A magnetic nano-sorbent incorporating antimicrobial papain for the rapid and efficient removal of levofloxacin and Pb(ii) from aqueous systems

Abstract

In the contemporary century, bio-based magnetic nanomaterials have received tremendous interest as promising candidates in adsorption procedures owing to their magnetic nature, modifiability, approachability, bioactivity, and pH-responsive dynamics. In this study, a magnetic core–shell nano-sorbent was synthesized through papain incorporation as a high-performance adsorbent for the removal of levofloxacin and lead cation Pb(II) from aqueous solution with antibacterial activity. The physicochemical characteristics of the developed nanoparticles were profoundly impacted by surface functionalization using papain as a biocompatible material. The characteristics of the adsorbent in all respects, including its removal effectiveness, were investigated using various characterization techniques. Fundamental parameters, including adsorbent quantity, preliminary adsorbate concentration, pH, and time intervals, were optimized through batch experiments. The presence of electronegative heteroatom-containing groups such as carboxyl, amide, and imidazole ring in the papain molecule stimulates the effective establishment of hydrogen bonds, electrostatic interaction, π–π stacking, and chelation with the levofloxacin and Pb(II) contaminants. The adsorbent exhibits an exceptional adsorption capacity of 2445 mg g⁻¹ and 830 mg g⁻¹ against levofloxacin and Pb(II), respectively. The equilibrium isotherm outcomes were fitted to Langmuir, Freundlich, Temkin, and Halsey isotherm models to identify the adsorption mechanism, and the kinetic results were analyzed with pseudo-first-order, pseudo-second-order, Elovich, and liquid film diffusion models for rate-limiting phase identification. The experimental data for both adsorbates reveal significant agreement with the pseudo-second-order model and the Langmuir isotherm (R² ≃ 0.999). Data analysis demonstrates that film diffusion (R² > 0.990) controls the rate-limiting phase in the adsorption procedure. Moreover, the predicted value for maximum adsorption capacity from kinetic and isotherm studies shows a strong correlation with the experimental results. The synthesized nano-sorbent demonstrates prospective implications for effective wastewater treatment owing to the improved adsorption capacity and antibacterial activity.