Controlling Particle Morphology during Growth of Bayerite in Aluminate Solutions

To study the influence of the orientations of the faces of metal oxyhydroxides on their surface reactivity, the synthesis of bayerite [β-Al(OH)3] particles with different morphologies was studied. The growth of bayerite was performed in aqueous solution at 70 °C by continuously injecting a sodium aluminate solution and stabilizing the pH at a constant value by monitoring the injection of a nitric acid solution. The effects of the following parameters were studied: pH, flow rate of aluminate solution, total duration of synthesis, and seeding. The solids were characterized by high-resolution SEM, XRD, IR spectroscopy, thermogravimetric analysis, and surface area measurements. By choosing the growth parameters, we were able to control the morphology of particles with shapes ranging from agglomerates of rods or cones to ovoid crystallites. In certain cases, traces of gibbsite, norstandite, and pseudoboehmite were obtained in addition to bayerite, but their quantity can be minimized.