Influences of Freezing on the Reduction of Cr(Ⅵ) by Typical Components of Dissolved Organic Matter†

doi:10.7503/cjcu20170191

Abstract

Abstract:

The influences of freezing on the reduction of Cr(Ⅵ) by four typical components of dissolved organic matter(DOM), namely oxalic acid, tartaric acid, malic acid and citric acid, were investigated. The results show that under the condition of a low concentration in the experiments, Cr(Ⅵ) in the aqueous solution cannot be reduced by those four organic acids. However, in the ice, the four organic acids all facilitate to remove Cr(Ⅵ). Moreover, the removing effects gradually strengthens with the increasing concentration of organic acids. And the effects of these four organic acids rank as oxalic acid>tartaric acid>malic acid>citric acid. The concentration of inorganic salts and inorganic acid can inhibit the reduction of Cr(Ⅵ) by changing the thickness of liquid-like layers in the ice surface, but the inhibiting effect is independent of the kinds of inorganic salts. It is the initial pH of the solution and the structure of the organic acid that greatly influence the reduction of Cr(Ⅵ). Upon the experiment condition, the concentration factor of the freeze-concentration effect can reach 10³ at least, which apparently facilitates the oxalic acid to remove Cr(Ⅵ) in the ice.

Key words: Cr(Ⅵ), Reduction, Ice, Dissolved organic matter

CLC Number:

O647

TrendMD:

ZHONG Yubo, KANG Chunli, WANG Yueqi, XU Xiaolei, BAO Siqi, XUE Honghai, TIAN Tao. Influences of Freezing on the Reduction of Cr(Ⅵ) by Typical Components of Dissolved Organic Matter^†[J]. Chem. J. Chinese Universities, 2017, 38(12): 2289.

Figures/Tables 11

Fig.1 Effects of concentrations of the organic acids on the removal of Cr(Ⅵ) in ice c(Cr(Ⅵ)]=10 μmol/L. (A) Oxalic acid; (B) tartaric acid; (C) malic acid; (D) citric acid.Concentration of organic acid/(μmol·L-1): a. 10; b. 20; c. 30; d. 40; e. 50; f. 60.

Fig.2 Temperature variation curve in the sample freezing process

Table 1 Simulation of the first order kinetics of the reduction of Cr(Ⅵ) in ice

Acid	Concentration/(μmol·L^-1)	First order kinetics equation	k/h^-1	Coefficient of determination, R²
Oxalic acid	10	y=-0.0007x+0.0543	0.0007	0.8520
	20	y=-0.0065x+0.4814	0.0065	0.9109
	30	y=-0.0200x+2.1408	0.0200	0.9039
	40	y=-0.0273x+2.0323	0.0273	0.9107
Tartaric acid	10	y=-0.0002x+0.0333	0.0002	0.9000
	20	y=-0.0054x+0.5112	0.0054	0.9609
	30	y=-0.0142x+1.4327	0.0142	0.9097
	40	y=-0.0207x+2.0973	0.0207	0.9133
Malic acid	20	y=-0.0014x+0.1477	0.0014	0.9380
	30	y=-0.0056x+0.5608	0.0056	0.9406
	40	y=-0.0098x+0.9895	0.0098	0.9276
	50	y=-0.0159x+1.5606	0.0159	0.9372
Citric acid	20	y=-0.0011x+0.1103	0.0011	0.9145
	40	y=-0.0066x+0.6651	0.0066	0.9543
	50	y=-0.0104x+1.0119	0.0104	0.9469
	60	y=-0.0127x+1.2155	0.0127	0.9445

Table 2 Initial pH values of Cr(Ⅵ)-organic acid system under different concentrations of the organic acids

Concentration/ (μmol·L^-1)	Initial pH value				Concentration/ (μmol·L^-1)	Initial pH value
Concentration/ (μmol·L^-1)	Oxalic acid		Tartaric acid	Malic acid	Citric acid	Oxalic acid	Tartaric acid	Malic acid	Citric acid
10	5.19	5.27			40	4.60	4.64	4.75	4.68
20	4.98	4.98	5.04	5.02	50			4.60	4.46
30	4.86	4.86	4.95	60				4.39

Fig.3 Structures of the oxalic acid(A), tartaric acid(B), malic acid(C) and citric acid(D)

Fig.4 Removal of Cr(Ⅵ) by oxalic acid in watera. c[Cr(Ⅵ)]=10 μmol/L, c(oxalic acid)=40 μmol/L(ice); b. c[Cr(Ⅵ)]=2 mmol/L, c(oxalic acid)=8 mmol/L(water); c. c[Cr(Ⅵ)]=6 mmol/L, c(oxalic acid)=24 mmol/L(water); d. c(Cr(Ⅵ)]=12 mmol/L, c(oxalic acid)=48 mmol/L(water); e. c[Cr(Ⅵ)]=20 mmol/L, c(oxalic acid)=80 mmol/L(water).

Fig.5 Effects of the concentrations of inorganic salts on the removal of Cr(Ⅵ) in ice c[Cr(Ⅵ)]=10 μmol/L, c(oxalic acid)=20 μmol/L. (A) NaNO3; (B) NaCl; (C) Na2SO4.Concentration of inorganic salt/(μmol·L-1): a. 0; b. 15; c. 150; d. 1.5; e. 10; f. 100; g. 1.

Fig.6 Effects of initial pH values on the removal of Cr(Ⅵ) in Cr(Ⅵ)-oxalic acid system in ice c[Cr(Ⅵ)]=10 μmol/L, c(oxalic acid)=20 μmol/L; pH: a. 1.58; b. 3.58; c. 4.98; d. 5.52; e. 6.55; f. 7.56; g. 8.53.

Fig.7 Effects of initial pH values on the removal of Cr(Ⅵ) in Cr(Ⅵ)-H2SO4 system in ice c[Cr(Ⅵ)]=10 μmol/L; pH: a. 1.53; b. 3.58; c. 4.62; d. 5.20; e. 6.55.

Fig.8 Removal of Cr(Ⅵ) in Cr(Ⅵ)-oxalic acid system and Cr(Ⅵ)-H2SO4 system at the same initial pH value in icec[Cr(Ⅵ)]=10 μmol/L; a. oxalic acid, pH=4.60; b. H2SO4, pH=4.62.

Fig.9 Removal of Cr(Ⅵ) in Cr(Ⅵ)-H2SO4 system and Cr(Ⅵ)-oxalic acid-H2SO4 system at the same initial pH value(pH=3.58) in icec[Cr(Ⅵ)]=10 μmol/L, c(oxalic acid)=20 μmol/L; a. H2SO4; b. oxalic acid+ H2SO4.

References 21

[1]	Bower J. P., Anastasio C., J. Phys. Chem. A, 2013, 117(30), 6612—6621
[2]	Ge L. K., Li J., Na G. S., Chen C. E., Huo C., Zhang P., Yao Z. W., Chemosphere,2016, 155, 375—379
[3]	Fede A., Grannas A. M., Environ. Sci. Technol., 2015, 49(21), 12808—12815
[4]	Bower J. P., Anastasio C., Environ. Sci.: Processes and Impacts,2014, 16(4), 748—756
[5]	Tang X. J., Wang Y. X., Kang C. L., Liu H. F., Chen B. Y., Qiu S. L., Chem. J. Chinese Universities, 2015, 36(9), 1719—1723
	(唐晓剑, 王依雪, 康春莉, 刘汉飞, 陈柏言, 裘式纶. 高等学校化学学报, 2015, 36(9), 1719—1723)
[6]	Kahan T. F., Donaldson D. J., Environ. Sci. Technol., 2010, 44(10), 3819—3824
[7]	Takenaka N., Furuya S., Sato K., Bandow H., Maeda Y., Furukawa Y., Inte. J. Chem. Kinet., 2003, 35(5), 198—205
[8]	Bartels-Rausch T., Jacobi H. P., Kuhs W. F., Kuo M. H., Maus S., Moussa S. G., McNeill V. F., Newberg J. T., Pettersson J. B. C., Roeselova, M., Sodeau J. R., Atmos. Chem. Phys., 2014, 14, 1587—1633
[9]	Xue H. H., Tang X. J., Kang C. L., Liu J., Shi L., Wang H. L., Yang T., Water Sci. Technol., 2013, 68(11), 2479—2484
[10]	Bao S. Q., Kang C. L., Zhong Y. B., Zhou L., Yao Z. F., Huang D. M., Wang Y. H., Tian T., Chem. J. Chinese Universities, 2016, 37(12), 2253—2259
	(包思琪, 康春莉, 钟宇博, 周林, 姚志富, 黄冬梅, 王宇寒, 田涛. 高等学校化学学报, 2016, 37(12), 2253—2259)
[11]	Adorno W. T., Rezzadori K., Arend G. D., Chaves V. C., Reginatto F. H., Luccio M. D., Petrus J. C. C., Int. J. Food Sci. Technol., 2017, 52, 781—787
[12]	Heger D., Jirkovsky J., Klán P., J. Phys. Chem. A, 2005, 109(30), 6702—6709
[13]	Abida O., Osthoff H. D., Geophys. Res. Lett., 2011, 38, L16808—L16812
[14]	Zhang F., Wang B., Wang J. N., Li X. Y., Li C. J., Chem. J. Chinese Universities, 2016, 37(11), 2117—2124
	(张凡, 汪滨, 王娇娜, 李秀艳, 李从举. 高等学校化学学报, 2016, 37(11), 2117—2124)
[15]	Deng B., Stone A., Environ. Sci. Technol., 1996, 30, 2484—2494
[16]	Kim K., Chung H.Y., Ju J. J., Kim J. W.,Science of Total Environment, 2017, 590, 107—113
[17]	Wang Y. H., Chen W. Y., Gu H. B., China Leather, 2005, 34(3), 30—32
	(王应红, 陈武勇, 辜海彬. 中国皮革, 2005, 34(3), 30—32)
[18]	Kim K., Choi W., Environ. Sci. Technol., 2011, 45(6), 2202—2208
[19]	Dong X. L., Ma L. Q., Gress J., Harris W., Li Y. C., J. Hazard. Mater., 2014, 267, 62—70
[20]	Grannas A. M., Bausch A. R., Mahanna K. M., J. Phys. Chem. A, 2007, 111(43), 11043—11049
[21]	Kim K., Kim J., Bokare A. D., Choi W., Yoon H., Kim J., Environ. Sci. Technol., 2015, 49(18), 10937—10944