Abstract
A theoretical interpretation of the adsorption mechanism of tetracycline (TCCN) on biochar either in raw form (ADS1) or modified by chitosan-Fe/S (ADS2) is reported in the paper. An interpretative model is applied to the adsorption dataset, and considers that the adsorption of TCCN occurs with the formation of two layers on the investigated adsorbent. The theoretical model allows good data interpretation, confirming that TCCN adsorption capacity increases with temperature. The adsorption capacity at saturation (ACS) of TCCN on the ADS1 varied from 61.91 to 91.01 mg/g. while for ADS2 it varied from 135.76 to 202.50 mg/g. This difference is probably related to the difference in adsorbent properties and to the beneficial effect exerted by the adsorbent modification. Modeling results show also that TCCN is removed via a non-parallel orientation on both ADS1 and ADS2. For a thorough analysis of this mechanism, all adsorption energies (TCCN-ADS1, ADS2, and TCCN-TCCN) are determined at different temperatures.