Electrochemical Dechlorination of 2-Chlorophenol on Pd/Ti, Ni/Ti and Pd-Ni Alloy/Ti Electrodes

Abstract

The 2-chlorophenol has been treated by advanced oxidation processes (AOPs) and by electrochemical oxidation, but these methods show several disadvantages, such as: high-energy costs, hazardous substances production and electrode deactivation. To avoid the problems caused by oxidation, electrochemical reduction (dechlorination) was proposed as an alternative and promising method. Pd/Ti, Ni/Ti and Pd-Ni alloy/Ti cathodes were used for electrochemical dechlorination of 2-chlorophenol. The cathodes were prepared by electrodeposition under experimental conditions determined from both a thermodynamic study by using predominance existence and distribution species diagrams and a voltammetric study. The electrodes were characterized by SEM, XRD, and XPS. SEM images showed that Pd-Ni/Ti electrode has a different morphology from that of Pd/Ti and Ni/Ti electrodes and the alloy composition is 45% Pd and 49% Ni mol. XRD analyses showed that Pd-Ni alloy /Ti exhibits a network parameter different from those of Pd/Ti and Ni/Ti electrodes. The XPS proved the formation of Pd-Ni alloy. The efficient dechlorination of 2-chlorophenol to phenol was achieved under electrochemical conditions where proton reduction and atomic hydrogen adsorption took place. The Pd-Ni alloy/Ti electrode had the highest dechlorination efficiency (100% removal) and phenol formation (100% formation) at a potential of −0.40 Vvs Ag/AgCl (s) /KCl (sat) .

S-Scheme 2D/2D Heterojunction of ZnTiO3 Nanosheets/Bi2WO6 Nanosheets with Enhanced Photoelectrocatalytic Activity for Phenol Wastewater under Visible Light

“…According to Figure 6c-h, based on the photocatalytic experiments on p-nitrophenol, p-chlorophenol, and p-methylphenol, we found that the degradation efficiency of the photoelectrocatalyst for the methoxy electron-donating group was higher than that for the nitro electronwithdrawing group. This was because the electron-withdrawing groups such as nitro and chlorine groups could form conjugated and stable electrons with a benzene ring and the structure was stronger, and the hyperconjugation effect of electron donating groups caused the benzene ring to become strongly activated and easily reactive, so the characteristic group was easy to separate from the benzene ring, and the strong oxidizing group was more likely to attack the benzene ring and degrade phenols [37][38][39]. In addition, the most easily oxidized site for phenol and its derivatives was located at the ortho position to the phenolic hydroxyl group.…”

Understanding Electrocatalytic Hydrodechlorination of Chlorophenols on Palladium-Modified Cathode in Aqueous Solution

“…4,5 It can be represented as the exchange of chemisorbed hydrogen atoms ( H ads ), which are generated on the electrode surface by the electrolysis of water or hydrogen ions with chlorine atoms. 6−10…”

“…The selective removal of chlorine atoms can reduce their toxicity, which makes further treatment convenient and economical. Electrocatalytic hydrodechlorination (ECH), an efficient method, has been employed in recent research due to its rapid reaction rate, mild reaction conditions, and the absence of secondary contaminants. , It can be represented as the exchange of chemisorbed hydrogen atoms ( H ads ), which are generated on the electrode surface by the electrolysis of water or hydrogen ions with chlorine atoms. − …”

Computational Modeling of 2-Monochlorophenol and 2-Monochlorothiophenol

“…The sources of 2-monochlorophenol pollution are wastewaters from pesticide, solvent pharmaceutics, paint and paper and pulp industries as well as water disinfecting processes (Joseph et al, 2012;Muneer et al, 2012). 2-MCP is toxic, poorly biodegradable and recalcitrant and has been classified as priority pollutant by United States protection agency (USEPA) (Ajeel et al, 2015;Gonzalez et al, 2015). It imposes hazardous health effects towards humans and animals (Daraei & Kamali, 2014).…”