Functionalized boron nitride composite ultrafiltration membrane for dye removal from aqueous solution

Abstract

Two-dimensional (2D) hexagonal boron nitride (h-BN) nanosheets being isostructural to graphene, manifests robust properties for water treatment. However, it exhibits lower dispersibility in polar solvents limiting its utilization for membrane application. A facile two-step processes of (1) exfoliation of h-BN with urea followed by grafting polyethylene glycol using 3-Aminopropyl triethoxysilane to synthesize polyethylene glycol grafted boron nitride PEG-g-(NH2)BN and (2) deposition of as-fabricated nanosheets on the support membrane through vacuum filtration is carried. In the first step, the process leads to 6–14 layered amine-functionalized boron nitride BN(NH2) nanosheets of ~47 nm diameter and the later results of ~53 nm PEG-g-(NH2)BN nanosheets. In the second step, the deposition thickness was tuned through varying the concentration of the PEG-g-(NH2)BN nanosheet colloidal solution. The final functionalization imparts enhanced surface wettability through the transformation of superhydrophobic h-BN to superhydrophilic PEG-g-(NH2)BN. Improved wettability and porosity results in ultra-high water flux of 1253 L m−2 h−1 bar−1. Higher hydrodynamic resistance through the increasing thickness of deposited PEG-g-(NH2)BN nanosheets from approximately 3 μm–12 μm, results in permeance decrease from 1253 L m−2 h−1 bar−1 to 840 L m−2 h−1 bar−1 (about 33% decrement) and the MB exclusion improved to 98% removal even under different pH conditions. The exclusion properties of these membranes were tested stable with charge-neutral molecules.