On the Factors Influencing the Crystal Structure and Crystalline Size of Layered Double Hydroxides

Mg-Al layered double hydroxides(LDH) have been synthesized from Mg(NO 3) 2·6H 2O, Al(NO 3) 3·9H 2O, NaOH and Na 2CO 3 in a rotating liquid- film reactor. It is found that the aging temperature, degree of supersaturation in the course of aging and degree of supersaturation in the course of nucleation are the important factors affecting the crystal structures and crystallite sizes of hydrotalcites. Lower aging temperatures and addition of water during the aging process favour the formation of nano-sized hydrotalcites. When the concentration of Mg 2+ is between 0.1～1.6 mol/L the particle size of LDH increases with increase of the Mg 2+ concentration.