A Russian-Belorussian research team has come up with a new method for underground water deironing. Their findings show that modified refractory chamotte granules increase the efficiency of water deironing up to 78%, making underground waters safe to drink. The study was published in the Journal of Environmental Chemical Engineering.
Groundwater is one of the cleanest natural sources of drinking water available. At the same time, often requires deironing — removal of the dissolved iron ions — before the water could be used. For instance, the iron content in underground water could reach 40 mg/L and even higher while in accordance with the requirements of the World Health Organization (WHO) the permissible content of iron in drinking water is 0.2 mg/L. Such water requires purification before it could be safely used.
Today, the most common method for removing naturally occurring iron from water is oxidation with oxygen or other oxidizing agents, i.e potassium, chlorine and ozone. The process involves the oxidation of the soluble forms of iron to their insoluble forms and then removal by filtration. It is carried out using deironing filters, filled with granulated quartz sand, different types of coals, granite crumbs, and others. The efficiency of the deironing could also be increased by surface modification of the fillers. The most commonly used method for fillers’ surface modification is the soaking of the modified material in solutions of metal salts, followed by their drying and calcination within a long time. This approach is very energy- and time-consuming.
The solution combustion synthesis (SCS) approach is considered to be a more efficient and faster alternative. The SCS is based on a combination of homogeneous mixing of initial components in an aqueous solution and their self-propagate combustion in a high-exothermic redox reaction. The whole combustion synthesis process including heating, reaction, and cooling down takes from several seconds to 10 min, depending on reacting system. Besides energy efficiency, the method has several other advantages, including low cost and availability of required chemicals, repeatability, and high adaptiveness for the synthesis of a broad variety of nanomaterials.
The scientists from NUST MISIS and the Institute of General and Inorganic Chemistry of the National Academy of Sciences of Belarus have come up with an innovative method for underground water deironing based on the SCS reaction. They used refractory chamotte as the main component of filter filler. The study found that the modification of the surface of chamotte granules increases the efficiency of water deironing by
“The materials obtained are up to 3 times more efficient than those currently used at drinking water treatment plants. The modification process is up to 30 times more time-efficient than other commonly used techniques, and up to 100 times less energy consuming due to the exothermic and self-sustaining nature of the combustion,” said Valentin Romanovsky, Research Center for Structural Ceramic Nanomaterials at NUST MISIS.
Iron-rich waste (up to 60 wt% of iron) from water deferrization stations were used as a source of iron for the modification of the surface of chamotte granules. A combination of advantages of the solution combustion synthesis with the use of wastes (sediments, obtained during water deironing) as raw materials, will help to develop time and cost-efficient technology for the creation of efficient water deironing filters with a high degree of recycling of secondary resources, the researchers believe.