Preparation Of Ionic Rare Earth Based Geopolymer Porous Material And Its Properties Research

Ionic rare earth tailings is produced by the ionic rare earth bucket leaching and tank leaching in the early age.A large amount of tailings has a strong impact on ecological environment due to the backward mining technology and lax supervision.Thus,comprehensive utilization of ionic rare earth tailings is an urgent problem to be solved.Geopolymer is a new kind of binding material,which has many merit,such as wide raw material sources,a good performance similar to ordinary ceramic and cement even superior to the two in some ways,and the abroad application.However,systematic research is still needed in the field of porous materials application.In this study,rare earth tailings was used as the research object,to study on the activation of ionic type ra re-earth tailings,which can supply premise for ionic rare earth tailings comprehensive utilization;And the geopolymer porous thermal insulation performance and thermal stability were studied with the rare earth tailings as the main raw material.Rare earth tailings activation pretreatment was conducted by mechanical ball grinding and heating calcination to improve the activation of rare earth tailings.Alkali solution leaching method,XRD,FTIR was used to judge the activity of rare earth tailings.The results shows that silica and alumina leaching concentration in rare earth is biggest when it was ball milled for 4h and burned 2h at 750?,which means the activation level of rare earth tailings was biggest.Meanwhile,the composite in rare earth has changed,crystal disordered,and amorphous material produced.The main reason is due to the hydroxylation of rare earth tailing material inside was taken off.Then geopolymer was prepared by stirring and mixing the alkali-activator and activated rare earth tailing,then injection molding to get the geopolymer sample.geopolymer formula is optimized by orthogonal experimental method.The optimum sample was analyzed and characterized by XRD,FTIR and SEM.The experimental results show that Geopolymer prepared from rare earth tailings has a good compressive strength and dense structure.Molar ratio of Na/Al to geopolymer has the greatest effect in the compressive strength.The orthogonal experiment confirm that nNa/nAl is 0.8,the best sodium silicate modulus is 1.5,and water solid ratio is 0.5.The 7 d compressive strength of geopolymer sample is 18.89 MPa at this point.XRD,FTIR and SEM analysis show that polymer is a kind of composed of silicon oxygen tetrahedron and alumina tetrahedron mesh structure of the amorphous gel material,kaolinite in rare earth tailings is the main participation to polymerization,quartz and feldspar as aggregate.These materials will not take part in the reaction but were bound with the geopolymer gels,make the structure compact,and make the earth polymer formed certain strength.Geopolymer porous material was prepared with hydrogen peroxide and sodium dodecyl sulfate as foaming agent.The influence of dosage of foaming agent,stirring speed and the curing temperature on the strength of the porous materials and the volume density and porosity was studied.Moreover,the microscopic pore structure porous materials made by different foaming agent was analyzed by scanning electron microscopy(SEM).The test results show that the hydrogen peroxide has the biggest influence on the performance of porous materials.The porous porosity rate is between 43.32% ~ 76.68%,volume density between 0.56 ~ 1.36 g/cm3,compressive strength between 0.94 ~ 13.56 MPa with hydrogen peroxide as foaming agent.Hydrogen peroxide and sodium dodecyl sulfate composite foaming agent make the porosity of porous material between 66.89% ~ 87.36%,the volume between 0.30 ~ 0.79 g/cm3 density,compressive strength between 0.26 ~ 5.80 MPa.The weakest effects on porous materials is sodium dodecyl sulfate,the porosity of porous material was between 56.12% ~ 62.58%,the volume density arrange from 0.9 ~ 1.05 g/cm3,the compressive strength between 4.62 ~ 8.54 MPa.The former two kinds of foaming agent can get higher porosity of porous materials.When hydrogen peroxide was collected as foaming agent,the pore was uniformly distributed,and pore size is large r,more for close hole,which is suitable for materials emphasize compression strength;when using the composite foaming agent,uniformly distributed,small and close pore can be obtained,and it is good for heat reservation.The last foaming agent just get low porosity,well distributed,and connected pore,which is suitable for purification and filter materials.Composite foaming agent was used to mix with slurry,then foam slurry inject to 300 x 300 x 10 mm mould,curing 12 h under 80 ?,to get the sample.Double protection of hot plate method is used to measure the coefficient of thermal conductivity of the porous materials under different volume density.The compressive strength of porous material under different calcination temperature was also tested,Thermo gravimetric and differential thermal analysis,XRD,FTIR and SEM were used respectively to study the thermal stability of porous materials.The test results show that the coefficient of thermal conductivity of the porous materials is between 0.1238 ~ 0.2150 W/(m · K),and has a good heat preservation performance and higher thermal stability,of which smallest compression strength is more than 1.5 MPa.Phase change will be taken when the temperature increase higher than 600 ?,and shrink also will be happen after 1000?.This paper has confirmed that ionic rare earth tailings can serve as source materials to prepare geopolymer porous materials with good properties after activation.