Abstract: Co-MgAl ternary hydrotalcite-like compounds (HTLcs) were prepared by hydrothermal method.The different Co2+ ratios on the phase composition, crystal structure and crystal growth of HTLcs were investigated by the X-ray diffraction (XRD) and scanning election microscopy (SEM).Simultaneously, the growth mechanism was discussed by the ligand field theory.The adsorption performance and mechanism of calcined Co-MgAl-HTLcs and MgAl-LDHs were comparative investigated with methyl orange (MO) as the adsorption object.The results show that there is exchange exists in Mg2+ and Co2+ at layer board.The lamellar structure of hydrotalcites are not affected at different Co2+ ratios, but the each crystal planes growth of Co-MgAl-HTLcs are affected during the crystal formation process.The calcined Co-MgAl-HTLcs of Co∶Mg∶Al=1∶2∶1 can maintain sheet structure after 500 ℃ calcining.But the crystal size and thickness slightly are decrease compared with that before calcined, the homogeneity and regularity of the product became relative poorer than before calcined.The adsorption decolorization performance of Co-MgAl-LDO is slowly increasing with the time increase on MO simulated dye wastewater.It took the longer to reach adsorption equilibrium for 70 min.The decolorization rate is only to 60;, which is the lower than the MgAl-LDO (90;).The adsorption kinetic study shows that the adsorption process of Co-MgAl-LDO on the MO is more consistent with the quasi-second-order kinetics equation, and the adsorption isotherm is in accordance with the Freundlich model.The adsorption process of MgAl-LDO is more consistent with the quasi-first order kinetic equation, its adsorption isotherm conforms to the Langmuir model.

Key words: Co-MgAl ternary hydrotalcite-like compounds (HTLcs) were prepared by hydrothermal method.The different Co2+ ratios on the phase composition, crystal structure and crystal growth of HTLcs were investigated by the X-ray diffraction (XRD) and scanning election microscopy (SEM).Simultaneously, the growth mechanism was discussed by the ligand field theory.The adsorption performance and mechanism of calcined Co-MgAl-HTLcs and MgAl-LDHs were comparative investigated with methyl orange (MO) as the adsorption object.The results show that there is exchange exists in Mg2+ and Co2+ at layer board.The lamellar structure of hydrotalcites are not affected at different Co2+ ratios, but the each crystal planes growth of Co-MgAl-HTLcs are affected during the crystal formation process.The calcined Co-MgAl-HTLcs of Co∶Mg∶Al=1∶2∶1 can maintain sheet structure after 500 ℃ calcining.But the crystal size and thickness slightly are decrease compared with that before calcined, the homogeneity and regularity of the product became relative poorer than before calcined.The adsorption decolorization performance of Co-MgAl-LDO is slowly increasing with the time increase on MO simulated dye wastewater.It took the longer to reach adsorption equilibrium for 70 min.The decolorization rate is only to 60;, which is the lower than the MgAl-LDO (90;).The adsorption kinetic study shows that the adsorption process of Co-MgAl-LDO on the MO is more consistent with the quasi-second-order kinetics equation, and the adsorption isotherm is in accordance with the Freundlich model.The adsorption process of MgAl-LDO is more consistent with the quasi-first order kinetic equation, its adsorption isotherm conforms to the Langmuir model.