Separation of nickel from cobalt using electrodialysis in the presence of EDTA

Optimum conditions are determined for the removal of nickel from cobalt solutions by electrodialysis exploiting the greater stability of the EDTA complex with nickel. The Ni–(EDTA)^2– complex and hydrated Co²⁺ ions are transferred from the feed solution to the electrodialysis anolyte and catholyte chambers, respectively. A three compartment cell is required to prevent the transfer of hydrated Ni²⁺ from the anolyte chamber as the EDTA present is destroyed at the anode. Complete removal of nickel from cobalt can be achieved but there is a compromise between cobalt purity and the percentage of cobalt transferred to the catholyte chamber for recovery.     

Separation of cobalt and zinc from concentrated nickel sulfate solutions with Cyanex 272

BACKGROUND: Removal of cobalt and zinc from concentrated nickel solutions separately using two Cyanex 272 circuits has been practised in the nickel industry. However, no detailed study has been conducted and data are scarce for further improvement. This study aims to optimise the operating conditions and to simplify the process flowsheet. RESULTS: With a synthetic solution containing 100 g L^?1 Ni, 1.4 g L^?1 Co and 0.8 g L^?1 Zn and the organic solution containing Cyanex 272 and TBP in Shellsol D70, the operating conditions of extraction, scrubbing and stripping were optimised. McCabe–Thiele diagrams were constructed to determine the theoretical extraction and stripping stages and a flowsheet to separate cobalt and zinc from nickel was proposed. With this flowsheet, more than 99% cobalt and zinc could be separated, resulting in a pure nickel solution with less than 10 mg L^?1 of cobalt and zinc. CONCLUSIONS: The current study shows that Cyanex 272 can be used to separate cobalt and zinc in one Cyanex 272 circuit effectively from concentrated nickel solutions to obtain very pure nickel solutions suitable for nickel electrowinning or hydrogen reduction. The cobalt and zinc in the loaded strip liquor were concentrated over 10 times and can be separated readily in another much smaller solvent extraction circuit. Copyright © 2010 Society of Chemical Industry     

红土镍矿酸浸沉镍废水制备硫酸镁

以元江红土镍矿硫酸溶出液沉镍废水为原料,加入碱式碳酸镁,在室温下利用不同离子水解pH值差异,实现富镁除杂的目的。实验研究了pH值、反应时间、静置时间对废水中离子浓度的影响,确定了较优操作条件为：pH 值 6.5、搅拌通气时间 5 h、静置时间3 h。在此条件下,废水中镁离子的含量提高7.6%,铁、铝、钙、镍杂质离子的去除率分别为99.85%、99.9%、28.57%、35.8%。将此沉镍废水净化液真空浓缩、结晶,分离干燥得七水硫酸镁产品,其质量达到HG/T 2680—95工业七水硫酸镁合格品的要求。     

Separation of cobalt and nickel from sulfate media using P507-N235 system

Separation of cobalt and nickel from sulfate media was investigated, using a extraction system of 30% 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507)+15% trioctyl/decylamine (N235)+55% sulfonated kerosene. About 41 wt% Co²⁺ was extracted with 1.6 wt% co-extraction of Ni²⁺ at O/A ratio of 2:1. Scrubbing of Ni²⁺ and stripping of Co²⁺ could be achieved from the loaded organic phase, using water and 0.05 mol/L H₂SO₄, respectively. Cobalt extraction percentage decreased with increasing Mg²⁺ concentration, but this influence was negligible as [Mg²⁺] < 0.1g/L. The favorable equilibrium pH was 4–4.8. A different E-pH curve was observed in the P507-N235 system compared to the saponified P507 system.     

分光光度法测定光亮镀镍溶液中的钴

以硫氢酸铵络合钴离子，随后用乙酸丁酯进行萃取，利用分光光度法测量光亮镀镍溶液中的钴离子。探讨了测量波长、硫氢酸铵的加入量、温度、时间、酸度、共存离子对测量结果的影响。结果表明，当钴离子含量为0.04-0.1mg/mL，吸光度与钴离子浓度间的关系遵守比耳定律。加标回收试验结果表明，该方法回收率为96.4%，具有很好的实用价值和应用前景。     

含氮杂环化合物与有机酸协同体系在镍、钴萃取分离中的应用

近年来开发了多种含氮杂环化合物与有机酸类萃取剂的协同体系,明显提高了镍、钴的萃取性能,同时增强了对杂质元素的分离效果,具有较大的实际应用价值。本工作综述了一些具有代表性的含氮杂环化合物与有机酸类萃取剂组成的协同萃取体系,探讨了萃取体系对镍、钴的协同萃取效果及与常见杂质元素的分离,并讨论了协同萃取体系潜在的工业应用。协同体系对镍、钴的萃取及对杂质元素的分离主要是由酸性萃取剂本身性质和含氮杂环协萃剂的影响共同决定,有机磺酸、羧酸、膦酸等萃取剂与含氮杂环化合物组成的协同萃取体系在萃取镍、钴的过程中对金属杂质元素分离的选择性不同,在镍、钴的提取及生产过程中也展现出不同的应用价值。     

Effects of cobalt, temperature and certain impurities upon cobalt electrowinning from sulfate solutions

The effects of cobalt concentration, temperature and the presence of zinc, copper and iron ions in the electrolyte on current efficiency and cathodic quality were investigated by cyclic voltammetry and galvanostatic methods during cobalt electrowinning. The results showed that high cathodic efficiency of cobalt deposition was obtained from solutions containing cobalt concentration in the range 30–60 g l^–1. Current efficiency increased from 94% to 97% with increase in cobalt concentration to 60 g l^–1 at 20 °C. It was also found that increase in temperature to 50 °C enhanced the cobalt deposition reaction, along with the rate of hydrogen evolution, resulting in little change in current efficiency. The presence of foreign cations in the electrolyte not only adversely affects current efficiency but also promotes cracking and peeling.     

Equilibrium characteristics for the extraction of cobalt and nickel into di(2-ethylhexyl) phosphoric acid

The liquid-liquid extraction of cobalt and nickel from aqueous sulphate solutions into di(2-ethylhexyl) phosphoric acid, DZEHPA, has been investigated at 25°C and 60°C. The system studied was made up as follows: the aqueous phase-cobalt and nickel dphates; the organic phase-20% D2EHPA, 75% Esso solvent DX3641 and 5% tri-butyl phosphate. Analogies to vapour-liquid equilibria were made to develop three methods to correlate the binary equilibrium data, namely: 1) a delta Y method, 2) a method based on the correlation of solvent free mole fractions in both phases and 3) a “pseudo activity” coefficient or pseudo gamma method, γ_AB. The methods were evaluated as to their suitability for the prediction of binary isotherms. The delta Y and pseudo gamma methods were found to give the best results.     

废金刚石刀具中铜钴镍的回收工艺研究

为了使废金刚石刀具循环再生和综合利用，以废金刚石刀具为原料，通过盐酸浸溶、氧化还原、钴镍分离等过程，系统地研究了金刚石、碳化钨、铜粉、钴粉和镍粉的回收工艺，并优化了最佳工艺参数。结果表明，金属钴和镍的回收率可达96％，而纯度在98％以上。该方法工艺简单，回收率高，经济效益显著。     

Electrochemical studies of the nickel electrode with cobalt modification

The electrochemical behaviour of the paste-type nickel hydroxide electrode with cobalt-modified nickel foam was investigated using galvanostatic charge–discharge, electrochemical impedance spectroscopy, cyclic voltammetry and current pulse relaxation methods. Experimental results showed that the performance of the nickel electrode with substrate deposition of a thin layer of cobalt was improved markedly. This improvement could be attributed to the enhanced electrical conduction between the substrate and the active material. The enhanced electrical conduction increases the charge efficiency and the discharge depth of the nickel electrodes and therefore increases the utilization of the active material. This suggests that the electrical conduction between the substrate and the active material is essential to the practical use of paste-type nickel hydroxide electrodes.     

红土镍矿脱硅渣碳化制备碳酸镁

以红土镍矿脱硅渣为原料,采用碳化、热解工艺制备出碳酸镁产品,并使NiO在碳化渣中富集到2.96%。研究表明,氧化镁的提取率随着搅拌强度、反应时间及液固比（ml:g）的增加而增加,随着反应温度的升高先增加后减少。在搅拌强度600 r·min^-1、反应温度15 ℃、反应时间36 h及液固比（ml:g）40:1的条件下,氧化镁的提取率可达91.57％。经XRD分析,产品为碱式碳酸镁;产品理化性能符合国家化工行业HG/T 2959—2000标准。     

镁合金化学镀镍工艺

研究了采用碱式碳酸镍作为镍源在AZ91镁合金表面直接化学镀镍的工艺。该工艺采用酸洗活化一步法,即经过脱脂除油,再用H3PO4、NH4HF2以及缓蚀剂处理,无需活化。通过比较3种酸洗液的应用效果,确定60mL／LH3PO4,40g／LNH4HF2,30g／LH3BO3的混合液作为酸洗液。酸洗最佳pH约为2,时间为25s。实验发现,该法较HF活化得到的镀层表面颗粒更均匀。该Ni-P镀层结合力合格,硬度可达356．7HV。讨论了热处理温度对镀层硬度的影响,结果表明随热处理温度的提高,镀层硬度也随之提高,在热处理温度为250℃时,硬度达最大。通过Tafel曲线分析得出,AZ91镁合金采用该工艺进行化学镀镍后,耐蚀性有了很大改善。     

褐铁型高锰红土矿微波预处理-酸浸提取镍钴

以褐铁型高锰红土矿为研究对象,采用微波预处理-酸浸工艺提取Ni、Co。对矿样物相组成及Ni、Co、Fe、Mn等主要元素赋存状态进行X射线衍射（XRD）和电子探针（EPMA）表征,研究常压条件下硫酸浓度、浸出时间、浸出温度等因素对微波预处理矿样中Ni、Co浸出效果的影响。结果表明：矿样中镍钴品位较高但物相结构复杂,Ni主要与Mn以NiMn₃O₇?3H₂O形式赋存,Co伴生于针铁矿和碱式氧化锰中;在最优浸出条件下,即硫酸浓度300g/L、浸出时间5h、浸出温度90℃、液固比6∶1（以mL/g计）、搅拌速度280r/min,Ni、Co浸出率分别达到95.4%和97.1%,与相同浸出条件下未经微波处理的矿样相比,Ni、Co浸出率分别提高了69.4%和70.1%,实现镍钴的高效浸出;对比微波处理前后矿样XRD图谱,发现微波作用下矿物中Ni、Fe、Mn等物相结构出现明显转变,利于Ni、Co酸浸反应。     

碱式硫酸镁烧结法制备氧化镁晶须

以价格低廉的硫酸镁和氢氧化钠为原料,通过前驱体烧结法制备氧化镁晶须。首先以硫酸镁和氢氧化钠为原料,通过常温反应—水热晶化,制得了结晶良好、具有纤维状外形的前驱体碱式硫酸镁[MgSO4.5 Mg(OH)2.2 H2O]的单一物相。通过控制前驱体的分解速度使其在低温下缓慢分解以保持晶须状外形,然后在高温下烧结,得到烧结良好、分散均匀、长径比大的氧化镁晶须。利用SEM和XRD对产物进行表征,氧化镁晶须是由纳米氧化镁颗粒烧结而成的“假象”体,直径在0.2~1.5μm,长径比≥50。实验证明该工艺简捷、易行、条件温和,为氧化镁晶须的工业化生产提供了有效可行的新途径。     

2.5次微分溶出伏安法同时测定水中痕量钴和镍

在０．０１ｍｏｌ／ＬＮＨａ·Ｈ２Ｏ＋ＮＨ４Ｃｌ（ｐＨ＝８．９）和２．０×１０－６ｍｏｌ／Ｌ酸性铬兰Ｋ（ＡＣＢＫ）溶液中，钴和镍均产生非常灵敏的还原波，峰电位分别是－０．５２Ｖ和－０．６４Ｖ（８８·ＳＣＥ），峰电流与钻和镍的浓度分别在３．０×１０－８～５．０×１０－７ｍｏｌ／Ｌ和２．０×１０－～４２×１０－７ｍｏｌ／Ｌ范围内成直线关系，该法用于测定水中痕量钴和镍，结果令人满意。     

球形镍氧化物制备硫酸镍的方法研究

以球形镍氧化物为原料,研究了制备高纯硫酸镍的方法。首先借助X射线衍射仪（XRD）和X射线光电子能谱仪（XPS）对球形镍氧化物的主要成分进行表征,确认其主要成分为氧化镍;其次对球形镍氧化物浸取制备较高纯度的硫酸镍条件进行了优化,确立了硫酸浓度为1.84 mol/L、反应温度为200 ℃、固液比为0.3 g/mL、反应时间为6 h为最优反应条件;最后利用高温条件下（250 ℃）获得的一水合硫酸镍固体,提出了将其再次溶解生产pH和镍浓度可控的高纯硫酸镍溶液的方法。     

Separation of copper from cobalt in sulphate solutions by using CaCO3

Lime neutralization is widely used to precipitate heavy metals including copper and cobalt from wastewater. Limestone (calcium carbonate: CaCO₃) is too stable to be used directly for this purpose. Grinding of CaCO₃ in the solutions of copper and cobalt sulphate was conducted to raise its reactivity. During the mechanochemical activation, CaCO₃ reacted with copper sulphate but not significantly with cobalt sulphate and this phenomenon allowed an easy separation of copper from cobalt. The residual of Cu(II) ions in solution could be controlled at less than 0.1%, meanwhile more than 90% of the Co(II) ions remained in aqueous solution.     

Selective conversion of propane to propene by the catalytic oxidative dehydrogenation over cobalt and magnesium molybdates

Catalytic performances of various metal molybdates were tested in the oxidative dehydrogenation of propane to propene with molecular oxygen under an atmospheric pressure. Most of the molybdates tested promoted the selective oxidative conversion of propane to propene and among them cobalt and magnesium molybdates were found highest in the activity and selectivity. It was also found that their catalytic activities were highly sensitive to the catalyst composition, and it turned out that Co_0.95MoO _x and Mg_0.95MoO _x catalysts which have slightly excess molybdenum showed the highest activity in the oxidative dehydrogenation of propane. Under the optimized reaction conditions, higher reaction temperatures and lower partial pressures of oxygen, these catalysts gave 60% selectivity to propene at 20% conversion of propane. Since the molybdates having the surface enriched with molybdenum oxide tended to show high activity for the propane oxidation, surface molybdenum oxide clusters supported on metal molybdate matrix seem to be the active sites for the selective oxidative dehydrogenation of propane.     

Effect of thiourea and saccharin on the roughness of electrodeposited ultrathin nickel and cobalt layers

Ni and Co films were produced by electrodeposition from plating baths containing either thiourea or saccharin. The effect of the organic additives on surface roughness was studied for the Ni-thiourea, Ni-saccharin, Co-thiourea and Co-saccharin systems. Layer thicknesses were varied from 1 to 10 nm and the additive concentration was varied from about 1 M to 1 mM. Contact mode atomic force microscopy was used to measure both the root mean square (RMS) peak height (nm) and the areal peak density (m^–2) of each film. Although the RMS peak height and areal density were both influenced by film thickness and by additive concentration, the two roughness measures provide complementary information on the layer morphology and growth mechanisms. The four systems studied responded differently to changes in the concentration of the added organic. For example, for films 8 nm thick, addition of 1.22 × 10^–3 thiourea reduced the Ni peak density about 80%; in contrast, the Co peak density was increased over 180% by addition of 1.25 × 10^–3 thiourea. Use of peak height and peak density data to infer growth mechanisms for ultrathin films is discussed.