SYNTHESIS OF MIXED COPPER-LINE BASIC CARBONATES AND ZN-DOPED TENORITEBY HOMOGENEOUS ALKALINIZATION

Spherical equally sized mixed copper-zinc basic carbonates and Zn-dope d tenorite particles have been prepared by coprecipitation from copper -zinc nitrate solutions that become homogeneously alkaline by the hydr olysis of urea at 363 K. The nature of the synthesized solids depends on the initial zinc to total metal mole ratio (X(Zn)) and aging time. At short aging times, amorphous copper hydroxide particles, with varia ble carbonate and zinc contents, precipitate irrespective of initial s olution composition. The subsequent evolution of this amorphous precur sor is strongly affected by X(Zn). At low zinc contents, i.e., X(Zn) = 0.06, a mixture of zincian-malachite and Zn-doped tenorite forms; bot h solids have the same zinc content, which is 4.0 mol%. Upon further a ging, zincian-malachite dissolves and Zn-doped tenorite grows. In the range 0.50 greater than or equal to X(Zn) > 0.30, on the other hand, o nly aurichalcite forms; the final solid composition is essentially tha t of the starting solution. Mixtures of aurichalcite, zincian-malachit es and Zn-doped tenorite, in varying proportions, form at intermediate X(Zn) values. The evolution of the studied systems is contrasted agai nst the precipitation behavior of the individual metal ions. Such a co mparison shows that copper and zinc nucleation are separate events, wh ich are little influenced by each other. The thermodynamic and kinetic factors that determine the overall evolution of the systems are thoro ughly discussed.