Magnesium hydroxide suspension, due to its excellent properties, has important applications in environmental protection, medicine, rubber modification, flame retardancy, food additives, and other fields. Especially in the environmental protection field of flue gas desulfurization, neutralizing acidic wastewater, and removing metal ions, the products generated are mainly magnesium salts, which are harmless to the environment and can be directly discharged. Moreover, it is mildly alkaline, with a saturated solution pH of less than 10, hence it is known as a “green environmental protection neutralizer.”
Magnesium hydroxide suspension has the advantages of easy production, high activity, and strong buffering capacity. It also has the safe characteristics of being non-toxic, non-corrosive, and mildly alkaline during use. In recent years, it has been widely researched and applied, especially in flue gas desulfurization. Unlike gypsum desulfurization which easily generates calcium sulfate and causes caking, leading to pipe blockage, magnesium desulfurization produces soluble magnesium sulfate, which does not cause blockage. It is more practical when the pipes are relatively narrow, especially in marine desulfurization situations such as on ocean-going freighters, where it is widely used. Therefore, the preparation of magnesium hydroxide suspension is necessary.
Magnesium hydroxide suspension has good suspension performance, low viscosity, stable and uniform quality; the viscosity range is 139.8~1571.2mPa·s; under static conditions for 7 days, the solid content change of the upper, middle, and lower layers of the suspension does not exceed 1.8%, and the maximum solid content difference between the layers does not exceed 2.45%, with no sedimentation or scaling at the bottom of the container; when used for ship flue gas desulfurization, it has a good desulfurization effect and can meet the strictest emission standards for sulfur oxides in ship flue gas, that is, the ship exhaust detection S/C value is less than 4.3, and the emission effect of S content in fuel is less than 0.1%.
If the prepared magnesium hydroxide suspension is not stable enough, due to the fact that magnesium hydroxide is an insoluble precipitate and has a strong surface polarity, stratification may occur under long-term static placement or frequent vibrations during transportation, causing magnesium hydroxide to settle at the bottom, and the upper layer to be a relatively clear liquid, resulting in uneven suspension concentration, making it difficult to determine the concentration during use; or gelation may occur, making the entire substance appear jelly-like, losing fluidity, making it impossible to transport, and even damaging transportation equipment during transportation, leading to its loss of use value. Therefore, magnesium hydroxide suspension is required to not stratify or gel after long-term storage, and to be easy to use.