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AssigneeAluminum Pechiney
InventorJean-Philippe Puig
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A process for the production of pure aluminum trihydroxide having a controlled median diameter of less than 4 microns with a unimodal distribution and a minimum deviation. The process comprises contacting, for a short time, sodium aluminate solution with a small quantity of ground aluminum trihydroxide having a specific BET surface area of at least 8 m.sup.2 /g, separating the sodium aluminate solution from the solid phase comprising ground aluminum trihydroxide and aluminum trihydroxide precipitate containing impurities, then decomposing the purified sodium aluminate solution in the presence of a quantity of pure ground aluminum trihydroxide from a preceding decomposition operation to precipitate a very pure aluminum trihydroxide having the specified median diameter.
In a process for producing aluminum trihydroxide having a median diameter of less than 4 micrometers with unimodal distribution and minimum deviation comprising the steps of decomposing a supersaturated sodium aluminate solution by adding to said solution an amount of crushed aluminum trihydroxide seed having a BET specific surface area of at least 8 m.sup.2 /g such that the total surface area of said seed is at least 100 m.sup.2 per liter of sodium aluminate solution, and agitating the resulting suspension until a weight ratio of dissolved Al.sub.2 O.sub.3 to caustic Na.sub.2 O of at most 0.7 is obtained, the improvement comprising performing a pre-decomposition process prior to decomposition of the supersaturated sodium aluminate solution to remove impurities from said solution, said pre-decomposition process comprising the steps of
A process for producing a highly pure aluminum trihydroxide having a median diameter of less than 4 micrometers with unimodal distribution and minimum deviation, from the decomposition of a supersaturated sodium aluminate solution, said process comprising the steps of
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