Fe containing MoO3 nanowires grown along the [110] direction and their fast selective adsorption of quasi-phenothiazine dyes

Abstract

Herein, MoO₃ nanowires (Fe–MoO₃ NWs) along the [110] direction were successfully synthesized in the presence of Fe³⁺ cations. The Fe–MoO₃ NWs present a large specific surface area of 174.7 m² g⁻¹ and rich surface –OH groups, and the possible formation mechanism of such a structure is due to the adsorption of Fe³⁺ cations toward non-(110) planes of MoO₃ in solution with pH greater than its isoelectric point. The obtained Fe–MoO₃ NWs show excellent and highly selective adsorption capacity toward quasi-phenothiazine dyes (methylene blue, toluidine blue, azure I, and acridine orange). The dye removal rate could reach 99% in 3 min, and the maximum adsorption capacity is up to 144.3 mg g⁻¹ and the adsorption is up to 28.86 mg g⁻¹ per minute, which is 11 times greater than that of pure MoO₃ and far greater than that of the recently reported MoO₃ nanostructures. This excellent selective adsorption performance of Fe–MoO₃ NWs was mainly attributed to the enhanced chemical adsorption of quasi-phenothiazine dyes by rich surface –OH groups and Fe species through hydrogen bond and coordination bond adsorption with N and S, respectively, which was confirmed by adsorption isotherms and adsorption kinetics. These results suggest the potential application of Fe–MoO₃ NWs in the field of water pollution treatment.