Statistical Physics Modelling of Dye Adsorption on Modified Cotton

Abstract

Experimental adsorption isotherms for four anionic dyes (Acid Blue 25, Acid Yellow 99, Reactive Yellow 23 and Acid Blue 74) on to cationized cotton have been analyzed using a multilayer adsorption model. For such purpose, the double-layer model showed the best fit with a high correlation coefficient R 2. The analytical expression of the model has been established from an application of the grand canonical ensemble of statistical physics. This method allowed an estimation of all the mathematical parameters in the model. Thus, the receptor site density and the half-saturation concentration have been related to physicochemical variables such as the chemical potential, the adsorption energy, the anchorage number, etc. A physical interpretation of the model parameters has been provided and some results relating to the adsorption process discussed.

Dye Adsorption by Modified Cotton. Steric and Energetic Interpretations of Model Parameter Behaviours

“…anchorage number, receptor site density and half-saturation concentration, as determined theoretically (Khalfaoui et al 2002) and related to the adsorption energy, exhibited different behaviours when examined in terms of the adsorption of various dyes on to modified cotton. When plotted against the percentage nitrogen content of these cottons, variations in the effective receptor site density and the inverse of the adsorbed molecules anchorage number allowed the adsorption process to be described topographically in terms of the parallel or perpendicular adsorption of the dye molecule on to the adsorbent surface.…”

“…Thus, by reacting glycidyl trimethylammonium chloride with cellulose in a basic solution, Baouab et al (2000) have shown that the nitrogen content of the resulting material was the most important parameter governing adsorption capacity. In our previous paper (Khalfaoui et al 2002), four cottons with nitrogen contents varying from 0.5% to 1.85% of the support mass referred to as cottons 1-4 were used for modelling experimental isotherms based on the Langmuir, Freundlich and Jossens' models. Of these various models, the last gave the best fit to the experimental *Author to whom all correspondence should be addressed.…”

Morphologic, Structural, Steric, Energetic and Thermodynamic Studies of the Mechanical Alloy Mg50Ni45Ti5 for Hydrogen Storage

“…Initially, the hydrogen is considered as a perfect gas [30][31][32] supposing that the mutual interaction between the gaseous hydrogen molecules will be ignored. Usually, below the critical pressure (P=13 bar) and higher than critical temperature (T=33 K), hydrogen is an ideal gas [31,33].…”

“…It encompasses the relative motion and interaction among only the system's own particles [47]. We will focus, especially, on the existing interactions between absorbate and absorbent [32].…”

“…F=E int -TS (32) It is thus the free energy while TS is called the bound energy or the isothermally unavailable energy [55]. When absorption is achieved, in Figure 16, the free energy F takes negative values.…”