Fabrication of carboxylated cellulose nanocrystal/sodium alginate hydrogel beads for adsorption of Pb(II) from aqueous solution.

Carboxylated cellulose nanocrystal-sodium alginate (CCN-Alg) hydrogel beads were easily prepared through a cross-linking method. The structure and properties of the composite beads were characterized by TEM, FTIR, SEM, XPS, thermogravimetric analysis (TGA), and zeta potential measurement. A high ratio of 76% of the Pb(II) ion was adsorbed within the first 2h, and the adsorption equilibrium was nearly reached after 3h. The experimental isotherm could be fitted by the Langmuir model, yielding an extreme adsorption capacity of 338.98mgg-1. The adsorption process followed a pseudo-second-order kinetic model, and thermodynamic analyses confirmed that the adsorption is a spontaneous and endothermic process. Regeneration tests with acid treatment indicated that the CCN-Alg beads performed well in repeated Pb(II) adsorptions, as they could maintain an adsorption capacity of 223.2mgg-1 after five repeated cycles. These results indicate that these CCN-Alg beads are a potentially effective and sustainable adsorbent for application in wastewater treatment.