Electronic Structure, Morphological Aspects, and Photocatalytic Discoloration of Three Organic Dyes with MgWO4 Powders Synthesized by the Complex Polymerization Method

Abstract

Heterogeneous photocatalytic (PC) degradation of organic dyes in aqueous solution with semiconductor oxides has been very effective in relation to conventional methods for the wastewater treatment. In this paper, MgWO4 powder was synthesized by the complex polymerization method and heat-treated at 900 °C for 2 h. Their structure, morphology and optical behavior were characterized by different techniques. First-principles quantum mechanical calculations based on the DFT in the B3LYP level was employed to obtain their electronic band structure (EBS) and density of state (DOS). Moreover, we have investigated the PC properties for the discoloration of three organic dyes. XRD patterns indicate that MgWO4 powders present a monoclinic structure. FE-SEM and TEM images showed that these powders are composed of several nanoparticles. UV–Vis spectrum displays an optical band gap of 4.33 eV, while EBS calculation showed a direct band gap value of 4.49 eV. DOS data revealed that the main orbitals involved in the electronic structure are O-2p orbitals in the valence band and W-5d orbitals in the conduction band. Finally, it was obtained the best PC activity of MgWO4 powders with discoloration of 84% for bromocresol green dye, while the discoloration for methyl orange and rhodamine B dyes were 56% and 29%, respectively. The electronic structure, morphology and photocatalytic properties of MgWO4 powders synthesized by complex polymerization method calcinated at 900 °C for 2 h have been explained for the first time.