Preparation Of High-purity Magnesium Hydroxide Via Utilizing Carbide Slag And Magnesium Chloride From Salt Lakes

High purity magnesium hydroxide was prepared by using carbide slag and salt magnesium chloride asraw materials. The extraneous component of carbide slag was complex, thus use carbide slag reacted withsodium sulfate and ammonium chloride respectively, and magnesium hydroxide was obtained through thereaction of magnesium chloride and the alkali that was obtained through the above reaction. Two kinds oftechnologies of preparing magnesium hydroxide were got through single factor experiment and orthogonalexperiment. The purity of magnesium hydroxide was measured by using ICP and the EDTA titrationmethod, and characters of product were carried out using XRD, SEM.The optimally technological conditions of using sodium sulfate were listed bellow. Saturated sodiumsulfate solution put20hours with carbide slag quietly, and the reaction temperature of the filtrate andmagnesium chloride solution was40℃and the reaction time35minutes. The purity of product was above99.07percent, the result of XRD completely consistent with standard atlas of magnesium hydroxide, andthe result of SEM showed that the product was flaky and the grain size was about1μm.The optimally technological conditions of using ammonium chloride were listed bellow. The mol rateof ammonium chloride and magnesium chloride was5.0, the concentration of magnesium chloride2.0mol/L，the reaction time60minutes, the reaction temperature at25℃, the ageing time2hours. In theseconditions, the productive rate of magnesium hydroxide was above89.08percent, the purity of productabove99.09percent, the result of XRD completely consistent with standard atlas of magnesium hydroxide,magnesium hydroxide agreed with the HG/T3607-2007standard,and the result of SEM showed that theproduct was flaky and the grain size was about1μm.Compared with the two methods, dissolvability of calcium hydroxide in sodium sulfate and carbideslag was small, effecting the productive rate of magnesium hydroxide, big water consumption, colloidalmagnesium hydroxide, adsorbing extraneous component easily, effecting the filter performance, and thereaction of sodium sulfate and carbide slag was imperfection, the complex component of devil liquor,reclamation and recycle not easy. The method of preparing magnesium hydroxide by using ammoniumchloride was through the reaction of magnesium chloride and alkaline air that was prepared through thereaction of ammonium chloride and carbide slag. The ammonium chloride in filter liquor could react withcarbide slag again, realizing recycling. Calcium chloride could be obtained as by-product with purity over94.64percent, a calcium chloride as by-product agreed with the HG/T2327-92standard. The ammoniumchloride also realized recycling, recycle ratio could reach69.47%.The on-line modification of magnesium hydroxide proceeded by using lauryl sodium sulfonate, laurylsodium sulfate and neopelex as modifying agent. Then studied the consumption of modifying agent andmodified time, the results showed that the optimally modifying agent was neopelex and activated exponentof magnesium hydroxide was over96.05percent after modification. In summary, preparing magnesium hydroxide using carbide slag and salt magnesium chloride, andusing on-line modification, not only shortened the process. The comprehensive utilization of waste andclosed recycling were the feature of this study, which promoted energy conservation and low-carboneconomy and had good environmental benefits, social benefits and remarkable economic benefits...