The primary method for removing oil products, pesticides and heavy metals from wastewater is the use of membranes – porous polymer compounds that retain foreign substances as water passes through them during filtration. A cheaper alternative is the use of ceramic membranes, which can be produced from industrial waste, including ash that is formed during the combustion of fuel at coal-fired TPPs. “Ceramic membrane substrates have a number of advantages over polymer membranes, including strength, chemical and temperature stability, regenerability and long service life. On the surface of a substrate, a number of layers are formed, with pore size decreasing from layer to layer. The membrane’s retention properties depend on the uppermost selective layer,” Ilya Ryzhkov, doctor of physical and mathematical sciences, is quoted as saying by the Krasnoyarsk Science Center RAS.
Ash contains aluminosilicate microspheres, which, thanks to their composition, spherical shape and low density, are suitable for obtaining lightweight ceramic materials. In order to obtain membrane substrates from this material, the authors pressed ash powder and put it into a furnace, where it was burned at a temperature of 1,100 degrees Celsius. After two hours of exposure, flat substrates with a diameter and thickness of 26×3 millimetres were obtained. Due to the high sintering temperature, the substrates were very durable, but remained quite porous.
The scientists conducted an experiment, in which water contaminated with microsilica particles was passed through samples of membrane substrates made of coal waste. The samples showed an almost 100% purification efficiency. “The resulting substrates can be used as a basis for creating micro-, ultra- and nanofiltration membranes, including those with electrically conductive selective layers. Our method and the use of ash waste in the production of membrane materials will help reduce emissions of fine microparticles into the environment and facilitate the development of technologies for comprehensive processing of thermal power waste,” Ilya Ryzhkov, doctor of physical and mathematical sciences, is quoted as saying by the Krasnoyarsk Science Center RAS.
