Boron Removal by Polymer-Assisted Ultrafiltration

Boron contamination of natural waters is a widespread environmental problem which lacks a cost-effective solution. Polymer-assisted ultrafiltration is a method of boron removal that is compatible with other water-treatment processes. This boron removal technique exploits the pH-dependent complexation between boric acid and a macromolecule containing vicinal diol groups to prevent boric acid from passing through an ultrafiltration membrane. The concentration of boron in treated water was reduced from 10.5 ppm to less than 2 ppm through ultrafiltration of an aqueous solution containing boric acid and a polymer synthesized by grafting N-methyl-D-glucamine (NMG) onto poly(epichlorohydrin). The NMG groups, when tethered to the polymer, exhibited stronger affinity for boron than expected from equilibria between NMG and boric acid.