Studies On Capability Of Ion Exchange On The Self-Made Molecular Sieve

In the paper, the stability of the self-made molecular sieve were studied. The stability is as follows: heat-resistant capacity, acid-resistant capacity and alkali-resistant capacity. We determined effect of granularity and velocity on exchange capacity to K⁺ of the molecular sieve. We also studied the exchange capacity to K⁺ of the molecular sieve in sea water. The research of adsoorptional and elutional capabilitys of K⁺ in sea water were finished. According to the study, we knew the adsoorptional rate to K⁺ of the molecular sieve in sea water is over 80%, the elutional peak is 109g/L,the elutional rate is 92.3%. Otherwise, we determined effect of Ca²⁺,Mg²⁺ on exchange capacity to K⁺ of the molecular sieve.The thermodynamics and kinetics of ion exchange systems were studied. The thermodyna- mics is as follows: First, we determined the capability of ion exchange to K⁺ in pure potassium and in sea water; Second, we finished the isotherm of ion exchange equilibrium of the molecular sieve under different temperature by static method. Further more, by the figure of isothermal ion exchange equilibrium,we protracted Kielland diagram and Langmuir model was simulated. According to thermodynamics theory,the expression of ion exchange equilibrium constant was deduced and enthalpy, Gibbs free energy and entropy were figured out. Furthermore we proved that the process is unprompted and the exothermic reaction; The low temperature is advantageous to potassium absorption.The kinetics is as follows: First, rate-controlling mechanism of ion exchange was found out.That is ,film diffusion control. At the same time, we utilized two ways, which were broken phase contact and shallow-bed tech.,to confirm the correctness of the mechanism. Second, under arieties of conditions, such as concentration, temperature and current velocity of solution, we got the mass transfer coefficient. The experimental results were that the mass-transfer coefficient extended when temperature and current velocity of solution rased but the influence of concentration to the mass-transfer coefficient was not obvious.