Preparation of carboxylate-functionalized cellulose via solvent-free mechanochemistry and its characterization as a biosorbent for removal of Pb2+ from aqueous solution

Carboxylate-functionalized cellulose can be used as a low cost but effective biosorbent for heavy metals remediation. In this study, it was simply fabricated from wood cellulose and succinic anhydride via solvent-free mechanochemistry in the absence of catalyst at ambient temperature through pan-milling. Fourier transform infrared spectra (FT-IR) confirmed the realization of mechanochemical esterification of cellulose. Reaction kinetics study showed that this solid-state mechanochemical reaction was governed by "slow followed by fast" kinetics model. The reaction sites were mainly at the new surface of cellulose powder where hydrogen bondings in cellulose were broken up and hydroxyl groups were activated due to the fairly strong forces imposed by the pan-mill. X-ray photoelectron spectroscopy (XPS) indicated that the mechanochemical succinylation of cellulose occurred even in a short milling time. The exponential increment of surface area of cellulose during pan-milling was correlated to the increasing substitution degree. Preliminary adsorption studies showed that the modified cellulose possessed excellent adsorption capacity towards Pb(2+), with lead ion uptake value of 422 mg/g and 84.4% metal removal from a 500 mg/g Pb(2+) solution, significantly higher than those values for unmodified cellulose.