【作者】 甄世杰；

【导师】 覃文庆；

【作者基本信息】 中南大学 ， 矿物加工工程， 2010， 博士

【摘要】 我国金川公司(JNMC)拥有约400 Mt低品位硫化镍矿,平均品位为Ni 0.60%、Co 0.026%、Cu 0.30%、Fe 10.4%、S 2.2%、MgO 32%、CaO 0.80%、SiO2 39%和Al2O32.0%,是典型的高镁型低品位硫化镍矿。由于高昂的成本和日趋严紧的环保要求,采用处理富矿的生产工艺处理这些贫矿是不可行的。因此,有必要开发一种经济的低品位硫化镍矿处理工艺。另外,公司在处理冶炼烟气的过程中,会产生一些酸性废水,其pH值为0.0-0.3,这些酸性废水必须经过处理达标后才能排放,增加了生产成本,因此酸性废水的综合利用也势在必行本文选育了命名为Jc-1的A. ferrooxidans (FJ427686和FJ427687)、命名为Jc-2的A. thiooxidans (FJ427688)和编号为DSM2391的L. ferrooxidans混合菌(其中Jc-1和Jc-2来自金川尾矿坝,L.f.菌购自DSMZ),对金川高镁型低品位硫化镍矿的生物浸出进行了系统的试验研究,得到如下结论：(1)金川矿的脉石矿物为橄榄石、辉石、蛇纹石、绿泥石、透闪石和碳酸盐,MgO含量高,为30-35%；硫化物主要为磁黄铁矿镍黄铁矿和黄铜矿(2)金川尾矿坝代表了一个高度特异的人工地球化学环境。矿浆中含有少量硫化矿,矿浆pH为1-3,在适合细菌生长的同时,由于矿浆中富含高浓度的无机盐和浮选药剂残留,对细菌有较大的选择压力。故该极端环境仅检出A. ferrooxidans和A. thiooxidans,菌群相对比较简单。(3)野生的Jc-1经紫外线诱变处理后,亚铁氧化能力显著提高,但诱变育种不适合耐高镁浸矿菌的选育。(4)镁对于细菌生长是必需的,但是当Mg2+超过细菌的调节范围时,过高的渗透压会导致细菌死亡。在金川细菌浸出体系的所有离子中,对混合菌生长负面影响最大的是Mg2+。在驯化前,当溶液中的Mg2+浓度为0.6 mol/L (14.6 g/L)时,细菌的生长繁殖非常缓慢；当Mg2+浓度为0.8 mol/L (19.4 g/L)时,细菌开始死亡。因此采用15g/L为最初的Mg2+驯化浓度,通过逐渐提高培养基中Mg2+的浓度,逐步提高细菌对Mg2+的耐受力。经过2年的耐Mg2+驯化,浸矿混合菌的耐Mg2+能力为：当溶液中的Mg2+浓度在1.04 mol/L (25 g/L)时,细菌生长良好；但当溶液中Mg2+浓度升至1.25 mol/L (30 g/L)时,细菌生长非常缓慢；当溶液Mg2+浓度升至1.46 mmol/L(35 g/L)时,细菌开始死亡。随着Mg2+驯化浓度的提升,驯化时间明显延长,在15 g/L的Mg2+浓度下细菌驯化时间为8周,在25 g/L的Mg2+浓度下细菌驯化时间则需要37周,表明随着驯化浓度的不断升高,细菌耐Mg2+驯化难度不断加大。(5)采用Jc-1和镍黄铁矿、磁黄铁矿的纯矿物进行了一系列生物浸出试验研究。结果表明：在常温和pH 2.0的试验条件下,镍黄铁矿以接触浸出为主,磁黄铁矿以非接触浸出为主,细菌的存在大大加强了矿物的溶解。(6)采用混合菌进行了金川高镁型低品位硫化镍矿柱浸试验研究以考察其技术可行性。结果表明：在室温下,金川低品位硫化镍矿经过300天的浸出(包括55天的硫酸预浸和245天的细菌浸出),有价金属浸出率为Ni 90.3%、Co 88.6%和Cu 22.5%。在预浸阶段,采用高酸度硫酸尽可能多地浸出矿石中的MgO以减少MgO在细菌浸出阶段的浸出,在细菌浸出阶段采用经过耐Mg2+驯化的细菌并通过排液以减小溶液中Mg2+对浸矿细菌的抑制,以上3种方法联合使用可以有效降低矿石中MgO的浸出对细菌浸出过程的影响。(7)在细菌柱浸试验的基础上,对金川低品位硫化镍矿进行了0.5 Kt的细菌堆浸试验以考察细菌堆浸法处理金川矿的经济性。经过350天的堆浸试验(包括80天的硫酸预浸和270天的细菌浸出),有价金属浸出率分别为Ni 84.6%、Co 75.0%和Cu 32.6%,浓硫酸消耗总量为600 kg/t矿石,酸性废水处理量为1.06 m3/t矿石。该有价金属回收率表明试验室试验可以成功有效地转化为扩大的工业级试验。(8)细菌浸出液经除铁、CCD浓密洗涤和镍钴铜共沉,镍钴铜的总回收率均不低于96%。(9)经济可行性模型和环境友好性评价结果表明：如果能获得廉价硫酸,采用细菌浸出工艺处理金川低品位硫化镍矿不但经济可行,而且环保安全。更多还原

【Abstract】 Jinchuan Groop (JNMC) has about 400 Mt of low-grade nickel sulfide ore. The average grades of the ore are Ni 0.60%, Co 0.026%, Cu 0.30%, Fe 10.4%, S 2.2%, MgO 31%, CaO 0.80%, SiO2 39% and Al2O3 2.0%, it is typically a low-grade nickel-bearing sulfide ore containing high levels of magnesium. Due to the high cost of fuels and the implementation and enforcement of stricter environmental regulations, the existing process for high grade ores is not feasible for low-grade ores. Therefore choosing an economical recovery process for the low-grade ore is necessary. In addition, a large quantity of acid wastewater (dilute sulfuric acid solution; pH 0.0-0.3) is produced by off-gas treating during smelting. This effluent is costly to treat so that it meets the discharge standards, it is therefore important to utilize the acid wastewater comprehensively.In this paper, breeding a mixture of mesophiles composed of A. ferrooxidans (FJ427686 and FJ427687) named Jc-1, A. thiooxidans (FJ427688) named Jc-2 and L.f. numbered DSM2391 (Jc-1 and Jc-2 were collected from the tailings dam of JNMC and DSM2391 was purchased from DSMZ), a systematic experimental study on the bioleaching of Jinchuan low-grade nickel-bearing sulfide ore contaning high levels of magnesium was carried out and coclusions are drawn as follows:(1) The gangue minerals of Jinchuan ore are olivine, pyroxene, serpentine, chlorite, tremolite and carbonate and the content of MgO is high (30-35%); the sulfide minerals of the ore mainly are pyrrhotite, pentlandite and chalcopyrite.(2) Jinchuan tailings dam represents a highly specific artificial geochemical environment. The pulp is suitable for the bacterial growth due to a low quantity of sulfide minerals at pH 1-3; but it also has a great selection pressure on the bacteria due to high concentrations of inorganic salts and flotation reagent residue. Therefore only a simple bacterial community was achieved in the extreme environment, which includes A. ferrooxidans and A. thiooxidans.(3) The capacity of the ferrous oxidation has significantly increased when the wild strains of Jc-lwas treated by ultraviolet mutagenesis, but the mutation breeding is not suitable for improving the resistant of the bacteria to high levels of magnesium.(4) Magnesium is indispensable in the growth of bacteria. However Mg2+ beyond the range of bacteria regulation will lead to exorbitant osmotic pressure which is lethal to bacteria. Of all the ions in the Jinchuan bacterial leaching system, the greatest negative impact on the growth of mixed bacteria is Mg2+.Before adaptation, the mixed bacteria reproduce very slowly when the concentration of Mg2+ is 0.6 mol/L (14.6 g/L) and the mixed bacteria die out when the concentration of Mg2+ is 0.8 mol/L (19.4 g/L). Thereafter, the adaptation of the mixed bacteria to 15 g/L Mg2+ as the initial adaptation concentration in the medium is performed through serial sub-culturing and gradually the Mg2+ concentration in the medium is increased over nearly 2 years. After adaptation, The mixed bacteria are eugenic under 1.04 mol/L (25 g/L) Mg2+, reproduce very slowly under 1.25 mol/L (30 g/L) Mg2+ and die out at a concentration of Mg2+ (1.46 mmol/L or 35 g/L). With the upgrading of the adaptation concentration of Mg2+, adaptation time is prolonged markedly:only 8 weeks’acclimation time is needed at the concentration of 15 g/L but 37 weeks’acclimation time is needed at the concentration of 25 g/L, which indicates that the adapatation of the bacteria to magnesium is becoming increasingly difficult with the the upgrading of the adaptation concentration of Mg2+.(5) Using Jc-1, a serial of experimental studies on the bioleaching of the pure mineral of pentlandite and pyrrhotite were carried out. The results show that the contact leaching plays an important role in the bioleaching of pentlandite while the non-contact leaching plays an important role in the bioleaching of pyrrhotite at room temperature and pH 2.0. The effects on the dissolution of the minerals were significantly strengthened at the presence of bacteria.(6) Column bioleaching was performed to investigate the technical feasibility to process Jinchuan low-grade nickel-bearing sulfide ore containing high levels of magnesium using a mixture of mesophiles. The results show that an extraction of nickel (90.3%), cobalt (88.6%) and copper (22.5%) were achieved within a 300 days leaching process including a 55 days acid pre-leaching stage and a 245 days bioleaching stage at the room temperature. The results of the valuable metals extraction indicate that three effective means are effective to successfully reduce the disadvantages of magnesia in the ore. They were preleaching to remove most leachable magnesia, adaptation of the mixed mesophiles to improve the tolerance and periodic bleeds of a portion of the pregnant leaching solution to control the Mg2+ concentration based on the tolerance of the mixed microorganisms.(7) Based on the results of the column bioleaching,0.5 Kt heap bioleaching of the Jinchuan low-grade nickel sulfide ore was performed to test the economical feasibility of using heap bioleaching to process the Jinchuan low-grade nickel sulfide ore. A nickel (84.6%), cobalt (75.0%) and copper (32.6%) extraction was achieved after 350 days of heap leaching, including 80 days of acid pre-leaching and 270 days of bioleaching. The overall concentrated sulfuric acid consumption was 600 kg per ton of the ore and the acid wastewater produced by off-gas treating during the smelt process was utilized efficiently with consumption of 1.06 m3 per ton of the ore. The results of the valuable metals extraction indicate that the process of translation of the basic lab achievements into a cost-effective, reliable and robust plant-scale operation is successful.(8) The respective overall recoveries of nickel, cobalt and copper are not less than 96% after the iron removal, CCD thickening wash and co-precipitation of Ni, Co and Cu from the bioleaching solution.(9) Economical feasibility model and overall evaluation show that the bioleaching process is profitable and eco-friendly if the cheap acid is available on site.更多还原