Method for improving the purity of high-purity alumina

The following is a brief introduction from the improved Bayer process.

Modified Bayer Method：

The Bayer process is the mainstream method for preparing alumina in the past. The modified Bayer process is based on the traditional Bayer process to prepare high-purity alumina through several processes such as desiliconization, deironing, and decomposition. The preparation process is as follows: Sodium aluminate Solution→desilication→iron removal→hydrolysis→high-purity aluminum hydroxide→high-temperature calcination→grinding→high-purity alumina

The main impurity of this process comes from the sodium aluminate solution with insufficient purity, so whether the purity of sodium aluminate can be controlled is one of the key steps in improving the Bayer process.

To this end, a scavenger can be added to the sodium aluminate solution, so that the scavenger and the impurities in the sodium aluminate solution form a compound, and then desorb. For example, the sodium aluminate solution is deeply purified by using barium salt as a decontamination purification agent, thereby removing silicon ions, iron ions, phosphorus ions, titanium ions, vanadium ions and other organic impurities from the sodium aluminate solution. In order to remove barium ions from the sodium aluminate solution, quicklime and a desilication agent are added in the process of purifying the sodium aluminate solution, and then the introduced calcium ions are removed by oxalic acid.

Desodiumization is another key step in improving the Bayer process. There are two effective ways to remove sodium ions. The first is to add a sodium removal agent during the aluminum hydroxide hydrothermal phase inversion process, and the other is to add a mineralizer during the roasting of aluminum hydroxide.