Research and development to overcome fouling of membranes Page: 4 of 47
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as piezoelectric drivers. Even when high voltage pulses were applied to polymorph PVDF
membranes, no significant permeate flux enhancement was recorded.
Detailed feasibility studies were conducted to measure the long-term effect of a piezoelectric
horn on ultrafiltration. Flux was enhanced by a factor of 4 for the filtration of a 1.0% polyethylene
glycol solution through a regenerated cellulose UF membrane when a nominal power of 10 watts
was applied to the piezoelectric horn in contact with a 47-mm membrane. This specific experiment
was run over 21 days, after having reached constant fouling of the membran;.
Even higher permeate flux enhancements were obtained with piezoelectric PZT disc
drivers. Permeate flow rate was increased by a factor of 8 during the filtration of a 0.45% dextran
solution through a UF polysulfone membrane (47 mm diameter) assisted 1 - a 2.5-mm-thick lead
zirconate titanate piezoelectric disc driven at 40 watts (2.3 W/cm2). We ha not yet attempted to
optimize the power consumption and performance of the piezoelectric PZT disc driver. PZT disc
experiments have been repeated many times over a period of one month with consistent
enhancement of the flux. No cross flow velocity experiments have been carried out in detail.
However, the feed flow rate was maintained between 1.4 and 1.6 I/min.
Our experiments show that the PZT disc produces higher flux enhancements (up to a factor
of 8) than the piezoelectric horn (up to a factor of 4). We believe that the PZT disc is a more
efficient driver since it is free floating on the permeate side of the ultrafiltration membrane, while
the piezoelectric horn that is adapted to constitute the top portion of the test cell is immobilized and
therefore does not efficiently transmit energy to the membrane~
Because of the high efficiency and ease of adaptability of ceramic element drivers, we plan
a detailed study of their long-term performance on piezoelectric-driven ultrafiltration in Year 2.
This study will provide a basis for applying piezoelectrically assisted ultrafiltration to industrial
processes such as whey protein filtration and solvent recovery in deasphalting. We will also
pursue the development of ceramic piezoelectric drivers with controlled porosity to overcome the
major limitation of the PZT disc drivers and still provide a backing support to the ultrafiltration
membrane. Further, we will configure one or more backing supports prototypical of the supports
necessary for winding into spiral modules.ii
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Narang, S. C.; Sharma, S. K.; Ventura, S. C.; Roberts, D. L. & Ahner, N. Research and development to overcome fouling of membranes, report, June 1, 1992; Menlo Park, California. (https://digital.library.unt.edu/ark:/67531/metadc1447425/m1/4/: accessed July 15, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.