Biosynthesis of α-MoO3 nanoparticles and its adsorption performance of cadmium from aqueous solutions

Ibrahem M A Hasan, Ahmed R Tawfik and Fawzy H Assaf

Abstract

Molybdenum (VI) oxide nanoparticles (α-MoO₃ NPs) were green synthesised using buckthorn leaf extract as the reducing and capping agents. The α-MoO₃ NPs were characterised by thermogravimetric analysis, fourier transforms infrared spectroscopy, X-ray diffraction, field emission scanning, and transmission electron microscopy, energy-dispersive x-ray spectroscopy, and Brunauer–Emmett–Teller surface area analysis. The analyses showed the formation of spherical-shaped α-MoO₃ NPs with ∼50 nm mean crystallite size, 3.825 m² g^-1 surface area, and 0.005 cm³ g^-1 total pore volume. The synthesised α-MoO₃ was then applied for adsorption of Cd (II) from aqueous solutions. Optimisation of various adsorption parameters resulted in complete Cd (II) removal under the conditions: 0.1 g α-MoO₃ dose, 60 min contact time, 50 mg l^-1 initial Cd (II) concentration, pH 7 and 298 K. The experimental results were further assessed using different kinetic, isotherm and thermodynamic models. The data were best described by pseudo-second-order (R² = 0.992) and Langmuir (R² = 0.98) models with a maximum adsorption capacity of 57.5 mg g^-1 at optimum conditions. Thermodynamic results indicated that the adsorption process is feasible, spontaneous, and endothermic in nature. Moreover, upon regeneration and interference results, α-MoO₃ is stable and selective for Cd (II) adsorption in presence of other cations. Upon these results, the biosynthesised α-MoO₃ NPs can be used as a selective adsorbent for the efficient removal of Cd (II) from aqueous media.