Sorption study of some organic pollutants on titanium dioxide. +CD

number: 
2249
إنجليزية
department: 
Degree: 
Imprint: 
Chemistry
Author: 
Qabas Mohammad Abd-Al-Hussani
Supervisor: 
Dr. Khulood A. Al-Sa'adi
year: 
2009

Abstract:

The subject of this thesis involves studying the possibility removed of four organic compound by TiO2. 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, R2 (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 TiO2 with thermodynamic values H = +(5.962-26.57)J, G = -(966-999)J, S = +(3.45-9.1906)J. The thermodynamic parameters were studied by using the sorption process of the three pollutants on TiO2 of different temperatures ranging (293-318)K, and from the sorption isotherms the values of H, G, and S for PVA H = -(133.4-212.83)J, G = +(78-157.4)J, S = -(500)J, LAS H = +(53.14-66.14)J, G = -(1.21-1.38)kJ, S = +(4-14)J. The sorption process of dye and LAS a positive H values, negative G values and positive S values, which indicates the spontaneous absorption process, which for the negative H values,positive G values and negative S values are due to the non spontaneous adsorption process for PVA. The kinetic study of pollutants sorption on TiO2 was studied depending on three kinetic equations: 1- Lagergren equation: it was used to obtain the order of the sorption process, and the results showed a good obey with R2 = (0.9477- 0.9995) for dye, R2 = (0.956-0.9942) for PVA, R2=(0.9948) for LAS, to this equation, which indicates that the sorption process followed a pseudo- 1st 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 TiO2 surface, which is considered the rate-limiting step. 3- Reichenberg model: was employed and it gave a good linear relationship between Bt and time with acceptable correlation coefficient R2 = (0.9891) for dye, R2 = (0.9306) for PVA, R2 = (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).