Study On The Structure And Characterization Of The Sericite Treated By Fluorosilicate

Sericite is possessed of excellent physical and chemical properties, and the full using of the excellent performances of sericite’s nano-structured layers to prepare polymer-layered silicate （PLS） nanocomposite or the stripping of Nano sericite is the important direction of development. The structure of sericite is so firmly stabilized that it is hard to directly form nanometer sericite of PLS nanocomposite, so the sericite need to be modified first.Thermal activated sericite is as the research object of thesis, and technology of the structure modification of the sericite modified respectively through sodium fluorosilicate treatment and sodium fluorosilicate and nitric acid together treatment were studied. The products of sericite treated by sodium fluorosilicate and nitric acid together were characterized and the action mechanisms were discussed.The technology and characterization of the thermal activated sericite modified through sodium fluoride treatment was studied. The results show that sodium fluoride treatment can make part of Al³⁺ of the thermal activated sericite dissolute, and the highest dissolution was 2.55mg/g. The optimal processing conditions is concentration of sodium fluorosilicate solution 0.025mol/L, reaction temperature 50℃, agitation time 1h and solid-liquid ratio 3g:200ml. After treated by sodium fluoride, the crystal structure of the sericite remains intact, but compared with the sericite raw materials, the degree of crystallization is decreased.The technology and characterization of the thermal activated sericite modified through sodium fluoride and nitric acid together treatment was studied. The results show that the dissolution amount of Al³⁺ reaches 65mg/g at the optimal processing conditions. And the optimal processing conditions is concentration of sodium fluorosilicate solution 0.015mol/L, nitric acid volume 10 ml, reaction temperature 90℃, agitation time 5h and solid-liquid ratio 3g:200ml. The results of XRD analyses show that the structure of sericite modified through sodium fluoride and nitric acid together treatment is integrated. Compared with the sericite modified only through sodium fluoride treatment, the dissolution amount of Al³⁺ gets significantly increased, and the structure modification of the sericite is more evident.After modified through sodium fluoride and nitric acid tighter treatment, the cation exchangeability （CEC） value of the sericite increased to 11.87mmol/100g （sericite raw material 4.94mmol/100g）. And after been Na⁺ treated （Na-exchange）, the CEC value reaches 14.34mmol/100g, so the results show that the interlayer cation exchange of the sericite greatly enhanced.After modified through sodium fluoride and nitric acid tighter treatment, the results of ²⁷Al-NMR analyses indicate that both 4-fold and 6-fold aluminum in the structure are dissolved, the Si/Al in tetrahedron gets increased and the holes in tetrahedral is reduced. The Zeta electric potential changes show that sodium fluoride and nitric acid toghter treatment can reduce the number of remaining negative charge of the sericite interlayer.The analysis of the mechanism which sodium fluoride on the four-coordinate Al of the sericite’ structure, shows that the F^- dissociated from sodium fluorosilicate and the H⁺ from nitric acid will generate HF, and it can make sericite dissolute Al:...