The influence of temperature on the adsorption of CTAB on coals

Abstract The influence of temperature on the adsorption behavior of the cationic surfactant cetyltrimethyl amonium bromide (CTAB) has been studied. Batch mode was used for the adsorption of CTAB on three different types of coal, namely oxidative altered coal (BO), subbituminous coal (SB) and bituminous coal (BC). Adsorption from aqueous solutions was carried out at 25, 40, 60 and 80 °C. The linear as well as nonlinear regression of experimental data confirmed that the adsorption process can be described using the Langmuir adsorption theory of monolayer coverage. Thus, the equilibrium constant of adsorption could be calculated from the Langmuir binding constant b . Further, thermodynamic parameters such as enthalpy Δ H ads , entropy Δ S ads and Gibbs energy Δ G ads were determined from the dependence of the b constant on temperature. The calculated thermodynamic parameters indicate that the adsorption of CTAB on coals is an exothermic (Δ H ads G ads ξ -potential, making the zeta potential values more positive.