<scp>NO_<i>x</i></scp> removal from simulated marine exhaust gas via wet absorption using <scp>TBAB</scp>/<scp>PBS</scp> composite solution and subsequent reduction by adding <scp>Na₂SO₃</scp>

Abstract With the aim to develop wet denitration process for marine application, it is still challenging to simultaneously achieve high‐efficiency NO x removal from flue gas and low nitrate concentration in scrubbed solution. Herein a novel two‐step method was proposed to solve this issue: phosphate buffer solution (PBS) with organic additive was used to absorb NO x efficiently from flue gas, and in next step, Na 2 SO 3 as a reductant was added in the scrubbed solution to reduce NO x off‐line. Five typical organic additives were chosen to compose with PBS. The tetrabutylammonium bromide and phosphate buffer solution (TBAB/PBS) composite solution exhibited superior NO x absorption performance. Furthermore, the effects of TBAB concentration, NO x oxidation degree, solution pH, temperature and O 2 concentration on NO x absorption performance of TBAB/PBS composite solution were investigated systematically, and a high NO x absorption efficiency of &gt;90% could be achieved. It was mainly attributed to a physical complex between PBS and NO 2 , , , together with a mass transfer enhancement by TBAB. A long‐run test showed that nitrate concentration was much lower than the limit value of IMO. Cyclic absorption and regeneration tests confirmed that Na 2 SO 3 could effectively regenerate the scrubbed solution in the absence of O 2 .