Phase equilibrium experiments on the simulated high-level waste glass containing platinum group elements

Figures & data

Table 1. Chemical composition of the KMOC glass.

Oxides	wt%	Oxides	wt%
SiO2	47.92	MoO3	0.73
B2O3	13.42	TeO2	0.09
Al2O3	5.13	RuO2^a	0.25
Li2O	3.76	Rh2O3^a	0.08
Na2O	9.58	PdO^a	0.37
Cs2O	0.94	Others^b	16.17
CaO	3.07

^aAll Pd, Rh and Ru are assumed as Pd²⁺, Rh³⁺ and Ru⁴⁺, respectively.

^bZnO, MnO, Fe₂O₃, ZrO₂, La₂O₃, Ce₂O₃, Pr₂O₃, Nd₂O₃, Gd₂O₃, etc.

Table 2. Chemical compositions (wt%) of Pd metal phase and Ru oxide phase included in the KMOC glass. Numbers in parenthesis represent standard deviation.

	n	Pd	Rh	Ru	Te
Pd metal phase	64	91.3 (1.8)	5.5 (1.8)	0.2 (0.2)	3.6 (0.4)
	n	RuO2	RhO2
Ru oxide phase	42	88.1 (1.4)	11.9 (1.5)

Note: n: number of analyses.

Figure 1. Temperature and oxygen fugacity of Pd/PdO, Rh/Rh₂O₃ and Ru/RuO₂ equilibria calculated from FACT thermodynamic database [30]. Dashed and dotted lines represent $f_{O_2}$ in air and equilibrium $f_{O_2}$ of CO₂ = CO+0.5O₂, respectively. Experimental temperature and oxygen fugacity are indicated by solid circles.

Figure 2. Methods of sample holding tested in this study. (a) Wire-loop method, (b) crucible method, (c) SiO₂ tube method and (d) Al₂O₃ tube method. In all methods, molten samples are held by a surface tension between glass melt and Pt wire or tubes.

Figure 3. Plots of chemical compositions of the glass matrix after phase equilibrium experiments against temperature: (a) SiO₂, (b) Al₂O₃, (c) B₂O₃ and (d) Na₂O. Open squares with cross represent concentration in the starting KMOC glass.

Table 3. Chemical compositions of the Pd metal phase and the Ru oxide phase crystalized in the phase equilibrium experiments and calculated partition coefficient of Rh (lnK_Rh). Values normalized to total 100wt%. Numbers in parenthesis represent standard deviation.

	Temperature	Run duration			Metal phase/wt%						Oxide phase^b/wt%
Sample no.	/ K	/ Hours	Atmosphere	Method	n^a	Te	Ru	Rh	Pd	Total	na	RuO2	RhO2	Total	lnKRh
M14-1	1473	24	Air	Al2O3 tube	6	0.71 (0.15)	0.61 (0.09)	20.64 (1.27)	77.03 (2.96)	98.99	10	95.40 (1.74)	4.60 (1.25)	100.00	−1.56
M14-2	1473			SiO2 tube	7	1.20 (0.52)	0.75 (0.29)	20.77 (1.44)	76.43 (1.26)	99.15	10	95.68 (3.51)	4.32 (1.84)	100.00	−1.64
M15-2	1373			Al2O3 tube	8	1.55 (0.41)	0.18 (0.21)	8.03 (0.85)	89.91 (2.03)	99.67	10	87.60 (1.39)	12.40 (1.27)	100.00	0.38
M15-1	1373			SiO2 tube	7	1.16 (0.49)	0.12 (0.05)	10.16 (0.44)	88.45 (1.95)	99.89	10	87.95 (0.79)	12.05 (0.83)	100.00	0.12
M11-7, M11-8	1273	48		Crucible	12	1.60 (0.12)	0.33 (0.30)	3.74 (0.35)	94.57 (1.62)	100.24	15	87.20 (0.88)	12.80 (0.79)	100.00	1.18
M5-1, M5-2	1073	96			11	9.92 (1.16)	0.29 (0.46)	2.03 (0.46)	87.46 (2.24)	99.70	10	86.86 (1.99)	13.14 (1.74)	100.00	1.80
M14-3	1473	24	CO2	Al2O3 tube	6	2.27 (0.63)	3.12 (0.58)	24.40 (3.34)	69.55 (4.10)	99.33	7	98.17 (0.83)	1.83 (0.94)	100.00	−2.65
M14-4	1473			SiO2 tube	8	1.90 (1.29)	5.10 (1.64)	28.52 (6.69)	63.71 (5.82)	99.23	10	98.67 (1.19)	1.33 (1.09)	100.00	−3.12
M15-4	1373			Al2O3 tube	7	5.37 (0.84)	0.51 (0.07)	17.54 (1.03)	75.82 (1.33)	99.24	10	94.57 (1.67)	5.43 (1.45)	100.00	−1.24
M15-3	1373			SiO2 tube	8	6.16 (1.97)	0.91 (0.46)	15.57 (2.90)	78.25 (2.15)	100.89	9	96.94 (2.41)	3.06 (1.48)	100.00	−1.68
M16-2	1273	48		Al2O3 tube	9	12.27 (1.27)	0.22 (0.04)	4.42 (0.53)	85.56 (1.41)	102.47	10	93.66 (2.01)	6.34 (1.90)	100.00	0.31
M16-1	1273	48		SiO2 tube	6	12.60 (1.37)	0.66 (0.28)	4.35 (0.79)	84.07 (1.66)	101.67	8	96.66 (3.26)	3.34 (2.24)	100.00	−0.33
M17-3, M17-4	1073	96		Wire loop	10	7.70 (1.61)	0.06 (0.07)	2.50 (0.92)	90.73 (1.40)	100.99	20	86.57 (1.92)	13.43 (1.33)	100.00	1.62

^aNumbers of analyses.

^bValues normalized to total 100wt%.

Table 4. Chemical compositions of the Pd metal phase and the platinum wire used for sample holding by the crucible method and the wire-loop method above 1373 K. Numbers in parenthesis represent standard deviation.

	Temperature	Run duration					Metal phase/wt%
Sample no.	/ K	/ Hours	Atmosphere	Method	Phase	n	Te	Ru	Rh	Pd	Pt
M11-1, M11-2	1473	24	Air	Crucible	Pd-rich metal	9	0.97(0.28)	0.40(0.37)	16.44(5.91)	82.00(6.56)
					Rh-rich metal	11	0.02(0.04)	2.04(0.50)	88.43(5.63)	9.27(5.63)
					Pt wire (rim)	3		0.80(0.28)	4.03(5.81)	3.15(1.00)	92.02(5.68)
M11-4, M11-5	1373	24	Air	Crucible	Pd-rich metal	13	1.26(0.11)	0.17(0.06)	13.02(0.89)	85.70(1.60)
					Pt wire (rim)	3		0.08(0.08)	0.55(0.07)	6.00(0.57)	93.37(1.17)
M13-5, M13-6	1373	24	CO2	Wire loop	Ru-rich metal	8	0.06(0.09)	74.52(7.22)	15.62(4.21)	10.80(8.46)
					Pt wire (rim)	4		0.20(0.22)	1.78(0.63)	4.98(1.27)	93.04(1.78)

Note: n: numbers of analyses.

Figure 4. Chemical compositions of the Pd metal phase in experimental samples; (a) Pd, (b) Rh, (c) Te. Solid circle and open circle are results in air and in CO₂ atmosphere, respectively. Open square represents composition of Pd metal included in the starting KMOC glass. Error bar is a standard deviation (1σ).

Figure 5. Chemical compositions of the Ru oxide phase in experimental samples; (a) RuO₂ and (b) RhO₂. Values normalized to total 100wt%. Solid circle and open circle are results in air and in CO₂ atmosphere, respectively. Open square represents composition of Ru oxide included in the starting KMOC glass, respectively. Error bar is a standard deviation (1σ).

Figure 6. Mass fraction of the Pd metal phase and the Ru oxide phase in the sample of phase equilibrium experiments as a function of temperature. Amount in the KMOC glass is also shown.

Figure 7. Partition coefficient of Rh (K_Rh) between Pd metal and Ru oxide. Solid circle and open circle are results in air and in CO₂ atmosphere, respectively. Open square represents the K_Rh calculated from crystal compositions in the KMOC glass. Dash lines are the K_Rh calculated from thermodynamic data assuming three difference oxygen fugacities: 0.21(air), 0.021 and equilibrium $f_{O_2}$ of CO₂ dissociation. Errors are comparable to symbol size.

Bale CW, Bélisle E, Chartrand P, et al. Fact sage thermochemical software and databases – recent developments. Calphad. 2009;33:295–311.

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