Influence of alkali metal ions (K+ and Na+) on the preparation of magnesium hydroxide hexagonal flakes

Abstract

Magnesium hydroxide (Mg(OH)₂), as a green halogen-free flame retardant, has attracted significant attention in the field of flame retardant composite materials. In addition to conventional indicators such as purity and whiteness, Mg(OH)₂ is required to take the form of regular hexagonal sheets to ensure the dispersion of composite materials. We use irregular large particles of Mg(OH)₂ prepared by the magnesium factory in western Qinghai as raw materials to study the influence of alkali metal ions K⁺ and Na⁺ mainly present in salt lakes on the physicochemical properties of Mg(OH)₂. The products were characterized via X-ray diffraction, scanning electron microscopy, automatic nitrogen physical adsorption apparatus, and other modern characterization techniques. Results show that alkali metal ions K⁺ and Na⁺ considerably influence the crystal surface polarity, particle size, and morphology of the prepared Mg(OH)₂. The mechanism analysis shows that the presence of K⁺ and Na⁺ alters the dissolution, recrystallization, and growth characteristics of Mg(OH)₂. This study provides theoretical support for the realization of high-performance Mg(OH)₂ using salt lake resources and demonstrates the value for promoting the large-scale industrial application of the salt lake industry.