Study On The Structure Of Potassium Salt Aqueous Solutions

Solution structure research involves almost all solution system and various physical and chemical processes, however, as a long time, there is no specific test equipment and index method for study of solution structure. Therefore, understanding of the aqueous solution structure is still in the theoretical prediction level. Therefore, no unified results were got for the structure of the potassium salt aqueous solution. In this paper, the potassium salt aqueous solution and related mixed solution were systematically studied by X-ray diffractometer and Raman spectrometer. It is hoped to provide a scientific basis for preparation of potassium separation materials and development of new methods for extracting potassium from seawater.In order to obtain X-ray scattering data of the aqueous solution, the X-ray diffractometer(D8-Focus) were modified. Compared with the original configuration, low background capillary can be installed on the modified diffractometer as a sample cell,which can solve the problem of background subtraction. So the modified diffractometer has great advantage for measuring the aqueous solution. To ensure data quality, scattering data tested by the modified laboratory diffractometer were compared with that measured by synchrotron radiation. The results prove that the modified X-ray diffractometer can obtain accurate solution scattering data.In this paper, PDFgetX3 was used to analyze the X-ray scattering data of three kinds of inorganic salt(KCl, K2SO4, NH4Cl) aqueous solution systems for the first time. The experimental results show that, for the low concentration aqueous solution, the peak at r=2.81 ?(representing O-O interactions between water molecules) in the reduced pair distribution function changed regularly with the increase of solute concentration. For the KCl aqueous solutions, with the raise of solute concentration, this peak broadened and moved to 3.15 ? gradually, and the peak tended to split, which proved the appearance of K+-Cl- contact ion pairs in the solution; for K2SO4 aqueous solutions, the peak just slightly broadened with the rise of solute concentration, which meant the tetrahedral O-O relation became more and more loose; for NH4 Cl aqueous solutions, with the increase of solute concentration, the peak gradually moved to the 3.3 ?, which proved that interaction between water molecule and ammonium ion(3.05 ?) as well as NH4+-Cl- contact ion pair(3.3 ?) were enhanced. In this paper, besides the above aqueous solution system, the Raman spectroscopy also was used to study the structure of the NaCl aqueous solutions.The experimental results show that, with the increase of solute concentration, the tetrahedral hydrogen bonded networks were damaged more and more serious for different aqueous solution systems. These results are consistent with that obtained by X-ray scattering method.Based on the study of above aqueous solutions, research on the structure of three groups of mixture solution was carried out. The solutes in the mixture solutions are as follows, KCl and K2SO4, KCl and NH4 Cl, KCl and NaCl. It is showed that the structure of mixture aqueous solution is impacted by the two solutes, but influence of the solute with greater solubility and smaller molecular weight is more intense. With the variation of the mixture aqueous solution composition, the reduced pair distribution function and the excess Raman spectra have undergone significant changes, which showed certain regularity.