Electrochemical oxidation of organic pollutants for the wastewater treatment: direct and indirect processes

Abstract

In recent years, there has been increasing interest in finding innovative solutions for the efficient removal of contaminants from water, soil and air. The present tutorial review summarizes the results of an extensive selection of papers dealing with electrochemical oxidation, which is proposed as an alternative for treating polluted wastes. Both the direct and indirect approaches are considered, and the role of electrode materials is discussed together with that of other experimental parameters. Apart from discussing the possibility of removing selected contaminants from water using different anodes, efficiency rates for pollutant removal have been collected, the dependence of these rates on operational conditions advantages and disadvantages determining the further full-scale commercial application.

Electrodeposited lead dioxide coatings

“…111,[203][204][205][206] It is widely believed that complete mineralisation occurs by mechanisms dominated by oxygen transfer and adsorbed or free OH radicals rather than direct electron transfer from the organics to the anode. 71,207,208 This requires anodes that are stable at very positive potentials; lead dioxide and B-doped diamond have proved the most suitable materials.…”

Conductive diamond electrodes for water purification

“…The principal aim is complete oxidation of organics to CO 2 or the conversion of toxic organics to biocompatible compounds 28 . These films represents an efficient anode material for the degradation of refractory or priority pollutants such as ammonia, cyanide, phenol, chlorophenols, aniline, various dyes, surfactants, alcohols and many other compounds 28 . Unlike PbO 2 , SnO 2 and TiO 2 , the BDD thin films deposited on Si, Ta, Nb and W by CVD have shown excellent electrochemical stability 8 .…”

“…Unlike PbO 2 , SnO 2 and TiO 2 , the BDD thin films deposited on Si, Ta, Nb and W by CVD have shown excellent electrochemical stability 8 . However, the application of BDD electrodes for wastewater treatment has been mostly studied with Si-supported devices (Figure 2), in spite of the difficulties related to their industrial application, due to the fragility and the relatively low conductivity of the Si substrate 28 .…”

A Kinetic Study of Oxalic Acid Electrochemical Oxidation on a Manganese Dioxide Rotating Cylinder Anode

“…The reaction is usually carried out at room temperature and at a normal pressure [3]. Several anodic materials have been tested, but most of them presented substantial disadvantages, such as rapid loss of activity (graphite), high cost (Si-borondoped diamond (BDD)), release of toxic ions (PbO2), limited service life (SnO2) and an incomplete oxidation (IrO2) [4,5]. Therefore, a considerable effort is devoted to investigate cheaper anode materials with comparable performances, to be used in the treatment of wastewater containing organic compounds.…”

“…In the electrochemical process, pollutants are destroyed by either a direct or indirect oxidation process. It has been generally observed that the direct oxidation of organic compounds at the electrode surface is very difficult, and that the rate of reaction is too slow [4,16]. Bonfatti et al [16] showed that OA electrochemical oxidation could be carried out with higher current efficiency at Pt, in the presence of suitable amounts of NaCl.…”