【作者】 李丹；

【导师】 陈启元；

【作者基本信息】 中南大学 ， 冶金物理化学， 2012， 博士

【摘要】 为了系统研究机械球磨黄铁矿粉体在液相介质中的界面行为,本文采用多种表征方法从体系的分散性、润湿性、表面张力、运动粘度等方面研究黄铁矿超细粉体在不同有机酸、有机醇介质中的界面行为；研究了多种钠盐添加剂对黄铁矿粉体界面行为的影响并进行了理论计算,利用量子化学中密度泛函理论平面波赝法对FeS2晶体机械活化前后的结构模型的态密度、费米能级等微观结构进行研究,并推导出态密度、费米能级和机械化学晶格畸变之间的本质联系。得到了如下主要结论：(1)制备黄铁矿粉体时,加入助磨剂六偏磷酸钠湿磨得到尺寸均匀,粒径较小的超细粉体。XRD结果显示：添加助磨剂六偏磷酸钠使晶粒尺寸减少和晶格畸变程度增大。对所制备的黄铁矿粉体在无水乙醇中的Zeta电位进行测量,结果表明粉体的Zeta电位为负值,说明所制备粉体带负电。相同条件下,黄铁矿粉体在一定浓度的有机酸-乙醇溶液中的润湿性能由强至弱的顺序依次为油酸、己酸、乙酸、丙酸、乳酸、甲酸,且在油酸-乙醇溶液中具有最佳分散性能。通过分光光度法得到了黄铁矿粉体在油酸-无水乙醇体系中的最佳分散工艺条件,即：pH≤2,油酸添加量为体积百分比为2%,超声时间为30min。(2)四种有机醇对黄铁矿粉体的润湿效果为：甲醇>乙醇>正丁醇>环己醇,而四种有机醇表面张力的大小顺序为：乙醇<甲醇<正丁醇<环己醇,分散性能顺序为：乙醇<甲醇<正丁醇<环己醇,可见,黄铁矿粉体在有机醇类中的分散性能与有机醇的表面张力大小顺序具有一致性。加入不同分子量的聚乙二醇分散剂后可显著提高其黄铁矿粉体的分散稳定性,其中在添加8%的PEG-20000中的黄铁矿粉体溶液的分散稳定性最好。润湿性能实验结果表明,PEG-20000溶液对黄铁矿粉体的润湿性能最好,其中适宜的pH值为5-6之间,超声分散功率为100W。红外光谱分析表明,黄铁矿矿石粉体颗粒与聚乙二醇之间是靠氢键吸附结合在一起,两者并没有发生化学反应生成新的化合物；黄铁矿矿石粉体表面吸附聚乙二醇后,增加了颗粒间的空间位阻作用,有效地阻止了黄铁矿矿石粉体在水溶液中的凝聚,提高了其分散稳定性。(3)根据黄铁矿粉体在六偏磷酸钠、油酸钠、硅酸钠、多聚磷酸钠、十二烷基硫酸钠5种钠盐添加剂中的分散效果,油酸钠与十二烷基硫酸钠的分散效果明显好于其他三种添加剂。不同添加剂,对于浓度为2g/L的粉体悬浮液,其最佳悬浮条件各异,其中油酸钠作为添加剂时控制浓度为0.008mo1/L,pH在1-3,超声时间45min左右对黄铁矿粉体有最佳的分散效果；十二烷基硫酸钠为添加剂时最佳浓度为0.008mo1/L,pH值在10-11,超声45min左右可得最佳分散效果。油酸钠和十二烷基硫酸钠对黄铁矿粉体的润湿性能较蒸馏水好,且油酸钠优于十二烷基硫酸钠。计算结果表明：在不同pH值的十二烷基硫酸钠水溶液中,溶剂化作用能占主导地位,即黄铁矿颗粒间良好的分散稳定性主要依靠溶剂化作用。随着pH值的降低,黄铁矿颗粒间的总作用能升高,在pH值较低的十二烷基硫酸钠水溶液中的黄铁矿粉体的分散稳定性最好。在不同pH值的油酸钠水溶液中,黄铁矿颗粒间的总作用能均为正值,黄铁矿粉体均具有良好的分散稳定性。但在pH=1或10的油酸钠水溶液中,主要依靠静电作用能实现黄铁矿颗粒间的分散；而在pH=6的油酸钠水溶液中,主要依靠溶剂化作用能实现黄铁矿颗粒间的分散；在碱性条件下的油酸钠水溶液中总作用能较高,黄铁矿粉体的分散稳定性最好。(4)随着机械活化过程的进行,晶格畸变程度的增大,FeS2的能隙降低,费米能级升高；体系的态密度峰降低,且有向低能量移动的趋势,能量的分布范围增大；晶格畸变作用下的FeS2出现了更多的价键重叠和轨道杂化现象,且晶格畸变作用下其被氧化能力增大了,电化学反应活性增大,表面吸附特性发生显著变化。更多还原

【Abstract】 To systematically study the interfacial behavior of mechanical ball-milling pyrite powder in liquid medium, this thesis utilized various characterization techniques to investigate the interfacial behavior of pyrite powder dispersed in organic acids and organic alcohols from disperisibility, wettability, surface tension and kinematic viscosity. The effects of sodium salt additives on the interfacial behavior of pyrite powder as well as the related theoretical calculations were demonstrated. Moreover, the density functional theory-plane wave pseudopotential method was employed to study the density of states of structure model and Fermi level before and after mechanical activation of FeS2crystal. The essential relations among density of states, Fermi level and mechanochemical lattice distortion were deduced. The main conclusions were summarized as follows.(1) For preparation of pyrite powder, adding sodium hexametaphosphate as grinding additive could obtain ultrafine powder with uniform size and small diameter. The XRD results indicated that adding sodium hexametaphosphate as grinding additive reduced the crystal size but increased the lattice distortion degree. The Zeta potential for obtained pyrite in ethanol was negative, indicating that the prepared pyrite was negatively charged. Under the same condition, the wettability of pyrite powder in organic acid-ethanol solutions followed the order: oleic acid> hexanoic acid> acetic acid> propionic acid> lactic acid> formic acid. Moreover, oleic acid-ethanol showed the best dispersibility to pyrite powder. The optimum technical condition for pyrite dispersed in oleic acid-ethanol was obtained by the UV-visible spectrometric measurement, namely pH≤2,2%volume percentage of added oleic acid, and ultrasonication time of30min.(2) The wettability of four alcohols to pyrite powder followed the order:methanol> ethanol> butyl alcohol> cyclohexanol. However, the surface tension of four alcohols followed the order:ethanol<methanol<butyl alcohol<cyclohexanol. The dispersibility followed the order: ethanol<methanol<butyl alcohol<cyclohexanol, indicating that the dispersibility of pyrite in alcohols was consistent with the surface tension order of alcohols. On the other hand, the weak dispersion stability of pyrite powder could be remarkably improved by adding polyethylene glycol (PEG) with different molecular weights. Among these, PEG-20000with8%addition amount showed the best dispersion stability of pyrite powder. The wettability experimental results also indicated that PEG-20000had the best wettability to pyrite powder. The optimum condition was pH at5-6and100-W ultrasonication power. The infrared adsorption spectrum analysis showed that the adsorption between the PEG and pyrite ore powder was via the hydrogen bonding and there was no new compound formed between them. The adsorption of PEG onto the surface of pyrite powder provided a high degree of steric stabilization, which effectively prohibited the aggregation of pyrite powder, and thus the dispersion stability of as-formed aqueous suspension was promoted.(3) According to the dispersion stability of pyrite in five sodium salt additives namely sodium hexametaphosphate, sodium oleate, sodium silicate, sodium polyphosphate, and sodium dodecyl sulfate, the dispersion effects of sodium oleate and sodium dodecyl sulfate were obvious better than other three additives. For2g/L pyrite powder suspended in different additives, the optimum suspension conditions were different. When sodium oleate was employed as the additive, the optimum concentration was0.008mol/L, pH was1-3, ultrasonication time was45min. While sodium dodecyl sulfate was employed as the additive, the optimum concentration was0.008mol/L, pH was10-11, ultrasonication time was45min. The wettability of sodium oleate and sodium dodecyl sulfate to pyrite powder was much better than that of distilled water and sodium oleate was superior to sodium dodecyl sulfate. The calculation results for pyrite in sodium dodecyl sulfate aqueous solution at different pH showed that the solvation interaction played the main role. That was to say, the excellent dispersion stability between pyrite particles were mainly dependent upon the solvation interaction. With decreasing pH, the total interaction potential between pyrite particles was increased, and sodium dodecyl sulfate aqueous solution at low pH showed the best dispersion stability of pyrite. While in sodium oleate aqueous solution at different pH, the total interaction potential between pyrite particles was always positive, and the pyrite powder had excellent dispersion stability. In sodium oleate aqueous solution at pH1or10, the dispersion of pyrite particles was mainly dependent upon electrostatic interaction. Nevertheless, the dispersion of pyrite particles was mainly dependent upon solvation interaction for sodium oleate aqueous solution at pH6. In sodium oleate aqueous solution under alkaline conditions the total interaction potential was high, thus the pyrite powder had the best dispersion stability.(4) During the mechanical activation, the lattice distortion degree was increased, the energy gap of FeS2was decreased and Fermi level was increased. With the process of mechanical activation, the lattice distortion degree was increased; the density peak of state was decreased and showed the tendency to shift to low energy; whereas the energy distribution domain was increased. The FeS2under the interaction of lattice distortion showed more phenomenons of valance bond overlapping and orbital hybridization, and its oxidized ability was improved. This further demonstrated that the lattice distortion caused by the mechanical activation could promote the activity of pyrite. With the increase of the lattice distortion degree, the energy of FeS2gap reduced, and the Fermi level increased, the electrochemical reaction activity increased, thus the surface adsorption characteristics change significantly.更多还原