Study And Application Of High Efficiency Collector In Bauxite Flotation

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%.