A Simple Way of Calculating the Change in the Gibbs' Free Energy of Ion Adsorption Reactions

Abstract

Adsorption experiments of Zn 2+ and Cd 2+ ions from aqueous solutions onto vermiculite were conducted to test the applicability of two basic functions derived for calculating the change in the Gibbs' free energy (∆G 0) and the chemical potential (∆µ) between the initial and equilibrium states in ion adsorption systems. The functions were deduced on the basis of the thermodynamic principle that the chemical potentials of the reactants and products of a physicochemical reaction should be equal in the equilibrium state and, consequently, the change in the Gibbs' free energy between the initial and equilibrium states of the reaction should be equal to the sum of the initial molar quantity of each reactant multiplied by its change in chemical potential. The results of the analysis conducted indicate that the two functions considered could well be used not only for calculating ∆G 0 and ∆µ but also for determining the adsorption capacity of an adsorbent under the conditions considered.

Adsorption of silver from aqueous solution onto pre-treated bentonite clay: complete batch system evaluation

“…Adjustment results demonstrated that adsorption of silver onto calcined Verde-lodo clay is mainly controlled by external transport although internal diffusion also influences in process kinetics. The equilibrium study was performed at four different temperatures and followed by a thermodynamic analysis through Henry's Law and the method established by Xiaofu et al (2009). The former evaluation revealed that adsorption of silver is exothermic and spontaneous, which was also verified by the other method.…”

“…In this work, we used two methods for this objective: Henry's law and the method developed by Xiaofu et al (2009).…”

“…Method established by Xiaofu et al (2009) The method stated by Xiaofu et al (2009) aims at measuring Gibbs energy specifically for adsorption processes. According to this method, the Gibbs energy involved in the process is given by Eq.…”

“…Xiaofu et al (2009) The method stated by Xiaofu et al was used for the calculation of Gibbs energy for all the temperatures analyzed in this study. Table 4 presents the results obtained by this method for each silver concentration A 0 , including the values of x and y.…”

Selective and enhanced nickel adsorption from sulfate- and calcium-rich solutions using chitosan

“…SI-1) of -17.94 kJ/mol and -10.75 kJ/mol were obtained for the respective systems, indicating that the adsorption process was spontaneous. The larger ∆G° in the presence of SO4 2-and Ca(II) suggests that when greater quantities of reactants are employed in the reaction, the released Gibbs free energy in the system will also increase, indicating a higher adsorption driving force [53,54]. to the other adsorbents used in Ni(II) adsorption without SO4 2in the system, such as Saccharomyces cerevisiae and chitosan(chitin)/cellulose composites, which both achieved a qmax of 0.2 mmol/g [55,56].…”