Sorption of Cd2+ ions onto Daphne alpina mediated titanium dioxide nanoparticles

Abstract

The Daphne alpina (D. alpina) fresh leaves extract was used as a reducing agent for the synthesis of titanium dioxide nanoparticles (TiO2 NPs). The surface area of synthesized titanium dioxide nanoparticles (TiO2 NPs) was found to be 240.67 m2 g−1 derived from nitrogen adsorption/desorption data using Brunauer–Emmett–Teller (BET) method. The crystallite size was found to be 10.9 nm, calculated from Full width and half maxima of the x-ray diffraction (XRD) Reflection. The surface morphology was studied via Transmission electron microscope (TEM) and Scanning electron microscopy (SEM). The average particles size estimated from TEM and SEM micrographs are 21 and 54 nm respectively. The percent composition and purity of TiO2 NPs was studied by utilizing energy dispersive x-ray (EDX). The band gap was derived from the sharp raising portion of diffuse reflectance spectrum (DRS) and Fourier transform infrared spectroscopy (FTIR) was used to study the surface functional groups. The batch process was followed to study the adsorption behavior of TiO2 NPs against Cd2+ ions under the influence of pH, temperature and Cd2+ ions concentration. An increase was observed in the adsorption capacity of TiO2 NPs with increase in pH, temperature and initial Cd2+ ions concentration. The Langmuir parameters calculated from the adsorption data, show that maximum sorption capacity (Xm) and binding energy (Kb) increased with increasing pH and temperature. The exchange mechanism between cadmium and hydrogen ions was 1:1, suggesting that one hydrogen was released to solution due to the adsorption of one cadmium (Cd2+) ion. The thermodynamic study revealed that the adsorption process was endothermic and was more spontaneous at higher pH and temperature.