Electrochemical Oxidation Characteristics of p-Substituted Phenols Using a Boron-Doped Diamond Electrode

Abstract

Electrochemical oxidation of some p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) with electron-donating and -withdrawing substituents was studied to reveal the relationship between the structure and the electrochemical reactivity of p-substituted phenols using a boron-doped diamond electrode by voltammetry and bulk electrolysis. Voltammetric study shows that the oxidation peak potentials of p-substituted phenols become more positive with an increase of Hammett's constants, that is, the direct electrochemical oxidation of p-substituted phenol with an electron-withdrawing group is more difficult than that of p-substituted phenol with an electron-donating group. However,the p-substituted phenols with electron-withdrawing groups are degraded faster than those with electron-donating groups in bulk electrolysis, which is opposite to the result obtained on the Pt electrode. These results indicate that the p-substituted phenols are mainly degraded by indirect electrochemical oxidation with hydroxyl radicals on a boron-doped diamond electrode. Under the attack of hydroxyl radicals, the release of p-substituted groups from the aromatic ring is the rate-limiting step. Since electron-withdrawing groups are easy to be released, the p-substituted phenols with these groups are degraded faster than those with electron-donating groups. Therefore, the degradation rates of the p-substituted phenols rise with an increase of Hammett's constants.

New Determination Scheme of p‐Aminophenol by MnO2 Modified Electrode Coupled with Flow Injection Analysis

“…[3]. The PAP or PAP derivate compounds are common pollutants in effluents from cooking oil refineries, production of pesticides and herbicides, dyes and textiles, pharmaceuticals, pulp and paper, plastics, and detergent [4], because they are extremely toxic to aquatic life and impart a strong disagreeable taste to water [5]. Several researches have reported different PAP determination schemes including high performance chromatography (HPLC), capillary electrophoresis (CE) [6 -10], optical chemical sensors [11,12] and electrochemical sensor [13 -15].…”

Sonoelectrochemistry in Environmental Applications

“…From a vast variety of materials used as anodes for pollutant degradation, the BDD electrode has received much attention due to its excellent properties such as its wide electrochemical window, high oxygen overpotential, low background currents, and high anodic stability [33,34], and BDD has therefore been used for the efficient degradation of phenolic derivatives in ECT experiments [35][36][37]. BDD electrode performance has been compared with platinum for the electrochemical oxidation of phenol under silent and ultrasonic conditions (30 kHz, 50 W ultrasonic horn), from the viewpoints of both fundamental and applied aspects [38].…”

Enhanced electrochemical treatment of phenolic pollutants by an effective adsorption and release process

“…Under the attack of hydroxyl radicals, the release of psubstituted groups [3,47] from the aromatic ring is the rate-limiting step. Since electron-withdrawing groups are easily released, the p-substituted phenols with these groups are degraded faster than those with electron-donating groups [1]. In addition, the electrondonating groups increase the electron density of the aromatic ring, thus enhancing its stability and, consequently, strongly retarding the oxidation process [48].…”

“…Phenolic compounds are a group of common organic pollutants existing in the effluents of coking, oil refineries, production of pesticides and herbicides, dyes and textiles, pharmaceuticals, pulp and paper, plastics, and detergent [1][2][3]. Due to the wide prevalence of phenolic compounds in different wastewaters and their high toxicity, high oxygen demand and low biodegradability, it is essential to remove them before the discharging of wastewater into water bodies [4][5][6][7].…”

“…Due to the wide prevalence of phenolic compounds in different wastewaters and their high toxicity, high oxygen demand and low biodegradability, it is essential to remove them before the discharging of wastewater into water bodies [4][5][6][7]. Various methods such as adsorption [7,8], extraction with solvents [9], membrane separation [10], and advanced oxidation processes including Fenton oxidation, ozonation, wet air oxidation, photocatalytic oxidation and electrochemical oxidation have been widely studied for the treatment of the wastewater containing phenolic compounds [1,11]. Among them, adsorption technology is currently being used extensively for the removal of phenolic compounds from aqueous solutions [4,12] and electrochemical oxidation is becoming one of the most promising techniques for the degradation of phenolic compounds in wastewater [13][14][15].…”