Adsorption isotherms in liquid phase: Experimental, modeling, and interpretations

Abstract

Adsorption is a fundamental unit operation used for several purposes in the academy and industry. Particularly, adsorption in liquid phase is used to remove recalcitrant compounds from effluents (dyes, heavy metals, phenols, pharmaceuticals, and others), to recover valuable metals from leachates (gold, silver, cobalt, and others), and to purify products during the industrial processing (fuels, juices, liquors, wines, and others). For all these applications, the obtainment, modeling, and interpretation of the equilibrium isotherms are a key and fundamental study. Based on the abovementioned, this chapter presents the particularities of adsorption equilibrium isotherms in liquid phase from scientific and technological viewpoints. From the scientific viewpoint, the importance of adsorption isotherms will be addressed. For example, the equilibrium isotherms provide parameters for decision-making of the researcher in relation to the adsorption capacity of a particular adsorbent, give an idea how the interaction of adsorbent-adsorbate occurs, and provide means to find thermodynamic parameters, among others. From technological viewpoint, the adsorption capacity of the material is a basic parameter for the project. Thus, in this chapter the following points are highlighted: experimental procedures to obtain equilibrium curves, isotherm analysis, models used to correlate the equilibrium data and interpretation of its parameters, regression methods (comparison between linear and nonlinear regression methods), error analysis, adsorption thermodynamics, and the use of these data for equipment design.