Dear Mohammed Abdellaoui thank you for your interesting technical question. The following research article should be helpful in your analysis:

Alhydrogel (R) adjuvant, ultrasonic dispersion and protein binding: A TEM and analytical study

Article Alhydrogel (R) adjuvant, ultrasonic dispersion and protein b...

In this article it is stated that "AlhydrogelTM, a 2% (w/v) aqueous suspension of aluminium hydroxide gel adjuvant, was purchased from BRENNTAG Biosector, Frederikssund, Denmark (Batch No. 4072)." Perhaps it's not a bad idea to buy it instead of preparing it yourself.

Thank you too much Professor Edelmann for your answer, I already both the aluminium hydroxide powder coz it's cheap contrary to the gel, I think when we make 3g of Al(OH)3 powder in 100ml of deionised water (after 48h) we could get a yield between 1 to 2 % of alhydrogel after calculating the weight of the insoluble aluminium precipitate Chapter Hydrogels: Methods of Preparation, Characterisation and Applications