Regeneration of Caustic Soda Etch Solutions for Aluminum

摘要

The process utilizes precipitation and centrifugation to remove Al(OH)3 from caustic aluminum solutions. When etching aluminum in a solution of caustic soda prior to anodizing, sodium aluminate (NaAl02) increases in concentration in the caustic until a rock-like precipitate of Al(OH)3 drops out of solution. By precipitating Al(OH)3 in a separate crystallization tank without the use of sequestering agents, one obtains a potentially salable byproduct (Al(OH)3) and reduces caustic consumption by recycling recovered caustic.