Sorbents for Radioactive Metals Extraction
Development of High Efficient Selective Sorbents for Radioactive Metals Extraction from Industrial Waste
Tech Area / Field
- CHE-SYN/Basic and Synthetic Chemistry/Chemistry
- ENV-MIN/Monitoring and Instrumentation/Environment
- ENV-RWT/Radioactive Waste Treatment/Environment
8 Project completed
Senior Project Manager
Mitina L M
Karpov Institute of Physical Chemistry, Russia, Moscow
- VNIIEF, Russia, N. Novgorod reg., Sarov
- Pacific Northwest National Laboratory, USA, WA, Richland\nUniversity of Central Florida / Department of Mechanical, Materials and Aerospace Engineering, USA, FL, Orlando\nLos-Alamos National Laboratory / Chemistry Division, USA, NM, Los-Alamos\nUniversity of Akron / Institute of Polymer Engineering, USA, OH, Akron\nUniversity of North Carolina at Wilmington / Department of Chemistry, USA, NC, Wilmington
Project summaryThe purpose of the project consists in development of a method of selective sorbents preparation and creation of an effective and inexpensive method of heavy metals and radioactive elements extraction from aqueous solutions containing various amounts of these substances. Existing methods of liquid waste purification are very expensive, labor-consuming and inefficient in some cases. Moreover methods of chemical sedimentation used sometimes as well as electrochemical methods do not allow to carry out effective purification and cannot be used for processing of the diluted solutions of radioactive substances, which are very dangerous owing to cumulative effect.
The problems connected to purification of diluted and semi-diluted solutions of polluting substances, can be solved due to use absorbing systems. Thus the main difficulty consists in development of selective sorbents, capable to take out "harmful" heavy metal and, in particular, radioactive elements (Cu2+, Ni2+, Cr6+, Sr2+, Cs+, U6+, etc.) in the presence of a plenty of "ballast" metals (Ca2+, Mg2+, Na+, etc.) not rendering harmful influence on an environment.
Now various synthetic organic ion exchange resins and natural ionites (granulated bentonite, montmorillonite, etc.) are widely applied for sewage purification from various pollutions, in particular from heavy metal ions.
However technology of sewage purification from radioactive ions by using ion exchange resins has the essential lack consisting in very small economic efficiency of the subsequent extraction these ions from ion exchange resins for following recycling of these metals. In this connection, in practice ion exchange resins containing radioactive elements absorbing subject to entombment, that on the one hand does not allow to utilize the valuable radioactive elements allocated from sewage, and on the other - represents a serious environmental problem.
From this point of view creation of sorbents based on crown-ethers (CE) is very perspective. CE are capable to selectively form the stable complexes with heavy metals cations as well as with rare earth and radioactive elements. Such CE properties open up new possibilities for preparing the high selective sorbents by CE attachment to various substrates.
Now to prepare CE-based sorbents use the chemical methods consisting in introduction of special functional groups in CE and followed linking of these functional groups with a substrate by various chemical methods. However these methods are characterized by serious lacks:
- First of all it is necessary to carry out the complicated synthesis of CE, containing special functional groups, as the chemical industry does not produce such products;
- Besides it is necessary to carry out the chemical treatment of a substrate surface for its linking with CE.
These lacks result in high cost of such sorbents and essentially complicate process of their preparation. Besides the introduction of additional functional groups in CE structure can result in reduction of selectivity of such CE in the process of its complexing with metal cations.
To obtain more effective and selective CE-based sorbents we offer a method of CE fixation on a surface and in volume of solid matrixes using ionizing irradiations. Works are directed to such sorbents obtaining will develop in two directions:
1. CE grafting on substrates consisting of various mineral substances having high specific surface (silica, aluminum silicates, porous ceramic matrixes).
2. Preparation sorbents based on hydrophilic polymer films, containing CE. The most perspective in this respect are polymer films containing uniform distributed CE units in whole matrix volume, as at swelling of such films in a aqueous solutions their sorption capacity sharply grows.
Crown-ethers are capable to take out selectively radioactive ions from aqueous solutions containing ballast metal ions that concentration on 2-3 orders exceeds radioactive ions one. At the same time, the radioactive manufactures waste contains the various "ballast" metal ions, that concentration frequently more, than on 3-5 orders exceeds concentration of radioactive particles. Such high concentration of ballast ions appreciably reduces efficiency of radioactive ions selective extraction from a solution. In this connection it is profitable to carry out the purification of such aqueous solutions and following treatment of the taken out radioactive elements in some stages. The first stage of this process assumes the solution treatment by rather inexpensive easily accessible ion exchange resins that will trap the overwhelming majority of ballast metal ions, at the second stage the solutions after their treatment by ion exchange resins will be exposed to purification by CE-based sorbents. The further treatment of the radioactive elements allocated thus will allow to utilize them for subsequent use.
Thus, work under the project will include the decision of the following practical problems:
- Development of a preparation technology of selective high-efficient sorbents for absorption heavy and radioactive metals from solution;
- Development of an extraction technology of heavy and radioactive metals with the help of CE-based sorbents for subsequent utilizing of these metals;
- Design and creation of complex method for deep purification of solutions from radioactive elements in the presence of a plenty of ballast metal ions (calcium, magnesium, sodium, iron, etc.) by ion exchange resins and CE-based sorbents;
- Design and creation of high-sensitivity techniques of analyzing of sorbents efficiency and degrees of purification of treated solutions;
- Creation of basic elements of technological system for aqueous solutions purification by sorbents elaborated.
Results of this project can be used in industrial regions, in which environmental contamination (for example, Chernobyl, Chelyabinsk) is observed, for reservoirs and territories purification. Heavy metal cations and, in particular, radioactive elements extracted by the sorbents elaborated further can be allocated in the pure state and used for corresponding purposes.
Planned work has not only important applied value, but also represents significant scientific interest. The results received will bring essential contribution to the theory of chemical-radiation reactions at the solid surfaces of the various natures, and also to the theory of ion transfer processes in the diluted solutions and ions sedimentation on the active surfaces.
This project will be carried out by two organizations: State Scientific Center “Karpov Institute of Physical Chemistry” and Russian Federal Nuclear Center VNIIEF. Scientists and engineers of these scientific centers have high qualification for performance of the Project. They have necessary equipment that have been designed and fabricated partially within the framework of ISTC projects №№ 286 and 1229.
Scientists of Karpov Institute of Physical Chemistry have large experience in field of development of the sorbents based on CE as well as in field of studying of the mechanism and kinetic features of sorption processes of various heavy and nonferrous metals (copper, iron, chrome, nickel, zinc, cadmium, molybdenum, lead, etc.) by polymer ion exchange resins. For last 15 years they published over 40 articles and patents devoted these items. Moreover about 50 reports were submitted to various conferences and seminars. These results are generalized in number of monographies and reviews. Employees of Russian Federal Nuclear Center VNIIEF have large experience in the field of X-ray–fluorescent analysis of various elements.
Both institutions have necessary technological base for works performance on the project.
The work on the project will be pided between VNIIEF and NIFHI with the following way. NIFHI performs the development of sorbents preparation technology, the technology of waste and washing waters purification from "ballast" metal ions as well as radioactive and heavy ions, obtains pilot sorbent samples and carries out their investigation. VNIIEF creates experimental instrument base for investigation of sorbents efficiency, develops the analytical methods and software, and performs experimental studies of sorbents characteristics. The specialists of both scientific centers will jointly analyze the theoretical questions of metal ions transfer in aqueous solutions and their deposition onto active surfaces. Specialists of NIFHI and VNIIEF will carry jointly out the analysis of results obtained and the offers concerning the development technology of a waste purification from radioactive elements as well.
Twenty-two (22) scientists and engineers from NIFHI and VNIIEF, who earlier were busy with development and testing of nuclear weapon, will be involved in the activity on this Project. The work on the Project will allow reorientation of these scientists to the solution of important ecological tasks, thus use their scientific potential for peaceful purposes. Presenting alternative possibilities to Russian specialists, who earlier worked on classified topics, connected with the development of nuclear weapons, the work on the Project will promote their involvement into the international scientific community.
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