Fabrication and characterization of hydrogen-treated tungsten oxide nanofibers for cationic dyes removal from water

The pollution of water resources by various pollutants is one of the most common challenges in all over the world, which attracts much research interest in wastewater purification. In this work, WO3 nanofibers have been used as an adsorbent for the removal of RhB molecules from aqueous solution. The nanofibers were synthesized by an electrospinning method, followed by a hydrogen annealing in the temperature of 350 degrees C to create oxygen vacancies within WO3. It is observed the hydrogen-treated WO3 nanofibers exhibit higher adsorption performance than untreated nanofibers. Our results show that the effect of hydrogen treatment on the crystal structure, morphology, and specific surface area of the nanofibers is negligible. However, the surface of hydrogen-treated WO3 nanofibers was more negatively charged due to the induced oxygen vacancies, which enhances the surface adsorption of cationic dye molecules due to the electrostatic interaction between WO3 nanofibers surface and RhB molecules. Also, the mechanism of dye adsorption on nanofibers was investigated. The results indicated that the adsorption kinetics and adsorption isotherm could be described by pseudo-second order and Langmuir models, respectively. Furthermore, the maximum equilibrium adsorption capacity of hydrogen-treated nanofibers as adsorbent for RhB was 312.5 mg/g, which is higher than the previously reported values.