Fly ash waste as water purifier

A nanomembrane filter that uses inexpensive fly ash waste, a byproduct of thermal power plants, could offer anenvironment-friendly option to treatwater, says a new study.

Developed by a team of scientists from Nepal's Tribhuvan University and South Korea's Chonbuk National University and Hanyang University the nanomembrane filter is made of fly ash and polyurethane and is coated with silver nanoparticles.

Their tests show that the filter can adsorb arsenic and dyes; and killdisease-causing microorganisms, according to a report published in theJournal of Hazardous Materialson 15 January. The spider-web-like membrane captures particles and microorganisms bigger than its pores, resulting in better purification of water than conventional filters.

The technique offers new ways to use onepollutingwaste material to control other pollutants in scalable and inexpensive ways, the report says. Researchers are working on ways to improve the adsorption capacity and regenerative ability of these membranes for commercial water and air filters.

"The formation of spider-web-like nanonets not only increases the surface area of the membrane but also reduces the pore size," lead author Hem Raj Pant of the Institute of Engineering, Kathmandu, explained toSciDev.Net.As a result, impure water takes longer to pass through the filter and that traps impurities, he said.

Silver nanoparticles added to the membrane give it antibacterial properties, but the paper does not mention any water quality analysis, says Prakash Amatya, technical advisor at Handmade Water, a non-profit that treats waste water from dyeing units In Kathmandu.

Amatya also says that the paper sheds no light on how the toxic heavy metal compounds in the fly ash can be safely and cost-effectively prevented from leeching into water. "The findings seem promising but they still need to be tested to gauge water quality."

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Taxonomy

• Filtration
• Wastewater Treatment
• Filtration