The effects of the presence of potassium ion (K+) on the phase transformation and particle morphology of anhydrous magnesium carbonate (MgCO3) precipitation were investigated. The factors that influence the morphology of MgCO3 in the potassium citrate solution, such as reaction temperature, carbon dioxide pressure, have been studied. Powders were characterized by X-ray powder diffraction, scanning electronic microscopy and thermo gravimetric analysis. For reaction system with a low K+ salt concentration, the MgCO3 phase transformation and crystal growth were inhibited. On the other hand, the MgCO3 phase transformation and crystal growth were accelerated by high K+ salt concentrations. The morphology changed with reaction temperature and carbon dioxide pressure of the prepared samples in the K+ solution. Here, the effect of potassium salt presence on the phase transformation and crystal growth of MgCO3 was understood via carbonization of magnesium hydroxide processes. (C) 2019 Published by Elsevier B.V.