Arsenic Removal by Advanced Electrocoagulation Processes: The Role of Oxidants Generated and Kinetic Modeling

Abstract

Arsenic (As) is a naturally occurring element in the environment that poses significant risks to human health. Several treatment technologies have been successfully used in the treatment of As-contaminated waters. However, limited literature has explored advanced electrocoagulation (EC) processes for As removal. The present study evaluates the As removal performance of electrocoagulation, electrochemical peroxidation (ECP), and photo-assisted electrochemical peroxidation (PECP) technologies at circumneutral pH using electroactive iron electrodes. The influence of As speciation and the role of oxidants in As removal were investigated. We have identified the ECP process to be a promising alternative for the conventional EC with around 4-fold increase in arsenic removal capacity at a competitive cost of 0.0060 $/m3. Results also indicated that the rate of As(III) oxidation at the outset of electrochemical treatment dictates the extent of As removal. Both ECP and PECP processes reached greater than 96% As(III) conversion at 1 C/L and achieved 86% and 96% As removal at 5 C/L, respectively. Finally, the mechanism of As(III) oxidation was evaluated, and results showed that Fe(IV) is the intermediate oxidant generated in advanced EC processes, and the contribution of •OH brought by UV irradiation is insignificant.

Efficient and Rapid Combined Electrocoagulation–Filtration of Arsenic in Drinking Water

“…During the EC process, for the treatment of As, the dissolved form of As probably reacted with released ions Fe and Al in both electrode configurations and could have formed arsenate and/or arsenite that could have adsorbed and accumulated on the hydroxides of (Fe) and (Al) and residues [40]. Main anodic reactions with Fe or Al electrode: First, oxidation of Fe to ferrous ion occurs, and, depending on the anode potential, its subsequent oxidation to Fe ion may occur, as shown in the following equations [22,28,41,42]. With the Fe electrode configuration at the anode side of the EC system, the reactions (Equations ( 1)-( 6)) occurred to initi- Main anodic reactions with Fe or Al electrode: First, oxidation of Fe to ferrous ion occurs, and, depending on the anode potential, its subsequent oxidation to Fe ion may occur, as shown in the following equations [22,28,41,42].…”

“…Main anodic reactions with Fe or Al electrode: First, oxidation of Fe to ferrous ion occurs, and, depending on the anode potential, its subsequent oxidation to Fe ion may occur, as shown in the following equations [22,28,41,42]. With the Fe electrode configuration at the anode side of the EC system, the reactions (Equations ( 1)-( 6)) occurred to initi- Main anodic reactions with Fe or Al electrode: First, oxidation of Fe to ferrous ion occurs, and, depending on the anode potential, its subsequent oxidation to Fe ion may occur, as shown in the following equations [22,28,41,42]. With the Fe electrode configuration at the anode side of the EC system, the reactions (Equations ( 1)-( 6)) occurred to initiate the EC process and removal of As and other dissolved ionic, organic, inorganic and elemental species [22,43], as follows:…”

Electroprecipitation Mechanism Enabling Silica and Hardness Removal through Aluminum-Based Electrocoagulation

“…The removal of hardness through electrocoagulation has been proposed to occur through a coprecipitation reaction mechanism at the cathode. This coprecipitation reaction allows for the formation of Mg­(OH) 2 /MgCO 3 and CaCO 3 (pH > 10). , The aluminum polyhydroxide species can also facilitate hardness removal. , Previous studies of electrocoaglation have demonstrated that it can be used for organic contaminants, heavy metal removal, as well as fluoride removal. − …”