Base-resistant adsorbents prepared using diamino group-grafted mesoporous silica uniformly coated with zirconia

The mesopore walls of ordered mesoporous silicas were coated with zirconia layers at room temperature using zirconia tetra-n-butoxide dissolved in dry toluene. It was found that coating the silicas three times with zirconia layers was sufficient to completely cover their pore walls with zirconia. The coated mesoporous silicas demonstrated high resistance to a 2 M sodium hydroxide solution at 0 °C. Prior to being coated three times with the zirconia layers, the silica walls were partially coated with 3-(2-aminoethylamino)propyltrimethoxysilane so that diamino groups could be grafted onto the pore walls; this was done so that they could be used as base-resistant adsorbents for copper(ii) ions that had been dissolved in basic solutions. The grafted diamino groups, which captured copper(ii) ions, were protected from the basic solution, as the silyl in the diamino groups was covered with zirconia layers.