Ammonia removal from fertilizer plant effluents by a coupled electrostatic shielding based electrodialysis / electrodeionization process

Abstract

Electrically and ionically conducting graphite powder beds interposed between the anode and cathode inside an electrolytic setup are used as intermediate bipolar electrodes. The beds cause electric field discontinuity by eliminating the applied electric field locally within their mass and act as electrostatically shielded zones – ion and ionic current sinks and thus ion concentrating compartments, whereas the adjacent compartments become ion depleting compartments. The ion sinks were implemented in a coupled electrostatic shielding electrodialysis/electrodeionization process to remove ammonium nitrate from fertilizer plant wastewaters. The batch wise operated electrostatic shielding electrodialysis of a solution containing 1310 mg L-1 ammonium nitrate produced in 28 min at a current density of 15-30 A m-2 a concentrate ammonium nitrate solution which could be recycled to the fertilizer plant unit and a diluate containing 50 mg L-1 ammonium nitrate. The diluate was subsequently used as feed in the electrostatic shielding electrodeionization process to produce pure water of a NH4 + and NO3- ion concentration of less than 1 mg L-1 respectively with a flow rate of 5.51x10-4 dm3 s-1 and a current density of 50 A m-2.