title: Implication of diffusion and significance of anodic pH in nitrogen-recovering microbial electrochemical cells.
abstract: Microbial electrochemical cells (MXCs) using cation and anion exchange membranes (CEM and AEM) were tested in batch mode for ammonium recovery. Experimental results showed superior ammonium recovery of 61% in CEM-MXC. Migration effect accounted for 61% of the total ammonium recovery in CEM-MXC where other ammonium ions (39%) were transferred by diffusion. Current density was significant for improving the recovery rate of ammonium nitrogen, but proton accumulation deteriorated current density in CEM-MXC. The dissolution of ammonia hydrolyzed by urea produces hydroxyl ions, which can neutralize protons in the anode and maintain high current density in CEM-MXC. However, anodic pH increased over 9 at high current density (>2A/m(2)) in CEM-MXC fed by urea, which indicates that the rate of ammonia dissolution becomes faster than proton accumulation rate at high current density. Balancing proton-accumulating rate with ammonia dissolution rate in the anode is significant for improving ammonium recovery in CEM-MXC.
authors.affiliation: Department of Environmental Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Sakineh
authors.initials: S
authors.lastname: Haddadi
authors.forename: Elsayed
authors.initials: E
authors.lastname: Elbeshbishy
authors.forename: Hyung-Sool
authors.initials: HS
authors.lastname: Lee
mesh_terms: D064751:Ammonium Compounds / Q000737:chemistry; D001674:Bioelectric Energy Sources; D004058:Diffusion; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000302:isolation & purification*
chemical_list: D064751:Ammonium Compounds; D009584:Nitrogen
keywords: Alkaline pH; Ammonium recovery; Ion exchange membrane; Microbial electrochemical cell; Migration