Abstract
This paper describes a fundamental study on the conversion of ammonium sulfate to ammonia solution using bipolar-membrane electrodialysis. The electrodialyzer was composed of two electrode compartments and three compartments/unit, which were divided by three anion-exchange membranes and a bipolar membrane. The solutions including ammonium sulfate were circulated by chemical pumps through the compartments and reservoirs. When a voltage was supplied to the electrodialyzer, hydroxide ions were generated by the bipolar membrane, and partially moved to the anode side compartments through anion-exchange membranes, then sulfate ions were substituted with hydroxide ions. The concentration of generated ammonia solution was affected by the ammonium sulfate concentration in the raw solution. The solution pHs including ammonium hydroxide were explained using calculated values that considered the material balance of ammonium, dissociation of ammonia and water, and electroneutrality of ions in the solution.
