Effect of the mixing procedure on aluminium (oxide)-hydroxide obtained by precipitation of aluminium nitrate with soda

Three different mixing procedures of aluminium nitrate with soda were compared keeping identical aging conditions (T=60 °C, pH=9, 120-min aging): injection of nitrate aluminium solution into soda, injection of soda into nitrate aluminium solution and double jet. Each procedure led to a specific compound: microporous boehmite, bayerite and fibrillar boehmite, respectively. For single jet procedures, reactions were therefore driven locally in the mixing zone where the most influent parameter was the nature of injected solution. This allows obtainment of bayerite or boehmite at unexpected pH.