Increasing ammonia recovery from high-level ammonium wastewater via adding sodium sulfate to prevent nitrogen generation in the cathode

摘要

The high-level ammonium-nitrogen (NH_4~+ -N) is a contaminant for aqueous environment but a potential hydrogen fuel. This study investigated an approach of increasing ammonia recovery via adding sodium sulfate of 0-1.5 M to prevent from nitrogen generation. The results of experiment tests, electrochemical analysis and MD simulation demonstrated that the added Na_2SO_4 assisted ammonium transport inhibited nitrogen gas generation in a certain concentration range. In electric double layer (EDL), with Na_2SO_4 concentration increasing, both the migration velocities of NH_4~+ and Na~+ are accelerated for Na_2SO_4 of 0-0.25 M, whereas they are decelerated for concentrate Na_2SO_4 that 0.5 M). A thick layer formed by Na~+ that imposed a fierce competitive adsorption blocked the migration of NH_4~+ and the transportation of electrons. The decrease of electrons and the accumulation of water molecules caused the potential drop in the EDL. 0.25 M Na_2SO_4 was the optimal concentration from the aspect of ion transports. The results obtained in this study can allow the manipulation of EDI capacity optimization.