Abstract

THERMODYNAMIC STUDY OF THE ADSORPTION OF (E110, 122, 102, 133, 124, 123, 127) DYES EMPLOYED IN THE FOOD INDUSTRY USING ACTIVATED CARBON AS ADSORBENT SUBSTANCE

Ibrahim Y. Mohammed* and Khaleel Ibraheem A. Al-Niemi

ABSTRACT

This research included a thermodynamic study of the adsorption of some food coloring dyes (E110, 122, 102, 133, 124, 123, 127) on the surface of commercial activated carbon as an adsorbent. The analytical method was used to opted the calibration curves for each dye and to estimate the amount of adsorbed and remain of food coloring dyes according to (Beer's –Lambert law) by using spectrophotometric method for UV- visible spectrophotometric . The effect of temperature on the adsorption of food coloring dyes or food coloring molecules was studied within an experimental temperature range (298-318 kº) and calculate the thermodynamic functions of the adsorption process (∆H, ∆G°, ∆S°, ∆S) from the adsorption equilibrium constant(Kc) using the (Vant-Hoff) equation, as well as, calculating those functions from the adsorption isotherms from the Langmuir and Freundlich constants, All results showed that the adsorption process is endothermic and of a physical nature through positive ∆H values at all concentrations with range of temperatures used in this study. It was also found that the adsorption process occurs spontaneously, where the values of (∆G°) were negative and few, as well as, it turns into more spontaneous with increasing temperature, but some food coloring dyes have positive (∆Gº) values refers to that the adsorption process is a non-spontaneous process, In general, the entropy values (∆S°) were slightly greater than the values of ( ∆S) that is, the regularity of the adsorbed molecules at equilibrium is greater than their regularity at any step of adsorption. The results obtained for the thermodynamic functions calculated from the Langmuir and Freundlich constants showed great agreement with those that were calculated from the equilibrium constants, which indicates the possibility of using those Constants to calculate thermodynamic functions successfully.

Keywords: Adsorption, Thermodynamic functions, Activated carbon, Adsorption isotherms.