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Wednesday, 21 June 2017

Nanocellulose based functional membranes for water cleaning: Tailoring of mechanical properties, porosity and metal ion capture

Published Date
Received 21 February 2016, Revised 7 April 2016, Accepted 4 May 2016, Available online 13 May 2016.

Author
Zoheb Karim. Author links open the author workspace.a. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceb. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceSimon Claudpierre. Author links open the author workspace.a. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceMattias Grahn. Author links open the author workspace.b. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceKristiina Oksman. Author links open the author workspace.a. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceAji P. Mathew. Author links open the author workspace.Opens the author workspaceOpens the author workspacea. Numbers and letters correspond to the affiliation list. Click to expose these in author workspacec. Numbers and letters correspond to the affiliation list. Click to expose these in author workspace
a
Division of Materials Science, Luleå University of Technology, 97187 Luleå, Sweden
b
Division of Chemical Technology, Luleå University of Technology, 97187 Luleå, Sweden
c
Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden

Highlights

Nanocellulose based layered membrane for capturing metal ions from water was developed.
The membrane pore structure was controlled by processing conditions and acetone treatment.
High metal ions removal efficiency via surface adsorption followed by clustering of metal ions.
Modeling indicates that the nanofiber layer contribute significantly to the flux resistance.

Abstract

Multi-layered nanocellulose membranes were prepared using vacuum-filtration of cellulose nanofibers suspensions followed by dip coating with cellulose nanocrystals having sulphate or carboxyl surface groups. It was possible to tailor the specific surface area, pore structure, water flux and wet strength of the membranes via control of drying conditions and acetone treatment. Cellulose nanofibers coated with cellulose nanocrystal with carboxyl surface groups showed the highest tensile strength (95 MPa), which decreased in wet conditions (≈3.7 MPa) and with acetone (2.7 MPa) treatment. The membrane pore sizes, determined by nitrogen adsorption/desorption were in nanofiltration range (74 Å) and the acetone treatment increased the average pore sizes to tight ultrafiltration range (194 Å) with a concomitant increase (7000%) of surface area. The water flux, also increased from zero to 25 L m−2 h−1 at a pressure differential of 0.45 MPa, for acetone treated membranes. Modeling of the permeance showed that the middle layer of cellulose nanofibers was responsible for the majority of the resistance to flux and the flux can be improved by increasing the porosity or decreasing the thickness of this layer. The membranes irrespective of the surface functionality showed exceptional capability (≈100%) to remove Ag+, Cu2+ and Fe3+/Fe2+ ions from mirror industry effluents. Surface adsorption followed by micro-precipitation was considered as the possible mechanism of ion removal, which opens up a new generation of ultrafiltration membranes with high rejection towards metal ions.

Keywords

Nanocellulose
Membranes
Water purification
Heavy metal ions
Mechanical properties
Water flux
For further details log on website :
http://www.sciencedirect.com/science/article/pii/S0376738816303192

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