Removal of Phenol from Water in the Presence of NaCl in Undivided Cells Equipped with Carbon Felt or Ni Cathodes: Effect of Air Pressure

Abstract

Recently, the electrochemical treatment of wastewater polluted by recalcitrant organics and containing chlorides was shown to be significantly improved adopting proper operative conditions such as suitable anodes and cathodes and low current density. In particular, the use of suitable cathodes such as carbon felt or silver could increase the removal of TOC and reduce the formation of chlorinated by-products. In this study, attention was focused on the utilization of carbon felt cathodes with the main aim to evaluate the effect of air pressure on the process using phenol as model organic pollutant. It was shown that, in the presence of carbon felt cathode, the use of pressurized air allows both to increase the removal of TOC and to reduce the formation of chlorate. Moreover, the effect of the nature of the anode and of the presence of FeSO 4 , in order to study the involvement of electro-Fenton process, was evaluated.

Treatment of aqueous solutions of oxytetracycline by different electrochemical approaches: anodic oxidation, pressurized electro‐Fenton and oxidation by electrogenerated active chlorine

“…It recently has been shown that EF can strongly benefit from the utilization of pressurized air 17‐19,21‐23 and relatively low values of working potential and current density 18,19 . Hence, a series of electrolyses was carried out using a CF cathode, Ti/Ta 2 O 5 ‐IrO 2 anode, and different air pressures (1, 5 and 10 bar) and current densities (10 and 60 mA cm −2 ).…”

“…When the electrolysis was repeated with a pressure of 10 bar, a removal of TOC ≈38% was obtained. According to the literature, the remarkable effect of pressure on the performance of EF is due to the fact that a higher air pressure results in higher solubilities of oxygen, thus increasing the generation of H 2 O 2 and consequently that of hydroxyl radicals 17,19,21‐23 …”

“…Recently, it has been shown that the use of CF or Ag cathodes can the mineralization of organic pollutants and o decrease the generation of some byproducts. Carbon felt converts oxygen to H 2 O 2 [Eqn (3)] which can limit the formation of chlorate and perchlorate, as recently shown by the work of Rodrigo for the electrochemical treatment of urban treated wastewater 29 and by that of Scialdone for the remediation of an aqueous solution containing phenol 13,17 . Indeed, H 2 O 2 reacts with hypochlorite to give chloride [Eqn (21)], and with chlorate to yield the strong oxidant ClO 2 [Eqn (22)] 30 …”

“…The stirring rate was set at 400 rpm. Some EF experiments were performed with an undivided high‐pressure cell composed of AISI 316 stainless steel with a coaxial cylindrical geometry 17,18 . A borosilicate‐glass beaker was sited inside the reactor storing electrolyte.…”

“…Some EF experiments were performed with an undivided high-pressure cell composed of AISI 316 stainless steel with a coaxial cylindrical geometry. 17,18 A borosilicate-glass beaker was sited inside the reactor storing electrolyte. The upper part of the cell was equipped with a gas inlet, a vent, two electrical connections for the electrodes and a dip tube that allows extraction of liquid samples during the experiment.…”