At present, there are many kinds of preparation methods of aluminum hydroxide flame retardant, such as Bayer method, soda lime sintering method, ammonium bicarbonate method, etc. In addition to these three common methods, it can also be prepared by alumina reaction. This is a very complete chemical reaction process. The whole preparation process needs to master certain reaction knowledge. Let's introduce the reaction process to you. Because alumina is an amphoteric oxide that is insoluble in water, and aluminum hydroxide flame retardant is an amphoteric hydroxide that is insoluble in water. They can all be soluble in strong acid and alkali, but they will not be soluble in ammonia water (weak alkali) and will not be soluble in carbonic acid (weak acid). Therefore, the following methods can be used: 1. Dissolve alumina in sulfuric acid to obtain aluminum sulfate solution, and then add excess ammonia to the aluminum sulfate solution to obtain aluminum hydroxide precipitate, which can be filtered, washed and dried. Al2O3 3H2SO4 = Al2(SO4)3 3H2O Al2(SO4)3 6NH3.H2O=2Al(OH)3↓ 3(NH4)2SO4 2. Dissolve alumina in sodium hydroxide to obtain sodium metaaluminate solution, and then pass excess carbon dioxide into the sodium metaaluminate solution to obtain aluminum hydroxide, precipitate, filter, wash and dry. During the preparation process, it should be noted that the purpose of adding excess ammonia and carbon dioxide is to ensure that alumina can be completely converted into aluminum hydroxide flame retardant to obtain a purer product. The above is an introduction to the method of preparing aluminum hydroxide flame retardant by alumina reaction. In fact, the whole reaction process is very easy to master. It mainly uses the chemical principle of substances to make them react with each other. Through the above method, products with high purity can be obtained well, which will help our production and use.