Biogenic surfactant mediated facile synthesis of visible light sensitized Zn/Mg co-doped TiO2 nanomaterials – a green approach: evaluation of photocatalytic activity by degradation of Amido Black 10B

Abstract

Visible light-driven Zn and Mg co-doped TiO2 nanomaterials were synthesized by varying dopant concentrations in presence of biogenic surfactant Sapindus emerginatus (biogenic extract) via the Sol-gel method and have been successfully applicated to the degradation of Amido Black 10B (AB 10B), an exemplary anionic textile azo dye pollutant. This study explored the potent capping properties of biogenic extract surfactant by encapsulating the Zn/Mg co-doped TiO2. In a view to assessing the physical and optical properties of the as-synthesized catalysts, various advanced instrumental techniques were adopted. The Transmission Electron Microscopy and Scanning Electron Microscopy analysis show the formation of small particle sizes (6.9 nm) pertaining to biogenic surfactant-assisted Zn/Mg co-doped TiO2 (ZMT4S2). The substitutional doping of Zn and Mg into the TiO2 framework by substituting Ti4+ ion and the encapsulation of surfactant around catalyst was confirmed by Fourier Transform-Infrared Spectroscopy (FTIR) spectral studies. The surface area of the ZMT4S2 was found to be high (195 m2 g− 1) as compared with undoped TiO2 (74 m2 g− 1) and Zn (1.00 wt%) / Mg (0.25 wt%) co-doped TiO2 (ZMT4) (132 m2 g− 1). The red shift in the absorbance was observed for all the catalysts analyzed using UV-Vis-Diffuse Reflectance Spectroscopy (UV-Vis-DRS) confirms the ZMT4S2 showing less band gap of 2.1 eV than other catalysts. Further the electrical property of the catalyst was studied using Electrochemical Impedance Spectroscopy. The results obtained from impedance and Mott-Schotky plots show the reduced electrical resistance and electron hole recombination respectively. The sensitivity of the catalyst towards visible light was confirmed by its band gap energy measurement using UV-Vis-DRS. The anatase phase of all the catalysts was confirmed using powder X-ray diffraction. The composition and wt% of dopants revealed the Energy Dispersive X-ray spectra agree well with the calculated value. The slightly shifted frequency bands (FTIR) further confirmed the doping of Zn and Mg. The characterization analysis reports further accounts for the effective degradation of AB 10B dye (99%) taking place within 20 min of irradiation time at optimized reaction parameters such as best dopant concentration ZMT4, catalyst dosage (100 mg L− 1), dye concentration (10 mg L− 1) and solution pH 3.