Electrochemically assisted coagulation for the removal of boron from water using zinc anode Original Research Article

The present work provides a critical study on the adsorption of boron by electrochemically generated zinc hydroxide. The various operating parameters on the removal efficiency of boron were investigated, such as initial pH, current density, electrode configuration, inter-electrode distance, co-existing ions and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm− 2, at pH of 7.0 with the energy consumption of 1.007 kWh m− 3. First- and second-order rate equations, Elovich and intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Zn(OH)2 were determined and correlated with isotherm equations such as Langmuir, Freundlich and D-R models. Thermodynamic parameters, such as standard Gibbʹs free energy (∆Go), standard enthalpy (∆Ho), and standard entropy (∆So), were also evaluated by Vanʹt Hoff equation. The adsorption process follows second-order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules for all current densities and concentration. The adsorption of boron onto Zn(OH)2 was found to be spontaneous and endothermic thermodynamically.