Use of thermal analysis for the study of the adsorption of pharmaceuticals from water

Abstract

The contamination of water with pharmaceuticals is one of the serious problems in the modern world. Their occurrence in surface- and groundwater brings a risk to the environment as well as human health. Therefore, many methods are studied in order of their removal. Adsorption on activated carbon belongs to the most popular ones. This paper is aimed at using thermal analysis to study the adsorption of analgesic paracetamol (acetaminophen) on activated carbon. Adsorption experiments including adsorption kinetics, adsorption isotherms, the effect of temperature and the effect of pH were also performed. Two different samples of commercial activated carbon (one powdered activated carbon (PAC) and one granular activated carbon (GAC)) and different initial concentrations of paracetamol were used. Equilibrium concentrations were determined with the aid of UV-VIS spectrophotometry and compared with thermogravimetric curves. Adsorption of paracetamol led to an appearance of a weak additional DTG peak at around 300-400 degrees C and negligible DTA effect in this temperature range. The DTG peaks at around 600 degrees C were reduced, indicating the removal of the groups left after activation on the carbon surface. The low height and width of DTG peaks and DTA effects were connected with a low mass ratio of adsorbed paracetamol related to the adsorbent mass (about 10-20%), more distinctive peaks could be achieved by the use of better adsorbing contaminants with higher molar mass.