Influence of secondary carbide precipitation and transformation on abrasion resistance of a 3Cr15Mo1V1.5 white iron

The relationship between the secondary carbide precipitation and transformation of the 3Cr15Mo1V1.5 white iron and abrasion resistance was investigated by using optical microscope （OM）, transmission electron microscopy （TEM） and X-ray diffrac- tion （XRD）. The results show that the properties of secondary carbides precipitated at holding stage play an important role in the abrasion resistance. After certain holding time at 833 K subcritical treatment, the grainy （Fe, Cr）23C6 carbide precipitated and the fresh martensite transformed at the holding stage for 3Cr15Mo1V1.5 white iron improve the bulk hardness and abrasion resistance of the alloy. Prolonging holding time, MoC and （Cr, V）2C precipitations cause the secondary hardening peak and the corresponding better abrasion resistance. Finally, granular （Fe, Cr）23C6 carbide in situ transforms into laminar M3C carbide and the matrix structure transforms into pearlitic matrix. These changes weaken hardness and abrasion resistance of the alloy sharply.

Effect of titanium content on the precipitation behavior of carbon-saturated molten pig iron

The use of iron ores bearing titanium as a raw material is an effective measure to prevent hearth erosion and prolong the life of a blast furnace. In this research, the effect of titanium content on the precipitation behaviors of high-melting phases of carbon-saturated molten pig iron were studied by confocal scanning laser microscopy. The results showed that, when the titanium content was less than 0.25 wt%,Fe_3C was precipitated as a single phase from the molten carbon-saturated iron. The growth rate of the precipitated Fe_3C crystals was very high, reaching 7387 μm^2/s. When the titanium content in the molten pig iron was greater than 0.47 wt%, TiC crystals precipitated first. The shape and size of the precipitated TiC crystals did not obviously change. After TiC was precipitated, the fluidity of the molten pig iron worsened. With a decrease in temperature, Fe_3C was also precipitated but the growth rate of Fe_3C was limited by the presence of the first precipitated TiC phase. The crystal size of the precipitated Fe_3C was much smaller than that of pure Fe_3C.

Transformation behavior of ferrous sulfate during hematite precipitation for iron removal

The transformation behavior of ferrous sulfate was examined during hematite precipitation for iron removal in hydrometallurgical zinc.Specifically,the effects of the method used for oxygen supply(pre-crystallization or pre-oxidation of ferrous sulfate)and temperature(170–190℃)on the redissolution and oxidation–hydrolysis of ferrous sulfate were studied.The precipitation characteristics and phase characterization of the hematite product were investigated.The results showed that the solubility of ferrous sulfate was considerably lower at elevated temperatures.The dissolution behavior of ferrous sulfate crystals was influenced by both the concentrations of free acid and zinc sulfate and the oxydrolysis of ferrous ions.Rapid oxydrolysis of ferrous ions may serve as the dissolution driving force.Hematite precipitation proceeded via the following sequential steps:crystallization,redissolution,oxidation,and precipitation of ferrous sulfate.The dissolution of ferrous sulfate was slow,which helped to maintain a low supersaturation environment,thereby affording the production of high-grade hematite.

Modeling of goethite iron precipitation process based on time-delay fuzzy gray cognitive network

The goethite iron precipitation process consists of several continuous reactors and involves a series of complex chemical reactions,such as oxidation reaction,hydrolysis reaction and neutralization reaction.It is hard to accurately establish a mathematical model of the process featured by strong nonlinearity,uncertainty and time-delay.A modeling method based on time-delay fuzzy gray cognitive network(T-FGCN)for the goethite iron precipitation process was proposed in this paper.On the basis of the process mechanism,experts’practical experience and historical data,the T-FGCN model of the goethite iron precipitation system was established and the weights were studied by using the nonlinear hebbian learning(NHL)algorithm with terminal constraints.By analyzing the system in uncertain environment of varying degrees,in the environment of high uncertainty,the T-FGCN can accurately simulate industrial systems with large time-delay and uncertainty and the simulated system can converge to steady state with zero gray scale or a small one.

Two-stage precipitation process of iron and arsenic from acid leaching solutions

为贱金属恢复的沥滤的进程经常产生象铁和砷那样的杂质的可观的数量进解决方案。为最后的处理把非珍贵的金属分开成可管理、稳定的废物产品是挑战，没有松开珍贵成分。Boliden 矿物质 AB 获给很干净的铁砷的一个二阶段的降水过程专利由贱金属的最少一起沉淀猛抛。有好沉积和过滤性质的获得的产品表演，它使恢复铁砷容易弄空由过滤的答案并且 precipitate 洗。键盘乐器的低音部凳子规模测试被做了，显示出二阶段的降水过程完成的优秀结果。

Structural Analysis of Magnesium-Aluminium Hydrotalcites Modified with Iron III Obtained by Hydroxide Precipitation Method

Hydrotalcite-type anionic clays are a group of important materials used in adsorption processes, mainly for organic pollutants removal due the layered double hydroxide structure. The layer-interlayer interactions provide a structural memory even after dehydration and dehydroxylation process, since a very stable interlayer anions are part of material composition, like the carbonate one. A limited numbers of trivalent modifier cations can replace the aluminium cation due the ionic radii mismatch or oxidation state restrictions. Transition metal cations can replace the aluminium one in octahedral site of hydroxide lamellas in order to improve the adsorptive behaviors. In this work, we have investigate three compositions of carbonated magnesium-aluminium hydrotalcite with dif-ferent iron (III) contents through the co-precipitation method at pH 11 and aging step at 60°C for 6 hours. Thermal analysis was performed aiming the determination of the hydration water and hydroxyl amounts in dried precipitate samples, taking in account the results obtained for X-ray diffractometry, infrared spectroscopy, and nitrogen adsorption-desorption characterization for several thermally treated samples. All of synthesized samples showed high surface areas, even for high temperature of thermal treatment. The co-substitution with iron (III) reduced the temperature of dehydration and dehydroxylation process, but the co-substitution at 5 mol% provides other desirables characteristics, like a more amount of rhombohedral HDL phase and higher porosity, even after the thermal treatment at 500°C for 4 hours. This result makes that composition very applicable as a reusable adsorbent material in order to removal several types of micro-pollutant compounds in aqueous media.

UV/Fe(Ⅲ)工艺对络合态重金属的去除效果及机理

UV/Fe(Ⅲ)工艺是一种处理络合态重金属的新型组合工艺,该工艺先通过Fe(Ⅲ)的置换作用释放游离重金属离子,然后通过UV辐照对有机配体进行降解,最后通过碱性沉淀去除络合态重金属。以Cu(Ⅱ)-EDTA、Ni(Ⅱ)-EDTA为目标污染物,采用UV/Fe(Ⅲ)工艺对其进行去除,通过去除效果对比和机理分析,对组合工艺去除效果差异的内部机理进行阐述,并提出相应的优化方案。结果表明,UV/Fe(Ⅲ)工艺对Cu(Ⅱ)-EDTA、Ni(Ⅱ)-EDTA的去除效果存在较大差异,对两种络合态重金属中Cu、Ni的去除率分别为70%和41%。通过高效液相色谱(HPLC)、分光光度法、苯甲酸(BA)探针实验,确定Cu(Ⅱ)-EDTA、Ni(Ⅱ)-EDTA去除效果差异的主要原因是Fe(Ⅲ)对Cu(Ⅱ)、Ni(Ⅱ)的置换效果有明显差异,置换率分别是85%、22%。对Ni(Ⅱ)-EDTA置换过程分别进行Fe(Ⅲ)投加量和反应温度优化,结果表明,反应温度优化可以显著提升Fe(Ⅲ)对Ni(Ⅱ)-EDTA的置换效率。将反应温度提升至35℃,Ni去除率从41%提升至60%。反应温度在UV/Fe(Ⅲ)工艺中对Ni(Ⅱ)-EDTA的去除至关重要,适当升温有助于提高置换率,进而提升去除率。

Selective leaching and recovery of V as iron vanadate from industrially generated Mo-V residue

A commercial process was developed to treat a Ca-based Mo-V residue generated in Mo processing plant. Vanadium wasselectively leached using acetic acid and recovered as iron vanadate by hydro process. Process conditions for selective V leachingand iron vanadate precipitation were investigated. V recovery efficiency of 90.3% was achieved with a V content of 26.5% and an Fecontent of 29% in the iron vanadate cake suitable for ferrovanadium industry. The overall Mo recovery in the whole process was98.6%. The obtained leach residue containing 14.3% Mo with negligible impurities can be used as a feed material for the Moproduction process or ferromolybdenum industry. This simple and economical process generates two product streams from a singleoperation and has the potential to solve a long standing problem of handling such a mixed Mo？V residue.

氯离子体系铀溶液中铁、钍、稀土的去除研究

采用复盐沉淀法,用硫酸钠同时去除氯离子体系铀溶液中的铁、钍、稀土杂质离子,并研究了硫酸钠用量、反应温度、反应时间、体系pH等对除杂效果的影响。结果表明,反应的最佳条件为:硫酸钠用量为理论量的160%、反应温度95℃、反应时间2 h、体系pH=0.75~1.25。在此优化条件下,铁、钍和总稀土的平均去除率分别达到99.62%、99.42%和98.27%,铀的平均回收率为99.87%。方法具有除杂效果好、铀损失率低、易分离等优点。

镍电解除铜后液氯气氧化沉淀法除铁钴

以氯气(Cl_(2))为Fe^(2+)和Co^(2+)氧化的氧化剂、Na_(2)CO_(3)为沉淀剂,对镍电解阳极液—硫化氢除铜后液深度除铁钴、Cl_(2)利用率和除铁钴渣成分进行了系统研究,用正交试验和单因素条件试验确立了最佳的Cl_(2)氧化沉淀法除铁钴的最佳工艺条件,阐明了除铁钴渣中镍、铁、钴的存在形态。结果表明:Cl_(2)氧化沉淀铁、镍和钴的反应均属于放热反应,能够自发进行,且热力学反应优先顺序为Fe^(2+)>Co^(2+)>Ni^(2+);正交试验和单因素条件试验结果一致,最佳的除铁钴工艺条件为:通Cl_(2)前pH=5.0、通Cl_(2)终点ORP=1050 mV、反应终点pH≥4.5。在此条件下,Fe^(2+)和Co^(2+)去除率分别为99.8%和97%,Cl_(2)利用率大于97%,除铁钴渣的Ni(Fe+Co)=0.88。除铁钴渣主要由Ni、Fe、Co、O、S等元素组成;Ni以+2价为主,Fe和Co则以+3价为主。

Analysis on mechanical properties of nickel-iron steel after post-weld heat treatment

X-ray diffraction was utilized to measure the residual stress of 45 mm UNS N08810 plates after post-weld heat treatment at temperatures of 680℃ and 900℃, which showed reductions of 86.9% and 71.6% in the residual stress, respectively. This indicates that post-weld heat treatment can play a significant role in reducing residual stress, while no significant effects on tensile stress and micro-hardness of the welding joint were observed after treatment.

Characterization and Evaluation of Antibacterial Activities of Chemically Synthesized Iron Oxide Nanoparticles

The iron oxide nanoparticles have been synthesized in co-precipitation method using aqueous solution of ferric and ferrous ions with sodium salt. The synthesis of iron-oxide nanoparticles were validated by UV-Visible spectroscopy which showed higher peak at 370 nm as valid standard reference. An average size of iron oxide nanoparticle found by Diffraction Light scattering (DLS) particle size analyser, ranges approximately between 10 nm to 120 nm with mean particle size of 66 nm. The X-ray power diffraction (XRD) analysis revealed the crystallographic structure of magnetic particles. Characterization of the mean particle size and morphology of iron oxide nanoparticles confirmed that the iron oxide nanoparticles are nearly spherical and crystalline in shape. Further the antibacterial effect of iron oxide nanoparticles was evaluated against ten pathogenic bacteria which showed that the nanoparticles have moderate antibacterial activity against both Gram positive and Gram negative pathogenic bacterial strains and retains potential application in pharmaceutical and biomedical industries.

铁碳自养反硝化高效去除厌氧氨氧化出水硝酸盐氮效能分析

通过工艺连续运行研究、铁沉淀形态转化和微生物种群结构分析,考察铁碳自养反硝化工艺对厌氧氨氧化出水硝酸盐氮的去除效能,揭示铁碳载体与生物膜耦合的理论机制.结果表明:铁碳自养反硝化工艺可实现硝酸盐氮的高效去除.在水力停留时间(HRT)为16.6h时,厌氧氨氧化出水的总氮(TN)去除率可达(90.0±4.7)%;在HRT为13.3h时,厌氧氨氧化出水的TN去除率为(82.2±1.4)%.在运行阶段Ⅰ,Fe_(3)O_(4)是生物膜中的主要铁沉淀类型,而在阶段Ⅲ,生物膜中Fe_(3)O_(4)减少,密度更小的FeOOH型铁沉淀有所增加.铁碳自养反硝化工艺运行过程中,在接种污泥中占优势的兼养反硝化菌脱氯单胞菌(Dechloromonas)比例显著降低,而自养反硝化菌和铁转化细菌得到富集,热单胞菌属(Thermomonas)的相对丰度由第43d的0.70%提升至第120d的4.51%.

普鲁士蓝类钠电池正极生产废水预处理工艺研究

钠离子电池作为新兴产业,有关其生产工艺的研究较多,但是鲜少见到关于钠电池生产废水处理工艺的研究。因此,本文对普鲁士蓝类钠电池正极废水的预处理工艺进行实验研究,探究最佳处理工艺。最终确定了母液废水采用直接氧化法预处理工艺,即先加入H_(2)O_(2)(1.18倍理论投入量),然后用质量分数为30%的NaOH溶液调pH至9左右,静置30 min,再经过管式超滤膜过滤,母液中铁锰元素的去除率分别约为99.93%和99.99%。洗水废水采用两段式沉淀法预处理工艺,即第一阶段采用固氰除铁法,先用质量分数为30%的NaOH溶液调pH至7左右然后加入硫酸亚铁(硫酸亚铁投入量与废水中铁元素质量比为5.2),反应静置30 min。主要去除废水中绝大部分的铁元素和少部分锰元素。在一段处理的基础上再采用氧化沉淀法,先加入H_(2)O_(2)(0.83倍理论投入量),然后用质量分数为30%的NaOH溶液调pH至9,反应静置30 min,再经过管式超滤膜过滤,最终铁和锰元素的去除率分别约为99.87%和99.99%。为实际工程中钠电池废水预处理提供了重要技术参考。

有机酸-硫化零价铁处理高浓度含铬废液及铬铁资源化的研究

针对含铬废液净化污泥杂质含量高、铬含量低导致铬回收难的问题,以有机酸-硫化零价铁为铬废液净化剂,在高效去除废液中铬的同时,可净化污泥并直接制备铬铁合金。通过考察零价铁硫化程度、初始废液pH值、不同有机酸摩尔比、硫化零价铁用量等影响因素对废液铬净化与污泥铬富集的影响,探索铬污泥直接制备铬铁合金工艺。研究显示,采用有机酸-硫化零价铁协同处理后,废液总铬质量浓度可由5 324.1 mg/L降低至4.30 mg/L,与未改性零价铁技术相比,铬净化去除率由65.45%提高至99.92%。净化污泥铬铁元素平均质量分数大于46%,在1 500℃,氩气保护气氛下,添加质量分数为30%碳粉即可成功制备铬铁合金。铬铁合金产物中铬铁元素分布均匀,杂质含量较少。XRD分析显示,硫化零价铁的掺入质量增大可降低合金产品中杂相的生成。研究方法为冶金、化工等行业含铬废液的高效净化及资源化处理提供了一条新路径。

三级耦合技术处理含砷废水工程实例

以某光伏企业为例,以砷为主要考察指标,设计“板框压滤+砷铁共沉淀+活性砂过滤”三级耦合工艺,应用于含砷废水预处理。介绍该工艺技术特点,并给出主要构筑物的技术参数,阐述工艺控制要点及系统运行情况,分析运行效果。工程运行结果表明,该工艺可有效去除总砷,出水水质稳定达标。

湿法炼锌含铁溶液水热矿化沉铁行为研究

在常规湿法炼锌过程中,采用黄钾铁矾法、针铁矿法除铁工艺时存在铁渣中铁质量分数低而锌质量分数高、渣量大、无害化处理成本高等难题,为此,本文开展湿法炼锌含铁溶液水热矿化沉铁行为研究。研究结果表明:升高反应温度有利于Fe3+水解生成赤铁矿(Fe2O3),同时促进铁矾物相(MFe3(SO4)2(OH)6)向赤铁矿的转化,铁渣中铁质量分数显著升高;延长反应时间可提高Fe3+沉淀率,并使更多的黄钾铁矾(KFe3(SO4)2(OH)6)转化为赤铁矿;提高氧分压将加快Fe2+氧化成Fe3+的速率,促进赤铁矿物相的形成。在反应温度为180℃,氧分压为0.8 MPa、反应时间为3 h且控制碱金属离子浓度的优化条件下,溶液中94.29%的铁以赤铁矿(Fe2O3)形式沉淀入渣,沉铁渣中铁质量分数为57.75%、锌质量分数为0.82%。对比黄钾铁矾工艺,铁渣量减少约60%,铁渣中锌质量分数降低6.5%。采用水热矿化沉铁工艺,可在低酸条件下实现溶液中铁的矿化沉淀,得到铁质量分数满足氧化铁行业标准且可实现资源化利用的赤铁矿沉铁渣,可助力湿法炼锌行业向绿色低碳方向发展。

含镓锗硫酸盐溶液中砷铁的高效脱除

砷和铁是湿法炼锌系统回收镓、锗工艺中主要的杂质元素,萃取分离工艺可实现砷铁的高效脱除,但得到的反萃液为高砷铁溶液,且含有少量镓、锗。为实现镓、锗的高效回收,采用中和沉淀法实现砷、铁与镓、锗的分离,考察沉淀终点pH、反应温度、反应时间、搅拌速度等参数对各金属离子沉淀率的影响。结果表明,在沉淀终点pH=2.5、反应温度25℃、反应时间1 h、搅拌速度240 r/min的最优条件下,铁和砷的脱除率分别为92.80%、98.13%,镓、锗的损失率分别为45.61%、7.35%。中和渣中损失的镓、锗可用弱酸溶液洗涤,酸洗液与中和后液共同返回到萃取系统回收镓和锗,提高综合回收过程中镓和锗的直收率。

磷铁渣高温活化浸出-沉淀法制备电池级FePO_(4)的工艺及应用

磷铁渣是黄磷生产的副产物之一,化学性质稳定,常作为固体废物处理,不仅污染环境,也消耗了大量人力物力。如何合理利用磷铁渣中铁(Fe)、磷(P)元素是磷化工企业必须解决的问题。以磷铁渣制备磷酸铁(FePO_(4))的传统技术存在能耗大、副产物安全隐患大、难以实现工业化生产等缺点。有鉴于此,本文采用磷铁渣、磷酸、盐酸、氨水为原料,通过高温活化浸出-沉淀法制备了电池级FePO_(4)。在高温活化浸出阶段,探究了浸出时间、浸出温度、盐酸浓度、液固比与磷铁渣浸出率的关联规律。并研究了反应温度、时间、pH、投料比等条件对制备FePO_(4)性能的影响。对浸出液中Fe、P元素浓度和FePO_(4)晶体结构、形貌和粒度进行了分析。实验结果表明,磷铁渣浸出的最佳条件是:浸出时间3h、浸出温度90℃、盐酸浓度5.5mol/L、液固比20mL/g,在此浸出条件下Fe元素浸出率可达93.55%,P元素浸出率可达82.21%,固体渣浸出率可达90.06%。沉淀反应过程的最佳条件为:反应温度70℃、反应时间2h、反应pH=1.2、Fe/P投料比为1,此条件制备的磷酸铁(FePO_(4))材料结晶度高,形貌均匀,分散性好,一次粒径为100~200nm,铁磷比为0.97,杂质含量完全符合行业标准。以此合成的磷酸铁锂(LiFePO_(4))正极材料电化学性能较好,在1C倍率下,放电比容量可达到151.62mA·h/g,表明所制备的FePO_(4)完全满足LiFePO_(4)正极材料前体的要求。