Liquid-phase MnO₂-modification of clinoptilolite

Abstract

Formation mechanism of the MnO₂ phase in the reaction of heterogeneous synthesis between Mn²⁺ and MnO ^-₄ ions on a solid aluminosilicate surface in aqueous solutions was studied. It was shown that, for lowsilica forms, the Mn²⁺ ion is oxidized by the MnO ^-₄ ion uniformly across the grain depth to give the MnO₂ phase and manganese manganites. For high-silica materials, the MnO₂ phase is formed on the outer surface of grains, with the decomposition of the MnO ^-₄ ion and formation of the MnO₂ phase and molecular oxygen. It was found that, for the clinoptilolite rock used as a solid support, the yield of the MnO₂ phase and its distribution over the particle volume depend on the penetration capacity of the MnO ^-₄ ion into the porous structure of this rock, determined by its composition. It is shown that the amount of the MnO₂ phase grows with increasing concentration of the MnO ^-₄ ion and treatment duration, with the phase thickness being 15–20 and 350–1050 μm for, respectively, high- and low-silica samples.