Interaction of thermally activated aluminum hydroxide with aqueous solutions of nickel and cobalt nitrate salts

The paper studies the interaction processes of the product of centrifugal thermal activation of gibbsite (CTA-GB) with aqueous solutions of nickel or cobalt nitrate in a wide range of active component concentrations (15–50 wt. %). Using X-ray phase and thermal analysis methods, it was found that the synthesis products are layered double hydroxides and pseudoboehmite. The interaction of CTA-GB in an aqueous medium without nickel or cobalt leads to the formation of pseudoboehmite only. The effect of nickel in solutions is expressed in the complete absence of pseudoboehmite formation. In the case of cobalt, pseudoboehmite formation occurs up to its concentration of 30 wt. %, and above that (40, 50 wt. %) they are also not formed. According to the results of temperature-programmed reduction with hydrogen, the products of heat treatment at 350–850°C are mixed compositions of NiO/nickel aluminate and Co3O4/cobalt aluminate, the transformation of which into spinels of the NiAl2O4 and CoAl2O4 type occurs almost completely at 850°C, and their synthesis based on CTA-GB products is possible without using classical coprecipitation stages (sol-gel technology).