Nonlinear modeling of equilibrium sorption of selected anionic adsorbates from aqueous solutions on cellulosic substrates: part 2: experimental validation

The equilibrium sorption of CI Direct Blue 1, as a model anionic adsorbate, from aqueous solution on cotton fabric was experimentally studied. The equilibrium sorption data were employed to test the performance of a proposed nonlinear sorption model in describing the sorption behavior of anionic adsorbates on cellulosic substrates. The analysis of data based on the nonlinear least-squares curve fitting showed excellent correlation against experimental values as indicated by a high coefficient of determination (R ²). The V and −Δμ° parameters were determined based on the nonlinear model and employed to represent the internal accessible volume of cotton to CI Direct Blue 1 and the standard affinity of sorption. It was shown that variations in temperature and concentration of electrolyte (e.g. NaCl) in the sorption system result in slight variations in V. The findings extend the scope of the previous study and indicate that the nonlinear sorption model can be used to accurately determine the thermodynamic properties of a sorption system, such as the affinity (−Δμ°), enthalpy (ΔH°), and entropy (ΔS°), for anionic adsorbates on cellulosic substrates.