Adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) from water by in situ generated metal hydroxides using sacrificial anodes

This research paper deals with an evaluation of electrochemical coagulation process, where the metal hydroxides are generated in-situ, for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from water using different anode materials like iron, magnesium, zinc and aluminum with galvanized iron as the cathode. The optimization of different experimental parameters like current density, pH, temperature, and inter-electrode distance on the removal efficiency of 2,4-D was carried out. The results showed that the maximum removal efficiency of 91.0% was achieved with iron as anode at a current density of 0.10 A/dm(2) and pH of 7.0. The adsorption of 2,4-D preferably fitting the Langmuir adsorption isotherm. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the adsorption of 2,4-D on iron hydroxides was feasible, spontaneous and endothermic. In addition, the adsorption kinetic studies showed that the electrochemical coagulation process for adsorption of 2,4-D was best described using the second-order kinetic model at the various current densities. (C) 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.