| Other Abstract | Pillared interlayered clay (abbreviated as PILC), a novel class of mineral functional materials, possesses several interesting properties, such as high pore size, large specific surface area, tunable pore size (from micropore to mesopore), high thermal stability, strong surface acidity and active metal components contained. It has become a research focus in the fields of clay mineralogy, chemistry and material science. In this work, pillaring of irregular illite/smectite (hereafter I/S) interstratification from Dafang County, Guizhou Province, has been studied. Polyhydroxyaluminum was used as a pillaring agent. This paper systematically presented the mineralogical characteristics of irregular I/S interstratification, the species characteristics of AI13- pillaring agent, the preparation and characterization of Al-pillared I/S interstratification etc. The conclusions are as follows. I/S interstratification from Dafang County, which coefficient of variation is large, is irregular. Its XRD patterns exhibit three 001 reflections, which basal spacings are 2.72, 3.15 and 3.62nrn respectively. Its crystal structure maybe a mixed-type of IS, ISI and ISII. Its hydroxylation temperature is close to that of exogenetic illite, and is 100 ℃ lower than that of montmorillonite, which shows more extent of substitutions of Al~(3+) for Si~(4+) in its tetrahedral sheet. This structure is of great advantage in improving the thermal and hydrothermal stability of PILC. The Al-pillared I/S interstratification exhibits three basal spacings of rfboi: 3.36, 3.83 and 4.28nm. In contrast to I/S interstratification, the spacings increased by 0.66rmi on the average, which shows that AI13 has entered clay interlayer region. This experiment also shows that clays can be synthesized into PILC without Na exchange. It is simple and feasible to prepare Al13 by hydrolysis of AICI3, with (CH2)6N4, instead of NaOH, The Al-pillared I/S interstratification retains high dooi values (96%) and large specific surface area (80%) after calcination at 800°C, indicating its high thermal stability. There are diffent types of water molecules and hydroxyl groups attached to Al-pillared I/S interstratification with different bonding energies. Its dehydroxylation temperature, which starts at about 400 ℃, is a bit low. It is because of that protons released from the pillars during dehydration and dehydroxylation migrate into octahedral sheet, and interact with the structural hydroxyl groups. The pillaring mechanism of Al-pillared I/S interstratification is as follows: before calcination, there is a static electrical force between pillaring agents and clay layers, and then the Si-O-Al_(pillar) or Al~(IV)-O- Alpmar covalent bond is formed between pillars and clay layers after calcination. |
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