In this study, an adsorption experiment is proposed using commercial activated carbon as adsorbent and a textile azo dye, Mordant Blue-9, as adsorbate. The surface chemistry of the activated carbon is changed through a simple oxidation treatment and the ionic strength of the dye solution is also modified, simulating distinct conditions of water hardness. The purpose of this experimental work, directed to undergraduate (second-year) students is to allow them to understand the influence of surface chemistry and ionic strength on the interaction between the carbon surface and the dye molecule.

Refractive indices and ET values were measured for the ternary mixture methanol–acetonitrile–1‐propanol at 25.0 °C for 13 mole fractions, and also for the corresponding binary mixtures, methanol–1‐propanol, methanol–acetonitrile and 1‐propanol–acetonitrile, at 25.0 and 50.0 °C, at 10 different compositions. Solvent exchange equilibrium models were applied to the transition energy of the Dimroth–Reichardt ET(30) solvatochromic indicator in the binary systems and the Redlich–Kister polynomial was used to correlate excess ETN and nD values for the binary solvent mixtures data. The results allowed the analysis of synergetic behaviours, polarizability effects and preferential solvation trends both in the binary and in the ternary mixtures. Our results point towards the prevalence of specific solute–solvent–solvent interactions mainly due to hydrogen bonding by the hydroxylic components of the ternary mixture. Copyright © 2002 John Wiley & Sons, Ltd.

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