RADIOACTIVE WASTE TREATMENT

Natural zeolite has a high ion exchange capacity and a particular affinity for heavy metal cations. It can absorb elements such as strontium 90, caesium 137 and other radioactive isotopes from solution and hold them in its 3 dimensional crystal framework. Zeolites react readily with cement and glass systems thus allowing the radioactive waste to be entrapped and contained safely. Zeolites are physically robust and resistant to nuclear degradation, and they are less expensive than organic ion exchange resins.

Sorbent Barriers For Radioactive Waste

Permeable barriers incorporate sorbent materials, including zeolite, to selectively contain contaminants that are percolating from shallow land burial sites of low-level radioactive waste. The zeolites are combined with clays and other materials that retard the migration of leachate for a period long enough to allow exchange and/or decay of radioactive ions.

ZEOLITE MINERAL AGAINST RADIOACTIVE POLLUTION

Zeolites are hydrated aluminosilicates in crystal structures, capable of absorbing many different types of gases, odors, moisture, petrochemicals, ammonia, heavy metals, low-level radioactive elements and a multitude of various solutions. In the USA and Great Britain zeolite are routinely applied for the decontamination of radioactive wastewater to remove Cs and Sr radioisotopes. However, these are small-scale operations compared to the extensive use of natural zeolites at Chernobyl disaster in 1986.

ZEOLITE Mineral  Barriers Against Radioactive Pollution in CHERNOBYL

During the Chernobyl disaster, thirty to forty times the radioactivity of the atomic bombs dropped on Hiroshima and Nagasaki were released. The main radioactive isotopes from the Chernobyl accident were 137Cs, 134Cs, 90Sr, and 89Sr. The details of zeolite applications at Chernobyl remain rather obscure because of a secrecy problem still remaining after disintegration of the former Soviet Union.

About 500,000 tons of zeolite rocks, mainly containing clinoptilolite, were processed at various deposits in Ukraine, Georgia, and Russia specifically for use at Chernobyl.

The majority of the zeolites were used for the construction of protective barriers and for agricultural applications in polluted areas.

Decontamination of potable water of the Dnieper river by using a combination of dust-like clinoptilolite and aluminum sulfate followed by filtration through clinoptilolite layers led to a drastic decrease of radioactivity.

In addition, filters of clinoptilolite tuffs were suggested to extract radionucleides from the drainage water of the encapsulated Chernobyl nuclear power plant.

Filtration reduced 137Cs by 95% and 90Sr by 50-60%. After one year the filters carrying a radioactivity of 10-5 Ci/kg were exchanged and buried. To reduce Cs radionucleides in cow milk in Bulgaria 10% clinoptilolite was added to the cow feed resulting in 30% Cs reduction in the milk. For Cs decontamination of children chocolate and biscuits were prepared containing 2-30 wt.% pure and powdery clinoptilolite. In Western Europe clinoptilolite was tested to reduce radionucleide levels in soil, plants, sheep, broiler chicken, and fruit juice.