Effect of temperature on the kinetics of the process of nitric acid decomposition of Arvaten serpentinite

Abstract

Abstract The process of decomposition of serpentinite from the Arvaten deposit (Uzbekistan) with 30% nitric acid at its stoichiometric norm of 100% and temperatures of 313, 323, 333, 343 and 353 K for 120 min was studied in this work. It has been established that with increasing temperature, the decomposition coefficient (Cdec.) of MgO, Fe2O3 and Al2O3 increases from 11.48 to 82.5%; from 13.96 to 41.49% and from 38.87 to 96.61%, respectively. Meaning Cdec. iron oxide in the form of magnetite is relatively low than other components. Cdec. made it possible to reveal the rate constant of decomposition of serpentinite in nitric acid at the above temperatures. The rate of decomposition of the raw material is apparently limited by the diffusion of the layer of amorphous silica particles on the surface of the raw material. Depending on the temperature (313-353 K), the value of the apparent activation energy (Ea) of the Arvaten serpentinite lies from 21.79 to 7.53 kcal/mole or from 91.21 to 31.53 kJ/mole, and the average value (Eaver.) is 14.226 kcal/mole and 59.68 kJ/mole, respectively. It turned out that the data are similar to other serpentinite deposits. That is, Arvaten serpentinite is reactive towards nitric acid.