Coal; Adsorption; Surfactant; Temperature; Zeta potential

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 calculated thermodynamic parameters indicate that the adsorption of CTAB on coals is an exothermic (?Hads < 0) and spontaneous (?Gads < 0) process. It was proved that the adsorption capacity of CTAB on coal increased with a rise in temperature for all the studied samples; the highest adsorption capacity was observed for the oxidative altered coal. In addition, measuring the zeta potential proved that the adsorbed amount of CTAB on the coal surface corresponded to the zeta potential value. Addition of the cationic surfactant (CTAB) affects the value of ?-potential, making the zeta potential values more positive.