Removal of imipramine hydrochloride with natural and recycled adsorbents from aqueous solutions: effect of surfactants on the adsorption characteristics of pharmaceutically active compounds

Abstract

In this study, the adsorption properties of an amphiphilic cationic drug imipramine hydrochloride (IMP) on natural and recycled adsorbents, such as bentonite (BENT), Fuller’s earth (FE), and the eggshell (ES) in the aqueous medium has been aimed to report by means of absorption spectrophotometry. The adsorption of IMP has also been studied in the presence of cationic (dodecyl trimethylammonium bromide; DTAB) and anionic (sodium dodecyl sulfate; SDS) surfactants to clearly understand and identify the adsorption characteristics of IMP in different environments. Therefore, the association of IMP with surfactants has also been conducted using both absorption spectrophotometry and surface tension measurements to gain more information on the adsorption characteristics of IMP on BENT, FE, and ES. Micellar binding constants of IMP to SDS and DTAB micelles were calculated using the Benesi–Hildebrand Equation to ensure a more particular comparison of the effect of surfactants on the adsorption features of IMP. Additionally, the interfacial parameters Gibbs surface excess (Γ max) and the minimum area occupied by IMP (A min) were estimated in the case of DTAB and SDS. Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm equations were applied to the adsorption of IMP on natural adsorbents. Depending on their structure, the presence of surfactants in the environment diminished or completely inhibited the adsorption of IMP on all-natural adsorbents studied with the exception of IMP adsorption on FE in the presence of SDS monomers in the medium where the adsorption quantity increased significantly.