EURO-ECO 2011 Hanover 21 - 22 November 2011	Environmental, Engineering - Economic and Legal Aspects for Sustainable Living
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover University of Bremen, Bremen

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Surface-modified sorbents based on various natural and artificial organic and inorganic carriers may be used for decontamination of liquid radioactive wastes (LRW) and radioactive contaminated waters. Methods of synthesis of these sorbents consist in impregnation of sorption active compounds onto the surface of carriers. Physical properties of produced sorbents depend on matter of carrier; in turn chemical properties depend on both nature of carrier and properties of impregnated compound. Produced sorbents can acquire a whole number of properties that were absent in both carrier and impregnated compound. In these cases receiving of multipurpose, selective and specific complex sorbents is possible.

For radiochemical and radio-ecological problems a carrier with a number of necessary properties can be selected for further producing of a sorbent. The Radiochemistry and Applied Ecology chair of UrFU produced surface-modified sorbents based on natural aluminosilicates (clinoptilolite and glauconite), hydrated titanium and zirconium dioxydes and cellulose.

Sorbents based on hydrated titanium and zirconium dioxydes are promising for various LRW treatment and for use as a matrix for radionuclides immobilization with the view of their further dead storage or burial. For example, mixed nickel-potassium ferrocyanide based on hydrated titanium dioxyde (“T-55” sorbent) allows not only to concentrate long-lived ß-emitting radionuclides (such as Cs-137, Sr-90) and actinides into minimal volume, but also reliably retain them for a long time. It possesses high mechanical strength, chemical stability and radiation resistance as well as high selectivity and capacity for caesium (distribution ratio of Cs from tap water under pH 7.8±0.2 is 10^(5.6±1.0) mL·g^-1, static exchange capacity is not less than 270 mg·g^-1). In addition, the “T-55” sorbent is able to extract strontium, uranium and thorium (distribution ratio of Sr from tap water is 10^(2.7±0.2) mL·g^-1, capacity is not less than 36.4 mg·g^-1; distribution ratios of U and Th from pure nitrate solutions under ?? 4.5±0.5 are 10^(3.6±1.4) and 10^(2.7±0.8) mL·g^-1 respectively). The advantage of “?-55” sorbent is lower leaching rates of radionuclides as compared with these described in literature. If distilled water is used as a leachant, leaching rates are 3.7·10^-10 – 8.2·10^-12 g•cm^-2•d^-1 for caesium and 1.8·10^-10 – 1.2·10^-12 g•cm^-2•d^-1 for strontium; if tap water is used as a leachant, leaching rates are 1.4·10^-11 – 1.5·10^-12 g•cm^-2•d^-1 for strontium.

Nuclear tests, “peaceful” nuclear explosions, normal activity and accidents on nuclear fuel cycle enterprises, work of transport and research reactors led to radioactive contamination of surface and ground waters. Under realizing of environment rehabilitation sorption technologies using cheap and easily accessible materials may be applied for decontamination of large volumes of radioactive contaminated natural waters, including drinking water. Surface-modified sorbents based on natural aluminosilicates and grain farming waste materials (husk and haulm of oat, rice and buckwheat) may be used as such materials. Interest in natural aluminosilicates and their intensive study are attracted by both presence of proven deposits in many countries and their ion exchange features. Annual renewal of organic feedstock, low prime cost, simplicity of recycling and low ash content also make their use prospective. Distribution ratios of Cs for mixed nickel-potassium ferrocyanide based on clinoptilolite reach up to 10^(6.3±0.2) mL·g^-1, and for ferrocyanide based on cellulose rice husk and buckwheat haulm are 10^(5.6±0.1) and 10^(4.3±0.1) mL·g^-1 respectively.

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