【作者】 李鹏；

【导师】 许斌； 张元波；

【作者基本信息】 中南大学 ， 矿物加工工程， 2012， 硕士

【摘要】 褐煤腐植酸型铁矿球团粘结剂,既具有用量低、残留量小,能显著提高球团铁品位的优点,又利用了来源广泛的劣质资源褐煤,价格低廉,因而具有良好的开发前景。胡敏酸是褐煤腐植酸型粘结剂的主要成分之一,占到其有机成分的70-90%。本研究从褐煤中分离、纯化制备出高纯度的胡敏酸(HA),运用化学分析、傅里叶红外光谱(FTIR)、核磁共振(NMR)、热重红外联用(TG-FTIR)等技术,对其结构和性质进行了表征；基于此,查明了褐煤胡敏酸与磁铁矿、赤铁矿、锐钛矿、石英之间的吸附行为,运用动电位测试、傅里叶红外光谱(FTIR)等技术探明了胡敏酸在天然磁铁矿(Fe304)、赤铁矿(Fe203)、锐钛矿(Ti02)和石英(Si02)矿物表面吸附机理。胡敏酸是芳香化程度较高的高分子有机化合物,主要由碳、氢、氧、氮、硫等元素组成。芳香环和各种杂环构成了胡敏酸的骨架结构,羧基(-COOH)和酚羟基(-OHph)是胡敏酸中含量较多的含氧基团,胡敏酸还含有脂肪链以及酯基、醚键以及少量氨基(-NH2)、磺酸基(-S03H)等。加热条件下,HA的分解和氧化主要集中在350℃-650℃阶段,温度达到650℃以上,HA基本分解挥发完全,其分解产物以二氧化碳和水蒸气为主,还有少量小分子物质如烯、炔和醚等。溶液pH对胡敏酸在天然铁、钛、硅氧化矿物表面的吸附有重要影响。随pH降低,胡敏酸在矿物表面的吸附增强。在碱性体系(pH=10、11)中,不同氧化矿物对胡敏酸的吸附强弱顺序为：锐钛矿>磁铁矿>赤铁矿,而石英对胡敏酸基本不吸附。矿物颗粒比表面积的增大明显促进了胡敏酸在其表面的吸附。扫描电镜研究显示,胡敏酸通过在矿物表面发生吸附形成一层笼罩的胶体薄膜,使矿物颗粒之间的粘度增大。当胡敏酸达到一定浓度时,吸附在矿物颗粒表面的胡敏酸胶体相互粘连,在矿物颗粒之间形成网状骨架结构,使矿物细颗粒和胡敏酸混凝在一起,增强了颗粒之间的粘结作用。胡敏酸表面带有大量负电性官能团,在试验的pH范围(2-11)内都荷负电,磁铁矿、赤铁矿和石英的零电点(PZC)分别是4.7、6.7和2.4。在大于矿物PZC的pH条件下,磁铁矿、赤铁矿和锐钛矿对胡敏酸的吸附依靠化学作用。在较低的pH(低于矿物PZC)条件下,吸附依靠疏水作用、静电吸引和化学吸附(配位交换和络合作用)共同作用,其中疏水作用的贡献大于其他两者。更多还原

【Abstract】 Lignite humic acid pellet binder has promising development prospects for its many advantages including low addition amount, a small residual content, significantly increase effect on the iron grade of pellets, as well as the broad raw material source---lignite as a kind of poor quality coal, comparetively lower cost than other organic binders. Humic acid accounting for70to90percent of organic ingredients in this sort of pellet binder is one of the main ingredients.In this investigation, high grade humic acid was extracted and purified from lignite, and then the structure charaterization and properties of this humic acid was studied through comprehensive means including chemical analysis, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetry-infrared spectroscopy (TG-FTIR) technologies. And then the adsorption behaviors as well as the adsorption mechanism of lignite humic acid onto magnetite, hematite, quartz and anatase were investigated by potentiodynamic tests and Fourier transform infrared spectroscopy (FTIR).Humic acid is a complicated organic matter with high aromatic degree mainly composed of carbon, hydrogen, oxygen, nitrogen, sulfur and other elements. The aromatic rings and various miscellaneous rings, as well as some aliphatic chains and esters, constitute the main structure of the humic acid. The bulk organic groups are carboxyl (-COOH) and phenolic hydroxyl group (-OHph), but small amounts of amino (-NH2), sulfonic (-SO3H) are also found in humic acid.350℃-650℃is the main decomposition and oxidation stage of humic acid, and the decomposition and volatile progress has basically stopped by650℃with carbon dioxide and water vapor as the main decomposition products.Solution pH has vital impact on adsorption of humic acid onto natural iron, titanium and silica oxide ores particle surfaces, and the adsorption is enhanced as pH decreasing. The adsorption degree of humic acid onto mineral particles in the alkaline system (pH=10,11), should be in the order of anatase> magnetite> hematite, while the quartz has alomost non-adsorption for humic acid. Increasing specific surfaces of mineral particles promotes the adsorption of humic acid.Micro-adsorption behavior studies have shown that the adsorption of humic acid on mineral surface forms a colloid film enveloped fine mineral particles, which therefore improves the viscosity and friction between the particles. Under certain humic acid concentration, humic acid colloids adsorbed on mineral particle surfaces adhere and unit mutually to form a net structure between fine mineral particles, and therefore fine mineral particles are coagulated.Humic acid is negatively charged under the experimental solution pH conditions (2-11) for its amounts of negatively charged functional groups, the point of zero charge (PZC) of magnetite, hematite and quartz is4.7,6.7and2.4, respectively. Under higher pH conditions (pH higher than the mineral’s PZC), humic acid adsorbs to the surface of magnetite, hematite, and anatase particle surfaces mainly by chemical reaction. While at lower pH values, hydrophobic interaction, electrostatic attraction and chemical reaction (ligand exchange and complexation) all occur and contribute to the adsorption. Specificially, hydrophobic interaction contributes more than the other two.更多还原