外文翻譯---厭氧的硫代硫酸鹽浸出法-就地浸金工藝的研究

1、附 錄Anaerobic Thiosulfate Leaching: Development Of In Situ Gold Leaching SystemsJ.A. Heath, M.I. Jeffrey *, H.G. Zhang, J.A. RumballAbstractFerric EDTA and ferric oxalate complexes are both effective oxidants for the aero

2、bic and anaerobic dissolution of gold in thiosulfate solutions, and therefore are potential candidates for the development of an in situ leaching system. The thiosulfate and polythionates were quantified during leaching

3、using HPLC with perchlorate eluent and an anion exchange column, 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

4、 as a leaching catalyst. Anaerobic leaching experiments showed that both systems were still active after seven days leaching, and when 1 mM thiourea was present, there was significant gold dissolution. However in the abs

5、ence of thiourea, the gold leaching was very slow, and hence the 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 o

6、f finely ground pyrite, the iron(III) complex was rapidly reduced 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)

7、 complex, and therefore the quantity of gold leached was significantly lower in the presence of both these sulfide minerals. These problems associated need to be overcome if such a system is to be used in an in situ lea

8、ch environment.1. IntroductionIn situ leaching has been in use since the mid 1970’s inthe United States and the former Soviet Union for producing refined uranium (Mudd, 2001a, b). It has recently been implemented at Beve

9、rley (2000), and is soon to be used at Honeymoon Well in decrease as the reaction proceeds (Breuerand Jeffrey, 2000), and hence dissolved oxygen is required to oxidise copper(I) thiosulfate back to a copper(II)ammine. Th

10、is has been demonstrated by a number of authors, and a good summary of thiosulfate leaching experiments undertaken in the presence and absence of air sparging are presented by Senanayake (2007). Since the addition or con

11、trol of oxygen underground is likely to be difficult, the copper-ammonia system is unlikely to be effective for an in situ leaching environment. However two promising iron(III) oxidants have been independently developed;

12、 one using ethylenediaminetetraacetic acid(forming Fe (EDTA)_) (Zhang et al., 2005), and the other using oxalate (forming Fe(C2O4)33_) (Chandra and Jeffrey,2005). Both of these complexes are very stable, with logb(Fe(EDT

13、A)_) = 25.1 (Smith and Martell, 1989) and logb(Fe(C2O4)33) = 18.6(Smith and Martell, 1977). The main advantage in using iron(III) based oxidants is that they have been claimed to unreactive towards thiosulfate(compared t

14、o copper(II) ammine Therefore, they may potentially be used in an anaerobic environment, since oxygen may not be required to regenerate the oxidant. Another advantage of the iron(III) oxidants is that ammonia is not requ

15、ired to stabilise the oxidant. This enables their potential implementation into environments where legislation is strict on the use and release of ammonia into the environment.The focus of this work was to evaluate alter

16、native oxidants for the in situ, thiosulfate leaching of gold. Emphasis was placed on evaluation of iron(III) based oxidants in anaerobic or low-oxygen environments, to simulate conditions likely to be found in deposits

17、such as the Victorian Deep Leads.2. Experimental methods2.1. Aerobic leachingThe aerobic leaching experiments were carried out using a standard glass electro- chemical cell. The main cell compartment had a Luggin capilla

18、ry with a reference electrode attached through the bottom by a water-proof screw fitting.The gold sample used was a rotating disc electrode(RDE), 17 mm , 99.99% purity). The reference electrode used was an Activon single