高铁赤泥中钪钠选择性分离提取工艺基础研究

发布时间：2018-07-04 11:23

本文选题：赤泥 + 钪　；参考：《北京科技大学》2017年博士论文

【摘要】：赤泥是氧化铝生产过程中排出的固体废弃物。在大多数赤泥中都含有少量的稀贵金属元素,所以它也是一种具有重要潜在价值的二次资源。目前世界上的赤泥累积量已经超过27亿吨。对于如何有效处理赤泥已经迫在眉睫。从赤泥中回收钠、铝、铁等主要元素的同时,回收钪等其他稀贵元素吸引越来越多的研究人员关注。本文在综述赤泥的产生过程、物化特性及其应用现状,系统论述国内外有价元素的冶金工艺流程及溶液稀有元素萃取及反萃取的机理的基础上,针对山东某氧化铝厂拜耳法产出赤泥,提出了一种高效选择性分离提取钪和钠的新工艺。赤泥中钪与主元素矿物的赋存特性直接决定了钪提取工艺的选择,所以本文首先运用二次飞行时间质谱(ToF-SIMS)和电子探针(EPMA),研究了赤泥中元素Sc和Ga与主元素Fe、Al、Si、Ti以及Ca的亲和行为。通过二次飞行时间质谱、电子探针元素分布图以及电子探针微区量化分析表明,在赤泥矿相中Sc元素与Fe、Al、Ti、Si表现出了一定的亲和行为,并且其亲和顺序应按照TiFeAlSi进行。Ga元素与Fe、Al、Ti、Ca、Si表现出了一定的亲和行为,并且其亲和顺序应按照FeAlTiCaSi进行。钪的载体矿物主要是锐钛矿、赤铁矿和针铁矿。在锐钛矿中,异价类质同象方式4Sc~(3+)→3Ti~(4+)是其主要嵌入锐钛矿的方式。与赤铁矿或针铁矿的类质同象方式Sc~(3+)→Fe~(3+)相比,完全不同。富硅矿物的石英相中也存在部分钪。与Sc元素不同的是镓在各矿物中的分布相对均匀,仅与铁铝略微表现出更为密切的配位关系,即镓在岩相形成过程中可以较容易的置换赤铁矿、针铁矿和三水铝石晶体中被Fe~(3+)和Al~(3+)占据的位置。赤泥中Na离子的能否去除对后续赤泥的利用或元素综合提取有重大影响。通过TG-DTA、QXRD、FTIR、SEM等分析,探究了随炉冷却、空冷、水淬以及液氮冷却四种不同冷却方式对活化焙烧赤泥处理后钠离子浸出的影响。研究结果表明,冷却速率越快,钠离子的浸出率相对越高。因此,在四种冷却方式中同等条件下,液氮冷却活化焙烧赤泥样品的浸出液中钠离子浓度最高,其浓度可高达1202 mg.L-1(～25 w%回收率)。其原因是活化焙烧中,新相Na_2Ca(CO_3)_2的出现在较快冷却速率的样品中,该相可以容易地溶于水溶液中。部分霞石脱硅产物转变为NaCaHSiO_4和钠钾霞石。在液氮冷却样品中Ca(OH)_2的浓度增加到～4.8wt%,它在一定程度上有利于霞石和NaCaHSiO_4的溶解。非晶相量随冷却速率增快而增大。在随炉冷却样品中,非晶相量仅为～4.1 wt%;而在液氮冷却样品中,非晶相量却增加到了～13.5 wt%,非晶相量的增加无疑会促进钠离子的浸出。在微观形态方面,较快冷却速率样品主要呈蓬松的片状或絮状,这减弱了焙烧后赤泥物相的团聚程度;比表面积SSA值的相对增加,使浸出液与颗粒的有效接触面积也将增大。不同冷却方式下,微观形态变化亦对浸出有一定促进影响。综合可见焙烧样品较快冷却速率有利于钠离子的浸出。钪、钠与铁的分离通过硫酸化焙烧水浸工艺实现,该工艺相比于传统的直接酸浸工艺显示出极高的选择性与可操作性。主要内容包括探究拜耳赤泥中钙、铁、铝、硅、钠、钛、钪和镓在焙烧过程中物相转变规律,以及探究焙烧温度、焙烧时间、硫酸添加量、浸出温度、浸出时间、浸出液固比对这些元素浸出行为的影响。研究结果表明,焙烧温度和焙烧时间是能否选择性的从赤泥中回收钪和钠的最主要影响因素;另外,较高的浸出温度也会对铁离子的浸出产生负面影响。在焙烧过程中,钠离子对金属硫酸盐的分解具有抑制作用,并且改变铁铝金属硫酸盐的分解顺序。研究结论表明,硫酸盐的分解顺序如下:TiOSO_4Ga_2(SO_4)_3Fe_2(SO_4)_3NaFe(SO_4)_2NaAl(SO_4)_2～Al_2(SO_4)_3Na_3Sc(SO_4)_3Na_2SO_4CaSO_4。在此,需要强调的是在完成水洗涤焙烧料后,固液分离步骤可以非常顺利的进行。在最佳焙烧和浸出条件下,有95 wt%的 Na+,～60wt%的 Sc 以[Sc(H_2O)x(SO4)n]3-2(x≤6)形式被浸出,同时伴随有1wt%的Fe~(3+)、7wt%的Al~(3+)、～29wt%的Ca2+和3 wt%Si~(4+)较低杂质元素浸出,而Ti~(4+)和Ga~(3+)不被浸出,有效实现了赤泥中钪、钠与铁、钛、硅等元素的分离。浸出后的尾渣可以考虑作为高炉炼铁或建材原料。本文还研究了硫酸化焙烧赤泥浸出液中Sc的萃取分离。比较磷酸类萃取剂P204、P507和羧酸类萃取剂Versatic acid 10,发现P204对钪表现出较好的萃取性能。萃取实验的最佳萃取工艺条件是:水相与有机相比值(A:O)为10:1;萃取温度为15℃;萃取系组成为P204/磺化煤油(1%v/v)。在该条件下,～97%的Sc可被提取出来,同时得到硫酸钠副产物。另外,0.35～0.5的硫酸溶液可用于萃取有机相洗涤;反萃取条件可用2 mol·L-1 NaOH溶液进行。
[Abstract]:Red mud is a solid waste in the process of alumina production. In most red mud, a small amount of rare and precious metals are contained, so it is also a two resource with important potential value. The accumulation of red mud in the world is over 27 million tons now. It is imminent to recover red mud from the red mud and recycle it from red mud. The recovery of scandium and other rare elements attract more and more researchers at the same time, such as sodium, aluminum, iron and other major elements. This article reviews the production process, physicochemical properties and application status of red mud, and systematically discusses the metallurgical process of the valuable elements at home and abroad and the mechanism of extraction and reverse extraction of rare elements in the solution. A new process of selective separation and extraction of scandium and sodium by high efficiency and selective separation of red mud from the Bayer process in a alumina plant is proposed. The selection of scandium extraction process is directly determined by the occurrence characteristics of scandium and the main element minerals in red mud. Therefore, the two time time of flight mass spectrometry (ToF-SIMS) and electron probe (EPMA) are used to study the elements Sc and G in the red mud. The affinity behavior of a with the main elements Fe, Al, Si, Ti and Ca. Through two time flight time mass spectrometry, electron probe element distribution and electron microprobe microquantization, it is shown that the Sc elements in the red mud are shown to be compatible with Fe, Al, Ti, Si, and their affinity and order should be performed according to TiFeAlSi. A certain affinity behavior, and its affinity sequence should be carried out according to FeAlTiCaSi. The carrier minerals of scandium are mainly anatase, hematite and goethite. In anatase, 4Sc~ (3+) to 3Ti~ (4+) is the main form of anatase in anatase. Compared with Sc~ (3+) to Fe~ (3+) in the same way of hematite or goethite. Unlike the Sc element, the distribution of gallium in each mineral is relatively homogeneous and is only a little more closely related to the iron and aluminum. That is, gallium can be easier to replace hematite in the formation of the lithofacies, and Fe~ (3+) and Al~ (3+) in the crystals of the goethite and trihydrate. The removal of Na ions in red mud has a significant influence on the utilization of red mud and the comprehensive extraction of elements. Through the analysis of TG-DTA, QXRD, FTIR and SEM, the effects of four different cooling methods on the leaching of sodium ion after the activation roasting red mud are investigated with the cooling, air cooling, water quenching and liquid nitrogen cooling. The results show that the cooling is cooled. The faster the rate, the higher the leaching rate of sodium ions. Therefore, under the same conditions in the four cooling methods, the concentration of sodium ion in the leaching solution of the liquid nitrogen cooling activated red mud is the highest, and the concentration can be as high as 1202 mg.L-1 (to 25 w% recovery). The reason is that the new phase Na_2Ca (CO_3) _2 appears in the rapid cooling rate during the activation roasting. In the sample, the phase can be easily dissolved in aqueous solution. Some nepheline desilication products are converted to NaCaHSiO_4 and sodium potassium nepheline. The concentration of Ca (OH) _2 increases to 4.8wt% in the liquid nitrogen cooling samples. It is beneficial to the dissolution of nepheline and NaCaHSiO_4 to a certain extent. The amorphous phase increases with the cooling rate. The crystalline phase amount is only 4.1 wt%, but in the liquid nitrogen cooling samples, the amorphous phase increases to 13.5 wt%. The increase of the amorphous phase will undoubtedly promote the leaching of sodium ions. In the micromorphology, the rapid cooling rate samples are mainly fluffy flake or floc, which weakens the aggregation degree of the red mud phase after the calcination; the specific surface area SSA value. The relative increase of the effective contact area of the leaching solution and the particle will also increase. Under the different cooling methods, the micromorphological changes also have a certain effect on the leaching. The rapid cooling rate of the comprehensive visible roasting sample is beneficial to the leaching of sodium ions. The separation of scandium and sodium and iron through the sulphate roasting and water leaching process is compared with the traditional process. The direct acid leaching process shows high selectivity and maneuverability. The main contents include exploring the phase transformation of calcium, iron, aluminum, aluminum, silicon, sodium, titanium, scandium and gallium during the roasting process, and exploring the roasting temperature, calcination time, sulphuric acid addition, leaching temperature, leaching time, leaching behavior of leaching liquid and solid ratio. The results show that the baking temperature and the calcination time are the most important factors that can selectively recover scandium and sodium from the red mud. In addition, the higher leaching temperature can also have a negative effect on the leaching of iron ions. During the calcination process, the sodium ion has a inhibitory effect on the decomposition of metal sulfate and changes the iron and aluminum metal. The decomposition order of sulfate is found to show that the decomposition order of sulfate is as follows: TiOSO_4Ga_2 (SO_4) _3Fe_2 (SO_4) _3NaFe (SO_4) _2NaAl (SO_4) _2 to Al_2 (SO_4) _3Na_3Sc. It is necessary to emphasize that after completing the washing and roasting material, the step of solid-liquid separation can be carried out very smoothly. In the best roasting and leaching process. Under the conditions, 95 wt% Na+, 60wt% Sc are leached in the form of [Sc (H_2O) x (SO4) n]3-2 (x < < 6), and the leaching of 1wt% Fe~ and 3 lower impurity elements, and the separation of scandium, sodium and iron, titanium, silicon and other elements in the red mud. The tail slag can be considered as a material for blast furnace ironmaking or building materials. This paper also studied the extraction and separation of Sc in the leaching solution of the red mud by sulfuric acid roasting. Compared with the phosphoric acid extractant P204, P507 and the carboxylic acid extractant Versatic acid 10, it was found that P204 showed good extraction performance for scandium. The optimum extraction conditions for the extraction were as follows: the water phase and the available extraction conditions The ratio of the phase to phase (A:O) is 10:1, the extraction temperature is 15 C, the extraction system is composed of P204/ sulfonated kerosene (1%v/v). Under this condition, 97% of Sc can be extracted and the sodium sulphate by-product is obtained. In addition, 0.35 ~ 0.5 sulfuric acid solution can be used to extract organic phase washing; the extraction conditions can be carried out by 2 mol. L-1 NaOH solution.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X758;TF803.23

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