Capacitive Membrane Stripping for Ammonia Recovery (CapAmm) from Dilute Wastewaters

Abstract

A novel cost-effective flow-electrode capacitive deionization unit combined with a hydrophobic gas-permeable hollow fiber membrane contactor (designated “CapAmm”) is described here and used for efficient recovery of ammonia from dilute synthetic wastewaters. During operation, ammonia migrates across a cation exchange membrane and selectively accumulates in the cathode chamber of a flow electrode followed by transformation to dissolved NH3 with subsequent stripping via a membrane contactor and recovery as ammonium sulfate. Our results demonstrate that the CapAmm process can achieve an ammonia removal efficiency of ∼90% and a recovery efficiency of ∼60%. At current densities of 5.8 and 11.5 A m–2 (normalized by the effective cation exchange membrane area) and a hydraulic retention time of 1.48 min, the energies required for ammonia recovery were 9.9 and 21.1 kWh (kg of N)−1, respectively, with these values being comparable with those of other similar electrochemical ammonia recovery systems. These findings ...