Designing a robust biocompatible porous polymeric membrane using Laponite and graphene oxide for versatile and selective adsorption of water contaminants

Abstract

For reclaiming contaminated water, nanoparticle-incorporated porous polymeric membranes provide the requisite functionality for efficient and selective adsorption of toxic molecules. To this end, a simple yet innovative material selection strategy was adopted to prepare a robust and high-performance membrane system by the phase-inversion method using thermoplastic polyurethane (TPU), Laponite, graphene oxide (GO) and a hybrid derived from their aqueous “co-dispersion”, viz., Laponite/GO (LGO). The addition of 12 wt% LGO substantially improved the hydrophilicity, porosity, pure water flux (PWF), and mechanical properties of TPU membranes. Notably, the above membrane showed a striking 20-fold increase in PWF (from ∼27 to ∼652 Lm-2h−1), a 43-fold increase in elastic modulus, a 10-fold increase in tensile strength and a 3-fold increase in toughness and displayed synergistic improvement in mechanical properties. At 12 wt% LGO, the rejection efficiency of > 98%, >95%, and ∼86%, and the adsorption capacity of ∼47 mg/g, ∼49.3 mg/g and ∼16.8 mg/g for methylene blue (MB), crystal violet (CV) and rhodamine B (RhB) dyes, respectively were observed. The dye adsorption efficiency was comparable with that of poly(vinylidene fluoride) (PVDF)-LGO membranes. Owing to the anionic functional groups in LGO, the nanocomposite membranes displayed excellent selectivity of adsorption. The dye adsorption by the nanofiller-TPU membranes showed a pseudo-2nd-order kinetic behavior, indicating chemisorption; while the pristine TPU showed marginal physisorption of dyes. The LGO-filled membranes also showed efficient adsorption of Pb2+ and As5+ ions from water, with efficiency increasing with LGO content, showing > 90% efficiency with 15 wt% LGO. The nanocomposite membranes showed no cytotoxicity effect and supported the proliferation of human epidermal keratinocytes (HaCaT) cells. On these accounts, the LGO-TPU membranes promise the development of high-performance and cost-effective filtration membranes.