Theoretical study of the adsorption of sodium salicylate and metronidazole on the PANi

The focus of the current research is to evaluate the adsorption mechanisms of sodium salicylate and metronidazole on the polyaniline (PANi) using density functional theory (DFT) at B3LYP/6-31G(d) level of theory. The molecular electrostatic potentials of sodium salicylate, metronidazole and PANi were calculated. The theoretical data show that the oxygenated functional groups of adsorbates and amino groups of PANi are the nucleophilic and electrophilic attack sites, respectively. The structural, electronic and energetic properties of PANi complexed with sodium salicylate and metronidazole were investigated. The adsorption mechanism is due to the formation of hydrogen bond between polymer and adsorbate molecules. The low intermolecular electron transfer at solute/solid interface reveals that the sodium salicylate and metronidazole are physisorbed onto the PANi. In addition, the interaction energies between PANi and adsorbate molecules suggest the stability of the formed complexes, indicating a good adsorbate-adsorbent affinity. All quantum chemical data are in good agreement with the experimental observations.