Improving copper flotation recovery from a refractory copper porphyry ore by using ethoxycarbonyl thiourea as a collector

doi:10.1016/j.mineng.2011.01.009

Minerals Engineering

Volume 24, Issue 8, July 2011, Pages 817-824

https://doi.org/10.1016/j.mineng.2011.01.009 Get rights and content

Abstract

In this paper, N-propyl-N-ethoxycarbonyl thiourea (PECTU) collector was investigated to concentrate copper minerals from a refractory copper porphyry ore through bench-scale and industrial flotation tests. The flotation results indicated that PECTU had strongly collecting power for copper sulfide minerals and excellent selectivity against iron sulfide minerals under moderately alkaline conditions. Compared with sodium butyl xanthate (SBX), PECTU increased the grades and recoveries of Cu, Au and Mo in the copper concentrates, and performed the flotation separation of Cu/Fe sulfide minerals at cleaner pH ∼10.5 as well as decreased 2/3 lime consumption. The results of UV–visible measurements further demonstrated that PECTU could be used as a high selective collector for copper minerals. The experimentally obtained results have been explained from the structure–reactivity relationship of collector by density functional calculation.

Graphical abstract

The effects of cleaner times and cleaner pH values on the recoveries and grades of copper in Cu concentrates: PECTU, N-propyl-N-ethoxycarbonyl thiourea; SBX, sodium butylxanthate. The differential values Δ of Cu grades and recoveries between experimental and control system.

Research highlights

► N-propyl-N-ethoxycarbonyl thiourea (PECTU) had moderately electron-donating power and strongly electron-accepting power. ► PECTU had excellent selectivity against iron sulfides. ► PECTU performed the Cu/Fe flotation separation at the cleaner pH ∼10.5 with improving Cu, Au and Mo recoveries.

Introduction

Xanthates are powerful collectors that are commonly used for separating sulfide minerals. However, their selectivity is low without the use of additional reagents. For example, in flotation separation of Cu/Fe sulfide minerals, lime is used to maintain a pH value >10.5. Usually, the pH value is greater than 11.0 and this value can often reach as high as 12.0 or 12.5 (Fu and Wang, 1988). This approach not only consumes a large amount of lime, which increases operating costs, but it also depresses the flotation of some secondary CuS and CuO minerals (Liu et al., 2008a).

In order to separate copper sulfide minerals from Cu/Fe bulk concentrates which are commonly obtained by bulk flotation using sodium butyl xanthate (SBX) as a single collector, lime was used to maintain a pH >13 in the Dexing Copper Mine. Compared with xanthates, ethoxycarbonyl thiourea (ECTU) collectors were powerful for chalcopyrite and very selective against pyrite in alkaline and neutral pH conditions (Nagaraj et al., 1986, Nagaraj et al., 1988, Nagaraj et al., 1989, Fu and Wang, 1988, Fairthorne et al., 1997a, Fairthorne et al., 1997b, Fairthorne et al., 1998, Hope et al., 2004, Hope et al., 2007). Whereas, ECTU used as a commercial collector for the flotation recovery of copper minerals from Cu/Fe sulfide ores in practice has not been reported, and the theoretical investigation on the structure–reactivity relationship of ECTU collectors is not involved in the previous study. In the present study, we will compare the collecting performance of ethoxycarbonyl thioureas with xanthates not only in the flotation of copper sulfide minerals from a refractory copper porphyry ore in the Dexing Copper Mine, but also from their structure–reactivity relationship by density functional calculation at B3PW91/6-31G(D) level.

Section snippets

Materials and reagents

The test material was a refractory copper porphyry ore from the Dexing Copper Mine of Jiangxi Province in China, and the copper bearing minerals were chalcopyrite, chalcocite, digenite, covellite, tetrahedrite, tennantite, bornite, as well as some oxide copper minerals such as malachite and cuprite. The main iron bearing minerals were pyrite and marcasite. The molybdenum form was molybdenite and the gold forms were native gold and electrum. The significant amounts of non-sulfide gangue minerals

Effect of rougher pH

Under the flotation condition of particle size distribution (65% – 74 μm) and Na₂S (50 g/t), the effects of the rougher pH values on Cu recoveries and grades in the rougher concentrates were shown in Fig. 2. It indicated that the optimized rougher pH values for PECTU were 8.5–9.0 and for SBX were 8.0–8.5. For this refractory copper porphyry ore, PECTU obtained superior Cu recoveries as compared to the conventional SBX collector.

Effect of the feed particle size distribution

Under the flotation condition of rougher pH 8.5 and Na₂S 50 g/t, the

The flotation performance of PECTU

Lime is commonly used as a pH regulator and depressant against iron minerals during the flotation recovery of copper minerals from copper porphyry sulfide ore. It can also depress copper oxide, secondary copper sulfide or gold minerals (Allan and Woodcock, 2001, Sun, 2001, Liu et al., 2008a). More dosages of SBX were used in the Cu/Fe rougher operation, more amounts of lime for the Cu/Fe separation operation were needed.

Compared with 60 g/t SBX in the SBX scheme, the dosage of SBX was only 20 g/t

Conclusions

(1)
The industrial flotation results obtained in the Mineral Processing Plant at the Dexing Copper Mine indicated that PECTU had the strongly collecting power for copper minerals and excellent selectivity against iron sulfide minerals under moderately alkaline conditions. Compared with the 60 g/t SBX scheme, the 8 g/t PECTU + 20 g/t SBX scheme increased the grades of copper (0.93%) and gold (1.29 g/t), increased the recoveries of copper (1.03%), gold (7.51%) and molybdenum (5.23%), and decreased sulfur

Acknowledgements

The authors would like to thank the National Natural Science Foundation of China (Grant Nos. 51074183 and 50604016), the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 2007B52), the Program for New Century Excellent Talents in Chinese University, the National Basic Research Program of China (Grant No. 2007CB613602), the National High-Tech Research and Development Plan of China (Grant No. 2007AA06Z122), and the National Science and Technology Support

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Improving copper flotation recovery from a refractory copper porphyry ore by using ethoxycarbonyl thiourea as a collector

Abstract

Graphical abstract

Research highlights

Introduction

Section snippets

Materials and reagents

Effect of rougher pH

Effect of the feed particle size distribution

The flotation performance of PECTU

Conclusions

Acknowledgements

Miner. Eng.

Hydrometallurgy

Int. J. Miner. Process.

Anal. Chim. Acta

Int. J. Miner. Process.

Colloids Surf. A

Miner. Eng.

Miner. Eng.

Int. J. Miner. Process.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta