Catalytic reduction of methylene blue by sulfide ions in the presence of nanoAlMCM-41 material

This article reports the reduction of methylene blue (MB) by sulfide ions (S2−) in aqueous solution by a nanoAlMCM-41 catalyst. The results obtained showed that, under acidic conditions (pH=2) MB was reduced to the Leuco methylene blue (LMB) form by sulfide ions and by changing the pH between 2.0 and 7.0 a reduction of the MB dye to the MBH2+ form was observed. In alkaline media (pH=8), a reduction of methylene blue by sulfide ions to the MBH2+ form and demethylation of the dye was observed simultaneously. The demethylation of MB leads to a thionine dye product. Using nanoAlMCM-41 but with encapsulated CoS nanoparticles only causes demethylation of MB in aqueous solution.