What are the preparation method of aluminum hydroxide

1。 Bayer process, its principle is to use caustic soda ( NaOH) Heating stripping solution of alumina in the bauxite, sodium aluminate solution. Solution and residue ( Red mud) After the separation, lower temperature, the aluminum hydroxide as a seed, a long time of mixing, aluminum hydroxide precipitation decomposition of sodium aluminate, wash, and calcined at 950 ~ 1200 ℃ temperatures, he gets alumina products. Precipitation of aluminum hydroxide solution called mother liquor, after evaporating circulation use.

2。 Soda-lime sintering method is suitable for the processing of high silica bauxite, bauxite, sodium carbonate and lime mixture by certain proportion, burn formed in rotary kiln by sodium aluminate ( Na2O? 氧化铝) , iron, sodium, Na2O? Fe2O3, the original calcium silicate ( 2CaO? SiO2) And sodium titanate ( 曹? Clinker composed of TiO2. Then using dilute alkali dissolution clinker in the sodium aluminate solution. The iron sodium acid hydrolysis of NaOH into the solution. If dissolution conditions control properly, the original calcium silicate will not react with sodium aluminate solution in large quantity, and calcium titanate, Fe2O3? H2O, etc from red mud. Dissolution of clinker is specially the desilication process of sodium aluminate solution, sodium aluminosilicate hydrate SiO2O formation ( Called sodium silicon slag) Cao or hydrated garnet 3? Al2O3? xSiO2? ( 6 - 2x) Precipitation (H2O The x≈ 0. 1) , and make the solution purification. The CO2 gas is bubbled into refined sodium aluminate solution, and stir in the seed, and get the aluminum hydroxide sediments and main ingredients are sodium carbonate liquor. Aluminum hydroxide by calcining become alumina products. Hydrated garnet of Al2O3 can again with Na2CO3 mother liquor extraction recovery.

3。 Bayer sinter combination can give full play to the advantages of the reduced, complement each other, using aluminum silicon low bauxite, get better economic effect. Joint method has various forms, are given priority to with bayer process, the sintering process. According to the purpose of the joint method and the process connection in a different way, and can be divided into series and parallel method and mixture combination. the three kinds of technological process. (1) a series method is used in the sintering process recycling bayer process red mud Na2O and Al2O3, used for processing bayer process can't economic use of sanshui LvShiXing bauxite. Enlarged the raw material resources, reduce the alkali consumption, use cheaper soda instead of caustic soda, and the recovery rate of Al2O3 is higher also. (2) the parallel method, parallel operation is bayer process and sintering processing bauxite, respectively, but accounts for only 10 ~ 15% of total production capacity of sintering process, process with sintering, the conversion of NaOH added bayer process in the process of NaOH consumption.