Abstract: Magnesium hydroxide was obtained by using carbide slag and magnesium chloride as raw materials.Through reaction of carbide slag(calcium hydroxide)and ammonium chloride to prepare ammonia air,then put ammonia air into magnesium chloride solution to get magnesium hydroxide.Through single factor experiments,the optimum technology conditions were obtained:amount-of-substance ratio of ammonium chloride to magnesium chloride was 5.0,concentration of magnesium chloride was 2.0 mol/L,reaction time was 60 min,reaction temperature was 25 ℃,and aging time was 2 h.Under those conditions productive rate of magnesium hydroxide could reach 89% and its purity was higher than 98%.XRD and SEM results showed the product was flaky powder with about 800 nm in particle size.Method of preparing Mg(OH)₂ not only solves the stacked carbide slag,but also can get high-quality Mg(OH)₂.

Key words: carbide slag, ammonium chloride, magnesium chloride, magnesium hydroxide