Formation and reactivity of copper sulphide, part I, precipitation

Abstract Copper sulphide samples have been prepared by precipitation from aqueous solution under different conditions of pH, temperature, time of ageing and copper ion activity, and with different precipitants. The phase composition and particle size and form of the precipitates have been studied by x-ray powder diffraction, electron microscopy and sedimentation techniques, and have been correlated with the conditions of precipitation. The samples were prepared from copper(II) sulphate solutions, mainly of concentration 0.3 M, using hydrogen sulphide, thioacetamide and sodium sulphide as precipitants. The preparations were carried out at 22°C and 80°C, and were aged for different lengths of time. The copper ion was, in some cases, complexed by various ligands. Hydrogen sulphide formed particles which are agglomerations of smaller particles. Thioacetamide formed uniform, discrete particles, and sodium sulphide formed a wide range of particle sizes. Increasing the temperature and time of ageing encouraged precipitation of larger particles. Decreasing the pH and the copper ion activity (by using complexing agents) had the same general effect.