The Electronic Properties and Adsorption Performance of LDH/Graphene, and LDH/g-C3N4 for the Removal of Pharmaceutical Contaminants: A Molecular Dynamics Simulation

Abstract

Water shortages and pharmaceutical pollution are two interconnected crises that pose severe threats to global health, environmental sustainability, and economic stability. Pharmaceutical pollution is widespread and has reached potentially toxic levels in over 258 rivers in 104 countries. So far, more interest has been paid towards efficient water treatment processes in recent years. In this study, we explore the efficacy of layered double hydroxide (LDH) nanocomposites with graphene and graphitic carbon nitride (g-C3N4) as promising adsorbents of pharmaceutical contaminants. The LDH nanocomposite has been designed and simulated for the first time, consisting of two layers of sodium hydroxide with a layer of graphene and g-C3N4. We investigated the adsorption performance of LDH, specifically LDH/graphene and LDH/g-C3N4, for the removal of pharmaceutical contaminants including acetaminophen (AC), caffeine (CAF), and sulfamethoxazole (SMZ). Through comprehensive molecular dynamics simulations using the reactive forcefield (ReaxFF) software, we investigated the adsorption mechanisms, kinetics, and adsorption capacity of pharmaceutical contaminants onto these nanocomposite surfaces. Our findings showed that the combination of LDH/graphene had a higher adsorption capacity for the removal of pharmaceutical contaminants than LDH/g-C3N4. At 70 Picoseconds (Ps), 124, 129, and 142 molecules of each of the pharmaceutical contaminants AC, CAF and SMZ, respectively, had been adsorbed by LDH/graphene, with a higher exothermic energy equating to −1111, −1015, and −1150 × 103 kJ/mol, respectively. On the other hand, for LDH/g-C3N4 at 70 Ps, 108, 110, and 120 molecules of AC, CAF and SMZ, respectively, had been adsorbed, with exothermic energy equating to −978, −948, and −1173 × 103 kJ/mol, respectively. Finally, we calculated the electronic properties, including the band gap and density of state of the nanocomposite materials, to check their effect on the adsorption process. In addition, the results showed that the adsorption kinetics followed a pseudo-first-order model, while the adsorption isotherms for AC, CAF and SMZ adhered to the Langmuir model.