Acrylic acid grafted and acrylic acid/sodium humate grafted bamboo cellulose nanofibers for Cu2+ adsorption

Abstract

Bamboo cellulose nanofibers-graft-poly (acrylic acid) (BCN-g-PAA) and bamboo cellulose nanofibers-graft-poly (acrylic acid)/sodium humate (BCN-g-PAA/SH) were synthesized for the first time and sequentially utilized as biosorbents for removal of Cu²⁺ from aqueous solutions. The chemical structure and morphology of both modified nanofibers were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. Batch adsorption experiments were conducted to elucidate their adsorption behaviors on Cu²⁺. The influencing factors, such as pH, contact time and initial Cu²⁺ concentration, on Cu²⁺ adsorption were investigated in detail. It was discovered that pH strongly influenced the Cu²⁺ adsorption. When pH increased from 2.0 to 4.5, the adsorption capacities of both modified nanofibers were improved significantly. Adsorption isotherm studies indicated that the Cu²⁺ adsorption could be described well by the Freundlich equation. Meanwhile, their adsorption kinetics was more likely to follow the pseudo-second-order model. These nanocellulose-based adsorbents exhibited very fast adsorption rates. The calculated adsorption capacities at equilibrium (q^cal_e) for BCN-g-PAA and BCN-g-PAA/SH were 0.727 and 0.709 mmol g⁻¹, significantly higher than that of BCN (0.286 mmol g⁻¹). Adsorption/desorption cycling tests suggested that the introduced SH segments allowed for improved reusability of BCN-g-PAA/SH.