Precipitation of copper(II) hydrous oxides and copper(II) basic salts

Abstract

The precipitation of copper(II) hydrous oxides and basic salts from solutions that became homogeneously alkaline by forced hydrolysis of urea has been studied as a function of solution composition, ageing time and temperature. The time required for the onset of precipitation increased with the initial copper(II) concentration, [CuII]₀. The precipitate was found to be amorphous copper hydroxide containing variable amounts of carbonate; at the highest [CuII]₀, basic copper nitrate also precipitated. Upon further ageing of the systems, tenorite or malachite particles were formed at the expense of amorphous copper hydroxide; the nature of the final solid phase depended on [CuII]₀. In the presence of added sulfate anions, brochantite particles were precipitated; in these cases precipitation took place earlier. All processes occurred at rates that were strongly dependent on temperature, although the sequence of events remained essentially the same. Thermodynamic and kinetic factors influencing the formation of all possible solid phases are discussed. It is shown that spherical monodispersed copper(II) hydrous oxide particles can be synthesized when these factors are taken into account adequately.