Electrochemical removal of boron from produced water and recovery

Abstract

This study investigated boron removal from produced water by electrocoagulation using iron electrode and subsequent recovery by hydrothermal mineralization. Batch preliminary experiments conducted with synthetic wastewater were designed using Box Behken Model of the Response Surface Methodology (RSM) to evaluate four independent variables (pH, current density, initial boron concentration and contact time). The optimum conditions obtained (pH 7, current density 12.5mA/cm2, contact time 90min) resulted in 98% boron removal from initial boron concentration of 10mg/L. The optimization process was achieved by RSM, Boron removal increased when current density and contact time were elevated. Removal efficiency also increased when pH was increased from 4 to 7 and subsequently decreased at pH 10. Boron removal from produced water reached 97.6% at applied optimum conditions. Adsorption kinetics were evaluated using the Pseudo First and Second order models, Elovich and Intraparticle diffusion models. Kinetic data fitted best to Pseudo Second order kinetic model. Thermodynamics were investigated and signifies that boron adsorption was exothermic with decreasing negative values of the free energies indicating reaction spontaneity. The hydrothermal mineralization study showed that rare hydrated borate minerals (Inyoite, Parasirbiskite and Vimsite) can be recovered as recyclable precipitate from EC flocs of produced water.