Clorazepate removal from aqueous solution by adsorption onto maghnite: Experimental and theoretical analysis

The removal of a benzodiazepine (clorazepate, CLZ) from aqueous solution by adsorption onto maghnite clay is investigated supported by theoretical simulations. The Fourier-transform infrared (FTIR), Ultraviolet (UV), X-ray diffraction (XRD), and scanning electron microscope (SEM) analyses were used to characterize the adsorbent. To individuate the optimum conditions for adsorption, equilibrium, and kinetic tests are performed to assess the efficiency of this adsorbent to remove CLZ from polluted water in different operating conditions like pH, initial concentration, adsorbent dosage, and contact time. Adsorption is maximum at low pH, and it is mainly driven by electrostatic interactions between the benzenic ring of CLZ molecule and the montmorillonite layer of maghnite adsorbent. The kinetics obeys to the pseudo-first-order kinetic model, while the Freundlich isotherm model was found to better describe the adsorption equilibrium. The maximum observed adsorption amount of CLZ onto maghnite was about 50 mg g(-1) at pH 4.66. A complementary theoretical study is performed to quantify the CLZ/maghnite interactions using Monte Carlo simulations. Interestingly, the results show that the CLZ assumes a horizontal position on the maghnite surface upon adsorption, characterized by high energy adsorption. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigates the removal of benzodiazepine (clorazepate, CLZ) from aqueous solution by adsorption onto maghnite clay, supported by theoretical simulations. The results show that adsorption is maximum at low pH, driven mainly by electrostatic interactions, and follows the pseudo-first-order kinetic model. The complementary theoretical study reveals that CLZ assumes a horizontal position on the maghnite surface upon adsorption, characterized by high energy adsorption.