Effect of cobalt complexes on cobalt oxide particles for the activation of peroxymonosulphate in textile wastewater treatment

Abstract

This study provides a comparison of the chloride and nitrate anions, water and alcohol solutions in the formation of cobalt complexes, and their efect on the cobalt hydroxide polymorph formed and the subsequent impact on the catalytic performance of the resulting cobalt oxide. The formation of α- and β-cobalt hydroxide polymorphs as precursors to Co3O4 nanoparticles depended on the cobalt complex formed. In water only, the role of the anion on the phase of hydroxide polymorph is negligible. Annealed Co3O4 nanoparticles derived from the solvothermal synthesis of β-cobalt hydroxide using cobalt chloride hexahydrate dissolved in 100% alcohol performed better in sulphate radical-advanced oxidation of methylene blue than annealed Co3O4 particles derived from the hydro/solvothermal synthesis of α-cobalt hydroxide using cobalt nitrate hexahydrate dissolved in 50% alcohol. However, when impurities exist in samples produced from nitrate precursor salts, the performance of the α-cobalt hydroxide-derived Co3O4 noticeably improves. This study shows, for the frst time, the relationship between the cobalt hydroxide polymorph and the catalytic performance of the resulting Co3O4