EVALUATION OF SYNTHETIC CRYPTOMELANE AS AN ADSORBENT FOR SELECTIVE REMOVAL OF STRONTIUM IONS FROM WATER EFFLUENTS

Abstract

90Sr is a fission product of uranium, which has become a component of the environment due to nuclear weapon tests, the operation of nuclear fuel cycle enterprises and nuclear power plants, or radiation accidents. The chemical properties of strontium ions are similar to calcium, so the development of techniques for selective removal of strontium radionuclides from water effluents assumed greater importance in recent years. Manganese dioxide mineral species are considered promising adsorption materials for selective removal of strontium radionuclides from water effluents. Synthetic cryptomelane (manganese dioxide mineral with tunnel structure) was prepared by the hydrothermal method in an acidic solution. The results of X-ray diffraction and Fourier transform infrared spectroscopy confirmed the tunnel structure of the synthesized material. Results of scanning electron microscopy revealed that cryptomelane is formed as micron-sized rounded particles of cocoon-shaped morphology composed of nanofibers. To determine the efficiency of the as-synthesized cryptomelane in the selective removal of strontium ions from multicomponent solutions, the effect of contact time, foreign cations (Na, K, Ca), and pH on strontium ions adsorption was investigated in detail. The as-synthesized cryptomelan demonstrated fast adsorption kinetics and enhanced adsorption in an alkaline medium, as well as high adsorption efficiency in diluted multicomponent solutions. The desorption experiments demonstrated that strontium ions adsorbed by the synthesized cryptomelane cannot be easily desorbed. The obtained results allow considering synthetic cryptomelane as a promising material for selective removal of strontium ions from multicomponent solutions and further retention by the crystals.

Keywords

• manganese dioxide
• cryptomelane
• selective adsorption
• strontium radionuclides