Effects of Flotation Reagents on the Morphology of Magnesium Hydroxide: Experimental and Simulation Study

The flotation process to extract potassium salt from carnallite ores could produce the MgCl2 mother liquor with flotation reagents─octadecyl amine hydrochloride (ODA) and dodecyl morpholine (DMP). The organic impurities would further affect MgCl2 resource-integrated utilization for preparing magnesium hydroxide (MH). In this study, the effects of flotation reagents with different concentrations on the morphology of MH were investigated at a hydrothermal temperature of 200 °C for 6 h with the hydrothermal medium of a 4 mol/L NaOH solution. It was observed that the average thickness of MH crystal plates increased and the morphology of crystals changed from regular hexagonal plates to irregular polygonal plates with the increase of ODA and DMP concentrations. Molecular dynamics (MD) simulation was applied to further explain the effect mechanism. The results indicated that ODA and DMP molecules were more likely to be adsorbed on the (1 1 0) plane in contrast to the (0 0 1) plane due to the larger absolute values of adsorption energy on the (1 1 0) plane. The long carbon chains far away from the (1 1 0) plane would form steric hindrance to affect the growth rate of MH crystals in the [1 1 0] direction.