Effective destaining of methylene blue with low concentrations under visible light irradiation in the presence of Mg(OH)2

In this work, three types of Mg(OH)(2) nanomaterials with different morphologies (flower-like, plate-like and disklike) were synthesized and used for the decolorization of methylene blue (MB) with low concentrations. It turned out that the MB solution (10 mg/L) could be completely discolored within 2 h in the presence of flower-like Mg(OH)(2) under visible light irradiation. Further investigation showed that it was mainly the interface interaction between MB molecules and hydroxyl groups on Mg(OH)(2) surface that caused the decolorization of MB solution. The possible decolorization mechanism can be concluded to two steps. First, the MB molecules undergone a demethylation or methyl substitution process and converted into intermediate products owing to the existence of hydroxyl groups on the surface of Mg(OH)(2). Then, the intermediates were converted into other small molecule products via ring-opening reaction under visible light irradiation. This work provides a green, efficient and applicable method for treating MB wastewater with low concentrations.