Fabrication of Zero-Valent Iron Nanoparticles Impregnated Cross-Linked Chitosan Grafted β-Cyclodextrin for Removal of Cloxacillin from Aqueous Environment

A novel zero-valent iron nanoparticles impregnated cross-linked chitosan grafted β-cyclodextrin (Fe-CCS-g-β-CD) adsorbent was fabricated to eliminate cloxacillin from water. The characterization of Fe-CCS-g-β-CD was done using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) spectroscopy and thermogravimetry–differential thermal analysis (TGA-DTA) techniques. Response surface methodology (RSM) using Box-Behnken design (BBD) was utilized to optimize the independent variables (contact time, pH, adsorbent dose and initial cloxacillin concentration) for the adsorption of cloxacillin onto Fe-CCS-g-β-CD. The maximum removal of cloxacillin (99.93%) was achieved when the contact time, pH, adsorbent dose and initial cloxacillin concentration were 40 min., 6.5, 20 mg and 50 mg/L, respectively. The adsorption data were probed by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Flory–Huggins isotherm models. Freundlich isotherm model described well the adsorption process. The kinetic data were examined by surface based (pseudo-first order, pseudo-second order and Elovich models) and diffusion based (Furusawa-Smith external model, Urano-Tachikawa intra-particle and Bangham’s pore diffusion models) kinetic models. Pseudo-second order kinetic model fitted more accurately to the kinetic data. Diffusion based kinetic models suggested that various adsorption stages were occurred to control the adsorption process. The adsorption and pH studies indicated that C-π cation interaction was developed between the delocalized electron of zero-valent iron with aromatic ring of β-cyclodextrin and π-π interaction were also possible between phenolic ring of cloxacillin and glucose monomer of chitosan which enhance the removal efficiency of cloxacillin. The adsorption–desorption studies were carried out upto 10 cycles and suggested that the adsorbent can be effectively used for the removal of cloxacillin from aqueous environment.