Sorption study of Some Organic Pollutants on Titanium Dioxide

 The subject of this thesis involves studying the possibility removed of four organic compound by TiO . These organic compounds (considered as pollutants) which are; Birlliant blue (dye), polyvinyl alcohol (PVA), Linear alkyl benzene sulfonate (LAS) and Lambdacy holothrin as (pesticides). The thermal and photo-stability were studied and the results showed that all pollutants are stable in temperature range about (288-318) K, and stable against UV-linght in the wave length range (290-320) nm. Titanium dioxide successed in removing; 95-54% of dye, 6.2% of PVA, 13.19% of LAS and failed in removeing pesticides. UV-Vis absorption spectrophotometric technique was used to follow the pollutants concentration before and after adsorption process and after different periods of time, since the sorption isotherms were obtained by obeying Langmiur and Freundlich adsorption isotherms, with R2 (1-0.9993) for dye, R22 (0.9992-0.9574) for PVA, R2 (0.9503-0.9813)for LAS. The dye adsorption isotherms take S-shapes which related to a strong interaction between dye and TiO  with thermodynamic values DH = +(5.962-26.57)J, DG = -(966-999)J, DS = +(3.45-9.1906)J.2 The thermodynamic parameters were studied by using the sorption process of the three pollutants on TiO  of different temperatures ranging (293-318)K, and from the sorption isotherms the values of DH, DG, and DS for PVA DH = -(133.4-212.83)J, DG = +(78-157.4)J, DS = -(500)J,2LAS DH = +(53.14-66.14)J, DG = -(1.21-1.38)kJ, DS = +(4-14)J.The sorption process of dye and LAS a positive DH values,negative DG values and positive DS values, which indicates the spontaneous absorption process, which for the negative DH values,positive DG values and negative DS values are due to the non spontaneous adsorption process for PVA. The kinetic study of pollutants sorption on TiO  was studied depending on three kinetic equations:21- Lagergren equation: it was used to obtain the order of the sorption process, and the results showed a good obey with R = (0.94770.9995) for dye,R2  = (0.956-0.9942) for PVA, R 2=(0.9948) for LAS, to this equation, which indicates that the sorption process followed a pseudo- 1 st order kinetics, and from the linear Lagergren equation for the pollutants sorption the rate constants of sorption were calculated at different temperatures, and the activation energy for the sorption process was also calculated which reached 39.011 kJ.mol-1 for sorption of dye.2- Morris-Weber model: was employed and it gave a good match with the straight linear equation with R2 = (0.98-0.994) for dye,R2=(0.9892) for PVA, R2 = (0.9989) for LAS. This relation indicates that the diffusion process was so obvious, and it involves the transport of pollutant from the bulk solution into the TiO surface, which is considered the rate-limiting step.3- Reichenberg model: was employed and it gave a good linear relationship between B  and time with acceptable correlation coefficient R 2t = (0.9891) for dye, R2= (0.9306) for PVA, R =(0.9776) for LAS. This relation indicates that the rate limiting mechanism is the absorption and the sorption process involving three steps: absorption,adsorption and desorption).