【作者】 陈远道；

【导师】 冯其明；

【作者基本信息】 中南大学 ， 矿物加工工程， 2007， 博士

【摘要】 本论文从浮选药剂分子设计的角度出发，运用量子化学方法，结合表面张力、表面电性、红外光谱及单矿物浮选，对铝土矿主要组成矿物及其表面、常用浮选药剂及表面—药剂相互作用体系进行详细研究，围绕捕收剂选择性、硬水适应性和低温浮选等性能的改善进行筛选和设计，开发出了高效、实用的铝土矿浮选脱硅捕收剂KL，实现了KL捕收剂的工业化生产，并在“铝土矿选矿—拜尔法生产氧化铝”国家高新技术示范工程项目中得到了工业应用。主要研究内容与结果如下：1．铝土矿主要组成矿物表面电子结构差异采用基于密度泛函-赝势（DFT-pseudopotential）的量子化学方法，对铝土矿主要组成矿物表面电子结构进行模拟。计算结果表明，一水硬铝石（010）表面和高岭石（001）表面的电子结构有明显的差异，一水硬铝石（010）表面的前线分子轨道LUMO主要由表面铝原子和氢原子共同构成，而高岭石（001）表面的LUMO主要由表面氢原子构成，铝原子的贡献极小。所以，阴离子捕收剂（如脂肪酸）与一水硬铝石表面铝原子作用而可能产生化学吸附，而在高岭石表面只能与氢原子作用。量子化学计算结果也表明，一水硬铝石（010）表面的Al原子并没有直接暴露在表层，发生反应时存在一定立体位阻，所以阴离子捕收剂与一水硬铝石（010）表面铝原子较难发生化学反应，而可能与表面氢原子作用，如通过氢键方式产生特性吸附。2．铝土矿主要组成矿物与捕收剂的相互作用采用单矿物浮选、动电位测试、红外光谱等方法对铝土矿主要组成矿务与捕收剂的相互作用进行了较为详细的研究。结果表明，阴、阳离子捕收剂在矿物表面均发生明显的物理吸附，而且一水硬铝石表面可能产生了氢键吸附，但没有观测到表示化学吸附的特征峰位移；另外，运用半经验分子轨道理论量子化学方法对矿物表面-捕收剂相互作用体系进行模拟，计算结果显示，阴离子捕收剂氧原子与一水硬铝石表面铝原子能产生化学作用而吸附，但需要克服较高的能垒，而与高岭石表面则不能产生化学作用；捕收剂氧原子与矿物表面氢原子有可能以氢键方式相互作用，这与试验研究结果基本相符。3．常用阴离子捕收剂的结构性能关系采用量子化学从头算对常用阴离子捕收剂极性基的化学反应活性进行计算，结果显示：当捕收剂以分子形式存在时，化学反应活性顺序为：烷基羧酸＞烷基羟肟酸＞烷基砷酸＞烷基瞵酸＞烷基磺酸＞烷基硫酸；当捕收剂由分子变成离子后，化学反应活性顺序变为：烷基羟肟酸＞烷基砷酸＞烷基瞵酸≈烷基羧酸＞烷基磺酸＞烷基硫酸。这与单矿物浮选试验中油酸和苯甲羟肟酸浮选性能较好的结果一致。考察了捕收剂非极性基结构对极性基反应活性、捕收剂疏水能力及浮选性能的影响，结果表明，除了提供必要的疏水能力之外，非极性基种类和碳链长度对极性基的反应活性均有一定影响，但是对浮选捕收能力的影响不明显；羧酸根离子的化学反应活性随着不饱和度的增加而逐渐增强，同时在水中的溶解分散能力增加，所以非极性基中存在双键是油酸具有良好浮选捕收能力的主要原因之一。4．羧酸类捕收剂浮选性能的改善浮选试验表明，药剂改性和组合用药两种方式都能改善羧酸类捕收剂的浮选性能。氯化改性能大大拓宽羧酸类捕收剂的浮选pH范围，磺化改性能获得更高的浮选回收率，改性羧酸仍然没有克服药剂用量较大的缺点；带有聚氧乙烯官能团的非离子表面活性剂Tween及Triton系列，对低浓度油酸有着良好的浮选增效效果，少量添加便能明显提高一水硬铝石的浮选回收率。5．组合捕收剂的浮选性能和作用机理以油酸为捕收剂主要组分，添加一些表面活性剂进行组合（称为组合捕收剂）。单矿物浮选试验表明，组合捕收剂比油酸具有更好的抗硬水能力和较好的低温浮选性能；人工混合矿浮选试验中，组合捕收剂能在保证精矿铝硅比的情况下，获得比油酸捕收剂更好的精矿产率和Al₂O₃回收率；根据表面张力测试结果、捕收剂与矿物作用前后的红外光谱，对组合捕收剂的作用机理做了初步探讨。结果表明，表面活性剂OL4显著降低了油酸钠的水解浓度和CMC，相当于提高了油酸钠的有效作用浓度，进而由物理吸附或氢键吸附转化为化学吸附，使得油酸的浮选性能提高；而OL2和OL3对油酸的浮选增效作用可能与其本身的浮选能力有一定关系，可能是通过互补吸附和共吸附的方式提高药效。6．KL捕收剂的工业生产与应用根据理论和试验研究结果，设计了一种高效铝土矿浮选捕收剂KL，按照中铝中州分公司第一条选矿拜尔法氧化铝生产线设计规模，完成了捕收剂KL工业生产的工艺流程设计、设备选型、安装调试，制定了严格的生产操作规程，建立了原材料、中间产品及成品的一系列质量控制标准，生产出了合格的产品，各项指标均达到质量标准的要求。实际矿石小型浮选试验表明，捕收剂KL不仅具有良好的铝土矿浮选性能，而且对生产现场的水质条件具有良好的适应性，并且拥有较好的稳定性，可以保证工业生产稳定运行。捕收剂KL成功地应用于世界上第一条铝土矿选矿脱硅工业生产线，经过近7个月的连续运行，共处理铝硅比4.5～6.5的原矿25万吨，获得铝硅比10.5～12.0的选精矿20多万吨，尾矿铝硅比为1.4～1.9，Al₂O₃回收率为80％～88％，达到了设计指标，为解决目前面临的铝土矿资源危机，提供了一个有效的途径。更多还原

【Abstract】 Bauxite is the major raw material for manufacturing alumina. In China, diaspore type bauxite is the dominating one, which bearing higher aluminium, higher silicon and lower iron. The lower molar ratio of aluminium to silicon (A/S) in bauxite results in the higher cost of alumina industry, in order to reduce energy consumption and production cost, it is necessary to heighten the A/S of bauxite by desilica before alumina metallurgy. Ore dressing-Bayer process method is proved to be a efficient approach for utilization of the lower A/S bauxite, and application of high efficiency flotation collector is one of the key technique.From the viewpoint of molecular design, electronic structure of mineral surface, flotation collector and their interaction mechanism were detailly studied by quantum chemistry methods, combining with determination of surface tension, surface charge, infrared spectrum and flotation tests. Screening and designing of collector for bauxite flotation was carried out in order to improve the flotation selectivity and recovery,. An efficient and practical collector, KL, was developed, industrial manufacture and application of KL in ’production of alumina by ore dressing-Bayer process’ were achieved. Main elements and conclusions are as follows:1. Surface electronic structure difference of diaspore and kaoliniteSurface electronic structure of diaspore and kaolinite had been simulated by quantum chemistry method based on DFT-pseudopotential. Calculation results indicate that Highest Occupied Molecular Orbital (HOMO) of diaspore (010) surface is mostly composed of 2p orbital of surface O atoms, and Lowest Unoccupied Molecular Orbital (LUMO) is composed of 2p orbital of surface A1 atoms and 1s orbital of surface H atoms. It is concluded that anionic collectors should interact with surface O atoms and anionic collectors should interact with surface Al atomse or H atoms. On the other hand, Al atom isn’t exposured on the top layer of diaspore (010) surface directly, so chemical reaction between anionic collectors and surface Al atom is difficult to occur, it is tend to generate specific adsorption between collectors and surface H atom through hydrogen bond; Calculation results also show that HOMO of kaolinite (001) surface is mostly constituted by 2p orbital of surface H atom, LUMO is mostly constituted by ls orbital of surface H atom, so anionic collectors are favored to adsorb to kaolinite surface at H atom site.2. Interaction of mineral surfaces and flotation collectorsInteractions between minerals (diaspore or kaolinit) surface and flotation collectors had been detailedly studied by pure mineral flotation, electrokinetics and IR spectrum et al. Experimental results indicate that anionic/cationic flotation collectors adsorb to mineral surfaces with distinct physical interaction, and hydrogen bonding interaction should be existed between collectors and diaspore surface, but no evidence of chemical adsorption detected.Quantum chemistry simulation of interaction of mineral surface and flotation collector had been investigated by Semiempirical molecular orbital theory. Computational results reveal that O atom of anionic collector can chemically react with Al atom on diaspore surface, but the reaction process requires to overcome a higher energy barrage, and the hydrogen bond interaction between collector O atom and mineral surface H atom is possible as experimental results, but chemical interaction between collector and kaolinite is prohibited.3. Structure and performance relationship of usual anion collectorsChemical reaction activity of anionic collector polar group had been computed by using ab initio quantum chemistry theory. For molecular form of common collectors, the chemical reaction activity order is: carboxylic acid＞hydroxamic acid＞alkylarsenic acid＞alkylphosphonic acid＞alkylsulfonic acid＞alkylsulfuric acid; for anioic form, the chemical reaction activity order is changed: Hydroxamic acid＞alkylarsenic acid＞alkylphosphonic acid≈carboxylic acid＞alkylsulfonic acid＞alkylsulfuric acid. The calculated chemical reactin order is in agreement with the flotation experimental results.The influence of nonpolar group structure on polar group chemical reaction activity, hydrophobicity and flotation performance also investigated. Besides providing necessary hydrophobicity, species and cabon chain length of nonpolar group also influence the chemical reaction activity of polar group in some degree, but its effect on flotation ability is unconspicuous. The chemical reaction activity of carboxylate anion is enhanced along with the unsaturated degree increasing, at the same time, double bond can enhance the solubility of collector in water, so double bond in nonpolar group is one of the major element of the excellent flotation ability of oleic acid..4. Mehtods of flotaion performance improvement,of oleic acidFlotation test results show that reagent modification and reagent combination both can improve the flotation performance of carboxylic acid type collector. Chlorination modification can greatly extend the flotation pH range, sulfonation modification can obtain higher flotation recovery, however, reagent modification cannot decrease the collector consumption; Nonionic surfactants with PEO functional[ group, such as Tween and Triton series, are flotation synergists of oleic acid, which can remarkably improve the flotation recovery of diaspore with few amount added to oleic acid.5. Design, performance and mechanism of combinational collectorBased on a great deal of floitation tests, a high efficiency combinational collector, oleic acid(OL 1) as major element and OL2, OL3 and OL4 as synergists, had been developed, combinational collector exhibits better performance of anti-hard water and low temperature flotation than OL1 in pure mineral flotation tests, and gives higher concentrate yield and A12O3 recovery in artificial mixed minerals flotation tests. Flotation results of nature minerals in small-scale tests indicate that combinational collector has approved media flexibility and stability as well as efficient flotation performance, it can guarantee the stable working of industrial flotation process.Flotation mechanism of combinational collector had been studied by surface tension mensuration and IR spectrum before and after interaction of collector and minerals. Additive OL4 decrease the hydrolysis concentration and CMC of sodium oleate distinctly, which increase the efficiency concentration of sodium oleate in water, transform the physical or hydrogen bond adsorption into chemical adsoption, and improve the flotation performance of oleic acid; OL2 and OL3 also have a little flotation ability, it is supposed that the effct of enhanceing flotation performance of oleic acid result from complement adsorption or co-adsorption with the major collector.6. Industrial manufacture and application of collector KLIndustrial production process of flotation desilica collector KL for bauxite had been designed developed and according to the design scale of dressing-Bayer process, the first alumina product line in world projected by Zhongzhou branch china aluminum co.,ltd. Collector KL had been successfully applied in the industrial product line of bauxite flotation desilica, during about 7 months of continuous production, 250000 tons of bauxite raw mineral with A/S of 4.5～6.5 had been disposed, it yield more then 200000 tons of flotation concentrates with A/S of 10.5～12.0, the A/S of tailings range 1.4 to 1.9, recovery of A12O3 is 80～88%.更多还原