热活化高岭土制备地质聚合物研究

Thermal activation of kaolin for synthesis of geopolymers

将高岭土与氢氧化钠按不同的质量比混合,在980℃下煅烧35min进行固体活化,生成硅、铝前聚物。选取碱/土配比最佳的活化产物,经加水、成型和养护,制成有一定抗压强度的地质聚合物。采用FTIR、XRD和SEM方法对原料、活化产物和地质聚合物的表面键合、物相及微观结构进行分析。结果表明,高岭土的特征—Si—O—Si(Al)链在加碱热活化过程中断裂,形成无序的硅、铝前聚物,这些高能的硅、铝前聚物经水化生成具有连续有序三维—Si—O—Si(Al)网状结构的地质聚合物。这种加碱固体热活化方法可有效利用天然硅铝酸盐合成地质聚合物。

Kaolin was thermally activated with the addition of sodium hydroxide through solid reac- tions, forming Si and A1 precursors for the preparation of geopolymers. The surface bonding, mineralogy, microstructure and morphology of the raw material, activated products and synthesized geopolymers were fully characterized by using Fourier transform infrared spectroscopy （FTIR）, X-ray diffraction （XRD） and scanning electron microscope （SEM）. Kaolin was melted with 100~ NaOH （mass ratio referring to kaolin） at 950 ~C for 35 rain and then pulverized after cooling in the air. The formed precursors were moulded after water addition, and cured at 100% moisture, forming geopolymers with sound compressive strength. The bonding information shows that the ordered kaolin struc- ture collapses during thermal activation with NaOH, generating less ordered A1 and Si precursors. Reacting with water, the A1 and Si precursors polymerize to form more ordered geopolymers of con- tinuous three dimensional --Si O--Si（A1） structure. Thermal activation with alkaline provides an effective approach to the preparation of geopolymers using natural aluminosilicate minerals.