Use of cobalt(II) chelates of monothiol-containing ligands for the removal of nitric oxide

Highlights: • More than twenty chelates were investigated for wet denitration. • The use of cobalt-thiol complex solutions for NO removal was reported first time. • Co/Fe complexes of monothiol-containing ligands are effective for denitration. • Some side groups of ligands contribute to the denitration. -- Abstract: It is first reported herein that cobalt(II) complexes solution of monothiol-containing multidentate ligands are used to remove low concentration of nitric oxide (NO). These chelating ligands are water-soluble amines, alcohols or acids which containing at least one -SH group, include those of cysteine, mercaptosuccinic acid, mercaptoethanesulfonate, mercaptopropionic acid and the like. These -SH compounds when coordinated with cobalt ions, forming complexes are very effective for NO removal. The results indicate that the side group (methyl, carboxyl, carboxymethyl) on α-carbon atom of ligands contribute to the denitration of the chelate solution, whereas the substituents on sulfur atom of ligands deactivate the complexation system. In addition, we have found that several monothiol compounds with simple molecule structure and low cost exhibit good performance in denitration, and some of cobalt thiol complexes are more valuable in removing NO than ferrous thiol complexes.