ISSN 1002-1027  CN 11-2952/G2

Acta scientiarum naturalium Universitatis Pekinensis

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FT-IR Study of Water Structure in Water/NaDEHP/n-Heptane Microemulsion System

LI Quan, LI Yan, LI Weihong, WENG Shifu, WU Jinguang, XU Guangxian   

  1. College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871
  • Received:1996-12-04 Online:1997-07-20 Published:1997-07-20

Abstract: Microstructure of water in water/NaDEHP/n-heptane microemulsion system has been studied by means of Fourier transform infrared spectroscopy (FT-IR). The intensity and peak position of H2O bands in the system was found to vary with water content W0, (the molar ratio of water to NaDEHP). The frequency of O-H stretching band of water shifted from 3385 to 3417 cm-1 in the system when the W0 value increased from 1 to 25. The O-H stretching bands were resolved by using resolution enhanced technique of second derivative and curve fitting. Four peaks located at (3610+-10),(3512+-10),(3420+-10) and (3250+-20)cm-1 in the system were obtained. These four peaks were assigned to free water, phosphate-bonded water, bulk water and Na+-bonded water, coexisting in the same microemulsion solutions. Area fraction of the four types of water molecules were estimated quantitatively after O-H stretching bands were resolved by curve fitting. When the water content was increased, the area fraction of bulk water increased. Meanwhile area fractions of phosphate-bonded water and free water in the system decreased with water content. For Na+-bonded water, the area fraction increased with W0 up to the value of 11, after that, it decreased gradually. All these variations are due to the interactions of water molecules with both phosphate and Na+ in the microemulsion system.