Thermal Decomposition of High-magnesium Low-nickel Laterite: Theoretical Calculation and Experimental Study

The high-magnesium low-nickel laterite was taken as raw material, the thermal decomposition experiment by calcination was carried out to study the phase transformation of dehydroxylation and re-crystallization during the thermal decomposition of laterite. Based on the experimental study on phase transformation of thermal decomposition of serpentine, the experimental process was simulated by theoretical calculation to clarify the phase transformation of magnesite laterite during heating process. The results indicated that Mg3Si2O5(OH)4 was the major ingredient of laterite, dehydroxylation reaction occurred when temperature exceeded 612℃, and amorphous silicate mineral generated. Subsequently, the recrystallization occurred when heating up to 817℃, generating peridot phase, enstatite, as well as a small amount of SiO2. By means of density functional theory (DFT), the atomic bond length, state density and Millikan population of Mg3Si2O5(OH)4 were calculated, and its molecular dynamics calculation during thermal decomposition was simulated. The results showed that under the condition of kinetic simulation, the hydroxyl groups in Mg3Si2O5(OH)4 would be separated directly in the form of hydroxyl to form amorphous silicate products. With the rising temperature, the SiO2 in amorphous silicate tended to dissociate and separate, participating in re-crystallization process and producing peridot phase and enstatite with better crystallinity. The calculation simulated results were well fitted with the experimental results. © 2019, Materials Review Magazine. All right reserved.