Hydroxides of aluminum can exist in various crystal forms — the bimit, the bayerit, the gidrargillit, diaspora and some other. All of them differ the friend from the friend in arrangement of ions of aluminum and oxygen, also ways of their receiving are various.
Aluminum hydroxides in the form of thin are poroshkasushchestvut by a method of receiving hydroxides of aluminum in the form of thin powder. The precursor of aluminum is mixed with substance which is applied as inoculating material to formation of crystals of hydroxide. Then mix is calcinated in the atmosphere containing chloride hydrogen. This way is inconvenient because of need of filtration, at the same time for receiving fine powder it is necessary to carry out grind and extruding.
Receiving hydroxide from metal aluminum
It is more convenient to receive hydroxides in interaction of metal aluminum with water, however reaction slows down because of formation of an oxidic film on the surface of metal. In order that to avoid it, use various additives. For aluminum interaction process activation and also its connections with hydrogen I use installation which includes the reactor, the mixer, the separator, the heat exchanger and the filter for suspension division. For formation of hydroxides it is necessary to add substances which promote interaction of reagents, for example, organic amines in catalytic quantities. At the same time there is no opportunity to receive pure hydroxide.
Receiving in the form of a bemitainogd hydroxide of aluminum is received in the form of the bemit. For this purpose use installation with the reactor and the mixer in which there is an opening for input of powdery aluminum and water, the settler and the condenser is also necessary for reception of a parogaz. Reaction is carried out in the autoclave, previously load water and fine particles of aluminum into it then mix is heated to 250-370os. Then at the same temperature mix begins to be mixed under pressure sufficient in order that water remained in a liquid phase. Hashing is stopped when all aluminum reacted, the autoclave is cooled, after that separate the received aluminum hydroxide. Improved processdlya receiving hydroxide of aluminum of high purity take solid, but not powdery aluminum, for example, in the form of ingots. They are put in the water heated to 70 wasps, mixed within 20 minutes, then enter the solid substance forming alkali. As such substance it is possible to use sodium hydroxide. Mix is heated to boiling temperature then it is lowered to 75-80os and continue to mix everything within an hour. Temperature is reduced to room, and mix is filtered, receiving hydroxide of aluminum of high purity.