Study On The Structure Of Potasium Chloride Aqueous Solutions

Researches on the solution structure were widely studied,most of which were concentrated on single aqueous solutions.And most of experiments were carried out for the effect of concentration on the solution structure,while the factor of temperature,especially in the field of potassium salt,was rarely involved.According to the current researches of the solution structure,the effect of temperature on the solution structures of single potassium salt and mixed potassium salt aqueous solution were carried out in the article.And the results explained why the solubility of KCl and NaCl was different with the increase of the temperature on the atomic scale.X-ray diffractometer was modified by a special design platform for the test of aqueous solutions,and at the same time the temperature control function was realized.The saturated KCl and NaCl aqueous solution under 0℃and KCl-NaCl mixed aqueous solution were measured on 0,20,40,60,80℃.The solution structures of aqueous solutions at different temperatures were obtained after the treatment of software PDFgetX3 and the later partial peak fitting.Experimental results show that for the saturated KCl and NaCl aqueous solutions under 0℃,the change of KCl aqueous solution with the increase of temperature is significantly greater than that of NaCl,but the variation trend of them is consistent.In the two solutions,the hydration radius of Cl~-increases gradually,which of K~+and Na~+decrease.The number of water molecules in the first ion hydration layer decreases with the increase of temperature,and the degree of damage to the hydrogen bond between water molecules are getting worse.On the contrary,K~+-Cl~-and Na~+-Cl~-contact ion pairs gradually increase in the process of elevated temperature,then more and more hydration water change into free water to join in the new hydration of ions,which results in the solution solubility increases significantly.The variation trend of mixed aqueous solution is consistent with single aqueous solution in the process of elevated temperature.The hydration radius of K~+and Na~+decrease gradually,on the contrary,the hydration radius of Cl~-is increasing.With the increase of temperature,the number of water molecules in the first ion hydration layer decreases,and the degree of damage to the hydrogen bond between water molecules are getting worse.But in the same environment,the change of K~+is more obvious than that of Na~+.So many K~+-Cl~-and Na~+-Cl~-contact ions increase that more free water increases the solubility.