Unveiling the adsorption mechanism of beta-blockers and sulfonamides in aqueous environment using disulfide-linked polymer

Abstract

Herein, we investigated the environmental application of negatively charged disulfide-linked polymer (DCOP) for selectively removing charged pharmaceuticals, such as beta-blockers and sulfonamides. To compare the effect of surface charge on the adsorption affinity of DCOP for target compounds, atenolol (ATL) and propranolol (PPL) were selected as positively charged beta-blockers, whereas sulfamethazine (SMZ) and sulfasalazine (SFS) were selected as negatively charged sulfonamides. Adsorption experiments, including those considering kinetic, isotherm, and water matrix effects, were performed to study the adsorption behavior of DCOP. Further, density functional theory (DFT) calculations were performed to verify the adsorption mechanism through computational calculation. Accordingly, DCOP exhibited faster and higher adsorption performance for beta-blockers than sulfonamides. The maximum adsorption capacities calculated by the Langmuir model of ATL (Qm,ATL 28.57 mg/g) and PPL (Qm,PPL 20.75 mg/g) were higher than those of SMZ (Qm,SMZ 13.72 mg/g) and SFS (Qm,SFS 13.42 mg/g). Moreover, the relatively hydrophobic compounds, such as PPL and SFS, were removed more efficiently than the hydrophilic compounds such as ATL and SMZ, revealing the importance of hydrophobic interaction. Moreover, DCOP exhibited a similar adsorption performance in the presence of humic acid and tap water. The adsorption energy calculated via DFT modeling corroborated the preferential adsorption of beta-blockers, supporting the experimental results. Consequently, DCOP could be used as a practical adsorbent in terms of one-pot synthesis, structural stability, and anti-interference ability by water matrix factors.