Adsorption of lead ions from aqueous solutions by porous cellulose nanofiber–sodium alginate hydrogel beads

Herein we report a new type of adsorbent for the efficient removal of Pb(II), which is prepared from cellulose nanofiber (CNF) and sodium alginate (SA) via a simple cross-linking method. During this process, the porous structure of the hydrogel beads was formed by the disintegration of calcium phosphate. The performance and structure of the prepared beads were systematically examined by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, zeta potential measurements, and scanning electron microscopy. Investigations revealed that the adsorption equilibrium was attained after approximately 120 min. In addition, 82% of Pb(II) ions were absorbed in the initial 40 min at 297 K. The adsorption process was consistent with a pseudo-second order kinetic model and the Langmuir adsorption isotherm model, and the limit adsorption capacity reached 318.47 mg g−1. Acid treatment and regeneration experiments verified that the adsorption capacity of Pb(II) on the beads was satisfactory, and the adsorption rate remained at >80% after 5 cycles. These results indicate that the prepared beads are potential adsorbents for water treatment.