Scientists Created Sorbent to Recycle Hazardous Chromium Containing Waste

12:06, February 4, 2022

The output is pure water and valuable chromium compounds

Scientists of the Institute of Metallurgy of the Ural Branch of RAS and Ural Federal University have synthesized a highly productive composite reusable sorbent for removal of chromium from water. Tests of the sorbent on wastewater of one of the enterprises of the Sverdlovsk region showed the possibility of extracting chromium from wastewater, purifying it to drinking water quality. The chromium compounds obtained in this process are returned to production processes.

Chromium easily penetrates into water, soil, and plants, being a toxic environmental pollutant - mutagen and carcinogen. The method of recycling accumulated chromium-containing waste proposed by Ural scientists is a way to solve the pressing problem not only for Russia, but also for many other countries.

The results of the experiments allow the researchers to claim that the synthesized composite sorbent is extremely effective, and the developed technology of water purification is extremely promising for practical application and is significantly superior to analogues. An article describing the scientific work was published in the journal Hydrometallurgy.

The scientists used the clay mineral montmorillonite, traditionally used in sorption technologies, as the basis for the created sorbent. At the first stage of development, the mineral was modified with magnetite nanoparticles.

"This weighed the small and light montmorillonite particles and then allowed them to easily precipitate together with the adsorbed chromium by applying a magnetic field," explains Denis Ordinartsev, head of the research group and a senior researcher at the Institute of Metallurgy, UB RAS.

At the next stage of the synthesis of the new sorbent, a molecule of the main sorption element from the group of cationic surfactants selective with respect to chromium was introduced into the layered structure of montmorillonite.

"This led to a significant expansion of the interlayer space of montmorillonite. As a consequence, the sorption capacity of the material increased by 5 times, from 20% in the initial mineral to 98-99% in the obtained composite," adds Denis Ordinartsev.

The synthesized sorbent was placed in an aqueous solution containing chromium.

"During their interaction, the sorbent layers are slightly compressed, firmly holding the chromium particles. When alkali is added to the solution, the reverse process - desorption - occurs: the sorbent releases chromium and is then sent for further use," Ordinartsev describes.

The remaining chromium in the solution was adsorbed by precipitation on iron ash (homogeneous suspension of nanoscale particles), a substance also selective for chromium. As a result, an aqueous solution purified of chromium and having the quality of tap water was obtained.

"At the same time, we obtained two groups of chromium-containing substances - pure chromium compounds formed as a result of adsorption by the synthesized composite sorbent, and chromium-iron concentrate - the product of solution post-treatment with iron ash. Pure chromium compounds are required, for example, in the manufacture of stainless and chrome-plated steel, electrical insulation and corrosion-resistant coatings, in the aerospace industry, and even in the manufacture of leather goods. Chromium-iron concentrate is used, among other things, in iron alloying to produce, for example, chromium iron," notes Svetlana Estemirova, research participant, co-author of the article, head of the educational laboratory of the Department of Metallurgical Science at UrFU.

In this way, scientists have created a waste-free technology for recycling chromium-containing waste.

"Our sorbent has maximum sorption efficiency and is designed for multiple use, which prevents the depletion of the clay stockpile. The use of the sorbent will not lead to the formation of new wastes," emphasizes Denis Ordinartsev.

Reference

The work was executed in accordance with the Basic Research Program of the State Academies of Sciences, approved by the Government of the Russian Federation.

The news article was translated by UrFU International Marketing Office
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