Synthesis of high-purity magnesium hydroxide using dolomite and bittern is important for use in various applications. We synthesized magnesium hydroxide using bittern and dolomite, which are domestic resources. In Bittern, there is a high concentration of Mg2+ ions, but the impurity Ca2+ ion content is also significant, requiring a purification process to remove it. There are two main methods for this purification. Firstly, there is a separation method that utilizes the difference in solubility between Mg2+ ions and Ca2+ ions by using sulfuric acid on dolomite. Adding MgSO4 solution from dolomite to Bittern removes Ca2+ ions as CaSO4. This process simultaneously purifies Ca impurities and increases the Mg/Ca ratio by adding extra Mg2+ ions. In this study, purified bittern was obtained by using dolomite and sulfuric acid to extract MgSO4, which was then used to purify Ca2+ ions. High-purity Mg(OH)2 was synthesized by optimizing the NaOH and NH4OH ratio as an alkaline precipitant. Mg(OH)2 synthesis technology made by effectively removing Ca ions from dolomite and bittern can contribute to domestic pilot production.

Magnesium hydroxide sulfate hydrate (MHSH) whiskers were synthesized via a hydrothermal reaction by using MgO as the reactant as well as the acid solution. The effects of the H2SO4 amount and reaction time at the same temperature were studied. In general, MHSH whiskers were prepared using MgSO4 in aqueous ammonia. In this work, to reduce the formation of impurities and increase the purity of MHSH, we employed a synthesis technique that did not require the addition of a basic solution. Furthermore, the pH value, which was controlled by the H2SO4 amount, acted as an important factor for the formation of high-purity MHSH. MgO was used as the raw material because it easily reacts in water and forms Mg+ and MgOH+ ions that bind with SO4 2- ions to produce MHSH. Their morphologies and structures were determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM).