دراسة امتزاز صبغة الكونغو الحمراء على متراكبات بوليمرية جديدة للكيتوسان

Study adsorption of Congo red dye on new polymeric composites for Chitosan

Abstract
This study included the adsorption of Congo red dye extract on the surface of the cross linked polymer Chitosan-Terephthaldehyde (TCCS) and chitosan-Terephthaldehyde-Vanillin (TVCCS). These polymers were diagnosed using infrared (FT-IR) and X-ray diffraction (XRD) techniques. The outer surface was used by scanning electron microscope (SEM) and the thermogravimetric analyzer (TGA) was used to determine the thermal stability of these polymers. The factors affecting the adsorption of Congo red were studied through a series of experiments, including:
Equilibrium time, adsorbing surface weight, pH, initial dye concentration and temperature effect .
The results showed that surface equilibrium (TCCS) was obtained at a time of (60min.), weight (0.02g) of the adsorbent surface and an acidity function (pH = 6.5), and the best dye concentration was (40 ppm). It was also observed a gradual decrease in the percentage of removal accompanied by significant increases in the values of adsorption capacity with increasing dye concentration, and the lowest removal percentage (84.23%) and the highest adsorption efficiency (73.70mg/g) were recorded at the concentration (70ppm).
The adsorption isotherms (Langmuir, Freundlich, Temkin) were studied, as the highest correlation coefficient (R2) was recorded for the Langmuir isotherm and this indicates that the adsorption conforms to the Langmuir isotherm. Equal to (0.0173) indicating that the adsorption of Congo red on the TCCS surface occurs as a preferred process for the Langmuir isotherm. The adsorption kinetics was also studied, and the results indicated that the adsorption follows a false second order. When studying the thermodynamic functions, it was found that the adsorption process is spontaneous and endothermic according to the values of thermodynamic functions.
As for the cross linked polymer Chitosan with Terephthaldehyde and Vanillin (TVCCS), the results showed that the equilibrium occurred at a time of (20min).
When studying the effect of the initial dye concentration, a decrease in the percentage of removal was observed, accompanied by an increase in the adsorption efficiency, where the lowest removal percentage (81.76% ) and the highest adsorption efficiency (102.09mg/g) was recorded at concentration (100ppm ). When studying the adsorption isotherms, it was found that it follows the Langmuir isotherm, and the value of the separation constant (RL) is equal to (0.0049), which indicates that the adsorption process is preferred. It was also found that it follows the second order false when analyzing the kinetic data. It was also found that the adsorption process is spontaneous exothermic according to the values of thermodynamic functions.