Preparation Of Zeolite W From Potassium Feldspar By Solid State Method And Its Potassium Ion Exchange Performance

Potassium feldspar is one of the most abundant minerals in the earth's crust.It is widely distributed in Sichuan,Anhui,Shandong,Shanxi,Xinjiang and other places.The proven potassium feldspar source reaches 62,with a total reserve of about 8 billion tons.The price of K-feldspar is very cheap,the current market price is less than 100 yuan per ton,if it is used as a basic raw materials to achieve high-value utilization,there will be good economic benefits.The main chemical composition of potassium feldspar K2O is about 16.9%,SiO2 is about 64.7%,and Al2O3 is about 18.4%.However,the structure of potassium feldspar is very stable.How to use the silicon and aluminum resources contained in potassium feldspar effectively,makes K-feldspar have considerable social and economic value,has become one of the hot spots for scientists to study.Considering that the potassium,silicon,and aluminum compositions of potassium feldspar are very similar to the composition of W zeolite and the amount ratio of material(Si/Al=1.5?2.4,K/Al=1).Therefore,explore a process for the preparation of W molecular sieves cleanly and efficiently with potassium feldspar as raw material can not only effectively and integrally convert potassium,silicon,and aluminum resources in K-feldspar into high-value-added molecular sieve products,but also avoid the traditional hydrothermal synthesis process for the preparation of W molecular sieves.After the single extraction of potassium resources,a large amount of waste liquid,waste residue,and the waste of silicon and aluminum resources are produced.The purpose of this study is to develop a clean and highly efficient new process for the preparation of W molecular sieves with high purity and good potassium ion exchange performance,using potash feldspar ore with rich reserves and low cost in Fujian Shaxian as a raw material.The effective overall conversion of potassium,silicon,and aluminum resources provides a new approach for the comprehensive utilization of potassium feldspar.It is of great economic and strategic importance to compensate for the severe shortage of potassium resources in China.Firstly,KOH and K2CO3 and potash feldspar were mixed according to a certain proportion,the potassium feldspar was activated by alkali melting roasting,and the effects of alkali type,quality ratio of alkali and potash feldspar,calcination temperature and roasting time on the activation of K-feldspar were studied in detail.The results show that the structure of K-feldspar is effectively destroyed under experimental conditions,which lays a foundation for the effective overall transformation of potassium,silicon and aluminum resources in minerals.In combination with the characterization results of the W molecular sieve prepared by the activated potassium feldspar solid phase method,the optimum activation condition of K-Feldspar was determined as follows:The mass ratio of K2CO3 and potash feldspar is 1.6,the roasting temperature is 800?,and the roasting time is 2 h.On the basis of the above activated potassium feldspar research,we have carried out the study on the preparation of W molecular sieve by mixing potassium feldspar?K2CO3?SiO2 and Al(OH)3 with solid phase method after alkali roasting.The effects of Al2O3/K2O and SiO2/K2O,crystallization temperature and crystallization time on the synthesis of W molecular sieve were investigated in detail.The best conditions for solid-phase synthesis were determined based on the determination of potassium ion exchange capacity in simulated seawater.The optimal preparation process of W molecular sieve for potassium feldspar,K2CO3,SiO2 and Al(OH)3 according to a certain proportion of mixed materials,adjusting system composed of Al2O3/K2O=0.36,SiO2/K2O=1.61,roasting at 800? for 2 h,milled the clinker after cooling for 0.5h,adding alkali after milling and amount of total alkali charge 40%,crystallized at 160? for 48 h.In order to further increase the exchange of potassium ions in simulated seawater by W molecular sieves,the third chapter uses simple etching of acid and alkali for W molecular sieves.The acid-base concentration,etching time,and temperature were investigated for W molecular sieves and simulations.The effect of potassium exchange in seawater.The results show that under the experimental conditions,when the etching temperature is 70 0C and the concentration of 0.2 mol·L-1 NaOH solution is etched for 4 h,the skeletal structure of the W molecular sieve is not damaged after etching,and the K+exchange capacity is 79.61 mg·g-1.Compared with the original W molecular sieve,it increased by 36.3%,which greatly increased the exchange of K+with simulated seawater.