Synthesis of inorganic/organic material doped/undoped titanium dioxide composites and their adsorption behavior

In this study, TiO2 nanoparticles and TiO2/SiO2 composites were synthesized by thermal hydrolysis method. The thermal hydrolysis process was performed at constant temperature, reaction time and stirring rate under reflux. In these studies silica (SiO2) obtained from rice husk ash of Edirne's Ipsala region was used as support material. SiO2 nano particles and TiO2/SiO2 (TS95) composites were loaded with 0.25 molar ratios of iron (Fe+2) element by wet impregnation method to increase the adsorption capacities of SiO2 and TS95 adsorbents. Additionally, it is aimed that the increase of adsorption capacities of T95, TS95 and SiO2 nano particle and composites by adding an cationic surfactant 1x10-4 M Hexadecyltrimethyl ammonium bromide (CTAB) to the solution. Adsorption and desorption of acetylsalicylic acids (ASA), which were considered as model drugs, in aqueous medium were investigated. The characterization studies by using different methods (Brunauer-Emmett-Teller (BET), X-ray Diffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscopy (SEM), zeta potential measurement, Fourier-transform infrared spectroscopy (FT-IR) and metal analysis (AAS) were also carried out to identify inorganic/organic material doped/undoped titanium dioxide composites synthesized and their adsorption behavior. The effects of pH, temperature and adsorption time were investigated on the adsorption of acetylsalicylic acids in aqueous medium onto inorganic/organic material doped/undoped titanium dioxide composites. The adsorption capacity of Acetylsalicylic acids (ASA) adsorbed by inorganic/organic material doped/undoped titanium dioxide composites produced were determined by adsorption kinetics and equilibrium studies. Pseudo-first-order, (PFO) pseudo-second-order (PSO) and Elovich kinetic and Weber Morris intraparticle diffusion models (WM) and Langmuir, Freundlich, Temkin and Dubinin-Radushkevic isotherm models were applied to the experimental data to elucidate adsorption kinetics and adsorption equilibrium, respectively. Thermodynamic parameters such as the changes in standard free energy, enthalpy and entropy were also determined for the adsorption process. The effects of different amount of adsorbent (0.1-3.0 g/L) adsorbed ASA concentrations (3.5-5.5 ppm), the effect of temperature and pH on the amount of adsorbed ASA by composites were examined. ASA concentrations were measured by HPLC spectrophotometer. It was seen that adsorption equilibrium time was found to be 24 hour for all adsorbent and ASA concentrations. The desorption studies were carried out to obtain information about the reusability of the adsorbents and the effects of pH and temperature on desorption were also examined. After the calculation methods it was seen that the diffusion between particles controls the adsorption and adsorption equilibrium data were fitted to Langmuir and Temkin isotherms for T95 and SiO2 adsorbents whereas it was fitted to Freundlich isotherm for TS95 adsorbent. Therefore; monolayer adsorption was occured between the ASA and doped/undoped composites (T95 and SiO2) molecules, multilayer adsorption was occured between the ASA and TS95 molecules.