Siberian Federal University

Coal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass phase – 95.4 wt.%; (SiO2/Al2O3) glass – 3.1) were used to fabricate lutetium-aluminosilicate microspheres as precursors of Lu‑177 bearing β-irradiation sources applied for the selective radiation therapy of tumors. To incorporate Lu3+ ions into cenosphere’s aluminosilicate material, the following strategy was realized: (1) chemical modification of cenosphere globules by conversion of aluminosilicate glass into zeolites preserving a spherical form of cenospheres; (2) the loading of zeolitized microspheres with Lu3+ by means of ion exchange 3Na+ ↔ Lu3+; (3) Lu3+ encapsulation in an aluminosilicate matrix by solid-phase transformation of the Lu3+ sorbed form into insoluble forms under the thermal treatment at 1000–1200 oC. The zeolitized microspheres containing the zeolite phase NaP1 (GIS) were synthesized and their sorption properties with respect to Lu3+ were studied. It was established that the sorption capacity of the zeolitized products is about 70 mg/g Lu3+. It was found that the long-time heating of the Lu3+-loaded zeolite precursor at 1000 oC in a fixed bed resulted in the crystallization of a monoclinic lutecium pyrosilicate (Lu2Si2O7). The fast heating–cooling cycle at 1200 oC in a moving bed resulted in amorphization of the zeolite component without the formation of the lutecium crystal phase preserving the precursor spherical form. The microspheres based on both crystalline and amorphous Lu forms are characterized by the low Lu leachability rate (Rn ≤ 3×10–7 g/cm2×day) in 0.9 % NaCl solution imitating blood