Research On The Alkaline Leaching Process And Kinetics Of Potassium Feldspar Under Microwave Irradiation

Potassium feldspar resources in China mainly include water-soluble and insoluble potassium feldspar.The available water-soluble potassium feldspar reserves are small and the insoluble potassium feldspar reserves were large,which is difficult to utilize efficiently.In this paper,aiming at potash feldspar from Bayan Obo rich potassium slate after iron removal,water-soluble potassium are obtained by the method of microwave alkali leaching,and the best k-feldspar leaching process and leaching dynamics analysis were investigated comparing with conventional heating alkali leaching process,which provides a new way for the comprehensive utilization of the insoluble potassium feldspar.The experiment results of microwave alkali leaching for potassium feldspar show that the leaching rate of potassium is highest,reaching to 93.05%under the conditions of the microwave holding time of 3 h,temperature of 220?and NaOH mass fraction of 35%;however,the potassium leaching rate only reached 87.44%under the condition of common alkali leaching at the same temperature and alkali content,and the holding time was extended for 15 h.Through chemical reaction control,diffusion control two kinds of models of potash feldspar microwave leaching isothermal kinetics analysis,the results show that in the 160?to 220?temperature range alkali leaching of potassium feldspar well accords with the unreacted shrinking core model very well,and microwave leaching is controlled by surface chemical reaction,the apparent activation energy is 52.01 kJ/mol,and the pre-exponential factor is 2.46×10⁴,so the kinetic equation of main reaction is:1-?7?1-X?8?^{1 3}?28?2.46?10⁴e^{-52.01?103/RT}t.But the alkaline leaching reaction process under conventional heating belongs to the chemical reaction model,and its apparent activation energy is 66.83 kJ/mol,the pre-exponential factor is 1.44×10⁵,and the main reaction kinetic equation is:1-2X 3-?7?1-X?8?^{2 3}?28?1.44?10⁵e ^66.83?103/RTt.Comparing the leaching effect and apparent activation energies of potassium feldspar under two alkaline leaching methods,it shows that microwave intensified the leaching reaction of potassium feldspar in the MH process and had a great non-thermal effect on the leaching reaction,could significantly reduce the activation energy of the reaction and shorten the reaction time,thus improve the leaching efficiency.By XRD,SEM,EDS and infrared detection analysis methods,the samples of the potassium feldspar before and after alkali leaching such as ores,leaching slags and leachates were analyzed.The results show that the main composition of the leach liquor is soluble potassium silicate,the main mineral in the leaching residue is sodalite.And the increase of Al-O groups and the decrease of Si-O groups in sodalite under the condition of microwave alkaline leaching indicated that microwave heating promoted the substitution of Al-O bond for Si-O bond,and the leaching efficiency is higher compared with ordinary heating leaching.Finally,two kinds of products are obtained by alkali leaching of potassium feldspar,in which water-soluble potassium silicate can be used to make potash fertilizer,ceramics and so on,and the other leaching slag can be used to prepare catalysts and hydrogen storage materials.