CAS OpenIR
方铅矿、黄铜矿和黄铁矿表面氧化与可浮性研究
牛晓鹏
Subtype博士
Thesis Advisor阮仁满
2019-07-01
Degree Grantor中国科学院大学
Degree Discipline化学工程
Keyword表面氧化,硫化矿,可浮性,关联
Abstract

纵观整个浮选流程,硫化矿始终处于水和溶解氧的环境中,氧化后的表面才是真实的表面,氧化是影响矿物可浮性的重要因素,然而氧化在目前的浮选研究和理论计算中经常被忽视,对表面氧化与药剂吸附,可浮性关联的认识不明确。本论文利用溶液化学和表面化学研究方法,特别在高碱高钙介质条件下,研究了黄铁矿、方铅矿和黄铜矿在浮选条件下的氧化产物及其对浮选药剂在矿物表面吸附作用的影响,深入研究了药剂与氧化前后的硫化矿表面作用机理,建立了硫化矿物表面氧化与可浮性的关联,为深入理解浮选过程,调控硫化矿浮选行为,开发硫化矿高效浮选分离新技术提供借鉴。主要工作及结果如下:(1) 从“吸附”和“氧化”角度揭示了高碱石灰体系下方铅矿和黄铁矿浮选分离机理。原位接触角和单泡管浮选实验结果表明高碱石灰体系下,方铅矿仍能保持良好可浮性而黄铁矿被明显抑制。离子色谱(Ion chromatography, IC)和高效液相色谱(High-performance liquid chromatography, HPLC)结果表明,高碱石灰体系下方铅矿表面硫的主要氧化产物是含氧硫化物(SxOyn-)而非单质硫(S0)。飞行时间-二次离子质谱(Time-of-flight secondary ion mass spectrometry, Tof-SIMS)结果表明pH 12.5时,捕收剂乙硫氮(Sodium diethyl dithiocarbamate, DDTC)在方铅矿表面的吸附强度是黄铁矿表面的3.9倍,而羟基钙CaOH+在黄铁矿表面的吸附强度是方铅矿表面的3.7倍,这与原位原子力成像(In-situ atomic force microscopy imaging)和密度泛函理论(Density-functional theory, DFT)计算的结果一致。高碱石灰体系下,方铅矿保持良好可浮性并非S0的疏水性贡献,方铅矿和黄铁矿能够实现高效分离的原因在于CaOH+与DDTC的竞争吸附。本章澄清了对高碱石灰体系下方铅矿和黄铁矿分离机理的认识,明确了S0对方铅矿表面疏水性的贡献。(2) 在浮选研究中,黄铁矿氧化产生的活性氧(Reactive oxygen speices, ROS)经常被忽视。以黄铁矿氧化过程中产生的含氧硫化物的量评价黄铁矿的氧化程度,通过IC/HPLC研究了黄铁矿在碱性条件下的氧化动力学,发现黄铁矿氧化速率随pH升高而加快,pH 12.5时的氧化速率是pH 4.5时的17.6倍。利用电子顺磁共振波谱(Electron paramagnetic resonance, EPR)测定了黄铁矿氧化过程中产生的ROS,结果表明pH影响ROS形式,结合电化学表征,发现黄铁矿在碱性介质中的氧化仍然遵循以“硫代硫酸盐”路径为基础的电化学机理。本章为理解黄铁矿氧化和可浮性关联,理解浮选溶液化学提供了新视角。(3) 基于对黄铁矿在碱性介质中氧化的认识,研究了氧化对黄铁矿可浮性的影响机理。通过IC/HPLC研究了黄铁矿在碱性介质中不同氧化程度下的硫氧化规律,发现随着氧化程度增大,含氧硫化物的含量增多,S0占比减小;X射线光电子能谱(X-ray photoelectron spectroscopy, XPS)结果表明,黄铁矿充分氧化后表面产物为FeOOH和SO42-。Tof-SIMS测试表明黄药在FeS2和FeOOH表面选择性吸附。根据XPS结果建立自洽电荷密度泛函紧束缚(Self-consistent-charge density functional tight binding, SCC-DFTB)计算模型,发现黄药在FeS2表面吸附而在FeOOH和Fe2O3表面不吸附,根据配位化学理论,黄药在FeOOH/Fe2O3和FeS2表面选择性吸附的根本原因在于它们Fe离子3d轨道电子结构的差异。本章建立了一套“氧化规律、表面实证、计算模型”的评价方法。(4) 基于硫化矿在浮选溶液体系中的氧化与可浮性的关联,研究了表面氧化程度和介质(Ca、Na体系)对黄铜矿和方铅矿可浮性及分离效果的影响,为进一步开发铜铅分离新技术提供借鉴。高碱Ca(OH)2体系下,黄铜矿表面主要氧化产物为SO32-,SO42-,CuO,Cu(OH)2和FeOOH,CaOH+优先吸附在氧化后的黄铜矿表面,促进调整剂DX吸附从而“抑铜”,而方铅矿仍能保持良好可浮性从而“浮铅”,铅铜分离比为1.8;高碱NaOH体系下,新鲜的黄铜矿和方铅矿表面都能保持良好可浮性,DX能选择性的吸附在新鲜方铅矿表面从而“抑铅”,铜铅分离比为2.6;高酸H2SO4体系下,强氧化后的黄铜矿表面硫的主要氧化产物为疏水性的S0而方铅矿表面为亲水性的PbSO4,从而实现“抑铅浮铜”。;Throughout the whole flotation process, sulfide minerals are always exposed to water and dissolved oxygen, and only the oxidized surfaces are the real surfaces of sulfide minerals. The surface oxidation is the key factor to influence sulfide mineral floatability. However, the surface oxidation was usually ignored in the flotation fundamental research and theoretical calculation. Notably, there is lack of clear understanding on the correlation of surface oxidation of sulfide minerals with flotation reagents adsorption and their floatability. In this work, by employing the analytical methods of solution chemistry and surface chemistry, under flotation solution environment especially at high alkaline and high calcium medium, we focused on studying the surface oxidation products of galena, chalcopyrite and pyrite and the adsorption of surface oxidation species and flotation reagents on their surfaces. The interaction mechanism of flotation reagents and the fresh and oxidized surfaces was studied in depth, and the relationship between surface oxidation and floatability was established. This work provide reference for further understanding flotation process, regulating flotation behavior of sulfide minerals and developing new technology of effective flotation separation process. The main work and results are summarized as follows: (1) The mechanism of flotation separation of galena and pyrite in high alkaline lime systems was clarified in terms of “ adsorption ” and “ oxidation ”. The in-situ contact angle and single mineral microflotation tests indicated that sodium diethyl dithiocarbamate (DDTC) collector only worked for galena, but not for pyrite. Ion chromatography (IC) and high-performance liquid chromatography (HPLC) tests showed that the main sulfur oxidation product of galena was sulfur oxyanions(SxOyn-) rather than element sulfur (S0) at pH 12.5. Surface chemistry analysis by time-of-flight secondary ion mass spectrometry (Tof-SIMS) confirmed at pH 12.5, the accumulative normalized intensities of DDTC on galena surface was 3.9 times than that on pyrite surface, while the accumulative normalized intensities of calcium hydroxyl species (CaOH+) on pyrite surface was 3.7 times than that on galena surface. This agreed with the results of in-situ atomic force microscopy imaging and density-functional theory (DFT) calculation. In high alkaline lime systems, the merit floatability of galena could exclude the insignificant contribution of S0. The efficient flotation separation of galena and pyrite in high alkaline lime systems was due to the competitive adsorption of CaOH+ and DDTC. This chapter claried the understanding of the separation mechanism of galena and pyrite in high alkaline systems and the hydrophobic contribution of S0 to galena. (2) In flotation fundamental research, the reactive oxygen species (ROS) during pyrite oxidation is always ignored. The degree of pyrite oxidation was evaluated by the amounts of occurring sulfur species, and pyrite oxidation kinetics in alkaline medium was studied by IC and HPLC. In alkaline solution, we found pyrite oxidation rate increased with pH and the oxidation rate at pH 12.5 was 17.6 times that that at pH 4.5. Meanwhile, ROS produced during pyrite oxidation was investigated by electron paramagnetic resonance (EPR) and it showed that pH influenced the structure of ROS. Combined with electrochemical characterization, pyrite oxidation in alkaline medium still followed the electrochemical mechanism based on the “thiosulfate pathway”. This chapter provide new insight on understanding the correlation of pyrite oxidation and floatability and floation solution chemistry. (3) Based on the understanding of pyrite oxidation in alkaline medium, we investigated the influence mechanism of surface oxidation on pyrite flotation. The sulfur oxidation of different degrees of pyrite oxidation was studied by IC/HPLC and the results indicated as the oxidation degree increased, the amounts of sulfoxy species increased and the S0 ratio decreased. X-ray photoelectron spectroscopy (XPS) showed the surface products were FeOOH and SO42- after sufficient surface oxidation of pyrite. Tof-SIMS tests confirmed that xanthate adsorption had strong selcectivity on FeS2 rather than FeOOH. The computational models of self-consistent-charge density functional tight binding (SCC-DFTB) were established according to the XPS evidence of the surface oxidation species. The SCC-DFTB calculations indicated that xanthate adsorbed on FeS2 but not on FeOOH and Fe2O3. In terms of the coordination chemisty theory, the different electron configurations of Fe led to the selective adsorption of xanthate on FeOOH/Fe2O3 and FeS2. This chapter established an evaluation method including “oxidation law, experimental evidence and computational model”.(4) Based on the correlation between the surface oxidation of sulfide minerals and floatability, the effect of surface oxidation degrees of chalcopyrite and galena and medium (Ca and Na system) was studied to provide reference for developing new technology of copper-lead separation. Under high-alkaline Ca(OH)2 systems, the main products of the oxidized chalcopyrite surface were SO32-, SO42-, CuO, Cu(OH)2 and FeOOH. CaOH+ adsorbed preferably on the oxidized chalcopyrite surface and promoted the DX adsorption on chalcopyrite, therefore suppressing chalcopyrite, while galena still flotated well. The separation selectivity of lead and copper was 1.8. Under high-alkaline NaOH systems, the fresh surfaces of chalcopyrite and galena could maintain good floatability, and the DX selectively adsorbed on the fresh surface of galena, therefore suppressing galena. The separation selectivity of copper and lead was 2.6. Under strong H2SO4 systems, the main sulfur species of strongly oxidized chalcopyrite surface was hydrophobic S0 while that of the oxidized galena surface was PbSO4, thus achieving “galena suppression and chalcopyrite flotation”

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/40671
Collection中国科学院过程工程研究所
Recommended Citation
GB/T 7714
牛晓鹏. 方铅矿、黄铜矿和黄铁矿表面氧化与可浮性研究[D]. 中国科学院大学,2019.
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