An experimental study of phase transformations of aluminum oxides in the processes of sub- and supercritical water oxidation of metallic aluminum

In this work, samples of metallic aluminum are objects of sub- and supercritical water oxidation. Experimental studies have been carried out, and dependences of the effect of temperature, pressure, reaction time, and $\rm pH$ of the oxidizing agent on the phase composition of the oxidation products and their adsorption properties have been revealed. Experimental studies have been carried out in the temperature range of $275$–$380^{\circ}$C, reaction time from $3$ to $12$ h, and different water $\rm pH$ of $7$–$12$. Maximum specific surface $S = 120.2$ m$^2/$g samples obtained at temperature $T = 380^{\circ}$C and reaction time $\tau = 3$ h with $\rm pH~12$. The phase composition of this sample included aluminum oxide $\gamma$-$\rm Al_2\rm O_3~(92.3$ wt $\%)$ and corundum $\alpha$-$\rm Al_2\rm O_3~(7.7$ wt $\%)$.