Wet chemical synthesis of apatite-based waste forms – A novel room temperature method for the immobilization of radioactive iodine

Abstract

The wet chemical synthesis of Pb10(VO4)6I2 apatite has been reported for the first time. The possibility of substituting Ca2+ for Pb2+ and (PO4)3− for (VO4)3− in the apatite structure has been explored.

Effect of solution chemistry on the iodine release from iodoapatite in aqueous environments

“…The results from this study and those from relevant literature suggest that the solution pH exerts significant effects on the dissolution rate and the secondary phase formation in aqueous environments such as chervetite and hydroxyvanadinite precipitated under acidic and basic conditions, respectively. 37,48,49…”

“…The site mixing is possible since Pb10(VO4)x(PO4)6-x(OH)2 can occur during wet chemistry reactions under similar conditions. 48 Carbonate is known to be incorporated into apatite structure by substitution. [50][51][52][53] Given that phosphate (PO4 3-, ionic radius 2.30 ± 0.42 Å) 46 can replace vanadate in iodoapatite, 48 it is reasonable to presume that carbonate of a smaller ionic radius (CO3 2-, 1.89 ± 0.19 Å) 46 can substitute vanadate in a similar crystal structure.…”

Mechanism of iodine release from iodoapatite in aqueous solution

“…Among the waste forms being evaluated, single phase ceramic iodoapatite Pb 5 (VO 4 ) 3 I has been proposed as a waste form for iodine-129, [6][7][8][9][10][11][12][13][14][15][16][17][18] and is simpler than multiphase waste forms 5 in terms of phase complexity, microstructure, and composition, which are a great challenge to evaluate their chemical durability because of the complications from their complexity. In the iodoapatite structure, Pb cations occupy two crystallographic sites with 8 and 9 coordination numbers and V forms tetrahedra with oxygen.…”

Light Absorption Properties and Electronic Band Structures of Lead‐Vanadium Oxyhalide Apatites Pb5(VO4)3X (X=F, Cl, Br, I)

“…Powdered Pb 5 (VO 4 ) 3 X specimens were synthesized by an aqueous solution method, based on a literature procedure with some modifications . Pb(NO 3 ) 2 (99.9 %, FUJIFILM Wako Pure Chemical Co.), Na 3 VO 4 (96 %, MP Biomedicals, LLC), NaF (99.0 %, Wako Pure Chemical Co.), NaCl (99.5 %, Wako Pure Chemical Co.), NaBr (99.5 %, Kanto Chemical Co., Inc.) and NaI (99.5 %, Kanto Chemical Co., Inc.) were used as the raw materials without further purification.…”