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对于在硫代硫酸盐溶液中需氧的和厌氧的溶解金来说,三价铁的EDTA(FeEDTA)和三价铁的草酸盐(FeOX)的络合物都是有效的氧化剂,因此对于研制一种浸出工艺来说,它们都是可能的选择对象。利用阴离子交换剂和使用高氯酸盐溶液作为洗提剂的高性能液相色谱法(HPLC),测定了在浸出过程中硫代硫酸盐和连多硫酸盐的数量。试验发现三价铁的EDTA和草酸盐的络合物,与硫代硫酸盐的反应活性都很低,而且在加入硫脲作为浸出催化剂时,它们都不会与硫脲发生反应。厌氧浸出试验结果表明,在浸出7d后,这两种络合物仍然是很有效的,并且在有硫脲存在时能使相当数量的金溶解。然而在没有硫脲存在的情况下,金的浸出是很慢的,因此对这两种Fe(Ⅲ)的浸出体系来说,都需要加入一些硫脲作为氧化金的一种催化剂。在有细磨的黄铁矿存在的条件下进行厌氧浸出时,由于黄铁矿催化氧化硫代硫酸盐的缘故,三价铁[Fe(Ⅲ)]的络合物迅速地被还原成二价铁[Fe(Ⅱ)]。试验发现,磁黄铁矿的存在也会带来一些麻烦,因为它们能直接地还原Fe(Ⅲ)的络合物。因此在有这两种硫化矿物存在时,浸出的金数量明显降低。如果要使这种工艺能用于金矿石的就地浸出,必须先要解决这些与存在硫化矿物有关的问题。
Complexes of ferric EDTA (FeEDTA) and trivalent iron oxalate (FeOX) are both effective oxidizers for aerobic and anaerobic dissolved gold in thiosulfate solutions They are all potential candidates for developing a leaching process. The amount of thiosulfate and polythionate during the leaching process was determined using an anion exchanger and high performance liquid chromatography (HPLC) using a perchlorate solution as the eluent. Trivalent iron EDTA and oxalate complexes were found to have very low reactivity with thiosulfate and none of them reacted with thiourea when thiourea was added as a leaching catalyst. The anaerobic leaching test results show that these two complexes are still very effective after leaching for seven days and can dissolve a significant amount of gold in the presence of thiourea. However, the leaching of gold is slow in the absence of thiourea, so for both Fe (III) leaching systems, some thiourea needs to be added as a catalyst for gold oxide. When anaerobic leaching is carried out in the presence of finely ground pyrite, the complex of ferric iron [Fe (III)] is rapidly reduced to di (II) due to the catalytic oxidation of thiosulfate by pyrite Iron [Fe (Ⅱ)]. It has also been found that the presence of pyrrhotite also gives rise to some troubles as they can directly reduce Fe (III) complexes. Therefore, in the presence of these two sulphide minerals, the amount of leached gold is significantly reduced. If this process is to be used for in situ leaching of gold ores, these problems associated with the presence of sulphide minerals must first be addressed.