The influence of activated carbon surface chemical composition on the adsorption of acetaminophen (paracetamol) in vitro: Part II. TG, FTIR, and XPS analysis of carbons and the temperature dependence of adsorption kinetics at the neutral pH

The presented paper is the subsequent one of the series concerning the results of the influence of carbon surface chemical composition on paracetamol adsorption from water solutions. The non-modified de-ashed commercial carbon D43/1, (Carbo-Tech, Essen, Germany) as well as modified ones (using conc. nitric acid, fuming sulphuric acid, ammonia, and modified via ionic exchange process with Cu2+) were used as adsorbents. For these, characterised previously, carbons the results of some additional measurements, i.e. thermogravimetry in He and in air, FTIR, and XPS are reported, to expose the type of carbon surface groups created by chemical modifications. The results of kinetic measurements (performed at three temperatures: 300, 310 and 320 K) are reported. They were described using very simple kinetic equation proposed by Korta and co-workers; moreover, this equation has been modified in the current paper. It is shown that, up to the relative adsorption value equal to 0.5 the kinetics of the process of paracetamol adsorption is determined by the hydrophilicity of carbon surface. The rate of this process increases linearly with the values of the enthalpy of carbon immersion in water. Moreover, for all the carbons, except for the modified one with Cu2+, the rate of adsorption is determined by the presence of surface groups and it increases with the total acidity of carbon.