Returning land contaminated as a result of radiation accidents to farming use

Abstract

An assessment is given of the possibility of sorbents based on natural aluminosilicates (glauconite and clinoptilolite) being used for remediation of radioactively contaminated land with the aim of returning it to farming use. A comparative study of selectivity and reversibility of radiocaesium and radiostrontium sorption by natural aluminosilicates as well as by modified ferrocyanide sorbents based on these aluminosilicates was made. It was found that surface modification of aluminosilicates by ferrocyanides increases the selectivity of synthesized sorbents to caesium by 100–1000 times, increases sorption capacity and makes caesium sorption almost irreversible, whereas, selectivity of these sorbents to strontium radionuclides remains approximately the same as for natural aluminosilicates. The caesium distribution coefficient for mixed nickel–potassium ferrocyanide on glauconite is 10(5.0±0.6) L kg−1, the static exchange capacity (SEC) is 63 mg g−1; for mixed nickel–potassium ferrocyanide based on clinoptilolite caesium distribution coefficients in various concentration ranges are 10(7.0±1.0), 10(5.7±0.4) and 10(3.2±0.7) L kg−1, total SEC was 500 mg g−1. Caesium leaching by various leaching solutions from saturated mixed nickel–potassium ferrocyanide based on clinoptilolite was lower than 2%; from saturated mixed nickel–potassium ferrocyanide based on glauconite it was 1.5–14.6%. Ferrocyanide sorbents, based on glauconite and clinoptilolite are recommended for remediation of land, contaminated by caesium as a result of the Fukushima accident in Japan. Use of these sorbents should decrease the transfer of caesium to agricultural vegetation up to a factor of 20.