Physico-chemical properties of tailing slurries during environmental desulphurization by froth flotation

Environmental desulphurization has been established as an alternative solution to control acid mine drainage due to the reactivity of sulphide tailings when exposed to open air conditions. In fact, this process placed at the end of the primary treatment circuit greatly reduces the amount of problem tailings by concentrating the sulphide fraction. An acceptable target for sulphide content can be estimated from the acidity potential (AP), neutralization potential (NP) and the net neutralization potential (NNP) of the mill tailings. To produce desulphurized tailings, non-selective froth flotation is the most common method used in previous work. In this paper, the authors have focused the physicochemical properties of the pulp as the main parameters affecting the non-selective sulphide flotation. The pyrite depression due to lime addition during the former process represents the main problem. Several laboratory tests were conducted using a Denver cell to choose the best and most economical collector. Other tests were done to select the best frothing agent. The pH and redox potentials were investigated as parameters of great importance in flotation performance. For studying the sulphide flotation kinetics, two mine tailings are chosen which are characterized by a weak neutralization potential (under 37 kg CaCO3/t). Tailings S and L are cyanide free and contain respectively 5.27 and 10 wt.% sulphur. Collector dosage was optimized for these tailings as well as the flotation time and the results show that tailings L needed more collector than tailings S. Desulphurization costs were estimated to be CND$0.35 per ton (dry tailings), which is very comparable and competitive to existing method for tailings management. (C) 2003 Elsevier Science B.V. All rights reserved.