Adsorption heats of phenol on activated carbon using adapted method of immersion calorimetry

Simple adaptation of the technique of immersion calorimetry enables determining both integral and differential adsorption heats as well as the course of the adsorption isotherm of phenol on activated carbon. The innovative aspect of the applied procedure consists in bringing the phenol aqueous solution to contact with the suspension of carbon with water. Thus, the “interfering” heat effect of carbon interaction with water is eliminated, and only the net adsorption heat of phenol is monitored. The value of −52.5 kJ mol⁻¹ was ascertained as the molar differential adsorption heat at the low surface coverage (cca 0.2 mmol g⁻¹) of the sample of microporous carbon. As the adsorption process continues, for adsorption uptakes exceeding the value of about 1 mmol g⁻¹, molar differential adsorption heats appear to be established at a level of about −20 + 5 kJ mol⁻¹.