New Water Filter can Purify Salt Water

Caroline Petrow-Cohen

Scientists have been working with Metal-Organic Framework membranes (MOF’s)  for some time to be able to filter various small particles from water. Filtering out lithium for lithium ion batteries, calcium for various household products, and small ions for distilled water have all been achieved with the usage of these MOF’s. One recent study focuses on Zirconium MOF’s with hollow fibers that capitalize on hard-acid to hard-base interactions within the membrane to attract specific Na+ ions. This attraction to the Zirconium membrane can hopefully prove to filter salt water into fresh water.

Diagram of hollow fiber filtration system

Hollow fibers are a way of filtration that involves a bunch of small hollow tubes inside a larger tube. The small tubes contain a filter that collects retentate, or the substance being filtered out, and they let the permeate, the clean water, out through the edges of the larger tube. This process has been proven to be effective in filtering out all sorts of small microorganisms as well as ions depending on the type of filter around the inside tubes.

 

 

 

In this study they form the membrane by mixing a ZrCl4 powder with water and other binding powders, pour it into the hollow fibers, and bake it at 120 degrees Celsius for 3 days. The Zirconium grows in a crystalline pattern on the hollow fiber to form the filter.

Through many tests the Zirconium filter showed no degradation or breakage. The rejection of various saline solutions was near 100% and showed that they could successfully filter out small Na+ ions from water.  No membrane degradation occurred in this study to the structure of the hollow fibers or membrane pores. This filter could be a next-generation membrane for water softening and desalination.

What this means for the future is that this could be a new survival necessity for campers, hikers, sailors, and general wilderness safety. This filter could also improve the lives of many people in developing countries to provide easier access to clean drinking water. The researchers point out the need for advanced membrane fabrication technologies to have better membrane attraction and function in the future in order to also make the manufacturing process easier.  Also the manufacturing of this filter is expensive, so inexpensive alternatives need to be discovered in order to create a serious impact. The potential to easily filter out salt from water would be a huge step in the clean water movement that could help save many lives in developing countries in the future.

Lauren Shelby ’19

Sources

http://advances.sciencemag.org/content/4/2/eaaq0066.full

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