Advanced oxidation phenomena in electrocoagulation process: a myth or a reality?

Abstract

A B S T R A C TThis review discusses the advanced oxidation process (AOP) phenomena in electrocoagulation (EC) process. AOPs have been broadly defined as near ambient temperature treatment processes based on highly reactive radicals, especially the hydroxyl radical ð Á OHÞ as the primary oxidant. In principle, as water-containing colloidal particulates, oils, or other contaminants move through the applied electric field, there may be ionisation, electrolysis, hydrolysis, and free-radical formation which may alter the physical and chemical properties of water and contaminants. Further, when the electrochemical reactors operate at a high cell potential and an anodic process occurs in the potential region of water discharge, hydroxyl radicals ð Á OHÞ are generated. In order to get more probabilities to have free radicals formation in EC, ultrasound during EC may be very useful as discussed by some authors. Further, EC process at pH less than 3 has more chance to produce hydroxyl radicals formation. Finally, this review concludes that there is no proof of the presence of AOP phenomena in EC process and more research is needed here focusing on free radicals formation.

Microalgae removal from Ghrib Dam (Ain Defla, Algeria) water by electroflotation using stainless steel electrodes

“…Moreover, Pt and boron-doped diamond (BDD) anodes are proved more convenient than other electrodes. Indeed, the great capability of a BDD anode to produce reactive oxygen species and other oxidising species during the electrolysis allows establishing a chlorine-free disinfection process [39]. Bergmann and Rollin [38] concluded that these electrochemical processes are very complex.…”

Influence of operating parameters on electrocoagulation of C.I. disperse yellow 3

“…The removal efficiency was directly dependent upon the metal concentration in solution [23][24][25]. The positive metallic species were produced by the Al anode neutralising the negative charges on the polluting molecules [26][27][28][29][30].…”

“…The species Fe(OH) n(s) formed (by the two mechanisms) remained in the aqueous phase in the form of gelatinous suspension which can then remove the pollutants from the water (Figure 13), either by complexation, or by electrostatic attraction, followed by coagulation and flotation or sedimentation [24,25,27,28]. [27,28].…”

“…Comparing the test results with aluminum electrodes (R = 98.96 %), we can say that iron is also effective in removing DY. The reactions involved in the EC using iron electrodes are as follows: The iron, after oxidation in the electrolytic system, produces iron hydroxide Fe(OH) n (s), with n = 2 or 3; and two mechanisms have been proposed [6,12,14,15,24,38] …”

Factors affecting the Faradaic efficiency of Fe(0) electrocoagulation

“…This technology is particularly applicable in decentralized and rural areas because of its low infrastructure requirements, ease of use and potential for scalability [1,2]. While EC systems are often accompanied by supplementary treatment steps, including settling tanks and filters [3], the technology centers on applying an electric current to Fe(0) electrodes in contact with an electrolyte solution to promote the oxidative release of soluble Fe(II) ions [4,5]. The Fe(II) ions migrate from the Fe(0) anode surface to the bulk solution, where contaminant removal occurs by several possible pathways.…”