外文翻譯---厭氧的硫代硫酸鹽浸出法-就地浸金工藝的研究 英文

1、Anaerobic thiosulfate leaching: Development of in situ gold leaching systemsJ.A. Heath, M.I. Jeffrey *, H.G. Zhang, J.A. RumballParker Centre (CSIRO Minerals), PO Box 7229, Karawara, WA 6152, AustraliaReceived 10 Septemb

2、er 2007; accepted 11 December 2007 Available online 25 January 2008AbstractFerric EDTA and ferric oxalate complexes are both effective oxidants for the aerobic and anaerobic dissolution of gold in thiosulfate solutions,

3、and therefore are potential candidates for the development of an in situ leaching system. The thiosulfate and polythionates were quantified during leaching using HPLC with perchlorate eluent and an anion exchange column,

4、 and it was found that both the iron EDTA and oxalate complexes have a low reactivity with thiosulfate, and they do not react with thiourea when it is added as a leaching catalyst. Anaerobic leaching experiments showed t

5、hat both systems were still active after seven days leaching, and when 1 mM thiourea was present, there was significant gold dissolution. However in the absence of thiourea, the gold leaching was very slow, and hence the

6、 addition of thiourea as a gold oxidation catalyst is required for the iron(III) leaching systems. When anaerobic leaching was carried out in the presence of finely ground pyrite, the iron(III) complex was rapidly reduce

7、d to iron(II) as a result of the pyrite catalysed oxidation of thiosulfate. Pyrrhotite was also found to be problematic as it directly reduced the iron(III) complex, and therefore the quantity of gold leached was signifi

8、cantly lower in the presence of both these sulfide minerals. These problems associated with the presence of sulfide min- eral need to be overcome if such a system is to be used in an in situ leach environment. ? 2007 Els

9、evier Ltd. All rights reserved.Keywords: Gold ores; Leaching; Hydrometallurgy; Reaction kinetics1. IntroductionIn situ leaching has been in use since the mid 1970’s in the United States and the former Soviet Union for pr

10、oduc- ing refined uranium (Mudd, 2001a, b). It has recently been implemented at Beverley (2000), and is soon to be used at Honeymoon Well in South Australia. It has also been uti- lised to recover copper (D’Andrea et al.

11、, 1977), and soluble salts such as halite, trona, and boron (Bartlett, 1992), and potash from phosphate rock (Habashi and Awadalla, 1988). The famous Frasch process for mining sulfur with superheated water may also be co

12、nsider as an in situ leach- ing process. However, in situ leaching technology has not been adopted for the recovery of gold, even though thereare a number of deposits which have favourable character- istics, including th

13、e Victorian Deep Leads. The Victorian Deep Leads are buried alluvial gold bear- ing gravels, deposited in ancient valleys about 30–60 mil- lion years ago. Since that time the valleys have filled with sand, gravel, water,

14、 clay and other minerals, and the leads now lie up to 100 m below the surface. They are below the water table, however the water is slow moving at only a few meters per year (Anon, 1982). The resource is very exten- sive

15、 – at least 700 km are known to exist in Victoria around the Bendigo, Ballarat and Avoca areas. As it is an alluvial gold deposit, the content is highly variable, but averages approximately 4 g/m3. The thickness of the l

16、eads varies up to 5 m, and the width up to 1 km (Anon, 1982). The sul- fur content is typically low, varying from 1% to 5% (Phil- lips and Hughes, 1996), with marcasite being the major sulfide present with some pyrrhotit

17、e. A further complica- tion is the presence of lignite, which has the potential of0892-6875/$ - see front matter ? 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.mineng.2007.12.006* Corresponding author. Tel.: +61

18、 8 93348081; fax: +61 8 93348001. E-mail address: Matthew.Jeffrey@csiro.au (M.I. Jeffrey).This article is also available online at: www.elsevier.com/locate/minengAvailable online at www.sciencedirect.comMinerals Engineer

19、ing 21 (2008) 424–433ground in a ceramic ball mill overnight to give a P80 of 10 lm) was also pipetted into each beaker to give a concen- tration of 5 g/L mineral. The gold sheet was then manually suspended in the leach

20、solution, and this was taken as ini- tiation of the experiment. At specific times, samples were withdrawn from the leach solutions and a sub-sample from these was stabilised for gold analysis by addition of a small, know

21、n volume of alkaline cyanide solution. After complet- ing the experiment the sub-samples were collectively ana- lysed by ICP-OES. A volume change correction was applied to the sample times, in accordance with the proce-

22、dure outlined by Choo et al. (2006).2.3. Solution speciationSolution speciation was carried out using a high perfor- mance liquid chromatography (HPLC) system. The HPLC system comprised a Dionex AS16 strong base anion ex

23、change column (4 ? 250 mm) with AG16 guard, coupled with a Waters 2695 separation module. Detection of UV active components was accomplished using a Waters 2996 UV Photodiode Array (PDA) detector (k = 190– 400 nm). An is

24、ocratic elution with perchlorate at 1 mL/ min flow rate was used to separate the anionic sample com- ponents. Waters Empower software was used for analysis of component peak areas, and the concentration deter- mined base

25、d on comparison to calibration standards.3. Results and discussion3.1. HPLC based solution speciation for leach solutionsInitially the use of 200 mM perchlorate as the eluent, which has previously been used for the analy

26、sis of cop- per-ammonia-thiosulfate leach solutions (Jeffrey and Brunt, 2007), was tested for quantification of solutions containing thiourea (Tu), ammonium thiosulfate (ATS), polythionates, and either the ferric oxalate

27、 (FeOx) or ferric EDTA (FeEDTA) complexes. It was found that although the negatively charged iron(III) complexes eluted between the thiosulfate and thiourea, there was considerable over- lapping of the peaks. However whe

28、n the perchlorate con- centration was reduced to 125 mM, a much better separation of the thiourea and the iron(III) complexes was obtained. This is shown in Fig. 1; the chromatogram at 200 nm for a 1 lL injection of solu

29、tion containing 5 mM thiourea, 5 mM iron(III), and either 12.5 mM oxa- late or 5 mM EDTA. Therefore 125 mM perchlorate was adopted as the eluent in the analysis of solutions from both aerobic and anaerobic leaching exper

30、iments. The chromatogram at 200 nm for a 5 lL injection of a standard solution containing 1 mM thiourea, 6 mM thio- sulfate, 2 mM trithionate, 2.6 mM tetrathionate and 0.9 mM pentathionate is shown in Fig. 2 for the 125

31、mM perchlorate eluent. All these species are eluted within 13 min, and the peaks were identified by their UV spec- trum, and also by comparison to the retention time of indi-vidual standards. If greater sample throughput

32、 is required, the run time for each sample can be decreased to 8 min by increasing the eluent flowrate from 1.0 to 1.6 mL/min. In terms of quantification, the PDA detector produces a 3 D matrix of absorbance vs. waveleng

33、th vs. time, and hence the chromatograph can be displayed for any wavelength. To obtain maximum sensitivity, thiosulfate, tetrathionate0 1 2 3 4 5 6FeOxTuTuFeEDTA Fe-EDTAAbsorbanceFe-Oxalate0.05 absorbance units0.05 abso

34、rbance unitsTime (min) Fig. 1. Chromatograms at 200 nm for solutions containing 5 mM thiourea, 5 mM iron(III), and either 5 mM EDTA (top) or 12.5 mM oxalate (bottom).0 2 4 6 8 10 12 140.00.10.20.30.40.5S5O62- S4O62-S3O62

35、-Absorbance / AUTime (min)TuS2O3 2-Fig. 2. Chromatograms at 200 nm for solution containing 1 mM thiourea, 6 mM thiosulfate, 2 mM trithionate, 2.6 mM tetrathionate, and 0.9 mM pentathionate.426 J.A. Heath et al. / Mineral