碱性岩型稀土矿的浮选理论与应用研究

【作者】 王成行；

【导师】 童雄； 邱显扬； 胡真；

【作者基本信息】 昆明理工大学 ， 矿物加工工程， 2013， 博士

【摘要】 稀土元素是镧系元素以及钪和钇等17种元素的合称,在新能源、新材料和尖端科技等领域应用日益广泛,具有“工业味精”的美誉,是不可再生的重要战略资源。至今,世界发现的稀土矿物约有250种,但现在用于工业提取稀土元素的矿物主要有氟碳铈矿、独居石、磷钇矿和风化壳淋积型矿等四种。四川牦牛坪碱性岩型稀土矿的稀土资源储量仅次于白云鄂博稀土矿,位居全国第二位。在选矿过程中,普遍采用基于摇床重选粗选的单一或组合工艺,如“摇床粗选-粗精烘干-干式磁选”工艺,只回收稀土矿物,而重晶石、萤石等伴生矿物根本未考虑进行综合回收,随之尾矿排放丢弃；由于分选工艺落后,稀土选矿回收率也仅有50%左右,造成了这一宝贵矿产资源的严重浪费；同时,工艺存在着生产不连续和粉尘作业的缺点。针对上述问题,基于矿石工艺矿物学研究,开发了一种全湿式组合选矿新工艺,实现了四川牦牛坪稀土矿资源的高效回收；以氟碳铈矿单矿物为研究对象,系统地进行了浮选理论研究,对氟碳铈矿的浮选回收应用具有一定的借鉴意义。在选矿新工艺开发研究方面,首先借助于电子显微镜能谱分析和Mineral Liberation Analyser (MLA)矿物自动检测技术进行了矿石的工艺矿物学研究,查明了稀土矿物和脉石矿物的组成与含量、嵌布关系与状态、解离度和有价元素的赋存状态等工艺特性,结合选矿分级、磁选、重选和浮选探索试验,为合理选矿工艺的原则流程提供了科学依据。在充分遵循利用矿石性质的原则基础上,本着资源综合回收的原则,论文提出了必须采用联合工艺流程的技术路线,开发了“强磁抛尾-重选富集-中矿浮选”的联合选矿工艺,不仅能较好的实现了稀土矿物的高效富集回收,大幅度提高了稀土精矿的回收率和品位,而且兼顾考虑到了共伴生组分归队和后续的综合回收。细粒稀土矿物的浮选回收效果是提高稀土总回收率的关键。为此,对影响浮选效果的磨矿细度、调整剂、捕收剂和辅助捕收剂的种类及用量、矿浆浓度、作用时间、温度、回水比例以及流程结构等主要因素系统地进行了对比试验研究,最终确定了采用选择性羟肟酸类捕收剂GSH在水玻璃分散抑制调浆的溶液体系中进行浮选闭路回收稀土矿物,取得了浮选稀土精矿REO品位65.11%,回收率17.05%的技术指标。与“磁-重”联合工艺获得的粗粒稀土精矿合并,最终全工艺流程获得了REO品位为65.08%,回收率为84.61%的稀土精矿,精矿中REO和非稀土杂质含量全部符合XB/T103-2010中000165牌号产品要求。在氟碳铈矿的浮选理论研究方面,进行了氟碳铈矿在油酸钠和水杨羟肟酸捕收剂作用下的浮选基本行为研究,借助溶液化学计算,动电位、红外光谱、吸附量、溶解量测试和ICP分析等手段系统地对多种调整剂和捕收剂与矿物之间的作用机理进行理论分析,通过对比阐明了调浆的必要性和选择性捕收的相关机理,为进一步的理论研究提供技术参考,也对浮选实际应用具有较好的指导意义。同时,进行了温度对氟碳铈矿的浮选作用机理探讨。氟碳铈矿溶液化学计算结果表明,矿物表面阳离子的水解产物影响着其浮选,一、二级水解产物RE(OH)2+和RE(OH)2+吸附在氟碳铈矿表面有利于药剂捕收,是主要的正活性质点；而三、四级水解产物RE(OH)3和RE(OH)4-吸附在氟碳铈矿表面不利于氟碳铈矿的浮游,是主要的负活性质点。油酸钠和水杨羟肟酸与氟碳铈矿表面作用机理研究结果表明,在pH=6～9时,油酸根离子在溶液中解离生成的离子-分子缔合物在氟碳铈矿矿物表面发生了以化学吸附为主,静电或分子吸附等物理吸附为辅的共吸附；在pH=8～9时,水杨羟肟酸根离子与矿物表面的羟基络合物发生了键合作用,生成稳定性的五元环螫合物,从而实现了氟碳铈矿选择性捕收。无机调整剂的作用机理研究结果表明,碳酸钠的抑制作用与溶液体系中水解的HCO3和CO32-离子和氟碳铈矿表面的CO32-定位离子发生的同离子效应有关；六偏磷酸钠、硅酸钠和氟硅酸钠都在矿物表面发生了吸附作用；碳酸钠、硅酸钠和氟硅酸钠对氟碳铈矿表面的阳离子溶解性基本无作用；六偏磷酸钠对氟碳铈矿的抑制作用明显,可归因于两个方面：(1)六偏磷酸钠吸附在矿物的表面,改变矿物表面的电性质和亲水性,降低了捕收剂吸附作用；(2)六偏磷酸钠电离水解的阴离子与矿物表面的正离子发生络合反应,生成可溶性络合物,使矿物表面的活性质点溶解于矿浆中,降低了矿物表面与捕收剂作用的正活性质点浓度,从而达到抑制效果。在油酸钠作捕收剂的浮选溶液体系中,金属阳离子Ca2+和Al3+对氟碳铈矿具有活化作用,可归因于两者及其部分水解产物能吸附在矿物表面,有助于在矿物表面生成油酸盐沉淀,提高矿物的疏水性；而以水杨羟肟酸作捕收剂时,Ca2+的抑制作用可归因于其静电吸附在氟碳铈矿表面,与稀土阳离子RE3+及其羟基络合物对水杨羟肟酸根离子发生无选择性竞争吸附；Al3+的抑制作用可归因于其可与水杨羟肟酸根离子反应生成比稀土阳离子更加稳定的络合物；两者都降低了氟碳铈矿表面的活性质点密度,从而达到抑制效果；Ca2+对氟碳铈矿的溶解度有一定的影响,这可能与Ca2+和CO32-离子对效应有关。无论是油酸钠还是水杨羟肟酸作捕收剂的单组分浮选体系中,升温均有助于氟碳铈矿的吸附捕收：而在捕收剂GSH浮选体系中,加温浮选实际矿石的效果却与之完全相反,原因初步确定与氟碳铈矿的溶解性无关,而加温可能与固体颗粒、药剂作用和气泡碰撞负载,以及矿浆的表面张力有关,但具体原因有待对多组分矿物进行分解模型化做进一步的检测分析。更多还原

【Abstract】 Rare earth elements (REEs) are a set of seventeen chemical elements that comprise the fifteen elements of the lanthanide series as well as yttrium and scandium. These elements, which are praised as "industrial monosodium glutamate", are important strategic resources of non-renewable and increasingly widely required for many different applications in field of new energy, new materials, cutting-edge technology, etc.. There are may be found in approximately250different minerals in the world to date, but the only REE bearing minerals that have been extracted on a commercial scales are bastnasite, monazite, xenotime and ion-adsorbed clays.The alkaline rock type rare earth ore in Maoniuping deposit, Sichuan, of which rare earth reserves after Bayan Obo rare earth ore. The most commonly utilized application of gravity separation with shaking tables as roughing or that combined with magnetic separation is in the beneficiation, such as gravity separation with shaking tables as roughing, drying and then dry magnetic separation. Those techniques just only recovered the rare earth bearing minerals, but a large number of barite, fluorite and other associated minerals are discarded as tailings instead of the comprehensive recovery. Because of the lag in beneficiation techniques, rare earth recovery rate is only about50%, resulted in an enormous waste of the valuable mineral resources. Meanwhile, the disadvantages of the combined beneficiation flowsheet are discontinuous operation and in the situation of full with dusts.As previously mentioned, based on a comprehensive study of mineralogy, a new wet combined beneficiation technique is developed to highly-efficiently recover the valuable minerals in this type of rare earth resource; in the meantime, basic theories of the bastnasite monomineral flotation are been systematically researched in order to provide a certain reference to the flotation separation of rare earth ore contains the bastnasite.In the beneficiation technique research, firstly, the process mineralogy is studied by means of Electron Microscope Energy Spectrum and Mineral Liberation Analyser, and several process characteristics such as composition as well as contents of the rare earth bearing minerals and gangue minerals, disseminating relationship and its state, degree of mineral liberation, occurrences of valuable elements, are determined. Then, a series of exploratory experiments including classification, magnetic, gravity and flotation separation are conducted. Consequently, a rational beneficiation process flowsheet is determined according to all of the performances above.The principle of beneficiation is in full compliance with the ore properties which could also be utilized. This dissertation has proposed that a technical route comprising magnetic separation combined with gravity separation plus flotation must be applied because valuable minerals in the ore should be recovered comprehensively in order to exploit the resource. Accordingly, a combined beneficiation flowsheet designed to concentrate rare earth bearing minerals. In the flowsheet, non-magnetic gangue including large amounts of slimes is discarded via wet high intensity magnetic separation, then gravity separation is used to discard any low specific gravity gangue and the final shaking table concentrate stream can be achieved. The middlings stream from shaking tables that remains contains a portion of the rare earth bearing minerals which are intergrowth as well as gangue minerals which are not removed in the first two steps. A flotation separation is then applied to exploit the different surface properties of the valuable bastnasite and gangue minerals and produce the final flotation concentrate stream. Consequently, it is not only achieved the highly effective recovery of the rare earth minerals and improved the final concentrate recovery, but also to take into account the concentration of barite and fluorite which should be recovered comprehensively in the successive beneficiation flowsheet.Magnetic and gravity separation are ineffective at separating very fine particles resulting in large losses of rare earths, but flotation separation is commonly applied to the beneficiation of rare earth ores is due to the fact that it is possible to process a wide range of fine particle size. Undoubtedly, flotation separation can be used to beneficiate the fine particles, which is of vital importance to the increase in overall recovery. In this connection, a series of parameters including grinding fineness, types and dosages of regulators, collectors and assistant collectors, pulp density, conditioning time, temperature, ratio of return water to new water and structure of flowsheet are all researched systematically by comparative trials. A selective hydroxamic acid collector, known as GSH, and sodium silicate as regulator are used to produce final flotation rare earth oxide concentrate with grade of65.11%at recovery of17.05%. The two concentration streams from shaking tables and flotation are combined to be the final REO concentration with grade of65.08%at overall recovery of84.61%, of which the contents of both REO and impurity meet No.000165product’s requirements in the rare earth industry standards (XB/T103-2010).In terms of the basic theory of flotation bastnasite, the basic flotation behaviors for the mineral are completed using sodium oleate and salicylhydroxamic acid as collector, respectively. The mechanisms of action between multiple regulators as well as collectors and minerals is analyzed systematically by means of solution chemistry calculation, zeta potential, infrared spectroscopy, adsorption measurements, dissolution measurements and Inductively Coupled Plasma (ICP) analysis. The necessity of regulating pulp before adding collectors and mechanism of selective adsorption are illuminated by a comparative analysis, which is provide references for further theoretical researches, but also offer guidance for practical application. Meanwhile, the effect of elevated temperatures on flotation is discussed.The calculation results of solution chemistry demonstrate that hydroxylated species produced from cations on the surface of bastnasite could influence the flotation. Because of active points, hydroxylated species RE(0H)2+and RE(OH)2+are propitious to the adsorption of collector on the surface of bastnasite. But it is clear that hydroxylated species RE(OH)3and RE(OH)4do not assist flotation and adsorption may be due to they are negative active points.The action mechanism research results of sodium oleate adsorbed on the bastnasite surface indicates that chemisorption plays the most important role as well as auxiliary electrostatic or molecular adsorption, which are due to the ion-molecular association originated from dissociated oleic acid radical ion during pH6-9. But in salicylhydroxamic acid terms, the results of this adsorption study indicate a surface reaction mechanism whereby the cations on the mineral surface form hydroxy complexies in solution, readsorb at the surface and then interact with the hydroxamate, namely the salicylhydroxamic acid group bonds with the hydroxylated species to generate stable five chelate ring to realize the selective flotation of bastnasite in the range of pH8-9.The investigation results demonstrate that depressing function of sodium carbonate relates to the coions effect of potential determining ions CO32-which originates both from bastnasite surface and the reagent in the water (these ions that can interact with both mineral surface and aqueous phase in forming the electrical double layer). There are adsorption on the bastnasite surface for sodium hexametaphosphate, sodium silicate and sodium hexafluorosilicate. There is no basically effect to increase the degree of solubility of bastnasite in water for sodium carbonate, sodium silicate and sodium hexafluorosilicate. The reasons for sodium hexametaphosphate exhibits significant inhibition are most likely twofold:(1) it adsorbs on the mineral surface that changing the mineral’s electrical properties and hydrophilic, directly reducing the collector adsorbs on the bastnasite;(2) the complexation reaction takes place between RE cations hydroxylated species on the mineral surface and hexametaphosphate anion and produces soluble complexes, which reduces the concentration of active points on the surface of minerals, therefore, the suppressing effect is presented.Cations Ca2+and Al3+in the solution reveal activation when sodium oleate as the collector, which could be attributed to these ions and their partial hydrolysates have adhered on the minerals surface that is beneficial to produce more oleate precipitates exhibiting hydrophobic. On the contrary, in the flotation solution system adding salicylhydroxamic acid as collector, the investigation demonstrates depressing for these two ions. In terms of Ca2+ion, the depression is attributed to the electrostatic adsorption on the bastnasite surface and the non-selective competitive adsorption among these RE3+ions as well as their hydroxy complexes and Ca2+ions with hydroxamic acid occur. Moreover, Ca2+ions have a certain effect on the solubility of bastnasite, which may be related to the ion pair (Ca2+,CO32-) effect. This inhibition of Al3+is mainly due to the complexes that reacted between salicylhydroxamic group and Al cations, which is more stable than that produced by rare earth cations. Both Ca2+and Al3+in solution may reduce the density of active points on the bastnasite surface, consequently, the mineral is depressed.It is established that elevated temperatures in the flotation system of single bastnasite component that using salicylhydroxamic acid or sodium oleate as collector promote selective adsorption of collectors. Just on the contrary, the results of floating the rare earth ore in Maoniuping with modified hydroxamic acid demonstrate that there are obvious drops both in concentrate grade and recovery observed during flotation above50℃. The reasons are preliminarily determined that there is no related to dissolution of minerals such as bastnasite, but may be connected with several parameters including particles movements, reagents action, bubbles collision and load, and surface tension of pulp, etc.. The real reasons are in need of further researches by decomposing the complex flotation system and establishing the models.更多还原