Investigations on dehydration processes of trisodium citrate hydrates

Abstract

The dehydration processes of trisodium citrate (Na₃C₆H₅O₇) hydrates were investigated using thermogravimetry (TG), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). It was found that the temperature of dehydration of trisodium citrate dihydrate was at 430.99 K. For trisodium citrate pentahydrate, there is a two-step dehydration process and the endothermal peaks appear at 337.23 K and 433.83 K, respectively. During the first step of dehydration process, the structure of trisodium citrate pentahydrate changed into the structure of trisodium citrate dihydrate. In addition, the kinetics of dehydration for trisoidum citrate hydrates was also investigated using TG data. According to the activation energies of dehydration calculated by Ozawa equation, it was found that the dehydration mechanisms of the two hydrates were different.

Key words： trisodium citrate; dehydration; TG/DSC; PXRD

Acknowledgment

The authors thank the State Research Center of Industrialization for Crystallization Technology (China) for financial support.

References

1 Bayes B, Bonal J, Romero R. Sodium citrate for filling haemodialysis catherters. Nephrology, Dialysis, Transplantation, 1999, 14(10): 2532–2533

2 Gao J Y, Xie C, Wang Y L, Xu Z, Hao H X. Solubility data of trisodium citrate hydrates in aqueous solution and crystal-solution interfacial energy of the pentahydrate. Crystal Research and Technology, 2012, 47(4): 397–403

3 Steiner T, Koellner G. Crystalline p-cyclodextrin hydrate at various humidities: fast, continuous, and reversible dehydration studied by X-ray diffraction. Journal of the American Chemical Society, 1994, 116(12): 5122–5128

4 Morris R E, Burton A, Bull L M, Zones S I. SSZ-51—A new aluminophosphate zeotype: synthesis, crystal structure, NMR, and dehydration properties. Chemistry of Materials, 2004, 16(15): 2844–2851

5 Boonchom B J, Vittayakorn N. Dehydration behavior of synthetic Al_0.5Fe_0.5PO₄·2.5H₂O. Journal of Chemical & Engineering Data, 2010, 55(9): 3307–3311

6 Frost R L, Kloprogge J T. Heating stage spectroscopy: infrared, Raman, energy dispersive X-ray and X-ray photoelectron spectroscopy. In: Brown M E, Gallagher P K, eds. Handbook of Thermal Analysis and Calorimetry. Oxford: Elsevier, 2008, 171–173

7 Sestak J. Thermodynamical Properties of Solids. Prague: Academia Publishers, 1984, 1–5

8 Young D. Decomposition of Solids. Oxford: Pergamon Press, 1966, 55–109

9 Arivanandhan M, Huang X M, Uda S, Bhagavannarayana G, Vijayan N, Sankaranarayanan K, Ramasamy P. Directional growth of organic NLO crystal by different growth methods: a comparative study by means of XRD, HRXRD and laser damage threshold. Journal of Crystal Growth, 2008, 310(21): 4587–4592

10 Duan Y, Li J, Yang X, Hu L, Wang Z, Liu Y, Wang C. Kinetic analysis on the non-isothermal dehydration by integral master-plots method and TG-FTIR study of zinc acetate dihydrate. Journal of Analytical and Applied Pyrolysis, 2008, 83(1): 1–6

11 Lee S B, Fasina O. Fasina O. TG-FTIR analysis of switchgrass pyrolysis. Journal of Analytical and Applied Pyrolysis, 2009, 86(1): 39–43

12 dos Santos A V, Matos J R. Dehydration studies of rare earth p-toluenesulfonate hydrates by TG/DTG and DSC. Journal of Alloys and Compounds, 2002, 344(1-2): 195–198

13 Yonemochi E, Hoshino T, Yoshihashi Y, Terada K. Evaluation of the physical stability and local crystallization of amorphous terfenadine using XRD-DSC and micro-TA. Thermochimica Acta, 2005, 432(1): 70–75

14 Fischer A, Palladino G. Trisodium citrate dihydrate. Acta Crystallographica. Section E, Structure Reports Online, 2003, 59(11): m1080–m1082

15 Voissat B, Rodier N. Crystal structure of sodium citrate hydrate. Bulletin de la Societe Chimique de France, 1986, 4: 522–525

16 Vyazovkin S. Isoconversional kinetics. In: Brown M E, Gallagher P K, eds. Handbook of Thermal Analysis and Calorimetry. Oxford: Elsevier, 2008, 504–506

17 Ozawa T. A new method of analyzing thermogravimetric data. Bulletin of the Chemical Society of Japan, 1965, 38(11): 1881–1886

18 Gamlin C D, Dutta N K, Choudhury N R. Evaluation of knietic parameters of thermal and oxidative decomposition of base oils by conventional, isothermal and modulated TGA, and pressure DSC. Thermochim Acta, 2002, 392-393: 357–369

19 Vyazovkin S. A unified approach to kinetic processing of nonisothermal data. International Journal of Chemical Kinetics, 1996, 28(2): 95–101