Removal of Environmentally Harmful and Hardly Degradable Pharmaceuticals Sulfamethoxazole, Diclofenac, and Cetirizine by Adsorption on Activated Charcoal

The removal of three environmentally harmful and hardly degradable pharmaceuticals, namely sulfamethoxazole, diclofenac, and cetirizine, from aqueous solution by the adsorption onto two types of activated charcoals (WSCl2 and HWOH) was investigated. The volume of micropores and mesopores in two charcoals was the main property affecting removal efficiencies. Using microporous WSCl2 as an adsorbent, higher removal efficiencies were achieved for all chosen pharmaceuticals. The highest removal efficiency was recorded in the case of sulfamethoxazole (79%). A direct correlation between log Kow and removal efficiencies and between the solubility of pharmaceuticals and removal efficiencies was not found. The adsorption behavior of individual pharmaceutical solutions can be described by the pseudo-second order kinetic model. The parameters obtained from the kinetic model show that the adsorption rate on HWOH was higher than on WSCl2. However, the amounts of adsorbed pharmaceuticals were lower on HWOH than on WSCl2, which can be linked to the textural difference between the charcoals. In the mixture consisting of all three compounds, overall removal efficiencies were lower than in the case when individual pharmaceuticals were present in the solution. Results also indicate that a certain fraction of the micropores can only be occupied by the smallest compound in the mixture (sulfamethoxazole).