Study On The Divestiture Dispersion Of Montmorillonite And Its Influencing Factors

Montmorillonite is a kind of natural nano-phyllosilicate mineral with unique physical and chemical properties,which is widely used in many fields,such as casting,drilling,chemical industry,food processing and so on.The special structure of layers,ion exchange and water swelling properties provide montmorillonite with good peeling and dispersion properties.After peeling,montmorillonite obtains a larger specific surface area and surface energy,results in the further improvement of physical and chemical properties.In this paper,experimental researches about the dispersedness of montmorillonite and it's influencing factors were carried out with the bentonites origin from three different places(Santai of Sichuan,Tiandong of Guangxi and Xiazijie of Xinjiang)as raw materials.The mineralogical study of raw bentonite was carried out at First.The experimental results show that bentonite from Santai and Tiandong are Ca-bentonite,while bentonite from Xiazijie is natural Na-bentonite,besides,all of these three bentonites contain quartz,calcite and some other impurities,which need to be purified and removed later.Namodification and purification experiments of the three bentonites were conducted by ultrasonic-centrifugation,and the effects of the experimental factors such as centrifugal speed,centrifuge time and dosage of Na-modification agent on purification were all discussed.Test results show that samples prepared under the optimal purification conditions have greatly improvement in expansion capacity,colloid index and CEC,in addition,the content of the montmorillonite is also raised to more than 93%.The physical and chemical properties of these samples were all optimized and meet the requirements of their practical application.In the research of inorganic peeling and dispersing of montmorillonite,the water swelling,stripping and directional stacking of montmorillonite were carefully studied.The results show that the crystalline layer of montmorillonite expand and be stripped after water absorption,and according to the analysis of diffraction and optical,the particles get smaller and the layers strip along the direction perpendicular to the c axis.The layers of montmorillonite stack again after dehydration,indicating that the stacking is the aggregation of twodimensional colloidal particles.Natural Na-montmorillonite has better dispersibility than modified Na-montmorillonite.In addition,the dispersity of the montmorillonite gel can be controlled by adjusting the p H value of the sample.The dispersion of montmorillonite keep in suspension for a long time when the p H value is 8-11,while in other p H agglomerate and settle.According to the test based on the standard of inorganic bentonite gel,the inorganic peeling montmorillonite samples are completely in conformity with relevant indicators.Different surfactants were selected to explore the effects of organic stripping of montmorillonite.The types of surfactants,the addition mode and the amount of surfactants were all discussed to explore their effects on stripping and dispersing of montmorillonite.The results show that the interlayer spacing of montmorillonite increases gradually after the addition of cationic surfactant CTAB,and there is a critical point in the conversion of montmorillonite from ion adsorption to molecular adsorption at 1.5 times of CEC concentration.The higher the charge number of montmorillonite layers,the higher the organic degree and the worse the dispersivity are.The nonionic surfactant OP-10 has little effect on the interlayer spacing of montmorillonite,only few of them can enter the crystal layers,which limit the intercalation effect and can not peel the montmorillonite.Cationic-nonionic surfactants and anionicnonionic surfactants were used on the composite intercalation of montmorillonite.The results show that the organic degree of montmorillonite get higher after the intercalation of cationic-nonionic surfactants compared with cationic surfactants,the interlayer molecular structure is more regular and the interval is larger as well.After the intercalation of anionic-nonionic surfactants,the layers of montmorillonite stripped,exhibiting with cloudy appearance according to the SEM photos,in combination with XRD analysis,montmorillonite has been well stripped and dispersed.According to the test based on the standard of organic bentonite and coating organic bentonite,the properties of organic peeling montmorillonite samples are better than standard.The contents and results of this research provide theoretical significance and practical value for the study of the stripping and dispersion as well as the deep application of montmorillonite.