Optimization of electrochemical dechlorination of trichloroethylene in reducing electrolytes

Abstract

Electrochemical dechlorination of trichloroethylene (TCE) in aqueous solution is investigated in a closed, liquid-recirculation system. The anodic reaction of cast iron generates ferrous species, creating a chemically reducing electrolyte (negative ORP value). The reduction of TCE on the cathode surface is enhanced under this reducing electrolyte because of the absence of electron competition. In the presence of the iron anode, the performances of different cathodes are compared in a recirculated electrolysis system. The copper foam shows superior capability for dechlorination of aqueous TCE. Electrolysis by cast iron anode and copper foam cathode is further optimized though a multivariable experimental design and analysis. The conductivity of the electrolyte is identified as an important factor for both final elimination efficiency (FEE) of TCE and specific energy consumption. The copper foam electrode exhibits high TCE elimination efficiency in a wide range of initial TCE concentration. Under coulostatic conditions, the optimal conditions to achieve the highest FEE are 9.525 mm thick copper foam electrode, 40 mA current and 0.042 mol L−1 Na2SO4. This novel electrolysis system is proposed to remediate groundwater contaminated by chlorinated organic solvents, or as an improved iron electrocoagulation process capable of treating the wastewater co-contaminated with chlorinated compounds.

Transient reactive transport model for physico-chemical transformation by electrochemical reactive barriers

“…Electrokinetic remediation is a valuable process for treatment of contaminated groundwater because of its environmental compatibility, versatility, energy efficiency, and low required maintenance [1–6]. The redox potential of the solution is altered during electrolysis, which can be manipulated to induce contaminant transformation and/or degradation reactions [7,8].…”

Electrochemical degradation of trichloroethylene in aqueous solution by bipolar graphite electrodes

“…Reduction via hydrodechlorination (HDC) is favorable degradation path for TCE from groundwater [23, 25, 26, 32–34]. HDC occurs via a reaction of chlorinate substance with atomic hydrogen that forms at the cathodes and is the main reduction mechanism at hydrogen formation potentials.…”

The influence of cathode material on electrochemical degradation of trichloroethylene in aqueous solution

“…Recently, electrochemically-induced reduction has gained interest for removal of COCs from groundwater (Li and Farrell, 2000; Petersen et al, 2007b; Mishra et al, 2008; Mao et al, 2011, 2012a, 2012b). Electrochemical reduction through hydrodechlorination (HDC) occurs at the cathode due to water electrolysis.…”

“…boron doped diamond) provide complete COCs transformation to CO 2 through reaction with hydroxyl radicals (Scialdone et al, 2010a; Randazzo et al, 2011). In mixed electrolyte systems, which are easier to implement and maintain in practice, the electrochemical degradation can be achieved by: a) reduction (Mao et al, 2011, 2012a; 2012b), b) oxidation via Fenton reaction (Yuan et al, 2012, 2013) or b) simultaneous oxidation and reduction with the selection of appropriate electrode materials (Gilbert and Sale, 2005; Scialdone et al, 2010a). When using an active anode, the presence of oxygen competes with the target contaminant for the reaction sites at the cathode and limits HDC and it can involve in creation of hydrogen peroxide and promote Fenton reaction.…”