Electrochemical Electron Transfer and Crystallization Process of Uranium(Ⅵ) in Sodium Salt Solution†

doi:10.7503/cjcu20160171

Abstract

Abstract:

Electrochemical beheaviors of uranium(VI) was investigated with cyclic voltammetry and chronoamperometry(CV). The reduction of U(Ⅵ) was analyzed by potentiostatic electrochemical and the kinetics was investigated with electrochemical impedance spectroscopy(EIS). In addition, crystallization of U(Ⅵ) were analyzed by X-ray diffraction(XRD), scanning electron microscopy(SEM) and energy-dispersive spectrometry(EDS). The results indicated that the reduction processes of U(Ⅵ) to U(Ⅳ) was significantly in fluenced by the pH value of solution, with the pH value changed from 3.87 to 4.50, the cyclic voltammetry showed that the reduction of U(Ⅵ) to U(Ⅳ) was in a manner of two-step one-electron process with a diffusion-controlled reaction mechanism. The cyclic voltammetry results presented a constant potential reduction method for removing U(Ⅵ) from aqueous solution, and the reduction efficiency can reach 90%. At a constant potential, U(Ⅵ) mainly crystalized into solid phases in the forms of UO₂ and (UO₂)₆O₂(OH)₈·6H₂O. These results could provide a basis for removing and collecting U(Ⅵ) from solution.

Key words: Uranium(Ⅵ), Electrochemistry, Electrochemical impedance spectroscopy, Crystallization

CLC Number:

O646

TrendMD:

ZONG Meirong, HE Huichao, DONG Faqin, HE Ping, SUN Shiyong, LIU Mingxue, NIE Xiaoqin. Electrochemical Electron Transfer and Crystallization Process of Uranium(Ⅵ) in Sodium Salt Solution^†[J]. Chem. J. Chinese Universities, 2016, 37(9): 1701.

Figures/Tables 10

Fig.1 Absorbance spectra of ultra-pure water(a), 0.10 mol/L NaCl(b), 0.10 mol/L NaCl+100 mg/L U(Ⅵ)(c) complexing with arsenazo Ⅲ(A) and linear relationship between Abs. and cU(Ⅵ)(B)

Fig.2 Cyclic voltammogram of FTO electrode in 0.10 mol/L NaCl(solid line) and 1.0 mmol/L U(Ⅵ) + 0.10 mol/L NaCl(pH=3.87)(dotted line) at 25 mV/s

Fig.3 Cyclic voltammogram of FTO electrode in 1 mmol/L U(Ⅵ)+0.1 mol/L NaCl(pH=3.87) at diffe-rent scan rates(A) and linear relationship between jop, -jrp and ν1/2(B) (A) Scan rate/(mV·s-1): a. 10; b. 25; c. 50; d. 75; e. 100; f. 250; g. 500; h. 750. (B) a. for peak A(oxidation); b. for peak B(reduction).

Fig.4 Cyclic voltammogram of FTO electrode in 1.0 mmol/L U(Ⅵ)+0.10 mol/L NaCl solution at pH values of 1.5(A), 3.0(B), 4.5(C) and 6.0(D) The scan rate was 25 mV/s.

Table 1 Speciation of U(Ⅵ) at different pH conditions calculated by MINTEQ software*

U(Ⅵ) Species	Percent(%)
U(Ⅵ) Species	pH=1.5	pH=3.0	pH=3.87	pH=4.5	pH=6
U $O 2 2 +$	95.015	93.977	80.362	78.776	—
UO₂Cl⁺	4.816	5.011	4.294	4.209	—
UO₂OH⁺	—	0.251	1.984	2.110	—
(UO₂)₂(OH $) 2 2 +$	—	—	9.794	11.071	0.028
(UO₂)₂OH³⁺	0.015	0.452	3.043	3.171	—
(UO₂)₃(OH $) 4 2 +$	—	0.157	0.196	0.255	0.135
(UO₂)₃OH⁵⁺	—	—	0.192	0.272	21.523
(UO₂)₄OH⁷⁺	—	—	—	—	78.307
UO₂N $O 3 +$	0.131	0.137	0.117	0.115	—
UO₂Cl₂(aq)	0.015	0.016	0.013	0.013	—

Table 1 Speciation of U(Ⅵ) at different pH conditions calculated by MINTEQ software*

U(Ⅵ) Species	Percent(%)
U(Ⅵ) Species	pH=1.5	pH=3.0	pH=3.87	pH=4.5	pH=6
U $O 2 2 +$	95.015	93.977	80.362	78.776	—
UO₂Cl⁺	4.816	5.011	4.294	4.209	—
UO₂OH⁺	—	0.251	1.984	2.110	—
(UO₂)₂(OH $) 2 2 +$	—	—	9.794	11.071	0.028
(UO₂)₂OH³⁺	0.015	0.452	3.043	3.171	—
(UO₂)₃(OH $) 4 2 +$	—	0.157	0.196	0.255	0.135
(UO₂)₃OH⁵⁺	—	—	0.192	0.272	21.523
(UO₂)₄OH⁷⁺	—	—	—	—	78.307
UO₂N $O 3 +$	0.131	0.137	0.117	0.115	—
UO₂Cl₂(aq)	0.015	0.016	0.013	0.013	—

Fig.5 Amperometric i-t curve of FTO electrode in 1 mmol/L U(Ⅵ)+0.1 mol/L NaCl(pH=3.87) at a constant applied potential of -0.50 V(vs. SCE)(A) and variation of the U(Ⅵ) concentration with electrochemical reduction time(B) with(a) or without(b) N2-purging

Fig.6 Electrochemical impedance spectra of FTO electrode in 1.0 mmol/L U(Ⅵ)+0.10 mol/L NaCl(pH=3.87) at a constant applied potential of -0.50 V(vs. SCE) with or without N2 purging(A) and equivalent circuit for FTO electrode(B)

Table 2 Value of the elements in equivalent circuit fitted by the Nyquist plot*

Sample	R_s(Ω)/error(%)	CPE1-T(F)/error(%)	CPE1-P(F)/error(%)	R_ct(Ω)/error(%)
Without N₂-purging	92.56/0.67	5.99×10^-5/1.98	0.96/0.50	6340/6.02
With N₂-purging	84.56/0.98	7.10×10^-5/2.94	0.94/0.75	4765/7.57

Fig.7 Photographs of FTO electrode after different time i-t measurements in 1.0 mmol/L U(Ⅵ)+0.10 mol/L NaCl(pH=3.87) at a constant applied potential of -0.50 V(vs. SCE) with N2-purging(A) and XRD pattern of FTO electrode before and after electrochemical reduction of U(Ⅵ) solution(B)

Fig.8 SEM images(A, B) and EDS spectra(C, D) of FTO electrode after electrochemical reduction in U(Ⅵ) solution for 4 h (C) and (D) are the EDS spectra of the framed area in (A) and (B), respectivery.

References 25

[1]	Leggett R. W., Health. Phys., 1989, 57(3), 365—383
[2]	Domingo J. L., Reprod. Toxicol., 2001, 15(6), 603—609
[3]	Sharma P., Tomar R., Micropor. Mesopor. Mater., 2008, 116(1/3), 641—652
[4]	Xie S. B., Yang J., Chen C., Zhang X. J., Wang Q. L., Zhang C., J. Environ. Radioactiv., 2008, 99(1), 126—133
[5]	Xie S. B., Zhang C., Zhou X. H., Yang J., Zhang X. J., Wang J. S., J. Environ. Radioactiv., 2009, 100(2), 162—166
[6]	Ozay O., Ekici S., Aktas N., Sahiner N., J. Environ. Manage,2011, 92(12), 3121—3129
[7]	Li H. Y., Wang B., Liu S. M., Chem. J. Chinese Universities,2015, 36(4), 665—671
	(李宏宇, 王博, 刘树明. 高等学校化学学报,2015, 36(4), 665—671)
[8]	Chen L., Li Y., Wang Z. W., Peng Z. Y., Yang Z. M., Yuan L. H., Feng W., Chem. J. Chinese Universities,2015, 36(8), 1485—1490
	(陈龙, 李艳, 王真文, 彭智勇, 杨泽明, 袁立华, 冯文. 高等学校化学学报,2015, 36(8), 1485—1490)
[9]	Abbasizadeh S., Keshtkar A. R., Mousavian M. A., Biochem. Eng. J., 2013, 220(15), 161—171
[10]	Sprynskyy M., Kovalchuk I., Buszewski B., J. Hazard. Mater., 2010, 181(1—3), 700—707
[11]	Wang G. H., Liu J. S., Wang X. G., Xie Z. Y., Deng N. S., J. Hazard. Mater., 2009, 168(2/3), 1053—1058
[12]	Wang G. H., Wang X. G., Chai X. J., Liu J. S., Deng N. S., Appl. Clay. Sci., 2010, 47(3/4), 448—451
[13]	Li X. Y., Zhang M., Liu Y. B., Li X., Liu Y. H., Hua R., He C. T., Water. Qual. Expos. Hea,2013, 5(1), 31—40
[14]	Liang F. Y., Wu R. R., Cao C. L., Zheng Y., Yang C. H., Zhao F., Chem. J. Chinese Universities,2014, 35(2), 372—376
	(梁方圆, 吴冉冉, 曹昌丽, 郑越, 杨朝晖, 赵峰. 高等学校化学学报,2014, 35(2), 372—376)
[15]	Wei Y. Z., Fang B., Arai T., Kumagai M., J. Radioanal. Nucl. Ch., 2004, 262(2), 409—415
[16]	Anderson C. J., Choppin G. R., Pruett D. J., Costa D., Smith W., Radiochim. Acta,1999, 84(1), 31—36
[17]	Ikeda Y., Hiroe K., Asanuma N., Asanuma N., Shirai A., J. Nucl. Sci. Technol., 2009, 46(2), 158—162
[18]	Zhang Q. Y., Huang X. H., Tang H. B., He H., Journal of Nuclear and Radiochemistry,2011, 33(2), 101—105
	(张秋月, 黄小红, 唐洪彬, 何辉. 核化学与放射化学,2011, 33(2), 101—105)
[19]	Wang Y., Liu Y. P., Wang X. Y., Zhu T. W., Journal of Nuclear and Radiochemistry,2013, 35(5), 263—269
	(王悦, 刘玉鹏, 王祥云, 褚泰伟. 核化学与放射化学,2013, 35(5), 263—269)
[20]	Tan X. F., Research on the Electrochemical Behavior of Uranium in Ionic Liquids, University of South China, Hengyang, 2014
	(谭绪凤. 铀在离子液体中的电化学行为研究, 衡阳: 南华大学, 2014)
[21]	Liu J. A., Feng X. G., Journal of Nuclear and Radiochemistry,2011, 33(1), 32—41
	(刘杰安, 冯孝贵. 核化学与放射化学,2011, 33(1), 32—41)
[22]	Qiu L. Y., Yuan L. Y., Tan X. F., Shi W. Q., Liu L. J., Journal of Nuclear and Radiochemistry,2014, 36(2), 65—74
	(邱凌云, 袁立永, 谭绪凤, 石伟群, 刘良军. 核化学与放射化学,2014, 36(2), 65—74)
[23]	Yuan K., Ilton E. S., Antonio M. R., Li Z., Cook P. J., Becker U., Environ. Sci. Technol., 2015, 49(10), 6206—6213
[24]	Kim Y. K., Lee S., Ryu. J., Park H., Appl. Catal. B-Environ., 2015, 163(2), 584—590
[25]	Ha D., Jin X., You Kaang Xuan Ye,1981, 4(3), 11—27
	(哈迪, 金鑫. 铀矿选冶,1981, 4(3), 11—27)