Fluorographite Nanoplatelets with Covalent Grafting of Anion-Exchange Resins for Water Purification

Abstract

We have developed a novel green synthetic method to covalently graft fluorographite (FGi) nanoplatelets, with quaternary ammonium polyelectrolyte chains under mild reaction conditions in water. Radical centers on the fluorographite layers react with the radical chain end on short strands of anion-exchange resins. While fluorographite is superhydrophobic, we show that the polymer radical chain end is necessary to initiate defluorination and delamination of the FGi in neutral pH water, without any pretreatment or caustic reagents. Scanning electron microscopy of thin films shows continuous and organized stacking of ellipsoidal nanoplatelets across large defect-free areas. We show that these new materials are highly effective at removing known and emerging contaminants to below environmentally relevant concentrations. Electron microscopy, vibrational spectroscopy, elemental analysis, and thermal analysis data are presented, and they are consistent with defluorination, partial exfoliation, and graphitization during the aqueous polymer grafting reaction. A radical-initiated mechanism is proposed that is consistent with the observed defluorination and oxidation of FGi nanoplatelets. The physicochemical properties, water flux, and morphology of these thin-film assemblies are described in detail. Thin membranes of polymer-functionalized fluorographite removed 99% of perfluorooctanoic acid to below 100 parts per trillion while maintaining a very high water flux over 1100 L h–1 m–2 bar–1. Percent removal of perfluorinated alkyl substances and heavy metal oxyanions versus polyelectrolyte-functionalized fluorographite membrane areal density is reported. The methodology presented in this study is a facile approach toward developing high-performance materials for sustainable and green applications.

Advanced Polymeric Nanocomposite Membranes for Water and Wastewater Treatment: A Comprehensive Review

“…Sahu et al fabricated short polymer brushes of anion exchange resins of vinylbenzyl trimethylammonium chloride and covalently functionalized it onto different carbon nanostructures (SWCNT, fluorographite) in aqueous media that gave rise to conformally coated pinhole-free mesoporous architecture and partially exfoliated stacked nanoplatelet-like thin films that delivered a flux capacity of 692 and 1100 , respectively. Functionalized SWCNT demonstrated a maximum adsorption capacity of 139 for sodium fluorescein and functionalized fluorographite removed 99% of the emerging contaminant perfluorooctanoic acid to below 100 parts per trillion, which is close to the health advisory limit set by US EPA [ 74 , 75 , 254 ].…”

“…Therefore, there is a tradeoff between cost efficiency and performance [ 393 ]. In order to ensure cost effectiveness and long-term use, regeneration and reusability are important factors to be considered for these nanocomposite membranes [ 43 , 54 , 74 , 75 , 393 ].…”

“…There is the possibility of pressure driven membrane deposition of a dispersion of nanomaterials and the polymer [ 70 , 71 ]. Alternatively, NPs can be chemically cross linked to the polymer substrate [ 72 , 73 ], NPs can be grown in situ on the polymer surface [ 68 ], or the polymer can be covalently attached to the nanomaterials surface [ 74 , 75 , 76 ]. TFNCs are typically thin films of NPs coated on a polymer layer or substrate by dip coating, self-assembly, pressure-driven deposition, and other related techniques [ 39 ].…”

Exploring the Self‐Cleaning Facets of Fluorinated Graphene Nanoarchitectonics: Progress and Perspectives

“…ZIF‐8/FG‐SiO 2 composites filled on micro‐pipette tip was utilized to extract chlorophenols which have potential implications in environmental and food samples [144] . There is potential exploration of water desalination, heat transfer, Joule heating impacts using the derivatives of fluorinated graphene and its hybrids [145,146] …”

Amphiphilically Modified Porous Polymeric Nanosandwich‐Based Membranes for Rapid and Efficient Water Treatment

“…The pure water permeation is as high as 1.2 × 10 4 L m −2 h −1 bar −1 , four orders of magnitude larger than that of GO membrane (1.3 L m −2 h −1 bar −1 ). This ultrahigh permeation of water has obvious advantage in the field of emerging porous materials-based membranes (20-3775 m −2 h −1 bar −1 , Figure 4a), [11,13,14,17,[41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] GO-based membranes (21.8-10720 L m −2 h −1 bar −1 ) [3,35,36,[56][57][58][59] and other 2D materialsbased membranes (450-2300 L m −2 h −1 bar −1 , Figure 4b), [60][61][62][63][64] which is attributed to their different separation mechanisms. Solution-diffusion and size exclusion are the two main separation mechanisms of commercial nanofiltration membranes (Figure S16a,b, Supporting Information).…”