【作者】 夏柳荫；

【导师】 李鑫钢；

【作者基本信息】 天津大学 ， 化学工程， 2009， 博士

【摘要】 本文针对我国铝土矿资源的特点,在研究铝土矿反浮选捕收剂分子结构与浮选能力之间构效关系的基础上,制备了一类新型的双季铵盐型Gemini阳离子捕收剂,并将其应用于铝土矿反浮选脱硅,研究结果具有一定的理论意义与实际应用价值。运用量子化学计算及溶液化学方法,研究了一水硬铝石与层状硅酸盐矿物的结构、晶体性质及溶解性质差异。一水硬铝石费米能级附近的能带主要由O原子的2p轨道和Al原子的3s和3p轨道组成,而高岭石的导带主要由O原子的电子能级组成,Al原子的贡献几乎为零。这揭示了一水硬铝石与高岭石的活性位点不同,在浮选药剂分子上增加能够与一水硬铝石Al原子发生键合作用的官能团,可提高选冶药剂对铝硅矿物浮选分离的选择性。通过量子化学计算、分子动力学模拟及分子中原子的理论分析,研究了胺类阳离子捕收剂在铝硅矿物表面的作用机理,揭示了捕收剂分子结构与浮选捕收能力之间的构效关系。十二胺与高岭石之间存在静电作用和氢键作用;铝硅酸盐矿物浮选捕收剂分子中N原子数量的增加,可改变捕收剂分子极性基团的荷电性质,增强捕收剂的静电作用能力,提高捕收剂分子对硅酸盐矿物的捕收能力。制备了一类双季铵盐型Gemini阳离子反浮选捕收剂,对其进行了理论计算研究,Gemini捕收剂在静电作用和氢键作用两方面均优于传统季铵盐阳离子捕收剂;验证了新型捕收剂对单矿物的浮选能力,在相同实验条件下,Gemini捕收剂对铝硅矿物的浮选回收能力大于传统季铵盐捕收剂;改进了双季铵盐型Gemini阳离子捕收剂对实际铝土矿反浮选脱硅的分离工艺,得到了Al2O3品位69.07%,铝硅比9.66的反浮选精矿,这个选别指标完全满足了铝土矿拜耳法的生产要求。最后,本文研究了双季铵盐型Gemini阳离子捕收剂在矿物表面的吸附特性与机理。双季铵盐在高岭石表面的吸附机理也系静电吸引与氢键作用,但Gemini捕收剂与硅酸盐矿物之间的静电作用能力更强;且Gemini捕收剂具有二聚的结构,使其具有更小的临界胶束浓度,更强的表面活性,更容易吸附在矿粒周围,能有效地增加矿粒的疏水团聚性能。更多还原

【Abstract】 Due to the character in most of the diasporic bauxite in China, a class of novel bis-quaternary ammionium salt cationic surfactants was used as revers flotation collector for the de-silication of bauxite ores, based on the invesgations of structure-activity relationship between the amine cationic collectors and their collecting ability. The results in this work have an important theory meaning and an actual application value.Differences of structure, crystal and solution properties between diaspore and the layered aluminosilicates are studied in this work by using quantum mechanical calculations and solution chemistry method. The electronic bands near Fermi level of diaspore are almost from the O 2p orbit and the Al 3s, 3p orbit, whereas the conduction bands of kaolinite are only associated with O atom, the contribution of Al atoms in kaolinite is little. This indicates that the reactive sites in diaspore and in kaolinite are different. Adding a functional group which can be selectively chemical bonding with Al atoms in diaspore may be beneficial to the separation of diaspore from the layered aluminosilicates.The mechanisms of cationic collectors adsorbed on kaolinite and the relationship between the surfactants structures and their flotation ability are discussed by quantum chemistry, molecular dynamics simulation and the atom in molecular theory. It is showed that flotation of kaolinite using dodecylamine as collector is mainly attributed to the physical electrostatic effect and the hydrogen bonds. Increasing N atoms in collector molecule can change the charge character of its cationic group, can enlarge the electrostatic effect, and thus can improve the collecting ability for the negative charged minerals.A class of bis-quaternary ammonium salt Gemini surfactants was synthesized aiming to be used as the reverse flotation collectors for kaolinite, illite and pyrophyllite. Firstly, by using density functional method, it is proved that the novel collector is superior to the corresponding conventional quaternary ammonium salt at the electrostatic attraction. Secondly, flotation tests of the single minerals show that, in the same condition, the floatability of the three silicate minerals with Gemini as a collector reveals far better than with the corresponding traditional cationic surfactant. Due to the optimization of flotation separation process, the bauxite concentrate with Al₂O₃ of 69.07%, the Al to Si mass ratio of 9.66 was obtained. This flotation results totally fulfill the requirements of bauxite Bayer processing. At last, the adsorption character and its mechanism of the Gemini adsorbed on kaolinite are studied. A detailed understanding for the merit collecting power of the Gemini is revealed. Although the physical effect accounts for its adsorption, the special dimeric structure of the bis-quanterany ammonium salt exhibits the lower CMC, the better surface activity, and thus the stronger hydrophobic aggregation ability.更多还原