Isobaric vapour-liquid equilibrium (VLE) data were measured for the binary system of {tert-butanol (1) + water (2)} and the ternary system of {tert-butanol (1) + water (2) + tris(hydroxymethyl) aminomethane (TRIS) (3)} at 101.3 kPa by using a modified recirculating type of Othmer equilibrium still. The concentration range of the biological buffer TRIS in the feed mixtures is from 0.05 to 0.20 in mass fraction. The experimental results show that the presence of TRIS induces significant shift of azeotropic composition and increases the relative volatility of tert-butanol to water. TRIS can be a promising mass separating agent for the separation of (tert-butanol + water) mixtures. The experimental VLE values were correlated with the NRTL-HOC model to determine the binary interaction parameters. Generally, the NRTL-HOC model well correlates the VLE data for the systems investigated in this study. The model parameters obtained from this study can be applied to design a new green process for separating -tert-butanol from its aqueous solution. (C) 2016 Elsevier Ltd. All rights reserved.