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Self-assembled TEMPO Cellulose Nanofibers – Graphene Oxide based Biohybrids for Water Purification Chuantao Zhu, Peng Liu, and Aji P Mathew ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 30 May 2017 Downloaded from http://pubs.acs.org on May 31, 2017
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ACS Applied Materials & Interfaces
Self-assembled TEMPO Cellulose Nanofibers – Graphene Oxide based Biohybrids for Water Purification Chuantao Zhu, Peng Liu and Aji P Mathew* Division of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden
ABSTRACT: Nanocellulose, graphene oxide and its combinations there off, have triggered great attention for the application of water purification recently, due to the unique adsorption capacity, mechanical characteristics, coordination with transition metal ions, surface charge density etc.
In the current work TEMPO (2,2,6,6-tetramethylpiperidine-1-oxylradical) -
mediated oxidation nanofibers (TOCNF) and graphene oxide sheets (GO) or graphene oxide nanocolloids (nanoGO) biohybrids were prepared by vacuum filtration method to obtain selfassembled adsorbents and membranes for water purification. The porous biohybrid structure, studied using advanced microscopy techniques, revealed a unique networking and selfassembling of TOCNF, GO and nanoGO, driven by the morphology of the GO phase and stabilized by the inter molecular H- bonding between carboxyl groups and hydroxyl groups. The biohybrids exhibited promising adsorption capacity towards Cu(II) mainly contributed by TOCNF and formed a unique ‘arrested state’
in water due to ionic crosslinking between
adsorbed Cu(II) and the negatively charged TOCNF and GO phase. The mechanical performance of the freestanding biohybrid
membranes investigated using PeakForce Quantative
NanoMechanics (PF-QNM) characterization confirmed the enhanced modulus of the hybrid membrane compared with TOCNF membrane. Besides, the TOCNF+nanoGO membrane shows
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unique hydrolytic stability and recyclability even under several circles of adsorption and desorption and strong sonication. The study shows that TOCNF and nanoGO hybrids can generate a new generation of water cleaning membranes with synergistic properties with respect to high adsorption capacity, flexibility, hydrolytic stability and mechanical robustness. KEYWORDS: TEMPO cellulose nanofibers, graphene oxide nanocolloids, biohybrid, water purification, Peak Force QNM
1. INTRODUCTION A tremendous amount of research are in progress to identify new robust materials and methods to address one of the most pervasive worldwide problems - Water pollution. 1,2 Nanocellulose, prepared by a top-down approach from abundantly available wood biomass and in particular the 3-7
TEMPO (2,2,6,6-tetramethylpiperidine-1-oxylradical) - mediated oxidised nanofibers
(TOCNF), modified by the position - selective catalytic oxidation of C6 primary hydroxyls from nanocellulose, have shown high efficiency for the removal of water contaminants and has been studied extensively in recent years. 8, 9 TOCNF have unique and characteristic properties in terms of high aspect ratios (>100), high crystallinity (65-95%), low ζ-potential in water (~-75 mV), high tensile strengths (200-300 MPa) and elastic moduli (6–7 GPa). 8, 10 The carboxyl and hydroxyl groups on the surface of TOCNF is found to co-ordinate effectively and capture heavy metallic cations (Cu(II), Co(II), Ni(II), Cd(II), Ag(I))
11-13
or different organic pollutants (p-
nitrophenol, 2,4,5-trichlorophenol, and amoxicillin) etc 14-16 Our recent studies showed that the adsorption capacity could even reach to 374 mg/g toward Cu(II) by in-situ TEMPO modified membranes 17 which is much higher than many other bio-based adsorbents (
