Current status and research progress of purification technology of electronic grade phosphoric acid

doi:10.11949/0438-1157.20230655

Abstract

Abstract:

As a kind of ultra-high purity chemical reagent, electronic grade phosphoric acid is mainly used for chip cleaning and etching in the microelectronics industry, and its purity will significantly affect the yield, electrical performance and reliability of electronic components. However, high-end electronic grade phosphoric acid with extremely low impurities (10^-9 level) has extremely high requirements for chemical separation and purification technology. Based on the application of electronic grade phosphoric acid in chip cleaning and etching, the main domestic and foreign standards of electronic grade phosphoric acid products are reviewed, and the main analysis and monitoring methods of impurity ions are summarized. The preparation and purification methods of electronic phosphoric acid are reviewed, especially the significant advantages of crystallization in purifying phosphoric acid. Finally, the prospect of purification technology of electronic phosphoric acid is prospected.

Key words: electronic grade phosphoric acid, electronic materials, purification, crystallization, technology integration, trace impurity

摘要：

电子级磷酸作为一种超高纯化学试剂，主要用于微电子行业中芯片的清洗与蚀刻，其纯度会显著影响电子元器件的成品率、电性能以及可靠性。然而，极低杂质(10^-9水平)的高端电子级磷酸，对于化工分离纯化技术的要求极高。从电子级磷酸在芯片清洗与蚀刻方面的应用出发，梳理了电子级磷酸产品的主要国内外标准，概述了杂质离子的主要分析监测方法。重点综述了电子磷酸的制备和纯化精制方法，特别是结晶法在磷酸深度净化方面的显著优势，最后，对电子级磷酸的净化技术发展做出了前景展望。

关键词: 电子级磷酸, 电子材料, 纯化, 结晶, 技术集成, 痕量杂质

CLC Number:

TQ 026.5

Liuyang YU, Shubo LIU, Shengzhe JIA, Hang MA, Banglong WAN, Qiwen SU, Jingkang WANG, Weiwei TANG, Yujuan HE, Junbo GONG. Current status and research progress of purification technology of electronic grade phosphoric acid[J]. CIESC Journal, 2024, 75(1): 1-19.

余留洋, 刘书博, 贾晟哲, 马航, 万邦隆, 苏琦雯, 王静康, 汤伟伟, 贺豫娟, 龚俊波. 电子级磷酸的纯化精制技术发展现状与研究进展[J]. 化工学报, 2024, 75(1): 1-19.

Figures/Tables 21

Fig.1 Evolution of the GaN surface for different durations in H3PO4[9]

Table 1 The purity of wet electronic chemicals in Semiconductor Equipment Materials International（SEMI）［10］

级别	单项金属杂质	控制微粒粒径	颗粒数	IC集成度
SEMI-C1、C2	≤100 ppb	≥1 μm	≤25个/ml	64 K
SEMI-C7	≤10 ppb	≥0.5 μm	≤25个/ml	4 M
SEMI-C8	≤1 ppb	≥0.5 μm	≤5个/ml	256 M
SEMI-C12	≤0.1 ppb	≥0.2 μm	协定	16 G

Table 2 Standard for electronic grade phosphoric acid in Semiconductor Equipment Materials International（SEMI）［11-12］

指标	SEMI指标
指标	Grade 1(G1)	Grade 2(G2)	Grade 3(G3)
chloride（Cl^-）/ppm	1	1	1
nitrate（NO $3 -$ ）/ppm	5	5	5
sulfate（SO $4 2 -$ ）/ppm	—	12	12
aluminum（Al）/ppb	500	300	50
antimony（Sb）/ppb	10000	3500	1000
arsenic（As）/ppb	50	50	50
barium（Ba）/ppb	—	—	50
cadmium（Cd）/ppb	—	450	50
calcium（Ca）/ppb	1500	1100	150
chromium（Cr）/ppb	200	200	50
cobalt（Co）/ppb	50	50	50
copper（Cu）/ppb	50	50	50
gold（Au）/ppb	300	150	50
iron（Fe）/ppb	2000	700	100
lead（Pb）/ppb	300	300	50
lithium（Li）/ppb	100	100	10
magnesium（Mg）/ppb	200	200	50
manganese（Mn）/ppb	100	100	50
nickel（Ni）/ppb	200	200	50
potassium（K）/ppb	1500	450	150
sodium（Na）/ppb	2500	500	250
strontium（Sr）/ppb	100	100	10
zinc（Zn）/ppb	2000	400	50
titanium （Ti）/ppb	300	300	50

Table 2 Standard for electronic grade phosphoric acid in Semiconductor Equipment Materials International（SEMI）［11-12］

指标	SEMI指标
指标	Grade 1(G1)	Grade 2(G2)	Grade 3(G3)
chloride（Cl^-）/ppm	1	1	1
nitrate（NO $3 -$ ）/ppm	5	5	5
sulfate（SO $4 2 -$ ）/ppm	—	12	12
aluminum（Al）/ppb	500	300	50
antimony（Sb）/ppb	10000	3500	1000
arsenic（As）/ppb	50	50	50
barium（Ba）/ppb	—	—	50
cadmium（Cd）/ppb	—	450	50
calcium（Ca）/ppb	1500	1100	150
chromium（Cr）/ppb	200	200	50
cobalt（Co）/ppb	50	50	50
copper（Cu）/ppb	50	50	50
gold（Au）/ppb	300	150	50
iron（Fe）/ppb	2000	700	100
lead（Pb）/ppb	300	300	50
lithium（Li）/ppb	100	100	10
magnesium（Mg）/ppb	200	200	50
manganese（Mn）/ppb	100	100	50
nickel（Ni）/ppb	200	200	50
potassium（K）/ppb	1500	450	150
sodium（Na）/ppb	2500	500	250
strontium（Sr）/ppb	100	100	10
zinc（Zn）/ppb	2000	400	50
titanium （Ti）/ppb	300	300	50

Table 3 Quality standard for Electronic Grade Phosphoric Acid in GB/T 28159—2011

项目	指标
项目	E1	E2
易氧化物（以H₃PO₄计）/%(质量分数)	≤0.005	≤0.001
硝酸盐（NO $3 -$ ）/ppm	≤5	≤0.5
硫酸盐（SO $4 2 -$ ）/ppm	≤10	≤5
氯化物（Cl^-）/ppm	≤1	≤0.5
铝（Al）/ppb	≤200	≤50
硼（B）/ppb	—	≤50
锑（Sb）/ppb	≤3000	≤300
砷（As）/ppb	≤100	≤20
钡（Ba）/ppb	≤100	≤20
镉（Cd）/ppb	≤100	≤20
钙（Ca）/ppb	≤1000	≤50
铬（Cr）/ppb	≤100	≤20
钴（Co）/ppb	≤100	≤20
铜（Cu）/ppb	≤50	≤20
镓（Ga）/ppb	≤100	≤10
金（Au）/ppb	≤100	≤10
铁（Fe）/ppb	≤300	≤50
铅（Pb）/ppb	≤100	≤20
锂（Li）/ppb	≤100	≤10
镁（Mg）/ppb	≤100	≤20
锰（Mn）/ppb	≤100	≤20
镍（Ni）/ppb	≤100	≤20
钾（K）/ppb	≤100	≤20
银（Ag）/ppb	≤100	≤20
钠（Na）/ppb	≤500	≤50
锡（Sn）/ppb	—	≤10
锶（Sr）/ppb	≤100	≤20
钛（Ti）/ppb	≤100	≤50
锌（Zn）/ppb	≤100	≤50

Table 3 Quality standard for Electronic Grade Phosphoric Acid in GB/T 28159—2011

项目	指标
项目	E1	E2
易氧化物（以H₃PO₄计）/%(质量分数)	≤0.005	≤0.001
硝酸盐（NO $3 -$ ）/ppm	≤5	≤0.5
硫酸盐（SO $4 2 -$ ）/ppm	≤10	≤5
氯化物（Cl^-）/ppm	≤1	≤0.5
铝（Al）/ppb	≤200	≤50
硼（B）/ppb	—	≤50
锑（Sb）/ppb	≤3000	≤300
砷（As）/ppb	≤100	≤20
钡（Ba）/ppb	≤100	≤20
镉（Cd）/ppb	≤100	≤20
钙（Ca）/ppb	≤1000	≤50
铬（Cr）/ppb	≤100	≤20
钴（Co）/ppb	≤100	≤20
铜（Cu）/ppb	≤50	≤20
镓（Ga）/ppb	≤100	≤10
金（Au）/ppb	≤100	≤10
铁（Fe）/ppb	≤300	≤50
铅（Pb）/ppb	≤100	≤20
锂（Li）/ppb	≤100	≤10
镁（Mg）/ppb	≤100	≤20
锰（Mn）/ppb	≤100	≤20
镍（Ni）/ppb	≤100	≤20
钾（K）/ppb	≤100	≤20
银（Ag）/ppb	≤100	≤20
钠（Na）/ppb	≤500	≤50
锡（Sn）/ppb	—	≤10
锶（Sr）/ppb	≤100	≤20
钛（Ti）/ppb	≤100	≤50
锌（Zn）/ppb	≤100	≤50

Fig.2 The comparison of ICP-OES、ICP-MS and GFAAS[13]

Table 4 The detailed comparison of ICP-MS， ICP-OES and GFAAS［13］

项目	ICP-OES	ICP-MS	GFAAS
检出限	绝大部分元素很好	绝大部分元素非常杰出	部分元素非常杰出
样品分析能力	5~30个元素/（样品·min）	2~6 min/样品中所有元素	4 min/（样品·元素）
线性动态范围	约10⁵	约10⁸	约10²
固体溶解量（最大可容忍量）	2%~25%	0.1%~0.4%	>20%
可测元素数	>73	>75	>50
样品用量	多	少	很少
半定量分析	能	能	不能
同位素分析	不能	能	不能
日常操作	容易	容易	容易
方法实验开发	需专业技术	需专业技术	需专业技术
无人控制操作	能	能	能
易燃气体	无	无	无
操作费用	高	高	中等
基本费用	高	很高	中等/高

Fig.3 Process flow chart of two-step process for producing phosphoric acid from yellow phosphorus[17]

Fig.4 Wet process phosphoric acid concentrator flow sheet[27]

Table 5 Comparison of raw materials and power required to produce one ton of industrial phosphoric acid in thermal and wet routes［3］

工艺路线	原料及动力	消耗量
热法磷酸工艺	磷矿	3.0~3.4 t
	黏土	0.2~0.3 t
	焦炭	0.5~0.6 t
	工艺用水	40 m³
	冷却用水	120 m³
	电力	5700~6000 kW·h
湿法磷酸工艺	磷矿	2.6~3.5 t
	硫酸	2.4~2.9 t
	工艺用水	3.6~52 m³
	冷却用水	100~150 m³
	电力	120~180 kW·h
	蒸汽	0.2~2.4 t

Fig.5 Deep purification technology of electronic grade phosphoric acid[30-32]

Fig.6 Effects of Marathon C resin on adsorption efficiency and capacity of U(Ⅳ), Mn(Ⅱ), Cu(Ⅱ), Zn(Ⅱ) and Cd(Ⅱ)[30]

Fig.7 Flow chart of P-15 extractant purification of wet phosphoric acid[44]

Table 6 Comparison of removal of impurity ions from phosphoric acid by solvent extraction

萃取元素	萃取剂	O∶A	提取效率/%	文献
I	煤油	1∶2	99.25	[45]
I	西甲硅油	3∶1	95.00	[46]
F	TBP和SIO	1∶5	98.40	[47]
Mg	PN-1	4∶1	89.09	[48]
U和Ree	N-propylpropan-1-amine	1∶1	U: 95.30 Ree: 98.70	[49]
Cd	DIBDPi	1∶1	86.00	[50]
Cd	C₁₁H₁₈N₂O	1∶1	98.60	[51]
Cd	D₂EHDTPA	1∶1	96.00	[52]
Fe	TBP和煤油	1∶1	100	[43]

Fig.8 Phase diagram of H3PO4-H2O system[1]

Fig.9 Temperature trajectories of melting crystallization[65]

Fig.10 Schematic diagram of solute and impurity migration during crystallization and sweating processes[74]

Table 7 Difference between suspension melt crystallization and layer melt crystallization［75］

特征	悬浮熔融结晶	层熔融结晶
结晶温度	根据相图确定	根据相图确定
生长速率	10^-8~10^-7 m/s	10^-7~10^-5 m/s
结晶过程热传递	通过熔体	通过晶体层
晶体生长模式	晶体以颗粒状的形式生长	晶体以晶体层的形式粘贴在结晶器内壁
固液分离	难	易
转动装置	有	无

Fig.11 Schematic diagram of the falling film and static melt crystallization[76]

Fig.12 Static layer melting crystallization of phosphoric acid purification[32]

Fig.13 Flow chart of preparation of electronic grade phosphoric acid by suspension crystallization[84]

Table 8 Comparison of phosphoric acid purification techniques

技术	优点	缺点	文献
离子交换法	快速有效；对有些金属具有高选择性；低成本的材料和树脂可以再生	成本限制（初始和维护成本）；金属离子在树脂上结垢；对pH高度敏感	[33]
溶剂萃取法	处理简单，操作快速便捷	耗时、对环境不友好；产生副产品、工艺昂贵	[88]
沉淀法	设备简单；能选择性去除金属；沉淀剂相对便宜	硫化物量不可控；需要化学稳定的沉淀剂处理；需要大量沉淀剂，引入新的杂质；产生大量的杂质残渣	[89]
膜分离法	易于放大，操作简单；分离选择性高，压力低	运行成本高，使用寿命低；膜污染	[57-58]
冷却结晶法	一次性降低各种杂质离子含量；工艺流程短，投资费用低；操作控制要求不高	存在杂质包藏，需要多级结晶；考虑对母液的循环利用	[90]
熔融结晶法	能耗低；杂质去除率高	设备要求高；需要有特殊的结晶器	[91]

References 91

1	Tang H. Purification of phosphoric acid by melt crystallization[D]. Saxony-Anhalt: Martin Luther University, 2016.
2	Wang B, Luo K B. Preparation and research advance of electronic grade phosphoric acid[J]. Advanced Materials Research, 2014, 881/882/883: 70-73.
3	Bahsaine K, El Mehdi Mekhzoum M, Benzeid H, et al. Recent progress in heavy metals extraction from phosphoric acid: a short review[J]. Journal of Industrial and Engineering Chemistry, 2022, 115: 120-134.
4	Qin K D, Li Y C. Mechanisms of particle removal from silicon wafer surface in wet chemical cleaning process[J]. Journal of Colloid and Interface Science, 2003, 261(2): 569-574.
5	Mouche L, Tardif F, Derrien J. Particle deposition on silicon wafers during wet cleaning processes[J]. Journal of the Electrochemical Society, 1994, 141(6): 1684-1691.
6	Kranz C, Wyczanowski S, Baumann U, et al. Industrial cleaning sequences for Al₂O₃-passivated PERC solar cells[J]. Energy Procedia, 2014, 55: 211-218.
7	Sreejith K P, Sharma A K, Basu P K, et al. Etching methods for texturing industrial multi-crystalline silicon wafers: a comprehensive review[J]. Solar Energy Materials and Solar Cells, 2022, 238: 111531.
8	Seo D, Bae J S, Oh E, et al. Selective wet etching of Si₃N₄/SiO₂ in phosphoric acid with the addition of fluoride and silicic compounds[J]. Microelectronic Engineering, 2014, 118: 66-71.
9	Benrabah S, Legallais M, Besson P, et al. H₃PO₄-based wet chemical etching for recovery of dry-etched GaN surfaces[J]. Applied Surface Science, 2022, 582: 152309.
10	张大洲, 龙辉, 卢文新, 等. 电子级磷酸研究现状及发展趋势分析[J]. 化肥设计, 2022, 60(4): 1-4, 20.
	Zhang D Z, Long H, Lu W X, et al. Analysis of existing researches and development trends of electronic-grade phosphoric acid[J]. Chemical Fertilizer Design, 2022, 60(4): 1-4, 20.
11	范相虎, 周聪, 袁军, 等. 电子级磷酸研发现状及芯片级磷酸展望[J]. 粘接, 2019, 40(5): 61-64.
	Fan X H, Zhou C, Yuan J, et al. Research progress on electronic-grade phosphoric acid and prospects of microchip-grade phosphoric acid[J]. Adhesion, 2019, 40(5): 61-64.
12	Kawabata K, Kishi Y, Thomas R. The benefits of dynamic reaction cell ICP-MS technology to determine ultratrace metal contamination levels in high-purity phosphoric and sulfuric acid[J]. Spectroscopy, 2003, 18(1): 16-31.
13	Balaram V. Current and emerging analytical techniques for geochemical and geochronological studies[J]. Geological Journal, 2021, 56(5): 2300-2359.
14	European Fertilizer Manufacturers Association. Booklet No. 4 of 8: production of phosphoric acid[Z]. Best Available Techniques for Pollution Prevention and Control in the European Fertilizer Industry, 2000.
15	Azaroual M, Kervevan C, Lassin A, et al. Thermo-kinetic and physico-chemical modeling of processes generating scaling problems in phosphoric acid and fertilizers production industries[J]. Procedia Engineering, 2012, 46: 68-75.
16	Zan C, Shi L, Song Y Z, et al. Evaluation method for thermal processing of phosphoric acid with waste heat recovery[J]. Energy, 2006, 31(14): 2791-2804.
17	Zheng G Y, Xia J P, Chen Z J. Overview of current phosphoric acid production processes and a new idea of kiln method[J]. Mini-Reviews in Organic Chemistry, 2021, 18(3): 328-338.
18	Williams T A, Thomson A. Manufacture of phosphoric acid: US3984525[P]. 1976-10-05.
19	Liu Q, Liu W Z, Lv L, et al. Study on reactions of gaseous P₂O₅ with Ca₃(PO₄)₂ and SiO₂ during a rotary kiln process for phosphoric acid production[J]. Chinese Journal of Chemical Engineering, 2018, 26(4): 795-805.
20	Wu P, Lv L, Tang S Y, et al. The fouling properties of SiO₂-CaO-P₂O₅ system in high-temperature rotary kiln phosphoric acid process[J]. Chinese Journal of Chemical Engineering, 2020, 28(7): 1824-1831.
21	Halmemies S, Gröndahl S, Arffman M, et al. Vacuum extraction based response equipment for recovery of fresh fuel spills from soil[J]. Journal of Hazardous Materials, 2003, 97(1/2/3): 127-143.
22	Osada I, Imamura K, Iso A. High purity phosphorus prodn. useful as semi-conductor material-by heat decomposition of crude phosphine: JP87-022924[P]. 1987.
23	Tang X J, Xue J J, Xing C. Catalytic decomposition of toxic phosphine gas on the developed nickel ferrite nanocrystals supported by Halloysite nanotubes[J]. Applied Surface Science, 2020, 530: 147264.
24	Ye C W, Li J. Wet process phosphoric acid purification by solvent extraction using n-octanol and tributylphosphate mixtures[J]. Journal of Chemical Technology & Biotechnology, 2013, 88(9): 1715-1720.
25	Al-Fariss T F, Özbelge H Ö, El-Shall H S H. On the modelling of phosphate rock acidulation process[J]. Journal of King Saud University - Engineering Sciences, 1993, 5(2): 243-255.
26	El-Shall H, Abadel-All E A, Moudgil B M. Effect of surfactants on phosphogypsum crystallization and filtration during wet-process phosphoric acid production[J]. Separation Science and Technology, 2000, 35(3): 395-410.
27	Bouchkira I, Latifi A M, Khamar L, et al. Modeling and multi-objective optimization of the digestion tank of an industrial process for manufacturing phosphoric acid by wet process[J]. Computers & Chemical Engineering, 2022, 156: 107536.
28	Peng B X, Ma Z, Zhu Y B, et al. Release and recovery of fluorine and iodine in the production and concentration of wet-process phosphoric acid from phosphate rock[J]. Minerals Engineering, 2022, 188: 107843.
29	Bolívar J P, Pérez-Moreno J P, Mas J L, et al. External radiation assessment in a wet phosphoric acid production plant[J]. Applied Radiation and Isotopes, 2009, 67(10): 1930-1938.
30	Taha M H. Sorption of U (Ⅵ), Mn (Ⅱ), Cu (Ⅱ), Zn (Ⅱ), and Cd (Ⅱ) from multi-component phosphoric acid solutions using Marathon C resin[J]. Environmental Science and Pollution Research, 2021, 28(10): 12475-12489.
31	He B B, Zhu Y Z, Xie D L, et al. Removal of Al³⁺ and Mg²⁺ ions in wet-process phosphoric acid via the formation of aluminofluoride complexes[J]. Environmental Technology, 2023, 44(7): 936-947.
32	Zhang B Y, Yang L, Wang H L, et al. Experiment and modeling of static layer melt crystallization in a crystallizer with an inner cooling tube[J]. Journal of Crystal Growth, 2022, 593: 126739.
33	Azimi A, Azari A, Rezakazemi M, et al. Removal of heavy metals from industrial wastewaters: a review[J]. ChemBioEng Reviews, 2017, 4(1): 37-59.
34	Taha M H. Solid-liquid extraction of uranium from industrial phosphoric acid using macroporous cation exchange resins: MTC1600H, MTS9500, and MTS9570[J]. Separation Science and Technology, 2021, 56(9): 1562-1578.
35	El Didamony A M, Youssef W M, Abdou A A. Modification of Amberlite XAD-2 resin for U(Ⅵ) adsorption from Egyptian crude phosphoric acid[J]. Egyptian Journal of Petroleum, 2019, 28(1): 71-76.
36	Reyes L H, Saucedo Medina I, Navarro Mendoza R, et al. Extraction of cadmium from phosphoric acid using resins impregnated with organophosphorus extractants[J]. Industrial & Engineering Chemistry Research, 2001, 40(5): 1422-1433.
37	Lloyd Philip J D. Principles of industrial solvent extraction[M]//Solvent Extraction Principles and Practice, Revised and Expanded. Boca Raton: CRC Press, 2004: 350-377.
38	Awwad N S, El-Nadi Y A, Hamed M M. Successive processes for purification and extraction of phosphoric acid produced by wet process[J]. Chemical Engineering and Processing: Process Intensification, 2013, 74: 69-74.
39	Hannachi A, Habaili D, Chtara C, et al. Purification of wet process phosphoric acid by solvent extraction with TBP and MIBK mixtures[J]. Separation and Purification Technology, 2007, 55(2): 212-216.
40	Radhika S, Kumar B N, Kantam M L, et al. Liquid-liquid extraction and separation possibilities of heavy and light rare-earths from phosphoric acid solutions with acidic organophosphorus reagents[J]. Separation and Purification Technology, 2010, 75(3): 295-302.
41	Xu Y, Meng D P, Li H Y, et al. Mechanism analysis for separation of cyclohexane and tert-butanol system via ionic liquids as extractants and process optimization[J]. ACS Sustainable Chemistry & Engineering, 2019, 7(24): 19984-19992.
42	Yang X C, Li H X, Cao C M, et al. Experimental and correlated liquid-liquid equilibrium data for water+1, 6-hexanediol+1-pentanol/3-methyl-1-butanol/2-methyl-2-butanol at different temperatures[J]. The Journal of Chemical Thermodynamics, 2021, 154: 106341.
43	Hu Z J, Zhang T, Lv L, et al. Extraction performance and mechanism of TBP in the separation of Fe³⁺ from wet-processing phosphoric acid[J]. Separation and Purification Technology, 2021, 272: 118822.
44	Wang B Q, Zhou Q L, Chen C, et al. Separation of phosphoric acid and magnesium from wet process phosphoric acid by solvent extraction[J]. Canadian Metallurgical Quarterly, 2023, 62(4): 791-802.
45	Benali K, Benhida R, Khaless K. A novel and complete process for iodine extraction and recovery from industrial wet-process phosphoric acid based on chemical oxidation and solvent extraction[J]. Process Safety and Environmental Protection, 2023, 176: 332-345.
46	He S Q, Chen Q L, Ao X Q, et al. A method for the removal of trace iodine from wet-process phosphoric acid[J]. Hydrometallurgy, 2020, 191: 105208.
47	Zuo Y H, Chen Q L, Li C Q, et al. Removal of fluorine from wet-process phosphoric acid using a solvent extraction technique with tributyl phosphate and silicon oil[J]. ACS Omega, 2019, 4(7): 11593-11601.
48	Xia Q, Zhang J P, Hong X F, et al. Ultrasound-assisted micro-channel extraction of magnesium from wet-process phosphoric acid[J]. Solvent Extraction Research and Development, Japan, 2022, 29(1): 9-19.
49	Orabi Ahmed H, Mohamed Basma T, Elyan Salah S. Simultaneous separation of rare earths and valuable actinoid element from wet process phosphoric acid using N-propylpropan-1-amine extractant[J]. Hydrometallurgy, 2021, 205: 105749.
50	Pavón S, Haneklaus N, Meerbach K, et al. Iron (Ⅲ) removal and rare earth element recovery from a synthetic wet phosphoric acid solution using solvent extraction[J]. Minerals Engineering, 2022, 182: 107569.
51	Berkalou K, Nounah A, Khamar M, et al. Removal of cadmium from phosphoric acid by the liquid-liquid extraction process using synthetic agent C₁₁H₁₈N₂O[J]. International Journal of Advanced Research in Engineering and Technology, 2020, 11(6): 28-35.
52	Touati M, Benna-Zayani M, Kbir-Ariguib N, et al. Extraction of cadmium (Ⅱ) from phosphoric acid media using the di(2-ethylhexyl)dithiophosphoric acid (D₂EHDTPA): feasibility of a continuous extraction-stripping process[J]. Hydrometallurgy, 2009, 95(1/2): 135-140.
53	Pohl A. Removal of heavy metal ions from water and wastewaters by sulfur-containing precipitation agents[J]. Water, Air, & Soil Pollution, 2020, 231(10): 503.
54	Sreekumar N, Udayan A, Srinivasan S. Algal bioremediation of heavy metals[M]//Removal of Toxic Pollutants Through Microbiological and Tertiary Treatment. Amsterdam: Elsevier, 2020: 279-307.
55	Kouzbour S, Gourich B, Gros F, et al. Purification of industrial wet phosphoric acid solution by sulfide precipitation in batch and continuous modes: performance analysis, kinetic modeling, and precipitate characterization[J]. Journal of Cleaner Production, 2022, 380: 135072.
56	Abdel-Ghafar H M, Abdel-Aal E A, Ibrahim M A M, et al. Purification of high iron wet-process phosphoric acid via oxalate precipitation method[J]. Hydrometallurgy, 2019, 184: 1-8.
57	Forouzesh M, Fatehifar E, Khoshbouy R, et al. Experimental investigation of iron removal from wet phosphoric acid through chemical precipitation process[J]. Chemical Engineering Research and Design, 2023, 189: 308-318.
58	Obotey Ezugbe E, Rathilal S. Membrane technologies in wastewater treatment: a review[J]. Membranes, 2020, 10(5): 89.
59	Sandu T, Chiriac A L, Tsyntsarski B, et al. Advanced hybrid membranes for efficient nickel retention from simulated wastewater[J]. Polymer International, 2021, 70(6): 866-876.
60	Duan X L, Wang C W, Wang T L, et al. Comb-shaped anion exchange membrane to enhance phosphoric acid purification by electro-electrodialysis[J]. Journal of Membrane Science, 2019, 573: 64-72.
61	Khaless K, Chanouri H, Amal S, et al. Wet process phosphoric acid purification using functionalized organic nanofiltration membrane[J]. Separations, 2022, 9(4): 100.
62	Xu S S, He R R, Dong C J, et al. Acid stable layer-by-layer nanofiltration membranes for phosphoric acid purification[J]. Journal of Membrane Science, 2022, 644: 120090.
63	肖立华. 冷却结晶法制电子级磷酸的研究[D]. 昆明: 昆明理工大学, 2008.
	Xiao L H. Study on preparation of electronic grade phosphoric acid by cooling crystallization[D]. Kunming: Kunming University of Science and Technology, 2008.
64	李天祥, 解田, 刘飞, 等. 一种电子级磷酸的生产方法: 1850590A[P]. 2006-10-25.
	Li T X, Xie T, Liu F, et al. Method for producing electron-level phosphoric acid: 1850590A[P]. 2006-10-25.
65	Jia S Z, Jing B, Hong W, et al. Purification of 2, 4-dinitrochlorobenzene using layer melt crystallization: model and experiment[J]. Separation and Purification Technology, 2021, 270: 118806.
66	Jiang X B, Wang J K, Hou B H, et al. Progress in the application of fractal porous media theory to property analysis and process simulation in melt crystallization[J]. Industrial & Engineering Chemistry Research, 2013, 52(45): 15685-15701.
67	Xiao W L, Huang B G, Li Y L, et al. Experimental investigation of continuous multistage countercurrent crystallizer for separation p-nitrochlorobenzene and o-nitrochlorobenzene[J]. Separation and Purification Technology, 2021, 267: 118648.
68	Chen L A, Li J, Matsuoka M. Experimental and theoretical investigation of the purification process of organic materials in a continuous inclined column crystallizer[J]. Industrial & Engineering Chemistry Research, 2006, 45(8): 2818-2823.
69	Mostefa M, Muhr H, Biget A, et al. Intensification of falling film melt crystallization process through micro and milli-structured surfaces[J]. Chemical Engineering and Processing: Process Intensification, 2015, 90: 16-23.
70	Shen L X, Dang M Y. Recent advances in melt crystallization, towards process intensification and technique development[J]. CrystEngComm, 2022, 24(10): 1823-1839.
71	Kim K J, Ulrich J. Theoretical and experimental studies on the behaviour of liquid impurity in solid layer melt crystallizations[J]. Journal of Physics D: Applied Physics, 2001, 34(9): 1308-1317.
72	Lu D P, Liu Y, He G H, et al. Fractal analysis for crystal layer structure and impurity distribution research of melt crystallization[J]. Fractals, 2015, 23(1): 1540002.
73	Ding S P, Huang X, Yin Q X, et al. Static layer melt crystallization: effects of impurities on the growth behaviors of crystal layers[J]. Separation and Purification Technology, 2021, 279: 119764.
74	Jia S Z, Yu L Y, Gao Z G, et al. Performance and analysis of key factors on the design of melt crystallization-based separation process[J]. AIChE Journal, 2023, 69(8): e18117.
75	姜晓滨. 熔融结晶法制备高纯磷酸过程研究[D]. 天津: 天津大学, 2012.
	Jiang X B. Study on the process of preparing high purity phosphoric acid by melt crystallization[D]. Tianjin: Tianjin University, 2012.
76	Jiang X B, Xiao W, He G H. Falling film melt crystallization (Ⅲ): Model development, separation effect compared to static melt crystallization and process optimization[J]. Chemical Engineering Science, 2014, 117: 198-209.
77	王静康, 姜晓滨, 侯宝红, 等. 液膜结晶制备电子级磷酸的方法: 101774555A[P]. 2010-07-14.
	Wang J K, Jiang X B, Hou B H, et al. Method for preparing electronic grade phosphoric acid through liquid membrane crystallization: 101774555A[P]. 2010-07-14.
78	林军, 吴小海, 苏杰文, 等. 一种U型管结晶生产电子级磷酸的方法: 103754847A[P]. 2014-04-30.
	Lin J, Wu X H, Su J W, et al. Method for producing electronic grade phosphoric acid by U tube crystallization: 103754847A[P]. 2014-04-30.
79	林军, 吴小海, 苏杰文, 等. U型管静态多级熔融结晶法制备电子级磷酸: 103754848A[P]. 2014-04-30.
	Lin J, Wu X H, Su J W, et al. Method for preparing electronic-grade phosphoric acid by U-shaped pipe static multistage melt crystallization: 103754848A[P]. 2014-04-30.
80	林军, 吴小海, 苏杰文, 等. 一种电子级磷酸热风加热结晶装置: 103771373B[P]. 2015-10-28.
	Lin J, Wu X H, Su J W, et al. Electronic-grade phosphoric acid hot air heating crystallizing device: 103771373B[P]. 2015-10-28.
81	林军, 吴小海, 苏杰文. 一种列管结晶生产电子级磷酸的装置: 203781851U[P]. 2016-03-02.
	Lin J, Wu X H, Su J W. Device for producing electronic grade phosphoric acid through tube crystallization: 203781851U[P]. 2016-03-02.
82	程景才, 张碧玉, 杨超, 等. 一种制备电子级磷酸的熔融结晶器: 216571627U[P]. 2022-05-24.
	Cheng J C, Zhang B Y, Yang C, et al. Melt crystallizer for preparing electronic grade phosphoric acid: 216571627U[P]. 2022-05-24.
83	Chen A M, Zhu J W, Chen K, et al. Melt suspension crystallization for purification of phosphoric acid[J]. Asia-Pacific Journal of Chemical Engineering, 2013, 8(3): 354-361.
84	Wang B M, Li J, Qi Y B, et al. Phosphoric acid purification by suspension melt crystallization: parametric study of the crystallization and sweating steps[J]. Crystal Research and Technology, 2012, 47(10): 1113-1120.
85	林军, 吴小海, 苏杰文, 等. 一种高纯度电子级磷酸的生产方法: 104030261A[P]. 2014-09-10.
	Lin J, Wu X H, Su J W, et al. A production method of high-purity electronic grade phosphoric acid: 104030261A[P]. 2014-09-10.
86	陈爱梅. 熔融悬浮结晶法提纯湿法磷酸[D]. 上海: 华东理工大学, 2012.
	Chen A M. Purification of wet-process phosphoric acid by melt suspension crystallization[D]. Shanghai: East China University of Science and Technology, 2012.
87	钟剑锋. 熔融结晶法净化磷酸过程研究[D]. 上海: 华东理工大学, 2015.
	Zhong J F. Study on purification process of phosphoric acid by melt crystallization[D]. Shanghai: East China University of Science and Technology, 2015.
88	Shinwari K J. Emerging technologies for the recovery of bioactive compounds from saffron species[M]//Saffron. Amsterdam: Elsevier, 2021: 143-182.
89	Crini G, Lichtfouse E. Advantages and disadvantages of techniques used for wastewater treatment[J]. Environmental Chemistry Letters, 2019, 17(1): 145-155.
90	Ma Y, Hu Z P, Wang M, et al. A simple method to study hemihydrate phosphoric acid crystals growth process[J]. Crystal Research and Technology, 2016, 51(5): 337-343.
91	Tsushima I, Maeda K, Yamamoto T, et al. Continuous crystallization of phosphoric acid using suspension crystallizer: effect of operating conditions on purity of crystals[J]. Crystal Research and Technology, 2022, 57(1): 2100102.

[1]	Xiangjun MENG, Yingxi HUA, Changjin ZHANG, Chi ZHANG, Linrui YANG, Ruoxi YANG, Jianyi LIU, Chunjian XU. Preparation and purification of 6N electronic-grade deuterium gas [J]. CIESC Journal, 2024, 75(1): 377-390.
[2]	Hongxin YU, Shuangquan SHAO. Simulation analysis of water crystallization process [J]. CIESC Journal, 2023, 74(S1): 250-258.
[3]	Xuejin YANG, Jintao YANG, Ping NING, Fang WANG, Xiaoshuang SONG, Lijuan JIA, Jiayu FENG. Research progress in dry purification technology of highly toxic gas PH₃ [J]. CIESC Journal, 2023, 74(9): 3742-3755.
[4]	Yu FU, Xingchong LIU, Hanyu WANG, Haimin LI, Yafei NI, Wenjing ZOU, Yue LEI, Yongshan PENG. Research on F₃EACl modification layer for improving performance of perovskite solar cells [J]. CIESC Journal, 2023, 74(8): 3554-3563.
[5]	Ao ZHANG, Yingwu LUO. Low modulus, high elasticity and high peel adhesion acrylate pressure sensitive adhesives [J]. CIESC Journal, 2023, 74(7): 3079-3092.
[6]	Bin CAI, Xiaolin ZHANG, Qian LUO, Jiangtao DANG, Liyuan ZUO, Xinmei LIU. Research progress of conductive thin film materials [J]. CIESC Journal, 2023, 74(6): 2308-2321.
[7]	Xiaodan SU, Ganyu ZHU, Huiquan LI, Guangming ZHENG, Ziheng MENG, Fang LI, Yunrui YANG, Benjun XI, Yu CUI. Optimization of wet process phosphoric acid hemihydrate process and crystallization of gypsum [J]. CIESC Journal, 2023, 74(4): 1805-1817.
[8]	Xuan ZHOU, Mengya LI, Jie SUN, Zhenkai CEN, Qiangsan LYU, Lishan ZHOU, Haitao WANG, Dandan HAN, Junbo GONG. The regulation mechanism of additives on the amino acid crystal growth [J]. CIESC Journal, 2023, 74(2): 500-510.
[9]	Weiyi SU, Jiahui DING, Chunli LI, Honghai WANG, Yanjun JIANG. Research progress of enzymatic reactive crystallization [J]. CIESC Journal, 2023, 74(2): 617-629.
[10]	Yuming CHEN, Wei LI, Xiang YAN, Jingdai WANG, Yongrong YANG. Research progress on regulation of aggregation structure for nascent polyethylene [J]. CIESC Journal, 2023, 74(2): 487-499.
[11]	Bo ZHANG, Zhuangzhuang LI, Dan ZHAO, Cuizhu QIAN, Bao WANG, Pengju PAN. Fabrication of isotactic polypropylene casting film and its structural evolution during stretching [J]. CIESC Journal, 2023, 74(12): 4997-5005.
[12]	Guangzheng ZHOU, Xuezhong WANG, Haoyu ZHOU. Multi-objective optimization and simulation of lysozyme protein crystallization [J]. CIESC Journal, 2023, 74(10): 4191-4200.
[13]	Xueying NAI, Peng WU, Yuan CHENG, Jianfei XIAO, Xin LIU, Yaping DONG. Study on hydrothermal crystallization kinetics of magnesium oxysulfate nanowires [J]. CIESC Journal, 2022, 73(7): 3038-3044.
[14]	Chuyue CAI, Xiaoming FANG, Zhengguo ZHANG, Ziye LING. Enhancing heat dissipation performance of paraffin/silicone rubber phase change thermal pad by introducing carbon nanotubes [J]. CIESC Journal, 2022, 73(7): 2874-2884.
[15]	Guoxin SUN, Mengxuan GOU, Cheng ZHOU, Pei CHANG, Gaohong HE, Xiaobin JIANG. Membrane distillation crystallization coupling process for the treatment of high concentration Na⁺//NO $3 -$ , SO $4 2 -$ -H₂O solution [J]. CIESC Journal, 2022, 73(7): 3078-3089.