Synthesis and characterizations of molybdenum-doped titanium dioxide nanoparticles for photocatalytic removal of chromium (VI) from aqueous solutions

Abstract

The photocatalytic removal of toxic heavy metals using titanium dioxide nanoparticles is an emerging technology for environmental remediation. Pure and Mo-doped TiO2 nanoparticles were synthesized using a modified sol-gel process, and then characterized by field emission scanning electron microscopy (FE-SEM) and particle size analysis (PSA) to determine their morphology and size, while X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) were used to determine their crystalline phase and composition. Brunauer–Emmett–Teller (BET) analysis was used to measure the surface area and porosity of the synthesized catalysts applying Langmuir and BET models. The catalyst was mainly composed of spherical anatase TiO2 particles, with a diameter in the range of 15–75 nm, and the maximum doping percentage of Mo was 3.3%. The Langmuir surface area of pure and Mo-doped TiO2was 91.63 and 128.73 m2/g, and the average pore volume was 0.029 and 0.032 cm3/g, respectively. The nanomaterials were used in the photocatalytic removal of Cr(VI) from aqueous solutions, and the adsorption isotherms indicated that the catalyst uptake (qe,max) amounts for Mo-doped TiO2 and pure TiO2 were 12.5 and 6.5 mg/L, respectively. Moreover, the equilibrium removal percentage was improved from 41% for pure TiO2 to 90% for Mo-doped TiO2, which confirms that photocatalytic activity is enhanced by doping TiO2 with molybdenum.