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Magnetically Activated Self-Cleaning Membranes

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Final rept.

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Membrane fouling, due to deposition of particulate matter on the surface of the membrane and concentration polarization, limits the use of membranes for water treatment. Mixing at the membrane interface can suppress deposition of particulate matter and break up the concentration boundary layer. We hypothesize that movement of magnetically activated polymer brushes on the membrane surface will create mixing at the membrane interface that suppresses fouling. Commercially available nanofiltration membranes were modified by growing polymer brushes from the surface of the membrane. Two different polymerization methods have been developed UV initiated free radical polymerization and atom transfer radical polymerization. Superparamagnetic nanoparticles were attached to the polymer brushes. In an oscillating magnetic field the brushes oscillate leading to mixing at the membrane surface. Particle image velocimetry has been used to visualize this mixing by comparing the velocity field in the presence and absence of an oscillating magnetic field for nonmodified and modified membranes. Magnetically activated nanobrushes induce mixing at the membrane surface. Moreover, the degree of mixing depends critically on the external field frequency. Filtration experiments were conducted using feed streams of DI water containing polyamide particles and hand soap. Permeate flux and rejection of the hand soap were significantly improved in the presence of an oscillating magnetic field for modified membranes. These results indicate that magnetically responsive brushes may be grafted to the surface of membranes. In an oscillating magnetic field movement of the brushes suppresses fouling and concentration polarization leading to enhanced performance and increased lifetime of membranes.

Subject Categories:

  • Biology
  • Polymer Chemistry
  • Manufacturing and Industrial Engineering and Control of Production Systems
  • Machinery and Tools
  • Electricity and Magnetism
  • Water Pollution and Control

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