:: Journal of International Environmental Application & Science ::

Year 2008, Volume III (Issue I)

Journal of International Environmental Application and Science , Vol. 3, No. 3 (2008), 29-36


Adsorption of p-xylene in dry and moist clay

Cetin Cakanyildirim, H. Canan Cabbar

Department of Chemical Engineering, Gazi University, 06570, Ankara, Turkey


Abstract: It is well known that volatile organic compound (VOC) adsorption on dry soils decreases as relative humidity increases causing water to adsorb and displace VOC. The objective of the current study is to suggest a quantitative explanation for the dependence on relative humidity of p-xylene adsorption isotherms between the limiting case of zero relative humidity and super-saturation. Adsorption of p-xylene on Na-montmorillonite clay was studied at different relative humidity (0, 27, 48 and 76 %) by using the dynamic pulse technique. Adsorption behaviours at dry condition can be explained by the BET isotherm. p-Xylene was successfully adsorbed on the surface of the Na-montmorillonite in dry condition. It was observed when surface is covered by water patches p-xylene adsorption decreases. The adsorption isotherm of p-xylene at moist clay surface was also obtained from a mathematical model. Based on the limiting cases of adsorption on a totally dry mineral surface and at an air-water interface, a mathematical model is provided for the nonlinear adsorption isotherm for p-xylene onto moist clay. The mathematical model correctly describes significant features of experimental VOC adsorption on moist clay. The experimental data and results of the mathematical model for the same humidity values are matches, mainly. The amount of water and p-xylene to cover the mineral surface by monolayer were found as; 2.0265, 21.314 mg/g, respectively.

 
Keywords: Adsorption, montmorillonite, volatile organic compounds