Direct electrosynthesis and separation of ammonia and chlorine from waste streams via a stacked membrane-free electrolyzer

This paper presents a membrane-free flow electrolyzer for the paired electrocatalytic upcycling of nitrate (NO₃⁻) and chloride (Cl⁻) from waste streams into ammonia (NH₃) and chlorine (Cl₂) gases. The electrolyzer integrates electrosynthesis and gas separation, minimizing the NH₃-Cl₂ reaction and product loss. A three-module system efficiently processed reverse osmosis retentate, yielding high concentrations of (NH₄)₂SO₄ and NaClO at a low electrical cost. Residual pollutants met wastewater discharge regulations. The study highlights the value of pairing appropriate half-reactions, using waste streams as electrolytes, and merging synthesis with separation.

Jianan Gao, Qingquan Ma, Zhiwei Wang, Bruce E. Rittmann, Wen Zhang