Kirkuk University Journal-Scientific Studies

Abstract

The kinetics and thermodynamics of the removal of Alzarin yellow and Congo red dyes from their aqueous solutions using local clay taken from Shoraw region northwest of the province of Kirkuk - Iraq as well as bentonite and activated charcoal as adsorbents was held, using UV- visible spectroscopy to follow the adsorption process. The equilibrium time of the adsorption process was determined and found that it reached a state of equilibrium in a period of time between 70-50 min, in the case of adsorption of the dyes on the activated charcoal and bentonite surfaces and 70-60 min, when using the clay. The results indicated that the best weight of the adsorbent surfaces is (0.1gm). Adsorption was studied in the natural pH of the basic dyes, as well as in the acidic and neutral pH. Isotherm (Freundlich and Langmuir) was used, and it was found that the best isotherm is Freundlich. Adsorption efficiency was calculated in the range of 15-65 oC of temperature. It was found that the adsorption efficiency decreased by increasing the temperature in the case of alizarin yellow dye adsorption on the three surfaces. Whereas the adsorption efficiency of Congo red on the clay surface decreased by increasing the temperature and this indicates that the reaction is exothermic. It has been found that the efficiency of adsorption is increased by increasing the temperature in the case of adsorption of Congo red dye on activated charcoal and bentonite surfaces and this indicates that the reaction is endothermic. The values of the thermodynamic parameters of the adsorption process and the adsorption kinetics study were calculated and found that the adsorption follows the pseudo- second order equation..