Novel Magnetite Nanocomposites (Fe₃O₄/C) for Efficient Immobilization of Ciprofloxacin from Aqueous Solutions through Adsorption Pretreatment and Membrane Processes

Abstract

The release of antibiotics into the aquatic environment enhances the drug resistance capabilities of microorganisms, as in large water reservoirs, their concentrations are lesser than their minimum bactericidal concentration, and microorganisms living there become resistant to such antibiotics. Therefore, robust hybrid technologies, comprising of efficient conventional adsorption processes and modern membranes processes, are needed to effectively remove such pollutants from industrial effluents. The present study is an attempt where iron-based magnetic carbon nanocomposites (Fe3O4/C) were prepared from mango biomass precursors and utilized as an adsorbent for the removal ciprofloxacin from wastewater in combination with three types of membranes that are robust but fouled by organic matter. The Fe3O4/C composite was characterized using energy dispersive X-Ray (EDX) technique, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET), Barrett–Joyner-Halenda (BJH) surface area, Thermogravimetric (TG)/Thermal differential analysis (DTA) and point of zero charge pH analyses. Initially, batch adsorption experiments were used to determine adsorption parameters. Then the adsorption unit was coupled with membrane pilot plant where the adsorption role was to adsorb CIPRO before entering into the membrane unit to control fouling caused by selected antibiotic. In batch experiments, the equilibrium time was found as 60 min and kinetics data were more favorably accommodated with the pseudo-2nd-order model (R2 = 0.99). Langmuir model (R2 = 0.997) more favorably accommodated the equilibrium data in comparison to other models used such as the Freundlich (R2 = 0.86), Temkin (R2 = 0.91) and Jovanovich (R2 = 0.95) models. The thermodynamic aspects of the adsorption process were also evaluated and the process was found to be spontaneous, feasible and exothermic. The influence of adsorbent dosage and pH, were also investigated, where the optimal adsorption conditions were: optimum pH = 7 and optimum Fe3O4/C dosage = 0.04 g. The CIPRO-loaded nanocomposite was regenerated with NaOH, CH3OH and distilled water several times. Improved percent rejections of CIPRO and permeate fluxes with the membrane/adsorption operation were observed as compared to naked membrane operations. Magnetic adsorbent was found as a best solution of foul control; a defect in the modern robust technology of membranes. However, further experimentation is needed to validate the present findings.

Keywords

• adsorption
• membranes
• fouling
• permeate flux