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

The high-level ammonium-nitrogen (NH₄⁺-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 Na₂SO₄ assisted ammonium transport inhibited nitrogen gas generation in a certain concentration range. In electric double layer (EDL), with Na₂SO₄ concentration increasing, both the migration velocities of NH₄⁺ and Na⁺ are accelerated for Na₂SO₄ of 0–0.25 M, whereas they are decelerated for concentrate Na₂SO₄ that 0.5 M). A thick layer formed by Na⁺ that imposed a fierce competitive adsorption blocked the migration of NH₄⁺ 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 Na₂SO₄ was the optimal concentration from the aspect of ion transports. The results obtained in this study can allow the manipulation of EDI capacity optimization.