Electrocoagulation treatment of reject brine effluent from Solvay process

Abstract

Solvay process is an efficient treatment technique for reject brine from desalination, where salinity is reduced by removing Na+ by adding NH3 . However, in this process large amounts of NH3 are consumed and Cl– ions are not affected. Electrocoagulation has been tested for removing Cl– and NH3 regeneration. When no current was applied, removal of the ions was insignificant. Applying a current density of 0.1167 A/cm2 increased the removal percentages of NH4+ and Cl– by 71.6% and 26.9%, respectively, which proved that the removal was due to electrocoagulation. It was found that the removal percentages and rates increased with increasing the current density and temperature but decreased as the initial ion concentration increased. Three-experiment design levels and response surface methodologies were used to model the system. A second-order polynomial model was developed and used to predict the optimum conditions, which were found to be at a 0.2 A/cm2 current density, 36.8°C temperature, and initial Cl− concentration of 7.4 × 103mg/L. The accuracy of the model was verified against an independent run, not used in the development of the model, and the error did not exceed 10% for both ions