Impurity removal method for high purity alumina
Aluminum hydroxide quick deoxidation powder is one of the raw materials for the preparation of high-purity aluminum oxide. Since aluminum hydroxide quick deoxidation powder contains silicate, sodium ion and potassium ion, it is bound to cause adverse effects on the purity of aluminum oxide products, so we need to find ways to remove them. We will learn about this knowledge through the following information:
As for the impurity silicate in high purity alumina, when the PH is in the range of 5.0~8.0, the silicate completely ionizes in the water in this PH range and exists in the silicate ion, as long as the filtration can remove the silicon impurity.Therefore, the method of silicon removal is: add dilute HNO3 with a concentration of 1:3 into the suspension of aluminum hydroxide quick powder, and adjust the PH to about 5.5 (the method of PH adjustment is to add two drops of dilute HNO3 prepared into the suspension, using a PH test paper ranging from 5.0 to 9.0 to measure the PH, and stop adding when the PH is 5.5).When the aluminum hydroxide suspension is heated below 85℃ and stirred for an hour, it is more conducive to remove the impurity silicon, because when heated and stirred, the large aluminum hydroxide quick deashing powder will dissolve into finer particles, making the impurities between the particles dissolved into water, which is conducive to remove.After PH is adjusted, filter with G4 funnel. In order to save filtering time, filter with suction machine and filter bottle to save filtering time.
For sodium ion, potassium ion and nitrate ion introduced, due to metal sodium and potassium high chemical activity, two ions completely dissolved in water, nitrate ion is also completely soluble in water, so remove high purity alumina sodium ion, potassium ion and nitrate ion, to wash several times.The cleaning method is to transfer the filtered alumina filter cake with silicon removed to the tissue mixing machine and add 20~50 times of water (the volume of water is a multiple of the volume of the filter cake).Stir for 10 minutes, then drain through A Brinell funnel.Repeat the cleaning step five times to remove sodium and potassium.
Based on years of production experience combined with relevant literature, xiaobian explored a set of methods to remove impurities.However, due to the variety of preparation technology of high purity alumina, its impurity purification process is also different, the above is only for the rapid removal of aluminum hydroxide powder to prepare high purity alumina impurity removal method.
