Control of grinding conditions in the flotation of chalcopyrite and its separation from pyrite

doi:10.1016/S0301-7516(02)00119-9

International Journal of Mineral Processing

Volume 69, Issues 1–4, March 2003, Pages 87-100

https://doi.org/10.1016/S0301-7516(02)00119-9 Get rights and content

Abstract

A specially designed mill which allowed the control of pH throughout grinding was used to study the effect of grinding conditions on chalcopyrite flotation and chalcopyrite separation from pyrite. The mechanism of galvanic interaction between minerals and grinding media was investigated by ethylene diamine-tetra acetic acid disodium salt (EDTA) extraction and X-ray photoelectron spectroscopy (XPS) measurements.

Chalcopyrite flotation was strongly dependent on both iron oxidation species and metal deficiency on the chalcopyrite surface. Iron oxidation species from grinding media played a dominant role in depressing chalcopyrite flotation, while metal deficiency from chalcopyrite oxidation improved chalcopyrite flotation. Therefore, chromium grinding medium produced a higher chalcopyrite recovery than mild steel grinding medium while gas purging during grinding had little effect on chalcopyrite flotation.

Chalcopyrite separation from pyrite was affected by the activation of pyrite flotation by copper species dissolved from chalcopyrite. Grinding media had a large effect on the reduction of copper(II) to copper(I) on the pyrite surface. The reducing grinding condition generated by mild steel medium favoured formation of copper(I) sulphide phase, which resulted in high pyrite activation. Thus, chromium medium produced better chalcopyrite selectivity against pyrite than the mild steel medium.

Introduction

It has been known for a long time that grinding conditions have a significant influence on the subsequent flotation of sulphide minerals. For chalcopyrite flotation, there is agreement that mild steel grinding medium results in a lower chalcopyrite recovery than stainless steel grinding medium in the presence or absence of collectors Rao et al., 1976, Forssberg et al., 1988, Van Deventer et al., 1991. The depression of chalcopyrite flotation by mild steel medium was attributed to the iron hydroxide species on chalcopyrite surface, which was closely related to the anodic iron oxidation (Yelloji Rao and Natarajan, 1988). The rate of anodic iron oxidation was found to decrease by nitrogen purging during wet grinding of chalcopyrite minerals (Natarajan, 1996). However, whether nitrogen purging during grinding with iron grinding media can improve chalcopyrite flotation needs to be confirmed.

Although mild steel grinding medium is detrimental to chalcopyrite flotation, it is favoured for chalcopyrite selectivity against pyrite. Yuan et al. (1996) found that chalcopyrite selectivity against pyrite was reduced when the minerals were ground in an oxidising environment with a stainless steel medium, but was restored when ground in a reducing environment with mild steel medium. A similar observation was found by Van Deventer et al. (1991). Clearly, it is desirable to investigate the effect of grinding with low iron content media on chalcopyrite separation from pyrite. Yuan et al. (1996) also indicated that air-sparged mild steel grinding gave no advantage in selectivity compared with ordinary mild steel grinding. However, oxygenation during conditioning and flotation is considered an important factor in the selectivity of flotation operations. As reported by Houot and Duhamet (1990) and Kuopanportti et al. (2000), oxygenation had a favourable effect on the separation of chalcopyrite from pyrite and the oxygen demand increased with the proportion of pyrite in mineral systems.

In this study, a specially designed mill which allowed the control of chemical conditions during grinding was used. The effects of two types of iron media, mild steel and 30 wt.% chromium (with approximate 70 wt.% iron), and three types of purging gases (nitrogen, air and oxygen) on chalcopyrite flotation and chalcopyrite separation from pyrite were investigated.

Section snippets

Materials and reagents

Chalcopyrite and pyrite samples were obtained from Willyama, Earth History Supplies, NSW, Australia and Huanzala Mine, Peru, respectively. The samples were crushed through a rolls crusher and then screened to collect the +0.6−3.2 mm particle size fraction. The processed samples were then sealed in polyethylene bags. The chemical composition of these samples analysed by ICP-MS is shown in Table 1.

Two types of grinding media were used. The tapered cylinder mild steel grinding medium was supplied

Effect of grinding conditions on chalcopyrite flotation

The effect of grinding media and gas purging on chalcopyrite flotation is shown in Fig. 1. It can be seen that 30 wt.% chromium medium produced a higher chalcopyrite recovery than mild steel medium. This is consistent with reports in literature that mild steel medium depresses chalcopyrite flotation Rao et al., 1976, Forssberg et al., 1988, Van Deventer et al., 1991. Meanwhile, for both mild steel and 30 wt.% chromium grinding media, gas purging had little effect on chalcopyrite flotation.

The

Conclusion

Grinding conditions had a significant effect on chalcopyrite flotation. This effect was closely associated with the presence of iron oxidation species and metal deficient sulphide present on the chalcopyrite surface. Iron oxidation species from grinding media played a dominant role in depressing chalcopyrite flotation, whilst the presence of metal deficient sulphide improved chalcopyrite flotation. As a result, 30 wt.% chromium medium produced a higher chalcopyrite recovery than mild steel

Acknowledgements

Financial support for this work from AMIRA International as well as scholarships to Y. Peng from the University of South Australia are gratefully acknowledged. Pasminco Mining, Elura, Australia and Magotteaux, Australia are thanked for the supply of grinding media.

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Control of grinding conditions in the flotation of chalcopyrite and its separation from pyrite

Abstract

Introduction

Section snippets

Materials and reagents

Effect of grinding conditions on chalcopyrite flotation

Conclusion

Acknowledgements

Int. J. Miner. Process.

Int. J. Miner. Process.

Int. J. Miner. Process.

Int. J. Miner. Process.

Int. J. Miner. Process.

Int. J. Miner. Process.

Colloids Surf., A Physicochem. Eng. Asp.

Int. J. Miner. Process.

Int. J. Miner. Process.

Min. Eng.

Miner. Eng.