Enhanced ammonia recovery from strong ammonia wastewater via a transmembrane electro-chemisorption system with authigenic acid and base

Abstract

A transmembrane electro-chemisorption system with authigenic acid and base was developed to enhance ammonia recovery from strong ammonia wastewater. The authigenic base from water electrolysis at the cathode could raise the wastewater pH, which transformed ammonium into free ammonia. Simultaneously, the authigenic acid from water electrolysis at the anode could adsorb free ammonia via transmembrane chemisorption. The recovered product was pure (NH4)2SO4, and two valued byproducts (pure H2 and pure O2) were obtained at the same time. Increasing applied voltage could promote the ammonia recovery. Keeping catholyte circulating flow or some headspace proportion in the cathode chamber was beneficial to the ammonia recovery. It took longer time for high influent NH4+-N concentration to achieve the same recovery efficiency with low influent NH4+-N concentration. Within the same operation time, the former could recover more amount of ammonia. Besides avoiding the addition of acid and base, the energy consumption of this system for ammonia recovery was low to 8.47 kWh/kg NH4+-N. Accordingly, the developed system showed good prospects in recovering ammonia from strong ammonia wastewater.