Non-hydrothermal synthesis of copper-, zinc- and copper-zinc hydrosilicates

Cu/SiO2, Zn/SiO2 and Cu-Zn/SiO2 samples have been prepared by the homogeneo us deposition-precipitation method. The samples were analyzed by thermal an alysis, X-ray diffraction and infrared spectroscopy after various heat trea tments and compared with data obtained for several minerals. It has been sh own that interaction between the components occurs through formation of hyd rosilicates. Copper-silica system at a Cu:Si ratio less than or equal to 1, gives rise to a hydrosilicate stable up to a calcination temperature of 93 0 K resembling the mineral Chrisocolla; at higher ratios a hydroxonitrate ( gerhardite type) is also formed. Zinc-silica interaction produces two hydro silicates such as a well crystallized Hemimorphite at Zn:Si = 2 and highly dispersed Zincsilite at Zn:Si less than or equal to 0.75, both stable up to 1073 K. The Zincsilite structure consists of three layered sheets tan octa hedral layer sandwiched by two tetrahedral ones) like the Stevensite minera l group. For the copper-zinc-silica system no copper hydrosilicate is forme d. Copper merely enters the Zincsilite structure independently of the appli ed (Cu + Zn):Si ratio. Resulting layered copper-zinc hydrosilicate may be d escribed by formula Znx-yCuy(Zn(3-x-z)Cu(z-y)rectangle (x)) [Si4O10] (OH)(2). nH(2)O, where Zn3-x-zCuz-y - ions are located in octahedral sites, Znx-yCuy-ions in the interlayer; rectangle (x) are vacancies in the layers. Copper and zinc in excess of the Zincsilite ratio of Me:Si = 0.75, gives rise to copper an d copper-zinc hydroxonitrates.