Upgrading Of A Low-grade Potassium Feldspar Ore In Southern Jiangxi And Its Application In The Synthesis Of Geopolymer

The cement production capacity in China has reached 2.4 billion tons by 2016,accounting for 60%of the total production amount in the world.Along this way,the carbon emissions have accounted for more than 11.3%of the total discharge in China.However,the proportion of this was less than 5%in 1990.The discharge amount of greenhouse gas has already brought severe challenges to the changes in global climate.In addition to this,cement production can also cause serious air pollution and endanger human health.Therefore,It is of great necessity and urgency to promote the development of cement substitute materials.Geopolymer material is a new type of green and environmental cementing material,and it is also recognized as the most potential material for cement replacement.Therefore,it is of great significance to promote industrial upgrading and low-carbon development in the field of cement materials via the research and application of geopolymer material.The raw material selections in the production of traditional geopolymer are narrow（mostly based on high-activity raw materials）,while few studies are focused on the low-activity raw materials of aluminum and silicon.Meanwhile,the traditional binary system“activator-silicon and aluminum raw materials”for the production of geopolymer is full of other trouble issues and problems.Therefore,in this paper,the low-grade potassium feldspar ore in a place in southern Jiangxi is first subjected to impurity removal and subsequent purification,and then it is used to be the raw material for geopolymer production via alkali-doped calcination process.After that,experiments are conducted to produce one-part mix geopolymers,followed by the evaluation of the product properties.Study on Preparation Technology of Water-integrated Geopolymers and Properties of Products.The details including the test contents and relevant conclusions are as follows:（1）The mineralogy of the feldspar ore was analyzed using the mineral analysis system（MLA）.The results showed that the useful minerals in the ore were potassium feldspar,quartz,and the gangue minerals were mica,tourmaline,garnet,kaolinite,etc.The grade of potassium feldspar in the ore was low,and it contained a large number of iron impurities in various forms,with tourmaline and biotite mostly.Because of the large differences in the nature of the impurities,it was difficult to remove them synchronously and a variety of combined methods to remove impurities were necessary.According to the results of the mineralogy analysis,experimental studies on the purification of potassium feldspar ore were performed.The results showed that,a concentrate could be obtained with grade of potassium and sodium 13.7 and Fe₂O₃ 0.12%on the basis of the flowsheet“high gradient magnetic seperation-desliming by classification-reverse flotation-quartz seperation”when using potassium feldspar ore（K₂O:5.5%and Fe₂O₃:1.12%）in southern Jiangxi as the raw material.The quality of the concentrate was up to flat glass grade（JC/T 895-2000）standard.A quartz concentrate with the grade of SiO₂99.26 and Fe₂O₃ 0.08%could also be obtained,which could meet the quality standards for quality ceramics for daily use（QB/T 1637-2016）.（2）Using K-feldspar concentrate as the main silica-alumina raw material,it was activated by sodium carbonate doping calcination process.The experimental results showed that the activation method can effectively destroy the crystal structure of potassium feldspar and increase its silicon-aluminum activity.The optimal activation conditions were as follows:the ratio of potassium feldspar and sodium carbonate was 1:0.8,the calcination temperature was850℃,and the calcination time was 60 minutes.The influence degrees of each factor on the activation effect of potassium feldspar were:calcination temperature>sodium carbonate content>calcination time.The results of XRD,FTIR,SEM,and TG-DTA showed that,with the increase of temperature in the environment of sodium carbonate-potassium feldspar system,the crystal phase of potash feldspar and quartz was continuously reduced,gradually turning into amorphous material and completely decomposed at 850℃.And meanwhile,there were some resultants of soluble ionic compounds including sodium metasilicate and potassium meta-aluminate in the system.（3）The effects of four conservation environments on the performance of water-integrated potash feldspar base polymer were investigated,and the process parameters were optimized by orthogonal experiment using compressive strength as the index in the optimal conservation environment.The results showed that the superior geopolymer sample with compressive strength up to 102 MPa could be obtained under the conditions as follows:liquid to solid ratio of 0.08:1,forming pressure of 25 MPa,oven curing temperature of 80℃,and curing time of24 h.FTIR and SEM analyses showed that higher molding pressure and lower liquid-solid ratio could facilitate the polymerization reaction,reduce the internal porosity of the sample,and increase the compressive strength of the sample.（4）The effects of four raw auxiliary materials on the strength and thermal stability of K-feldspar base polymer were investigated.It was found that the addition of a suitable amount of material containing the active silicon-aluminum components had a good promoting effect on the strength of the potassium feldspar base polymer sample.However,when the added amount was too high,it could induce the cracking and deformation of the geopolymer sample.The addition of non-active auxiliary materials had little effects on the improvement of the strength of K-feldspar base polymer samples.This was due to the fact that the addition of non-active auxiliary materials in the geopolymer sample did not participate in the polymerization reaction,but only played the role of aggregates.It should be also noticed that,with the increase of aggregates,the sample intensity dropped seriously.The results of XRD,TG-DSC,SEM analysis and thermal stability test show that the compressive strength of the water-integrated K-feldspar base polymer increases first and then decreases with increasing calcination temperature.The main geopolymer sample at 25⁷00℃ is In amorphous form and in the presence of a small amount of sodium metasilicate and sodium meta aluminate,the phenomenon of overburning at900℃ was evident and the sample collapsed and deformed.The maximum heat-resistant temperature is about 700℃.