科研之友
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摘要
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 (approximate to 3.7 MPa) and with acetone (2.7 MPa) treatment. The membrane pore sizes, determined by nitrogen adsorption/desorption were in nanofiltration range (74 angstrom) and the acetone treatment increased the average pore sizes to tight ultrafiltration range (194 angstrom) 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 (approximate to 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 ultra filtration membranes with high rejection towards metal ions.
- 出版日期2016-9-15
