Synthesis of mixed copper-line basic carbonates and Zn-doped tenorite by homogeneous alkalinization

Spherical equally sized mixed copper-zinc basic carbonates and Zn-doped tenorite particles have been prepared by coprecipitation from copper-zinc nitrate solutions that become homogeneously alkaline by the hydrolysis 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 variable carbonate and zinc contents, precipitate irrespective of initial solution composition. The subsequent evolution of this amorphous precursor 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; both solids have the same zinc content, which is 4.0 mol%. Upon further aging, 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, only aurichalcite forms; the final solid composition is essentially that of the starting solution. Mixtures of aurichalcite, zincian-malachites and Zn-doped tenorite, in varying proportions, form at intermediate X(Zn) values. The evolution of the studied systems is contrasted against the precipitation behavior of the individual metal ions. Such a comparison shows that copper and zinc nucleation are separate events, which are little influenced by each other. The thermodynamic and kinetic factors that determine the overall evolution of the systems are thoroughly discussed.