒ led to the lowest performance for phenol degradation. Highpressure liquid chromatography and total organic carbon techniques were used in order to quantify electrode efficiency. The formation of benzoquinone as well as of some aliphatic acids was observed. Electrodes with nominal composition Ti/Ru 0.3 Pb 0.5 Ti 0.2 O 2 and Ti/Ru 0.3 Pb 0.7 O 2 provided optimum response for phenol oxidation at the end of the electrolysis investigation ͑5 h͒, with high yields of total organic-carbon reduction.
[2013] Electro-Catalytic Treatment of Phenols
The day-to-day human activities and industrial revolution have influenced the quality and quantity of available fresh water. Many industries like textile, refineries, chemical, plastic and food-processing plants produce wastewaters characterized by perceptible content of organics (e.g. phenolic compounds) with strong color. Electro catalytic treatment was carried out to treat phenolic effluent in a batch electrochemical reactor using commercially available RuO2 coated titanium and SS as anode and cathode respectively. The effect of current density, supporting electrolyte concentration, pH and effluent concentration on the removal efficiency was critically analyzed. The results verified by FTIR analysis indicate that electro catalytic treatment is significant in effective removal of phenol.
Electrochemical oxidation of aqueous phenol at a carbon black slurry electrode
Applied Catalysis A: General, 1996
The electrochemical oxidation of an aqueous phenol solution was studied via a novel process. Experiments were conducted by recirculating a slurry electrode made of the product to be treated (phenol) and a catalyst (carbon black) through a flow-by electrolyser with a vertical stack of perforated Ti/Pt electrodes. Both the capacity of high adsorption of organic compounds and gases and the conductivity properties of Carbon Black allowed the acceleration of the degradation. High pressure liquid chromatography (HPLC) analysis was used to follow phenol loss and the formation of by-products. Gas chromatography (GC) analysis revealed the presence of two gases: oxygen -electrogenerated by the oxidation of water-and carbon dioxide produced by both phenol and CB oxidation. Other experiments under nitrogen and oxygen flow were performed in a closed reactor cell and proved that oxygen generated by Ti/Pt electrodes is sufficient to obtain the full degradation of phenol. The effects of CB concentration (ranging from 0 to 4 g 1-1), of the nature of CB and of the applied current (from 0 to 20 A) were investigated. An increase of CB concentration and applied current was found to shift product distribution to favour the formation of carbon dioxide. A removal efficiency of 100% was obtained in a reaction time of 15 min under the following conditions: an initial phenol concentration of 1 mmol 1-~, 4 g 1-~ of CB, an applied current of 10 A, a flow rate of 10 ml s 1 and a temperature of 30°C.
Water Science & Technology, 2009
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 signifi...
The degradation of phenol derivates from wastewaters by electrochemical treatment
Water Pollution IX, 2008
A group of carbon-based electrodes, i.e., glassy-carbon (GC), boron doped diamond (BDD), expanded graphite-polystyrene composite (EG-PS), expanded graphite-epoxy composite (EG-Epoxy) and expanded graphite-carbon nanofiberepoxy composite (EG-CNF-Epoxy) electrodes were investigated for electrochemical degradation of 4-chlorophenol (4-CP). Based on the investigated electrochemical techniques, e.g., cyclic voltammetry (CV) and chronoamperometry (CA), the operation conditions and the electrode suitable for electrochemical oxidation of 4-CP were selected. In addition, multiple pulsed amperometry (MPA) was applied for the in-situ electrochemical cleaning of the electrode surface to improve the electrode efficiency. The BDD electrode exhibited the best features related to the 4-CP electrochemical degradation efficiency.