The influence of water hardness on the sulphidisation and xanthate flotation of malachite.

摘要

Process water hardness is known to have a marked influence on the sulphidisation and flotation of base metals oxide ores. This paper highlights the mechanisms through which calcium and magnesium ions interact with the pulp during the activating sulphidisation step and the subsequent xanthate flotation of malachite. Microflotation tests were performed with pure malachite. While calcium ions at concentrations of up to 100 mg/L had a slight activating effect during the sulphidisation step (2.9 10~(-5) M NaHS), the magnesium ions, from concentrations as low as 50 mg/L inhibited the formation of the copper sulphide layer through magnesium hydroxide precipitation at the surface of the malachite due to the increase of pH during the hydrolysis of the sulphidiser. During the adsorption of xanthate after sulphidisation, both calcium and magnesium ions, from concentrations of 50 mg/L had a detrimental effect on the resulting fioatability of malachite. This work demonstrates that when evaluating the impact of process water chemistry on the sulphidisation-flotation of malachite a distinction between magnesian and calcian hardness is essential.