Adsorption of amoxicillin and paracetamol on modified activated carbons: Equilibrium and positional entropy studies

Two activated carbons were modified with iron benzoate and cobalt (MAC-1), and with iron oxalate and cobalt (MAC-2) to study the adsorption process of two pharmaceutical molecules named amoxicillin (AMX) and paracetamol (PCT). For this objective, a network of adsorption isotherms was well recorded at different temperatures ranged from 25 to 50 degrees C. New explanations were deduced by application the double layer model with two adsorption energies on adsorption isotherms formulated by the statistical physics approach. By investigation the number of adsorbed molecules per site, a lateral interaction between the (AMX) and (PCT) pharmaceutical molecules and modified activated carbons was successfully described. In addition to this, an aggregation phenomenon of AMX and PCT was studied and interpreted. When the adsorption saturation is reached; an adsorbed quantity was calculated and interpreted of each pharmaceutical molecule on both adsorbents indicating that the MAC-2 adsorbent could present higher efficiency for wastewater treatment. Thermodynamically, the positional entropy was treated giving a good explanation of AMX and PCT pharmaceutical molecules arrangement on modified activated carbons during the adsorption period. (C) 2017 Elsevier B.V. All rights reserved.