Preparation And Delamination Of Amino Acid-MgAl-LDHs And Its Composite With Montmorillonite

Layered double hydroxides(LDHs) have been paid to wide attention due to their particular structures and properties. Nevertheless, LDHs have the defects of small specific surface area, bad thermal stability, unexposed catalytic active site so as to prevent the application of LDHs to some extent. Montmorillonite (MMT) are conceived as a promising carrier for high specific surface area and better stability. Active component in catalysts are evenly dispersed on the surface of MMT. Therefore, the composites with new physicochemical property based on LDHs and MMT can be prepared.In this paper, in order to study the effect of amino acid on the delamination, Aa-MgAl-LDHs were synthesized by coprecipitation method and the delamina-tion process were researched. The effects of R groups, raw material ratio (Aa/NO3), pH of synthesis system were studied in detail. Using the layer board with opposite charge, delaminated MgAl-LDHs were intercalated compounding with MMT. The simples were characterized by XRD, FT-IR, BET and mi-cro-electrophoresis apparatus.In the synthesis process of Aa-MgAl-LDHs, Gly, Lys, Leu, Phe were se- lected for anionic. The arrangement of amino acid among layers and the effect of R groups on the delamination were researched. The results showed that simples had the characteristic diffraction peaks of LDHs. The interlayer spacing of Gly-MgAl-LDHs, Lys-MgAl-LDHs, Leu-MgAl-LDHs was0.34nm and the in-terlayer spacing of Phe-MgAl-LDHs was1.97nm. According to the interlayer spacing and amino acid molecular size, it can be known that Gly, Lys, Leu mo-lecules were obliquely oriented in the interlayers and the Phe molecules were vertically oriented by form of double-deck. By comparing pH of delamination system and time of stirring, it can be known that when R groups had alkaline group, the time of delamination was reduced. When R groups were hydrophobic group, the time of delamination was reduced drastically. Increased interlayer spacing had no effect on the delamination.A series of Gly-MgAl-LDHs were synthesized by changing Gly/NO3and pH of synthesis system. The samples were delaminated in aqueous solution for24h. The effects of Gly/NO3and pH of synthesis system were discussed. It was revealed that when Gly/NO3was between1/7and1/3, zeta potential was be-tween10mV and30mV and the stable time of LDHs nanolayers was48h. When Gly/NO3-was between1/2and1/1, zeta potential was between30mV and40mV and the nanolayers can exist for72h. The pH of synthesis system had no effect on the delamination. MgAl-LDHs/MMT layer composite were prepared by in-tercalation compounding. The interlay spacing, specific surface area and average pore size of composite was1.44nm,19.88m2.g-1,12.89nm respectively. A series of Lys-MgAl-LDHs were synthesized by changing Lys/NO3-and pH of synthesis system. The samples were delaminated in aqueous solution for18h. The results showed that when Lys/NO3-was between1/8and1/4, zeta po-tential was between30mV and40mV and the nanolayers can exist for72h. The pH of synthesis system had no effect on the delamination. The interlay spacing, specific surface area and average pore size of composite was1.46nm,36.59m1.g-1,11.82nm respectively.