赤泥中铁含量的测定及其回收试验研究

以HCl为浸出剂,对赤泥中的铁采用酸浸工艺浸出,利用重铬酸钾滴定法对赤泥中的铁元素进行了测定;同时,在浸出液中通过滴加稀NaOH碱液沉淀出氢氧化铁,3小时陈化后。过滤,放入干燥箱中在110℃下烘干,接着在500℃下烧结,经水洗、烘干,采用X-射线衍射对水洗前后试样进行物相分析。结果表明：采用酸浸工艺能够较好地浸出铁元素;另外,在加NaOH生成氢氧化铁沉淀时发生了包藏现象,经水洗后,生成了几乎纯净的Fe2O3。铁的平均回收率大约达到89．36％。     

电解剥离-生物质酸浸回收废旧锂电池

采用电解剥离-浸出正极材料、P204萃取除铝、秸秆硫酸浸出电池渣、草酸沉钴等工艺回收废旧锂电池中的钴。结果表明:经过20~30 min的电解剥离,实现了电池粉与铝箔的分离,钴的浸出率为50%,电流效率为70%;通过两次P204错流萃取除铝后,萃余液中Al3+含量可以降到0.4 mg/L,而钴却未损失;燕麦秸秆粉-硫酸浸出电池渣中钴的最佳工艺条件如下:硫酸2 mol/L、1 g电池渣加入0.5~0.7 g麦秆粉,固液比1:10,在80~90℃反应1~2 h,钴的浸出率达到98%以上;经三级浸出,COD的含量可降至1.3 g/L左右;草酸沉钴调节溶液温度为50℃,pH为2,保持n(2?Co)/n(2?42OC)=1,1 h后钴的一次沉淀率达到92%以上,滤液pH为0.2,其滤液可作为电解浸出液循环使用。     

砷滤饼的铜砷分离

采用浸出方法使砷滤饼中的铜砷元素进行分离,铜以硫化铜的形式沉淀,砷以砷酸根离子进入溶液中。考察NaCl浓度、Na_2S添加量、液固比、时间及温度等因素对砷滤饼中砷、铜浸出率的影响。得出最优的工艺条件如下:NaCl溶液浓度为20g/L、液固比7:1、Na_2S与砷滤饼质量比3:4、浸出时间4 h、温度80℃、H_2O_2 20 m L。在此最优工艺条件下,砷浸出率高达95.56%,铜浸出率低于0.5%,浸出渣铜含量富集至33.6%。浸出液采用硫酸亚铁沉砷方法,沉砷率可以达到98%,生成的砷酸铁晶体含砷量为32.15%,滤液含砷量为0.23g/L,滤液可以返回浸出过程,实现循环利用。     

草酸配位浸出二段焙砂中包裹金的赤铁矿

草酸根(ox^2-)对三价铁具有强的配位能力，可用草酸配位浸出二段焙砂中包裹金的赤铁矿，提高金的回收率。考察了草酸用量、液固比、浸出温度和时间对二段焙砂中铁浸出率的影响。结果表明，用1.17倍理论量的草酸在液固比为12 mL/g时于90℃浸出2 h，铁浸出率达到75.8%以上。除铁渣进一步氰化浸出，渣中金品位为8.8 g/t，低于直接氰化浸出渣12.3 g/t的金品位。草酸浸出液主要成分为具有光催化活性的Fe(ox)⁺和Fe(ox)2^-，可采用光催化法回收铁、再生草酸，再生的草酸可返回浸铁过程。     

铅阳极泥脱砷预处理研究

采用氢氧化钠溶液循环浸出法对铅阳极泥进行预脱砷,考察了液固比、氢氧化钠浓度、浸出温度和浸出时间对脱砷效果的影响;在液固比10∶1、氢氧化钠浓度2.5 mol/L、浸出温度80℃、浸出时间8 h的条件下,砷的浸出率可达94%以上;含砷浸出液经硫化钠沉砷后可返回浸出工序循环使用,硫化钠与砷质量比为3∶1时,沉砷率可达88%以上,同时回用浸出工序后,砷浸出率达94%以上,浸出液循环使用对脱砷没有影响。     

赤泥中钠元素回收的研究

采用柠檬酸对赤泥中的金属元素进行浸出,生成的柠檬酸钠在食品、医药、环保和电镀等行业应用广泛,具有很好的经济效益。实验通过考察浸出温度、浸出时间和柠檬酸添加量对钠、铁、铝、钙等元素浸出率的影响,并进行正交实验,确定柠檬酸浸出赤泥中钠元素最佳条件。用碳酸钠对浸出液中的少量铝、铁、钙进行去除,得到纯净的柠檬酸钠溶液。     

钨渣回收制备四氧化三锰新工艺

研究从钨渣中回收锰的新工艺,通过钨渣的低温硫酸化焙烧、烧结块浸出、浸出液除杂、溶液中水解沉锰及氢氧化锰氧化获得Mn3O4粉末,采用SEM和XRD对产品粉末进行分析。结果表明:在浓硫酸过量150%、焙烧时间90 min、浸出温度98℃、浸出时间120 min的条件下,Mn浸出率达到88.9%。浸出液可以通过硫化物沉淀除重金属、硫酸复盐沉淀法深度净化除杂、中和水解除Fe,水解沉锰也有一定的净化作用,溶液pH值为6.56时,除铁率达到99.91%。净化液经水解沉锰后采用10%H2O2氧化,在氢氧化锰氧化过程中,溶液pH值对产物物相的影响较大;溶液pH值为8时在50℃沉锰,并以过量150%的H2O2氧化反应20min,获得粒度小于0.1μm的Mn3O4粉末。     

基于隔膜电积的硫酸铅渣湿法提铅新工艺及电化学机理

根据物料平衡和电荷平衡原理,对Pb(Ⅱ)-Ac~--H~+-H_2O体系进行热力学分析,分析结果表明在接近于实际浸出液的pH值范围内,溶液中PbAc~+平衡浓度最高。以湿法炼锌产出的硫酸铅渣为原料,采用单因素实验法优化"乙酸盐配位浸出-隔膜电积提取铅"的主要工艺条件,采用单因素试验法优化乙酸铅溶液隔膜电积工艺条件,采用线性扫描、循环伏安等电化学测试手段研究Pb(Ⅱ)-Ac~--H_2O体系铅电积过程中阴极电化学行为。结果表明:在反应时间1h、浸出温度70℃、乙酸铵浓度4mol/L、液固比4:1的优化条件下浸出硫酸铅渣,铅浸出率93.28%。在电积温度30℃、Pb~(2+)浓度50 g/L、电流密度100 A/m~2的条件下阴极电流效率98%左右,每吨Pb直流电耗约700 kW·h。在此条件下以硫酸铅渣浸出液直接作为电积液隔膜电积8 h在阴极可以获得纯度99.2%较为致密平整的电铅,阴极电流效率96.16%。铅的还原沉积过程是一个不可逆过程,铅在电沉积初期遵循三维连续成核与颗粒长大机制,升高温度和提高阴极液Pb~(2+)浓度可以促进溶液离子扩散,提高电流效率。     

从废旧锂离子电池中分离回收钴镍锰

提出一种新型的从废旧锂离子电池中分离回收钴镍锰的工艺.该工艺采用物理擦洗-稀酸搅拌浸出的方法分离集流体与活性物质,采用H2SO4+H2O2为浸出剂对活性物质进行浸出,然后采用黄钠铁矾法去除浸出液中的铁,再采用N902萃取分离铜,通过水解沉淀法除铝,最后采用碳酸盐共沉淀法制备镍钴锰碳酸盐前躯体.结果表明:最优浸出条件为液固比10:1、H2SO4浓度2.5 mol/L、H2O2加入量2.0 mL/g(粉料)、温度85℃、浸出时间120 min;在此条件下,钴、镍和锰的浸出率分别达到97%、98%和96%;除去浸出液中的铁、铜和铝后,钴、镍和锰的损失率分别为1.5%、0.57%和4.56%;总体来说,废旧锂离子电池中钴、镍和锰的回收率均可以达到95%.     

钢铁厂烧结机头灰中铅的配位浸出行为与综合回收

针对钢铁厂烧结机头灰中富含铅、铁、碳、钾、氯等多种有价元素的特点,根据氯离子与铅配位的特性,采用配位浸出的方式实现铅与铁、碳等元素的选择性分离回收。SEM-EDS、XRD等研究分析表明,烧结机头灰中铅主要以絮状的KPb2Cl5等物相吸附于铁氧化合物、硅铝酸盐和碳颗粒表面,铁主要以Fe2O3和Fe3O4物相存在。实验考察了溶液pH值、温度、氯离子浓度、浸出时间和液固比等因素对铅浸出率的影响。研究表明,在溶液pH值为3.0,浸出温度为80℃,氯离子浓度为6 mol/L,液固比(mL/g)为10:1,浸出时间为2 h的优化条件下,烧结机头灰中铅化合物与氯发生配位溶解反应生成PbCl2 i i-(i=1~4)等易溶解的络合离子,实现铅的浸出,铅浸出率为95.7%;而烧结机头灰中对钢铁冶炼有用的铁、碳、硅、铝等元素不被浸出,富集在浸出渣中,较好地实现了选择性浸出。浸出液中的铅经冷却结晶、洗涤纯化后,获得纯度为99%的氯化铅产品。     

Anodic Behavior of White Iron Phases in Oxalic Media

Potential–pH diagrams of the iron–oxalic acid and ferric carbide–oxalic acid systems taking into account the equilibrium iron or ferric carbide and ferrous (II) oxalate are plotted. Kinetic investigations of the anodic dissolution of white iron, containing ferritic (99.975% Fe) and cementite (Fe₃C) phases, oxalic acid environment evidence that the alloy is passivated due to the formation of a FeC₂O₄ polylayer.     

Synthesis of Fe3O4-coated silica aerogel nanocomposites

Fe3O4:SiO2 nanocomposite powders were synthesized by a two-step process,which included the precipitation of FeCl2 and FeCl3 and the gelation of silicic acid solution derived from water glass.At first,Fe3O4 nanoparticles having a crystallite size of 20 nm were obtained by controlling the ratio of Fe(II) and Fe(III) precursors.In the second step,Fe3O4 particles were embedded in SiO2 matrix by the hydrolysis and subsequent condensation of the silicic acid solution containing Fe3O4 particles.It was found that the Fe3O4 nanoparticles homogenously disperse in the SiO2 matrix.The Fe3O4:SiO2 nanocomposite exhibited an enhanced thermal stability against oxidation compared with pure Fe3O4.FT-IR analysis indicates the presence of the Si-O-Fe bond in the Fe3O4:SiO2 (1:10,mole fraction) nanocomposite.     

Separation and Precipitation of Nickel from Acidic Sulfate Leaching Solution of Molybdenum-Nickel Black Shale by Potassium Nickel Sulfate Hexahydrate Crystallization

Nickel was separated and precipitated with potassium nickel sulfate hexahydrate [K₂Ni(SO₄)₂·6H₂O] from acidic sulfate solution, a leach solution from molybdenum-nickel black shale. The effects of the potassium sulfate (K₂SO₄) concentration, crystallization temperature, solution pH, and crystallization time on nickel(II) recovery and iron(III) precipitation were investigated, revealing that nickel and iron were separated effectively. The optimum parameters were K₂SO₄ concentration of 200 g/L, crystallization temperature of 10°C, solution pH of 0.5, and crystallization time of 24 h. Under these conditions, 97.6% nickel(II) was recovered as K₂Ni(SO₄)₂·6H₂O crystals while only 2.0% of the total iron(III) was precipitated. After recrystallization, 98.4% pure K₂Ni(SO₄)₂·6H₂O crystals were obtained in the solids. The mother liquor was purified by hydrolysis-precipitation followed by cooling, and more than 99.0% K₂SO₄ could be crystallized. A process flowsheet was developed to separate iron(III) and nickel(II) from acidic-sulfate solution.     

Removal of iron from ilmenite by KOH leaching-oxalate leaching method

Oxalic acid was used for the removal of iron from the intermediates of ilmenite leached by KOH liquor. Various parameters, such as pH, temperature, initial oxalate concentration, and illumination were investigated. Meanwhile, it was found that orthorhombic crystal Ti2O2(OH)2(C2O4)·H2O formed as the leaching proceeded. Scanning electronic microscope (SEM) images implied that the formation of Ti2O2(OH)2(C2O4)·H2O with good crystallinity proceeded through three stages. Calcining Ti2O2(OH)2(C2O4)·H2O, anatase (350°C) or rutile (550°C) type TiO2 was obtained, respectively. Element analysis found that the calcined product contained 94.9% TiO2 and 2.5% iron oxide, but only about 1600 ppm dissolvable iron oxide was left, which indicates that oxalic acid was comparatively effective on iron oxide removal from the intermediates. Finally, an improved route was proposed for the upgrading of ilmenite into rutile.     

A study on comprehensive recycling of waste diamond tools

This article puts forward a new method of recycling materials in diamond tools comprehensively and efficiently by means of analyzing and summarizing various methods of recycling waste diamond tools.After the waste diamond tools were decomposed in a mixed acid,metals contained in it went into solution in their ionic forms,while diamond and tungsten carbide particles formed into residues to be reclaimed.The amounts of metal ions in the leaching solution were adjusted according to the contents of metals in the diamond tools;then,the leaching solution was co-precipitated using oxalic acid as precipitation agent,and ammonia water was added to adjust the pH value of the oxalic acid.Under the right conditions,the comprehensive precipitation rate of metals reached above 98%.Finally,ultrafine pre-alloy powder was obtained by hydrogen reduction of oxalate.     

Coprecipitation thermodynamics of iron(II-III) hydroxysulphate green rust from Fe(II) and Fe(III) salts

Iron(II-III) hydroxysulphate GR(SO₄²⁻) was prepared by precipitating a mixture of Fe(II) and Fe(III) sulphate solutions with NaOH, accompanied in most cases by iron(II) hydroxide, spinel iron oxide(s) or goethite. Its [Fe(II)]/[Fe(III)] ratio determined by transmission Mössbauer spectroscopy was 2±0.2, whatever the initial [Fe(II)]/[Fe(III)] ratio in solution. Proportion of Fe(OH)₂ increased when the initial [Fe(II)]/[Fe(III)] ratio increased, whereas proportion of α-FeOOH or spinel oxide(s) increased when this ratio decreased. GR(SO₄²⁻) is metastable vs. Fe₃O₄ except in a limited domain around neutral pH. Precipitation from solutions containing both Fe(II) and Fe(III) dissolved species seems to favour GRs formation with respect to stable systems involving iron (oxyhydr)oxides.     

Extraction Separation of Sc(III) and Fe(III) from a Strongly Acidic and Highly Concentrated Ferric Solution by D2EHPA/TBP

The solvent extraction and separation process of Sc(III) and Fe(III) from a strongly acidic and highly concentrated ferric solution using mixtures of di(2-ethylhexyl) phosphate (D2EHPA) and tri-n-butyl phosphate (TBP) in sulfonated kerosene was studied. The effects of various parameters, including D2EHPA concentration, dosage of TBP, and phase ratio, were investigated for the extraction process. The results indicated that the extraction rate of Sc(III) was 99.72% with 1.09% Fe(III) co-extracted after two stages of counter-current extraction under optimal conditions. Moreover, saturation capacity and slope analysis were used to determine the reaction mechanism. Sc(III) is extracted in the form of HSc(SO₄)₂·4HL. Further separation of Sc(III) and Fe(III) was realized in a scrubbing and stripping process. First, 98.67% of the co-extracted iron in the loaded organic phase was scrubbed with a dilute HCl solution by a three-stage counter-current scrubbing. Then, 85.00% of Sc(III) can be stripped efficiently with a 2-mol/L NaOH solution saturated in 1-mol/L NaCl by three-stage cross-current stripping.     

A new mixed-valent iron arsenate black crystal

Scorodite (FeAsO₄·2H₂O) is the most popular phase for arsenic (As) immobilization while the reductive dissolution of Fe(III) to Fe(II) will promote As release. In the present study, an equilibrium between Fe(III) and Fe(II) was achieved in scorodite preparation system by introducing certain alcohol (methanol, ethanol, isopropanol or tert-butanol), and thus a new mixed-valent iron arsenate black crystal formulated as Fe(II)_5.2Fe(III)_8.8(HAsO₄)₄(AsO₄)₈·H₂O was prepared. In comparison with scorodite, the black crystal has higher As content (36.4%, mass fraction) and lower crystal water content (0.73%, mass fraction). Additionally, the leaching concentration of As can be lower than the threshold value (5 mg/L) regulated by identification standards for hazardous wastes of China (GB 5080.3–2007). Therefore, this new mixed-valent iron arsenate crystal could be classified as a non-hazardous and promising As-bearing phase in environmental applications.     

Zum Rosten des Eisens

Rust formation on iron - A model A model is presented on the basic of which the phenomenological variety of rusting can be reduced to a few basic process. The first step of the formation of rust results in the transfer reaction of iron (II)-ions from the metal surface into the adherent boundary layer, the ions being surrounded there by water molecules or hydroxid ions. Here or after their diffusion into the adhearent electrolyte solution they are oxidized to Fe(III)-ions by oxygen or other oxidants, eventually also electrochemically. The nuclei of the structures of FeOOH modifications develop from hydrogen bonded iron hydroxo- and/or-aquocomplexes by transposition of the iron ions and water loss. If only Fe(III)-ions participate in the nucleation process, then the stabile oxides or oxyhydroxides in relation to the solution are formed. The metastable structures result from simultaneous participation of Fe(II)- and Fe(III)-ions.