Removal of ciprofloxacin from aqueous solutions using GO/PVA/calcium alginate composite beads as an absorbent

Abstract

We prepared an eco-friendly graphene oxide (GO)-incorporated composite bead adsorbent, comprising sodium alginate (SA) and polyvinyl alcohol (PVA), via in situ cross-linking between GO and SA using calcium chloride as a cross-linking reagent, which is uniformly distributed within the PVA matrix. Fourier transform infrared (FTIR) spectroscopic analysis of the functional groups confirmed the successful preparation of the composite. The batch process was used to treat aqueous solutions containing CPX. Adsorbent characteristics are evaluated through measurements of moisture content, ash content, point of zero charge (pHpzc), pore volume, ion exchange capacity, specific surface area, oxidative stability, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray spectroscopy. The point of zero charge, specific surface area, moisture content, ash content, pore volume, ion exchange capacity, and oxidative stability of the adsorbent were 7.07, 1991 mg g⁻¹, 11.72%, 78.92%, 1.7%, 0.7857%, and 96.45%, respectively. Adsorption experiments revealed that the beads achieved the maximum adsorption capacity under optimal conditions and that the highest removal efficiency was 89.82%. Among the four linear and non-linear isotherms, the Langmuir adsorption isotherm model indicated that the adsorption occurred by monolayer formation. Thermodynamic and kinetic analyses indicate that the adsorption process is spontaneous and exothermic, and that it adheres to pseudo-second-order kinetics. These findings highlight the GO/PVA/CA composite beads as promising, economical, and eco-friendly adsorbents for the removal of pharmaceutical contaminants (especially CPX) from wastewater.