Efficient simultaneous removal of tetracycline and cefazolin from aqueous solution using a novel adsorbent based on zero-valent iron nanoparticles supported by montmorillonite and graphene oxide: isotherms, kinetic, and thermodynamic studies

ABSTRACT

In recent years, antibiotics in aqueous solutions have drawn extensive attention due to their harmful effect on human health and the environment. In this study, efficient and rapid adsorption of two antibiotics, including tetracycline (TC) and cefazolin (CFZ) on synthesised montmorillonite (Mt)/nano zero-valent iron (nZVI)/graphene oxide (GO) from aqueous solutions was studied. The prepared adsorbent was characterised by scanning electron microscope (SEM), energy dispersive X-Ray (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and vibrating sample magnetometer (VSM). One-factor-at-a-time (OFAT) method was used to optimise the experimental factors. The maximum removal percentage was achieved at pH of 7, an adsorbent dosage of 0.4 g, contact time of 7 min = TC and 10 min = CFZ, initial concentration of 5 mg L⁻¹, and a temperature of 298 K. The evaluation of isotherm models indicated that the Langmuir isotherm with a coefficient of determination (R²) value of 0.9992 for both antibiotics was selected as the best fitting model to describe the adsorption process. The maximum adsorption capacities (q_max) of Mt-nZVI-GO were obtained at 43.24 mg g⁻¹ for TC and 20.36 mg g⁻¹ for CFZ. Furthermore, the pseudo-second-order (PSO) kinetic model fitted well for TC (R² = 0.9937) and CFZ (R² = 0.9997). Thermodynamic parameters, i.e. adsorption Gibbs free energy (ΔG⁰), standard enthalpy (ΔH⁰), and standard entropy (ΔS⁰) were estimated. It was found that the adsorption had spontaneous and exothermic in nature. The results revealed that Mt-nZVI-GO could be used as a simple, efficient, and eco-friendly adsorbent for the simultaneous removal of contaminants in aqueous media.

KEYWORDS:

• Montmorillonite
• nano zero-valent iron
• graphene oxide
• removal
• tetracycline
• cefazolin

Disclosure statement

No potential conflict of interest was reported by the author(s).