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

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 of2-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).