Adsorption Study of A Number of Di-Azo Dyes On A Nano Activated Carbon ; Prepared From Stem of Eucalyptus Tree
الملخص
This work included equilibrium and thermodynamic studies of the adsorption of two azo dyes on activated carbon prepared from Fallen eucalyptus leaves collected from the forests of Mosul city which is located in the north part of Iraq. The preparation is followed by thermal stimulation where the efficiency and capacity of adsorption were estimated. The optimal conditions of the adsorption system such as; effect of amount of adsorbent (dose), contact time, temperature and initial concentration were conducted. The research included the application of three types of isotherms to the adsorption system under study, namely Langmuir, Freundlich, and Flory-Huggins (FH), The Freundlich isotherm equation is better fitted to the practical data of adsorption of the studied dyes at all temperatures indicated by the values of the correlation coefficients (R2) that, ranged between (0.9999 –0.9924) and this pointing to the possibility of the formation multi-layer adsorption distributed on a heterogeneous surface area. Thermodynamic study was also conducted at various initial concentration (35, 87, 140, and 197 mg/L), each concentration at range of temperatures (293-333 Kelvin). The results proved that, the values of equilibrium constant (K) decreases with increasing temperature. This is agree with the physical nature of the adsorption process. The values of the thermodynamic functions proved that adsorption system under consideration are spontaneous, the forces dominate the connection between the dye molecules and the active sites on the carbon surface are physical in nature. The adsorption process leads to more ordered system at a concentration of 35 mg/L, while at higher concentrations the results were more random order for both dyes (D1 and D2). This can be attributed to the fact that increasing the concentration increases the number of remaining molecules in the dye solutions, thus increasing the randomness of the system, especially after equilibrium.
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