粉煤灰—偏高岭土复合基地质聚合物的结构与性能研究

发布时间：2018-05-07 09:45

本文选题：地质聚合物 + 孔结构　；参考：《西南科技大学》2017年硕士论文

【摘要】：地质聚合物作为一种新型的无机聚合物胶凝材料,不仅具有优异的力学性能、耐高温、耐化学腐蚀性能以及化学性能,而且具有与沸石类似的三维网络结构。目前,其作为固化/稳定重金属和放射性废物等有毒有害离子的固化基材备受关注。对于固化体而言,除了力学性能的要求之外,更重要的是基体对离子具有长期滞留的能力,这包括固溶作用、吸附作用和物理固封作用,该固化能力与固化体基体的物相组成和致密程度密切相关。因此,本文以粉煤灰、偏高岭土、NaOH、水玻璃为主要原料制备了地质聚合物材料,借助XRD、SEM、MIP、AAS等测试技术对样品的物相组成、微观结构、孔结构、离子浸出率进行表征,系统研究了原料组成(包括碱激发剂的组成、粉料的掺合比、粉料的粒度)和工艺条件(包括低温养护制度、高温水热合成温度、成型压力)对地质聚合物的结构与力学性能的影响,并将该材料用于固化模拟放射性核素Cs,探索了Cs~+在地质聚合物基固化体中的浸出机制。主要结论如下:(1)通过研究原料组成对地质聚合物孔结构与抗压强度的影响发现,水灰比是影响地质聚合物孔结构的关键因素之一。当水灰比恒定时,碱激发剂的固含量与模数、粉料中偏高岭土与粉煤灰的掺合比、低温养护条件的改变对地质聚合物的总孔隙率基本无影响。此外,粉煤灰颗粒的细化可降低凝胶孔的孔隙率。试样FF6MF2MK5C1致密性和力学性能优异,养护28d的孔隙率和抗压强度分别为11.04%、62.6MPa。各因素对地质聚合物抗压强度的影响由大到小为偏高岭土与粉煤灰的掺合比、碱激发剂的组成和粉煤灰颗粒的细化。偏高岭土取代粉煤灰后,可减少未反应的粉煤灰颗粒与凝胶相之间的界面缺陷,形成更为连续的凝胶网络结构,使抗压强度明显增强。地质聚合物抗压强度与总孔隙率满足指数关系,其中MHS系列地质聚合物抗压强度与总孔隙率满足Y=844.27exp~（-8.06X)关系,相关系数为0.958,FMC系列地质聚合物则满足Y=84.07exp~（-2.64X）关系,相关系数为0.96。(2)通过研究制备工艺对地质聚合物孔结构的影响发现,高温水热条件对地质聚合物的孔结构影响显著。随着水热温度的升高,凝胶相逐渐向Na P1沸石转变,继而向方沸石相转变,总气孔率则不断升高;富方沸石相地质聚合物的总孔隙率高达40.12%。低温养护制度和压制成型方式对粉煤灰-偏高岭土基地质聚合物的总孔隙率无明显的影响。采用最佳成型压力200MPa可制备高强度(100MPa)地质聚合物,试样PS1的抗压强度由普通成型的58MPa增至106MPa;掺入树脂的地质聚合物的抗压强度更是由普通成型的几个MPa增加至110MPa。这将为地质聚合物固化放射性树脂提供新的思路。(3)根据地质聚合物固化模拟放射性核素Cs的研究发现,固化体中原位合成的方沸石、Na P1沸石对模拟核素Cs的吸附作用显著优于致密固化体对核素的物理固封作用。富方沸石相地质聚合物虽然具有高孔隙率(40.12%),但Cs~+在该固化体中42d累计浸出分数仅为9.9×10-5cm/d。优化地质聚合物中50nm的大孔孔隙率,可明显提高固化体对模拟核素的物理固封作用。地质聚合物固化体中Cs~+的浸出分数与浸出时间满足一级反应模型,即核素的主要浸出机制为浸出液向固化体中渗入与核素Cs从固化体表面交换至浸出液同时进行。
[Abstract]:As a new type of inorganic polymer cementitious material, geopolymer not only has excellent mechanical properties, high temperature resistance, chemical corrosion resistance and chemical properties, but also has a three-dimensional network structure similar to that of zeolite. At present, it is regarded as a curing substrate for curing / stabilizing toxic and harmful ions such as heavy metals and radioactive waste. In addition to the requirements for the mechanical properties of the solidified body, it is more important that the matrix have the ability to retain the ions for a long time, which includes solid solution, adsorption and physical sealing, which is closely related to the phase composition and density of the substrate of the solidified body. Therefore, the fly ash, the metakaolin, NaOH, and water are used in this paper. The glass is used as the main material to prepare the geopolymer material. With the help of XRD, SEM, MIP, AAS and other testing techniques, the composition, microstructure, pore structure and ion leaching rate of the samples are characterized. The composition of the raw materials, including the composition of the alkali activator, the blending ratio of the powder, the particle size of the powder, and the high temperature curing system, are systematically studied. The effect of warm water heat synthesis temperature, molding pressure on the structure and mechanical properties of geopolymer, and using the material to solidify the simulated radionuclide Cs, explore the leaching mechanism of Cs~+ in the geopolymer base solidified body. The main conclusions are as follows: (1) the influence of the composition of raw materials on the pore structure and compressive strength of the geological polymer It is found that water cement ratio is one of the key factors that affect the pore structure of geopolymer. When the ratio of water to cement is constant, the solid content and modulus of the alkali activator, the mixing ratio of the megakolinite and the fly ash in the powder, the change of the curing conditions at low temperature has no effect on the total porosity of the geopolymer. In addition, the refinement of the fly ash particles can reduce the gel hole. The porosity and mechanical properties of FF6MF2MK5C1 are excellent, and the porosity and compressive strength of the curing 28d are 11.04% respectively. The effect of 62.6MPa. on the compressive strength of geopolymer from large to small is the blending ratio of the high ridge and fly ash, the composition of alkali activator and the refinement of the fly ash particles. After that, the interfacial defects between the unreacted fly ash particles and the gel phase can be reduced, and a more continuous gel network structure can be formed to enhance the compressive strength obviously. The compressive strength of geopolymer and the total porosity meet the exponential relationship, and the compressive strength of MHS series geological polymers and the total porosity meet the relationship of Y=844.27exp~ (-8.06X), and the correlation is related to the relationship between the compressive strength and the total porosity. The coefficient is 0.958, and the FMC series geopolymer meets the Y=84.07exp~ (-2.64X) relationship. The correlation coefficient is 0.96. (2). Through the study of the influence of the preparation process on the pore structure of the geopolymer, the high temperature hydrothermal condition has a significant influence on the pore structure of the geopolymer. With the increase of the temperature of the water, the gel phase gradually transforms to the Na P1 zeolite. The total porosity of the zeolite phase is increasing, the total porosity of the rich zeolite phase geopolymer is up to 40.12%. low temperature curing system and the pressing molding method has no obvious effect on the total porosity of the fly ash and kaolin based geopolymer. The high strength (100MPa) geopolymer can be prepared by the optimum molding pressure 200MPa. The compressive strength of PS1 is increased from common formed 58MPa to 106MPa, and the compressive strength of the geopolymer added to the resin is increased from several MPa to 110MPa.. This will provide a new idea for the geological polymer solidified radioactive resin. (3) according to the study of the solidified radioactive nuclide Cs of the geopolymer, it is found that the solidified body is in situ. The adsorption of Na P1 zeolite to the simulated nuclide Cs is significantly better than the physical encapsulation effect on the nuclide. The rich zeolite phase geopolymer has high porosity (40.12%), but the cumulative leaching fraction of Cs~+ in the solidified body is only the pore porosity of 50nm in the optimized geological polymer of 9.9 * 10-5cm/ d.. The physical sealing effect of the solidified body on the simulated nuclide is obviously improved. The leaching fraction of Cs~+ and the leaching time in the geopolymer solidified body meet the first order reaction model, that is, the main leaching mechanism of the nuclide is the infiltration of the leach solution into the solidified body and the exchange of nuclide Cs from the surface of the solidified body to the leaching solution.

【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ177

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