Guanidine sulfate-assisted synthesis of hexagonal WO3 nanoparticles with enhanced adsorption properties

Abstract

Large surface area hexagonal phase WO₃ (h-WO₃) nanowires were synthesized by a hydrothermal route with the assistance of C₂H₁₂N₆O₄S. They were characterized by XRD, SEM, TEM, BET, FT-IR and XPS. It is shown that C₂H₁₂N₆O₄S not only acts as a stabilizer to facilitate the generation of a metastable hexagonal phase, but also functions as a structure directing agent to assist the construction of nanowires. The obtained h-WO₃ possesses a large specific surface area and numerous adsorption functional groups such as –OH groups. These characteristics result in an excellent adsorption performance for the removal of strontium from acidic aqueous solutions. A maximum adsorption capacity of 52.93 mg g⁻¹ was achieved on the h-WO₃ prepared in the presence of C₂H₁₂N₆O₄S. This value is almost two times higher than that of bare h-WO₃ (no C₂H₁₂N₆O₄S). The effects of pH, contact time, initial Sr²⁺ concentration and ion strength on Sr²⁺ removal from the solution by h-WO₃ were systematically investigated. The adsorption mechanism involving the combination of electrostatic attraction and ion exchange for the adsorption of Sr²⁺ is proposed. Based on our results, h-WO₃ with high adsorption capacity and good surface characteristics exhibits great potential for the removal of Sr²⁺ from radioactive wastewater.