三元体系Na2CO3-NaF-H2O 298.15 K和318.15 K相平衡研究

doi:10.19964/j.issn.1006-4990.2021-0240

Abstract

Abstract:

Wastewater containing sodium carbonate and sodium fluoride will be generated in the rare earth extraction process and the preparation process of sodium fluoride.The phase equilibrium of the ternary system of Na₂CO₃-NaF-H₂O was studied to provide theoretical guidance for the preparation of practical production and recovery of sodium fluoride and sodium carbon-ate.The isothermal dissolution equilibrium method was used to study the phase equilibrium relationship of the ternary system of Na₂CO₃-NaF-H₂O at 298.15 K and 318.15 K.The solubility of each component of the system and the density and pH of the equilibrium liquid phase were measured.The phase diagram and the relationship between physicochemical parameters and content of component were drawn according to the solubility data.The solid phase was analyzed and characterized by X-ray diffraction（XRD）.The experimental study showed that the system had no double salt and solid solution,and belonged to the I-type phase diagram of hydrate.The phase diagram included 1 all-liquid region,2 single-salt crystallization regions,1 mixed crystallization region,1 all-solid region,3 univariate solubility curves,and 1 co-saturation point.Na₂CO₃ had a strong salting-out rate for NaF.When the temperature was constant,the mass fraction of Na₂CO₃ was higher,the density was greater,and the pH of the solution was greater.When the mass fraction of Na₂CO₃ was constant,the temperature was higher,the density was greater,and the pH of the solution was lower.

Key words: isothermal solution equilibrium method, sodium carbonate, sodium fluoride, ternary water salt system, phase equilibrium

CLC Number:

LU Ziyu,LIU Zhaogang,WU Jinxiu,HU YanHong,LIU Xingyu. Study on phase equilibrium of ternary system of Na₂CO₃-NaF-H₂O at 298.15 K and 318.15 K[J]. Inorganic Chemicals Industry, 2022, 54(3): 66-70.

Figures/Tables 8

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References 13

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序号	饱和Na₂CO₃溶液中梯度加入NaF		饱和NaF溶液中梯度加入Na₂CO₃
序号	w（Na₂CO₃）/%	w（NaF）/%	w（Na₂CO₃）/%	w（NaF）/%
1	29.79	0.39	3.46	3.47
2	29.62	0.44	2.01	6.64
3	29.50	0.46	0.91	13.35
4	29.28	0.41	0.70	19.67
5	29.04	0.43	0.49	27.01
6	28.88	0.49	0.46	28.84
7	28.62	0.47	0.46	29.20
8	28.43	0.48	0.45	29.65
9	28.42	0.43	0.44	29.92

项目	w（NaF）/%	w（H₂O）/%	w（Na₂CO₃）/%
文献值	1.76	77.14	21.10
实验值	1.81	76.08	20.91

编号	平衡液相		密度/ （g·cm^-3）	湿固相		平衡固相
编号	w （NaF）/ %	w （Na₂CO₃）/ %	密度/ （g·cm^-3）	w （NaF）/ %	w （Na₂CO₃）/ %	平衡固相
1	4.05	0.00	1.034	—	—	S₁
2	3.70	0.92	1.084	64.75	1.53	S₁
3	3.40	5.65	1.120	62.64	2.96	S₁
4	3.05	8.19	1.138	61.28	5.28	S₁
5	2.16	16.23	1.202	60.64	7.69	S₁
6,E	1.81	20.91	1.264	59.04	9.01	S₁+S₂
7	0.96	20.85	1.310	59.59	15.33	S₁+S₂
8	0.90	21.33	1.346	60.60	21.82	S₁+S₂
9	0.65	24.12	1.354	54.49	26.83	S₁+S₂
10	0.51	25.12	1.356	42.43	35.21	S₁+S₂
11	0.00	25.63	1.374	—	—	S₂

编号	平衡液相		密度/ （g·cm^-3）	湿固相		平衡固相
编号	w （NaF）/ %	w （Na₂CO₃）/ %	密度/ （g·cm^-3）	w （NaF）/ %	w （Na₂CO₃）/ %	平衡固相
1	4.50	0.00	1.085	—	—	S₁
2	3.46	3.47	1.166	64.64	1.29	S₁
3	2.01	6.64	1.220	64.99	2.42	S₁
4	0.91	13.35	1.298	61.27	5.29	S₁
5	0.70	19.67	1.334	60.71	8.47	S₁
6,E	0.49	27.01	1.352	56.19	11.36	S₁+S₂
7	0.46	28.84	1.391	57.19	13.69	S₁+S₂
8	0.46	29.20	1.416	53.52	18.63	S₁+S₂
9	0.45	29.65	1.418	43.34	32.83	S₁+S₂
10	0.44	29.92	1.422	40.94	34.48	S₁+S₂
11	0.00	32.01	1.480	—	—	S₂

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Study on phase equilibrium of ternary system of Na₂CO₃-NaF-H₂O at 298.15 K and 318.15 K

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Study on phase equilibrium of ternary system of Na2CO3-NaF-H2O at 298.15 K and 318.15 K