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Electrochemical oxidation of phenol using a Ti/TiO 2 -RuO 2 -IrO 2 anode in the presence of chloride as the supporting electrolyte was investigated. The experiments were performed in an undivided batch reactor. Preliminary investigations showed that only a small fraction of phenol was oxidized by direct electrolysis, while complete degradation of phenol was achieved by indirect electrochemical oxidation using chloride as a supporting electrolyte. The effect of operating parameters such as initial pH, supporting electrolyte concentration, phenol concentration, and charge input was studied using Box-Behnken second order composite experimental design. The effect of current density on COD removal was studied separately. TOC removal and AOX formation were studied for selected conditions. It was found that the formation of chlorinated organic compounds was pronounced at the beginning of electrolysis, but it was reduced to lower levels by extended electrolysis.

This paper presents the results of the electrochemical degradation of cresols for wastewater treatment. The experiments were performed in an electrochemical undivided cell reactor using a Ti/TiO2−RuO2−IrO2 anode. Preliminary experiments were conducted using sodium chloride and sodium sulfate as supporting electrolytes to study the effects on the removal of chemical oxygen demand (COD). Operating variables such as the initial pH, chloride concentration, initial cresol concentration, charge input, and current densities were studied using chloride as the supporting electrolyte for maximum degradation. The current efficiency and energy consumption during the degradation were calculated. The present investigation showed the formation of a higher concentration of adsorbable organic halides at the beginning of electrolysis, but this decreased to lower levels during prolonged electrolysis. The total organic carbon removal values were between 50 and 60% though maximum COD removal values were achieved.

Electrochemical degradation of mixed phenolic compounds present in coal conversion wastewater was investigated in the presence of chloride as supporting electrolyte. Initially, the degradation experiments were conducted separately with 300 mg/L of individual phenolic compound in the presence of 2500 mg/L chloride using Ti/TiO 2 -RuO 2 -IrO 2 anode at 5.4 A/dm 2 current density. Comparison of the experimental results of the chemical oxygen demand (COD) removal versus charge indicated that the order of decreasing COD removal for various phenolic compounds as catechol > resorcinol > m-cresol > o-cresol > phenol > p-cresol. Degradation of the mixture of phenolic compounds and highpressure liquid chromatography (HPLC) determinations at various stages of electrolysis showed that phenolic compounds were initially converted into benzoquinone and then to lower molecular weight aliphatic compounds. The COD and the total organic carbon (TOC) removal were 83 and 58.9% after passing 32 Ah/L with energy consumption of 191.6 kWh/kg of COD removal. Experiments were also conducted to remove adsorbable organic halogens (AOX) content in the treated solution using granular activated carbon. The optimum conditions for the removal of AOX was at pH 3.0, 5 mL/min flow rate and 31.2 cm bed height. Based on the investigation, a general scheme of treatment of mixed phenolic compounds by combined electrochemical and activated carbon adsorption treatment is proposed.Résumé : La dégradation électrochimique des composés phénoliques mixtes présents dans les eaux usées de conversion du charbon a été étudiée en présence de chlorure comme électrolyte support. Au début, les expériences de dégradation étaient effectuées séparément avec 300 mg/L de composés phénolique individuels en présence de 2500 mg/L de chlorure en utilisant une anode en Ti/TiO 2 -RuO 2 -IrO 2 à une densité de courant de 5,4 A/dm 2 . La comparaison des résultats expérimentaux de l'élimination de la DCO par rapport à la charge a indiqué que l'ordre de l'élimination décroissant de la DCO pour les divers composés phénoliques était catéchol > résorcinol > m-crésol > o-crésol > phénol > p-crésol. La dégradation du mélange de composés phénoliques et les déterminations par CLHP à diverses étapes de l'électrolyse ont montré que les composés phénoliques étaient au départ convertis en benzoquinone, puis en des composés aliphatiques de poids moléculaire moindre. L'élimination de la DCO et du COT était de 83 % et de 58,9 % après avoir passé 32 Ah/L avec une consommation d'énergie de 191,6 kWh/kg de DCO éliminée. Des expériences ont également été effectuées afin d'éliminer le contenu en composés organiques halogénés adsorbables (COHA) dans la solution traitée en utilisant du carbone granulaire actif. Un pH de 3,0, un débit de 0,5 mL/min et une hauteur de lit de 31,2 cm constituaient les conditions optimales pour l'élimination des COHA. Un schéma général de traitement des composés phénoliques mixtes grâce à une combinaison de traitement électrochimique et d'adsorption sur carbone actif est pro...

Electrochemical oxidation of resorcinol for wastewater treatment in the presence of chloride was investigated. Titanium Substrate Insoluble Anode (TSIA) coated with TiO2-RuO2-IrO2 was used as an anode and graphite carbon sheet was used as a cathode. The extent of resorcinol electrochemical oxidation was determined in terms of COD removal. The Box-Behnken second order composite design was used to study the effect of operating parameters such as initial pH, chloride concentration, initial concentration of resorcinol and charge input. The experimental values were in good correlation with predicted values, and the correlation coefficient was found to be good. The effect of current density on resorcinol oxidation, the AOX level during the electrochemical treatment and TOC removal were also studied for selected conditions. It has been observed that the extended electrolysis brings down the AOX concentration to lower levels. The maximum current efficiency was observed at higher resorcinol concentration, higher chloride concentration and increasing current density.

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