Adsorption of sulfamethoxazole and ciprofloxacin on chitosan foam: Isotherms modeling and binding mechanisms

The paper investigates the adsorption of two pharmaceutical compounds (PCs) from polluted water, namely sulfamethoxazole (STZ) and ciprofloxacin (CRA), onto a new adsorbent formed by dispersion of chitosan on polyurethane (PU/C). Adsorption isotherms were determined on the investigated adsorbent as a function of temperature, in the range 298–328 K. For each temperature, PU/C showed higher affinity toward STZ with a maximum adsorption capacity at the maximum investigated temperature. A double-layer model was adopted for the interpretation of the entire adsorption data set. The number of adsorbate molecules bound per active site allowed for determining that an aggregation process occurs upon adsorption. The retrieved values for the CRA- PU/C system are 1.37, 1.61, 1.68, and 0.606 at 298, 308, 318, and 328 K, respectively, while for the STZ- PU/C system, the corresponding values are 0.76, 1.07, 1.23 and 1.36 at T = 298, 308, 318 and 328 K respectively. Finally, the values of adsorption energy define the phenomenon under investigation as a physisorption.