黄钠铁矾法除铁在阜冶的应用浅析

介绍了黄钠铁矾法除铁的操作和掌握及工艺控制条件。     

钠离子对水热臭葱石沉砷过程影响及亚稳态铁物相转变行为

采用水热臭葱石沉砷法研究高砷含铁溶液沉砷过程中钠离子及其它宏观技术参数对沉砷渣物相组成、目标元素含量、形貌特征、砷铁沉淀率以及沉砷渣中黄钠铁矾、碱式硫酸铁、次水合砷酸铁(FeAsO_4·0.75H_2O)等亚稳态铁物相转变行为的影响规律。结果表明:体系中Na~+的存在对水热臭葱石沉砷过程的影响显著,初始Na~+浓度为5 g/L时,形成以臭葱石、次水合砷酸铁为主并伴有部分亚稳态黄钠铁矾生成的沉砷渣,随着初始Na~+浓度的升高,有利于黄钠铁矾的生成,渣中SO_4~(2-)震动吸收峰随之增强,臭葱石的形成逐步受到抑制;当Na~+浓度达到10 g/L时,沉砷渣物相以次水合砷酸铁和黄钠铁矾为主,此时As、Fe的沉淀率分别为98.2%、93.3%,沉砷渣中Na、S的含量分别高达1.7%、4.6%。适当降低初始pH、缩短反应时间、降低反应温度均可抑制亚稳态黄钠铁矾物相的形成,有利于获得纯度较高的臭葱石沉砷渣;同时,延长反应时间可实现次水合砷酸铁向臭葱石的转化。     

采用铅黄铁矾去除硫酸体系中的铁

研究硫酸体系中铅黄铁矾的形成条件,考察pH值、温度、PbSO4用量、时间和晶种浓度对铅黄铁矾形成及除铁率的影响。结果表明:当pH>0.7,温度大于75℃时,形成铅黄铁矾;在维持溶液pH为1.3、温度95℃、硫酸铅的加入量为理论量的1.2倍、晶种浓度为8 g/L、时间2.5 h的最优条件下,平均除铁率高于95%;得到的铅黄铁矾渣平均含Pb 22.47%、Fe 23.74%、Zn 1.96%;经硫酸化焙烧水浸或直接用锌废电解液浸出锌和铁后,浸出渣含Pb均大于60%,可返回作沉矾剂,亦可作为炼铅的原料。     

稀盐酸中锰结核还原浸出溶液净化除铁

针对酸性氯化物中黄铁矿还原浸出锰结核的溶液成分特点，选择黄钠铁矾法进行了沉淀分离铁的研究。结果表明温度和晶种以及溶液ｐＨ值是影响铁矾沉淀的重要因素。在ｐＨ２．０左右，溶液温度高于９０℃，足量晶种加入的情形下，１５０ｍｉｎ后可将溶液中的铁含量降至０．１ｇ／Ｌ。沉矾过程的表观活化能为９４．６６ｋＪ／ｍｏｌ。黄铁矿氧化生成的硫酸根随铁一同沉淀，从而消除了ＳＯ２－４在氯化物体系中的积累。     

湿法炼锌危废铁矾渣水热分解及铁物相转化行为

湿法炼锌过程产出的铁矾渣含有大量的有价金属锌、铅以及伴生金属铁,在水热条件下,危废铁矾渣将发生高效分解与转化,有价金属转入溶液,伴生铁转化为赤铁矿。本文以湿法炼锌企业产出的铁矾渣为研究对象,研究了反应温度、反应时间、液固比、初始酸度、晶种浓度等宏观技术参数对铁矾渣分解与转化的影响规律。理论计算和实验结果均表明在高温水热体系中,铁矾渣中的黄钾铁矾、黄铵铁矾和铁酸锌物相均可有效转化为赤铁矿,而铅铁矾性质稳定不易转化。升高温度并延长反应时间有利于黄钾铁矾、黄铵铁矾和铁酸锌物相的水热分解与转化。在220℃下反应1 h后,铁矾物相转化基本完成,其转化率达94%;反应4 h后铁酸锌物相衍射峰完全消失,锌浸出率达87%,转化渣中赤铁矿含量达68%。适当提高初始酸度有利于铁酸锌的转化,但当体系初始酸度高于15 g/L时将抑制铁矾物相转化。在反应温度220℃、反应时间4 h、液固比(mL/g) 10:1、初始酸度0.01 g/L的条件下,锌浸出率为89%,铁矾物相的转化率可达95%,铁矾转化渣中主要物相为赤铁矿,其含量为68%。     

过渡层红土镍矿中的镁质矿中和沉矾浸出

采用沉矾浸出法将铁质矿浸出液对镁质矿进行沉矾浸出。结果表明:镁质矿酸浸过程中,在镁质矿粒度为106～150μm、搅拌强度为150 r/min、终点pHe值为1.3、温度为95℃的条件下,浸出镁质矿3 h,镍、镁、铁的浸出率分别为93.34%、78.28%、26.4%;在沉矾浸出过程中,在反应温度为95℃、搅拌强度为150 r/min、硫酸钠中的钠与形成黄钠铁矾中的钠的摩尔比x为1.3、镁质矿粒度为106～150μm、反应终点pHe为1.3±0.2的条件下,沉矾浸出5 h,镍浸出率能达到92%,镁浸出率在74%以上,铁质矿浸出液除铁率达到87%以上,铁质矿浸出液中铁的浓度在15.87～42.16 g/L的范围内,对镁质矿的镍、镁浸出及铁质矿浸出液中Fe的浓度没有显著的不利影响,溶液中铁基本上控制在4 g/L以下。     

铁矾渣热酸分解及硫脲提银

进行铁矾渣热硫酸分解和分解渣硫脲法提银的试验研究,考察硫酸用量、分解温度、反应时间、液固比对铁矾渣中Fe、Zn、Ag浸出率的影响,以及硫脲法提银的最优条件。结果表明:在硫酸用量为其理论值的1.5倍、分解温度95℃、时间2.5 h、液固比2.5:1的最佳条件下,铁矾渣中Fe和Zn浸出率分别为93.85%和92.25%,而Ag的浸出率仅为1.99%。分解液净化后可用中温水热法制备铁红,分解渣中Ag富集到1060 g/t。在液固比10:1、硫脲浓度15 g/L、浸出温度90℃、反应时间2.5 h的最优条件下,Ag的平均浸出率在93%以上,同时,渣中Pb的品位由1.7%提高到7.5%。     

利用黄钾铁矾渣处理赤泥的研究

赤泥中含有大量的OH-和Na+,而黄钾铁矾中富含硫酸盐和H+。赤泥和黄钾铁矾在水中反应将生成含硫酸钠的液相和以氢氧化铁为主的固相。液相可以蒸发浓缩沉淀出硫酸盐而固相煅烧后得到的含铁固体可以作为赤铁矿砂。本文尝试利用赤泥和黄钾铁矾的反应制备成有价值的石膏、芒硝和赤铁矿砂产品。     

界面耦合的PbSO4溶解和PbS沉淀及其对铅矾硫化浮选的影响(英文)

通过浮选试验、X射线光电子能谱(XPS)、场发射扫描电子显微镜(FESEM)、拉曼光谱和紫外-可见漫反射光谱(UV-Vis DRS)系统研究铅矾浮选中的硫化机理。浮选试验证明硫化钠对铅矾浮选具有活化作用；但必须控制硫化钠浓度，以避免过量硫离子对浮选的抑制。XPS、拉曼光谱和UV-Vis DRS结果表明，用硫化钠水溶液处理铅矾时，PbSO₄被PbS取代。FESEM观察结果显示硫化过程中PbSO₄的溶解和PbS纳米粒子的沉淀。因此，可认为铅矾与硫化钠水溶液的反应是通过界面耦合溶解–沉淀机制进行的：在与硫化钠水溶液接触时，铅矾溶解将Pb²⁺和SO₄^2–释放到流体边界层中，该流体边界层相对于PbS相变得过饱和；然后，PbS纳米粒子在铅矾表面成核并生长。生长在铅矾表面的PbS纳米颗粒可以提高铅矾的可浮性。     

电镀锌钢板的黑变机理

在发现铅是导致电镀锌钢板黑变发生的关键因素的基础上 ,对电镀锌钢板的黑变机理提出了锌铅共沉积假说和硫酸铅胶体膜假说 ;并对不同工艺中获得的电镀锌钢板进行了黑变培养 ,通过丁达尔和界面电泳实验研究了铅在硫酸锌溶液中的存在形式 ,通过钝化及破胶实验研究了钝化工艺和镀后清洗对黑变的影响 ,验证了黑变是由于硫酸铅胶体膜在镀锌层外表面被吸附而造成的。     

The effect of some alloying elements on the corrosion resistance of lead-antimony alloys — II. Silver

The effect of Ag on the stationary and non-stationary anodic corrosion rates of PbSbCd and PbSb alloys in H₂SO₄ has been studied. Anodic polarization curves were constructed under galvanostatic and potentiostatic conditions. Optical microscopic examination and microprobe analysis of the alloys were conducted. The beneficial effect of Ag was ascribed to a delay in closure of pores in the initial PbSO₄ film. The leaching out of Sb from the outermost layers and the simultaneous nucleation of PbSO₄ and Ag₂SO₄ from supersaturated solutions in the pores is thus made possible.     

The effect of hydrogen treatment of lead surface on its electrochemical behavior

The effect of the hydrogen treatment of a Pb/PbSO₄ electrode on the electrochemical behavior of a film of lead sulfate in a 2M H₂SO₄ solution is studied using the method of galvanostatic cycling. After the treatment, a lead sulfate film with a high resistance of ΔE/i ≈ 80 Ohm cm2 is found to appear on the lead surface. The increased resistance of the film can be attributed to the complete consumption of the hydrogen ions in the cathode reaction; it significantly decreases due to the ions’ diffusion from the solution. During the cycling (the first pulse is the hydrogen treatment, the second is the anodic formation of PbSO₄), the state of the surface of the electrode is not stabilized; it is rather modified according to the irregular periodic law. The nature of the change depends on the value of the potential, which switches the anodic pulse, as well as on the mode of the hydrogen treatment. The relaxation process of the currentless electrode potential after the hydrogen treatment shows the dynamics of the film growth with an abrupt increase in its resistance during the crystallization of a supersaturated solution in the pores.     

On the role of Ca in suppressing the corrosion of Pb anode in H2SO4

Abstract-The anodic behaviour of some Pb-Ca (0·2–0·8 per cent) alloys in H₂SO₄ solutions has been studied both under potentiostatic and galvanostatic conditions. It has been shown that the protective nature of the PbSO₄ film is markedly improved by alloying Ca with Pb. The role of Ca in increasing the corrosion resistance of Pb in H₂SO₄ is discussed.     

The effect of some alloying elements on the corrosion resistance of lead-antimony alloys—I. Cadmium

The role played by Cd in lowering the corrosion rate of PbSb alloys has been investigated. It has been shown that 0·1%Cd reduces the steady state corrosion rate of PbSb by ca. 50%. This effect is discussed with respect to results obtained from galvanostatic experiments and from microscopic examination and microprobe analysis. Cd is effective through modification of the nucleation rate in the pores of the originally formed PbSO₄ film.     

Studies on the interaction between oxygen and lead chalcogenide surfaces

The work function for PbS, PbSe, and PbTe has been measured in the temperature range of 100–350° C in oxygen and in vacuo. It was established that oxygen increases the work function for both PbS and PbSe and decreases the work function for PbTe. It was concluded that the process of oxygen chemisorption is followed by the formation of a heterophase layer. According to thermodynamic considerations, PbSO₄, PbSeO₄, and PbTeO₄ are the most stable compounds as a reaction product of the oxidation of lead salts under the conditions studied.Supported in part by the National Science Foundation through a postdoctoral fellowship given to J. Nowotny under Grant GK-1137 at Northwestern University.     

The effectiveness of jarosite species for precipitating sodium jarosite

The precipitation of jarosite-type compounds [e.g., NaFe₃(SO₄)₂(OH)₆] is commonly used in the zinc industry to remove iron solubilized in the processing circuit. The precipitation reaction is greatly accelerated by the presence of jarosite seed, and the rate increases in a nearly linear manner with increasing seed additions. As shown in this study, sodium jarosite, potassium jarosite, silver jarosite, and lead jarosite are equally effective as seed for the precipitation of sodium jarosite. By extension, any jarosite-type compound would likely be an effective seed for the precipitation of any other jarosite species. The implication is that the zinc industry can readily convert from one jarosite species to another without concerns about the efficiency of the seed used. For more information, contact J.E. Dutrizac, CANMET, 555 Booth Street, Ottawa, Ontario, Canada K1A OG1; (613) 995-4823; fax (613) 996-9041.     

Effects of synthesized 4PbO·PbSO4 on the Initial capacity and cycle performance of lead dioxide electrode prepared by cementation leady oxide

The service life of lead-acid batteries is often limited by disintegration of the positive active mass structure. It is known that the latter depends on the phase composition, crystal morphology and paste density. In general, the electrode whose active mass is prepared from 4PbO·PbSO₄ pastes (denoted by 4BS_pas) has about 30% longer cycle lives than those obtained by 3PbO·PbSO₄·H₂O. Therefore, the initial capacity and cycle performance of lead dioxide electrodes prepared from 10, 30 and 50 wt.% 4BS_syn (chemically synthesized 4PbO·PbSO₄) addition with regard to the amount of cementation leady oxide were examined. Lead oxide (denoted by cementation leady oxide) was prepared by the pulverization of sponge lead prepared from a cementation reaction under the conditions of 90°C and 1.0 wt%HCl solution. 4BS_syn crystals were chemically synthesized in 40.1 wt.%H₂SO₄ with \-PbO. Without 4BS_syn, crystals lead dioxide electrode has shown a higher initial capacity than any other 4BS_syn contents and cycle performance was the best although the initial capacity is relatively low for 50 wt.% 4BS_syn.     

Converting jarosite residues into compact hematite products

Sodium jarosite is readily converted into hematite by hydrothermal reaction at temperatures greater than 220°C. Although the initial acid and ferric ion concentrations must be kept low to avoid the unwanted formation of Fe(SO₄)(OH), the conversion reaction is unaffected by modest concentrations of ZnSO₄, FeSO₄ or Na₂SO₄. Hematite seeding is desirable to promote the reaction and to stabilize the reaction system. The hematite conversion product will likely contain ～0.5% Zn and ～2% SO₄; most of the arsenic in the jarosite will remain with the hematite.     

Effect of Thiourea and some of its Derivatives on the Corrosion Behaviour of Cobalt in Concentrated Hydrochloric Acid

Abstract

The corrosion rate of cobalt in 8·4 M hydrochloric acid with and without the presence of thiourea, phenyl thiourea, o-tolyl thiourea or sym di-isopropyl thiourea has been studied by gravimetric and electrochemical methods over the temperature range, 20–80°c.

In all cases these compounds brought about enhancement of corrosion so that, at the higher temperatures, corrosion rates some twenty times those experienced in acid alone were attained. These matched the degree of corrosion stimulation of cobalt developed in the presence of hydrogen sulphide and it is suggested that the thiourea compounds act as depolarisers for the hydrogen evolution reaction, with H₂S being a product of the chemical depolarisation stage. The H₂S is considered to be adsorbed in the molecular state, forming activated sites where anodic dissolution is thereby enhanced.     

Transmission electron microscopy study of interfacial microstructure formed by reacting Al–Mg alloy with mullite at high temperature

Transmission electron microscopy (TEM) has been used to study the interfacial microstructure formed by reacting Al–Mg alloy with mullite (Al₆Si₂O₁₃) at high temperature (>900°C). The TEM study was used in order to understand the strong effect of Mg addition on the nature of the reaction between Al and mullite used to form Al/Al₂O₃ composite. After reaction at 1050°C, the formation of a layered structure between the Al–1% Mg alloy and mullite was observed. An alloy layer with a much higher concentration of Mg than the starting alloy was found present next to the initial mullite surface. Between the alloy layer and mullite, a dense and continuous layer made of small MgAl₂O₄ (spinel) and Si particles was present. The layer apparently stopped further reaction between Al–Mg alloy and mullite by preventing transport of the metals to the reaction front and the Si reaction product away from the reaction front. The microstructure resulting from the initial reaction indicated the reaction proceeded by replacing Si atoms with Al and Mg atoms on mullite {210} lattice planes and forming MgAl₂O₄ {311} lattice planes simultaneously.