Preparation And Purification Of High Purity Al₂O₃ By Al（OH）3

This article mainly studied the preparation method of high purity alumina, aluminum hydroxide and purification methods of various impurities of alumina. Experiment chooses aluminium hydroxide is 7.9 g, the amount of sulfuric acid is 24 ml, reaction by using aluminum sulfate. aluminium hydroxide and sulfuric acid reacte completely, By controlling the amount of ammonium sulfate solution to control the ratio of raw material, found that along with the increase in quantity of the addition of ammonium sulfate, ammonium aluminum sulfate production gradually increased, but won’t increase after increased to a certain degree, so the experiment selected the ammonium sulfate solution for 10 ml. With the loss of the cooling temperature, the crystallization of ammonium aluminum sulfate speed faster, but the quality of the ammonium aluminum sulfate generated is the same, so we chosed to use in the constant temperature water bath of 10 degrees, p H value of 1-3 precipitation for granular crystal, for ammonium aluminum sulfate crystals, p H value of 4 to 5, the flocculent crystals appear in the solution, For flocculent crystal aluminum hydroxide precipitation, So experiment when choosing a p H value of 1-3.Use differential thermal phase, pyrolysis analysis, specific surface area, morphology analysis analyzed ammonium aluminum sulfate, the morphology and phase of alumina under different p H and different temperature were analyzed. Ammonium aluminum sulfate has experienced three times of weightlessness for thermal decomposition of ammonium aluminum sulfate crystals desulfurization, deamination, and loss of water of crystallization. Powder dispersion gradually increases, the particle size decreases. Alumina crystal grain with the increase of p H, crystal grain diameter increase gradually, particle dispersion gradually weakened.Eliminate the iron in alumina, the amount of EDTA is 0.004g/l and the mixing time is 40 min, removal of iron was 72.97%. In the amount of activated carbon for 10g/l, stirring time for 30 min, Fe removal rate was 45.33%. In 0.1g/l for the amount of molecular sieve, mixing time for 30 min, removal of iron was 50.67%. To remove impurities sodium, potassium, the elution method is adopted, the crystal when heated to 200℃-250℃, elution effect is best. Eliminate the calcium in alumina, for in addition amount of 001*7 resin is 0.7g/l, the mixing time of 40 min, the removal rate of the calcium is 12.97%, in addition amount D001 resin, is 0.8g/l, mixing time for 30 min, the removal rate of calcium is 26.44%. Use hydrofluoric acid to remove impurities calcium, the addition is 6 ml, calcium impurities removal rate reached 88.47%. For magnesium removal, in addition amount of 001*7 types resin is 0.8g/l, the mixing time of 40 min, the removal rate is 50.65%, use hydrofluoric acid to remove magnesium, in addition is 5ml, Mg impurities removal rate reaches up to 38.20%, use D001 ion resin, in addition amount is 0.6 g/l, the mixing time of 40 min, Mg impurities removal rate reaches up to 59.35%. Use hydrogen fluoride to remove silicon of alumina, in addition is 6ml, the maximum silicon removal rate is 88.47%.