PAN Guo-xiang1, QIAN Ping-ping2, CAO Feng1, NI Zhe-ming2
(1. Department of Materials Chemistry, Huzhou Teachers College, Huzhou 313000, China; 2. College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032, China)
Abstract: The physical and chemical properties, such as thermal stability and ion-exchange properties, of layered double hydroxides are in associate with the host-guest interaction which mainly contains electrostatic interaction, but the calculation for the lattice energy of LDHs is very difficult. In this study, the host-guest electrostatic model of layered double hydroxides (LDHs) was constructed via interlayer anion as a negative charge group, and corresponding hydroxides layer as a positive charge group. Then the lattice energy of LDHs was calculated by the second law of crystal chemistry, and interlayer anion exchange properties and thermal stabilities were compared. The results show that the order of lattice energy of LDHs is, Mg3Al-F-LDHs > Mg3Al-OH-LDHs > Mg3Al-Cl- LDHs > Mg3Al-Br-LDHs > Mg3Al-I-LDHs, Mg3Al-CO3-LDHs > Mg3Al-CrO4-LDHs > Mg3Al-SO4-LDHs > Mg3Al-NO3-LDHs, by changing the varieties of interlayer anions. The calculation data is in accordance with the reported anion exchange properties of LDHs in the literature. When varying the metal ions ratio within the layers, the order of lattice energy of LDHs is, Mg2Al-CO3-LDHs > Mg3Al-CO3-LDHs > Mg4Al-CO3-LDHs, which is associated with the thermal stability of interlayer carbonates of LDHs. As the species of metal ions of layers changed, the order for the thermal stability of interlayer carbonate of LDHs via the calculation of lattice energy is, Mg3Al-CO3-LDHs > Cu3Al-CO3-LDHs > Ni3Al-CO3-LDHs > Zn3Al-CO3-LDHs ~ Co3Al-CO3-LDHs > Fe3Al- CO3-LDHs > Mn3Al-CO3-LDHs > Cd3Al-CO3-LDHs > Ca3Al-CO3-LDHs; Mg3Al-CO3-LDHs > Mg3Ni-CO3- LDHs~Mg3Co-CO3-LDHs ~ Mg3Fe-CO3-LDHs > Mg3Cr-CO3-LDHs. The constructed electrostatic model and calculation of lattice energy provide theory basis for the prediction of the thermal stability and ion-exchange properties of LDHs, and it is also benefit for the calculation for lattice energy of the other layered host-guest materials.
Key words: layered double hydroxide; lattice energy; the second law of crystal chemistry
E-mail: pgxzjut@163.com
ACTA MINERALOGICA SINICA Vol. 33, No. 1, 2013, Page 25-30
