Hyperbranched Nanocellulose Enabling Rapid Boron Removal from Aqueous Environment

Abstract

The potentially toxic electroneutral and small boron species in water have presented a major challenge in their removal using conventional membrane technologies. The facile functionalization of cellulose nanocrystals (CNCs) with amino-polyol was successfully demonstrated and resulted in essential hydroxyl and amine functional groups for strong interactions with boron. The maximum boron uptake by the amino-polyol CNC (AP-CNC) was determined to be 71.9 mg g -1 at 303 K, and the sorbent nanomaterial was capable of reaching over 90% of its adsorption capacity within 1 minute. The as-synthesized AP-CNC showed excellent boron removal performance between pH 7 and 9 due to the predominant di-complexation of boron with the vicinal diols and amines. Furthermore, the larger aggregate of the hyperbranched polymer allowed for more accessible chemisorption sites, which explains the ultrafast kinetics of boron uptake. In this form, the regenerable AP-CNC, which outperformed all other reported sorbent materials, can be useful as a nanofiller in membranes or in sorbent cartridges for water purification and desalination applications.

Keywords: hyperbranched polymers, Cellulose nanocrystals, boron removal, rapid adsorption, water purification