【作者】 李晓晖；

【导师】 黄松涛；

【作者基本信息】 北京有色金属研究总院 ， 有色金属冶金， 2014， 博士

【摘要】 自20世纪90年代以来,生物冶金方法广泛应用于原生低品位硫化铜矿中铜的浸出,并逐渐扩展到浸出硫化钴镍矿中的钴、镍。一般而言微生物浸出液中有价金属离子浓度较低,通常采用溶剂萃取法来分离微生物浸出液中有价金属离子。然而在工业生产过程中,采用溶剂萃取法分离溶液中金属离子时经常产生界面乳化物,会造成有机相大量流失、分相时间延长等问题,给生产带来很大困扰。目前对于微生物浸出液在萃取分离过程中界面乳化的研究很少。为了提高萃取效率和减少有机相流失,解决微生物浸出液萃取过程中界面乳化问题已迫在眉睫。本研究从微生物浸出液基本特征出发,结合引发界面乳化物产生的其它主要影响因素,如固体微粒、胶体和杂质离子等,采用红外光谱、Zeta电位、SEM等测试手段,通过扩展DLVO理论和交流阻抗测试进行分析,研究了细菌、细菌与固体微粒吸附以及细菌与杂质离子共存时形成界面乳化物的稳定性及其影响原因。微生物浸出液中含有大量浸矿细菌,细菌对水相性质和乳化均产生影响。水相中细菌浓度的增加会增大水相粘度、密度和降低水相表面张力。水相中有机相含量随pH值升高、细菌浓度增加和电解质浓度降低而升高。随着pH值增加水相中有机相含量由0.07%(v/v)增加到0.14%(v/v),由于pH值影响了细菌表面氢键的形成和吸附电势。水相中细菌浓度由2.4x107个/mL增加到7.2x107个/mL时,水相中有机相含量由0.064%(v/v)增加到0.078%(v/v),与细菌表面亲疏水基团有关。采用离子可透过模型模拟细菌表面双电层结构发现,随着pH值增大,细菌吸附电势增加,增大了细菌对带电基团的吸附。溶液pH、细菌浓度和电解质浓度对细菌生长及其表面性质有影响。不同pH、细菌浓度和电解质浓度下,细菌在三种固体微粒(矿石、黄钾铁矾和二氧化硅)表面的吸附规律为：pH值为2-3时,细菌在矿石颗粒和黄钾铁矾表面吸附率较大,而在二氧化硅表面细菌吸附率随pH值升高略降低,且吸附率很低；随着悬浮液中细菌浓度的增加,细菌在三种固体表面吸附量逐渐趋于饱和；电解质浓度越高,细菌在矿石颗粒表面吸附率越大,而电解质浓度对细菌在黄钾铁矾和二氧化硅表面的吸附率影响较小。依据扩展DLVO理论对细菌与固体微粒之间作用能分析发现,酸碱作用能对细菌与固体微粒间吸附的影响明显大于静电作用能和范德华作用能,并且细菌与矿石颗粒和黄钾铁矾之间受强烈的酸碱吸引能,从而使细菌易于在矿石颗粒和黄钾铁矾表面吸附,而细菌与二氧化硅之间受酸碱排斥能作用,使细菌不易在二氧化硅固体表面吸附。另外,电化学测试发现细菌在固体表面吸附降低了固体电极双电层电容,并解释了实验得到的细菌在固体表面的吸附规律。在研究细菌与固体微粒吸附规律基础上,进一步研究了细菌吸附后固体微粒对形成界面乳化物稳定性影响。吸附细菌后的固体微粒萃取分相过程中乳化液滴聚结速度加快,形成界面乳化物稳定性增强。利用扩展DLVO理论计算乳化液滴间作用能,发现细菌在固体微粒表面吸附后,乳化液滴间聚结势垒降低,且液滴间总作用能由排斥能转变吸引能,使形成的乳化液滴聚结速度加快。采用交流阻抗法分析发现,细菌在矿石和黄钾铁矾表面吸附后增加了有机相在固体表面的吸附量,使乳化物中夹带有机相量增加,而有无细菌吸附对二氧化硅表面有机相的吸附量影响较小。当细菌与二氧化硅胶体共存时,萃取分相过程中乳化液滴聚结速度同样明显加快,这是由于细菌表面官能团与二氧化硅胶体表面硅醇基以氢键相连接,降低了硅醇基间形成硅氧烷量,使二氧化硅胶体不能以长链或网状结构存在,从而加快了乳化液滴聚结速度。微生物浸出液中杂质离子也是影响界面乳化物形成的重要因素。通常浸出液中含有大量Ca2+、Mg2+等杂质离子,尤其是细菌与Ca2+共存时,细菌在水油界面上的吸附增加了CaSO4晶体在界面上的累积,使形成界面乳化物生成率增加。用有机相萃取除铁后白山硫化镍矿微生物浸出液,发现在萃取过程中浸矿细菌、黄钾铁矾和二氧化硅等物质在界面层中逐渐累积,并且萃取过程中P204与Fe3+形成了配合物,降低了界面张力,使萃取分相难度增加。总之,萃取体系中有细菌存在时,细菌吸附增强了形成界面乳化物的稳定性,并使界面乳化层中夹带有机相含量增加。更多还原

【Abstract】 Bioleaching technology has been widely used in leaching of copper in the primary copper sulfide ores since the1990s. Then, the method was gradually extended to leach the cobalt, nickel from cobalt and nickel sulfide ores. The concentration of valuable metal ions is generally low in bioleaching solution, and solvent extraction was usually adopted to separate the valuable metal ions from the bioleaching solution. However, interfacial emulsion was always produced in the solvent extraction process of industrial production, bringing severe problems such as a loss of extractant and prolonged split phase time and so on. The effect of bacteria and bacteria-mineral absorption on emulsion has not been reported at present. It is imminent to solve interfacial emulsion in the bioleaching solution during the extraction process, which would improve the extraction efficiency and reduce the loss of organic phase.This study examined the major factors of causing the interfacial emulsion such as solid particles, colloid and metal ions on the basic characteristics of bioleaching solution. IR, Zeta potential and SEM were used as characterization methods. Extended DLVO theory and Ac impedance test were introduced to study the effect of bacteria, bacteria-solid absorption and bacteria coexist with impurity ions on the emulsion stability was studied.There are a large number of bacteria in the bioleaching solution, which influences aqueous phase properties and emulsion of oil-water system. The density and viscosity of aqueous phase increased and surface tension of aqueous phase decreased with bacteria density increasing. And the oil content in water was influenced by solution pH, bacteria density and electrolyte concentration. It was found that the oil content in water increased obviously at high pH, high bacteria density and low electrolyte concentration. The oil content in water increased from0.07%(v/v) to0.14%(v/v) with pH increasing, duo to the formation of hydrogen bonds on the bacteria surface and the adsorption potential. And the oil content in water was increased from0.064%(v/v) to0.078%(v/v) as bacteria density increased from2.4x107cells/mL to7.2x107cells/mL corresponds to the amount of hydrophobic functional groups on the bacteria surface. Ion-permeable model was introduced to simulate the electrical double layer structure of bacteria surface. It was found that the adsorption potential of bacteria surface increased with pH increasing, increasing the adsorption of charged group on bacteria. The growth and surface properties of bacteria were affected by environment in the solution. The adsorption behavior of bacteria to solid particles (mineral, jarosite and silica) was investigated under different solution pH, bacteria density and electrolyte concentration. It was found that the absorption rate of bacteria on mineral and jarosite surface was high at pH2-3. While the absorption of bacteria onto silica surface was low and did not change in the pH range. The adsorption quantity of bacteria at solid surface tended towards saturation with bacteria density increasing. The adsorption rate of bacteria onto mineral increased with electrolyte solution concentration increasing, but the adsorption rate of bacteria onto jarosite and silica did not change much. The extended DLVO theory was used to analyze the interaction energy between bacteria and solid particles. It indicated that the influence of acid-base interaction is significantly greater than the electrostatic interaction and Van Der Waals interaction. Bacteria can easily adsorb on the surface of mineral and jarosite because of the strong acid-base attraction interactions between them. Adhesion of bacteria onto silica particles is difficult due to the acid-base repulsion interaction between bacteria and silica. In addition, Ac impedance tests show that solid electric double layer capacitor was decreased by adsorption of bacteria, verifying the law of absorption of bacteria on solid surface obtained from experiments.Based on the study on the rules of bacteria-solid adsorption, the effect of bacteria-solid absorption on the emulsion stability was further studied. After bacteria absorbed to the solid particle surface, the coalescence rate of emulsion droplet is accelerated in the extraction process and the stability of interfacial layer was enhanced. Extended DLVO theory can be used to describe the interaction energy between two emulsion droplets. It was found that the coalescence barrier reduced after bacteria adsorbed and the repulsive force between droplets transformed into the attractive force, which speeded up the droplet coalescence. Ac impedance analysis showed that the adsorption of organic phase on the surface of mineral and jarosite increased obviously after bacteria-solid absorption. But the presence or not of bacteria had quite small impact on the absorption of organic on the silica surface. The coalescence rate of emulsion droplet is also significantly accelerated in the extraction process when bacteria and colloidal silica coexist. This is mainly due to the hydrogen bonding between the functional groups located on the surface of bacteria and the silanol groups (Si-O-H) on the colloidal silica surface. It would reduce the amount of siloxane and destroy the long chain or mesh structure of colloidal silica, accelerating the emulsion droplet coalescence.In addition, impurity metal ions in bioleaching solution are also an important factor of leading interfacial emulsion formation. There is generally a lot of Ca2+, Mg2+in the leaching solution. When bacteria coexist with Ca2+, the existence of bacteria increased the adsorption of CaSO4crystals on the interface, making the product rate of emulsion increase.The emulsification property of nickel sulfide ore bioleaching in baishan was investigated after extraction process. It was found that bacteria, jarosite and silica gradually accumulated in the interface layer. In addition, the results show that the structure and properties of organic phase changed by formation of complexes due to P204combined with Fe3+in the extraction process. The complex reduced the interface tension and increased the difficulty of split phase. The presence of bacteria in the extraction process would enhance the emulsion stability after the bacteria absorption, and result in an increase of organic phase in interfacial emulsion layer.更多还原