HOUSTON, Sept. 25 (Xinhua) -- Researchers from a U.S. university have turned a ceramic membrane with microscale pores into a superhydrophilic filter that can eliminate the common problem of fouling.
According to a news release on Monday by Rice University, Texas of the United States, the new filter produced by Rice University researchers has proven able to remove more than 90 percent of hydrocarbons, bacteria and particulates from contaminated water produced by hydraulic fracturing operations at shale oil and gas wells.
The researchers determined that one pass through the membrane should clean contaminated water enough for reuse at a well, significantly cutting the amount that has to be stored or transported.
The work by Rice chemist Andrew Barron and his colleagues is reported in Nature's Open Access Scientific Reports.
Barron and his colleagues used cysteic acid to modify the surface of an alumina-based ceramic membrane, making it superhydrophilic, or extremely attracted to water. The superhydrophilic surface has a contact angle of 5 degrees.
The acid covered not only the surface but also the inside of the pores, and that kept particulates from sticking to them and fouling the filter.
The filters keep emulsified hydrocarbons from passing through the material's ionic charged pores, which are about one-fifth of a micron wide, small enough that other contaminants cannot pass through. The charge attracts a thin layer of water that adheres to the entire surface of the filter to repel globules of oil and other hydrocarbons and keep it from clogging.
A hydraulically fractured well uses more than 5 million gallons of water on average, of which only 10 to 15 percent is recovered during the flowback stage.
"This makes it very important to be able to re-use this water and not every type of filter reliably removes every type of contaminant," Barron said.
