Biological leaching of nickel and cobalt from lateritic nickel ore of Sukinda mines

In the present study lateritic nickel ore was used for bacterial leaching using a mixed consortium of mesophilic acidophiles. The microorganisms were adapted to 1 gram nickel/L prior to leaching. For the experiments, lateritic ore in different forms such as raw, roasted, roasted ore presoaked in dilute sulphuric acid and palletized pretreated roasted (400 °C and 600 °C) ore were taken. The leaching experiments were conducted in 9 K+ with 40 L capacity bioreactor using 10% (v/v) inoculum concentration at 10% (w/v) pulp density. The aeration was maintained at 2–3 L/min and the speed of agitator and temperature at 400–500 rpm and 35 °C. The maximum extraction of nickel and cobalt was observed with pretreated ore (600 °C) at 10% pulp density (77.23% and 73.22%) respectively within 31 days at pH 1.5 and least extraction in case of raw ore i.e., 9.47% nickel and 41.12% cobalt respectively.     

Recovery of nickel from spent catalysts using ultrasonication‐assisted leaching

BACKGROUND: Solid catalysts containing metals or metal oxides play a key role in the chemical process industries to produce valuable products and fuels and consequently are left as solid wastes after a certain period of use. Disposal of these spent catalysts requires compliance with stringent environmental regulations because of their hazardous nature and content of toxic chemicals. Therefore recovery of the metals by various methods has been explored. In the present study recovery of nickel from spent nickel catalysts using ultrasonication‐assisted leaching has been investigated. RESULT: The effect on nickel recovery of acid concentration, temperature, solid to liquid (S:L) ratio, and time of digestion were studied in detail and optimized for the ultrasonication route. The results obtained are compared with the chelation route and conventional acid leaching technique. Using ultrasonication‐assisted leaching 95% extraction of nickel was achieved at 90 °C, 40% nitric acid concentration and S:L ratio 1:10 (g:mL) in 50 min from the spent nickel–alumina catalysts. CONCLUSION: Using an ultrasonication technique 95% recovery of nickel was significantly faster (50 min) than the chelation route (7 h), while with conventional acid leaching a maximum of 93% nickel recovery was obtained in 9 h. Compared with conventional acid leaching the purity of leached nickel salts was good and they could be recycled for the preparation of fresh catalysts after removing Al impurities. Copyright © 2011 Society of Chemical Industry     

Aqueous processing of nickel spent catalyst for a value added product

Nickel was recovered from a fertilizer industry spent catalyst by leaching with nitric acid followed by nickel hydroxide precipitation. The optimization of temperature, initial acid concentration and particle size for leaching of the spent catalyst was done through 2³ factorial design. A maximum extraction of 91.9% was achieved at 90 °C, 1.5M HNO₃ and 62.5 μm particle size. Temperature and acid concentration showed positive effect, while particle size showed no effect. A regression equation was developed and employed to predict conditions for 100% extraction which were experimentally tested. Nickel hydroxide was electrochemically precipitated from the leach liquor and its maximum discharge capacity was found to be 155 mAh/g. A 3-stage counter current leaching circuit was designed to obtain a leach liquor of suitable pH. XRD characterization of the precipitated Ni(OH)₂ shows to consist of both α- and β-forms.     

Recycling of nickel–metal hydride batteries. I: Dissolution and solvent extraction of metals

Nickel–metal hydride batteries contain valuable metallic components and although they are not considered a hazardous waste, recovery of these materials is necessary from an economic point of view. In this work a hydrometallurgical method for the dissolution and separation of the metals from cylindrical nickel–metal hydride rechargeable batteries was investigated. Hydrochloric acid was employed as the leaching agent to dissolve the metals from the batteries. Dissolution of metals was investigated as a function of acid concentration, leaching time and temperature. Suitable conditions for maximum metal dissolution were 3 h leaching with 4.0 mol dm^?3 hydrochloric acid solutions at 95 °C. Extraction of 98% of nickel, 100% of cobalt and 99% of rare earth elements was achieved under these conditions. Separation of the rare earths from nickel and cobalt was preliminarily investigated by single batch solvent extraction with 25% bis(2‐ethylhexyl)phosphoric acid. Efficient separation via complete extraction of the rare earths was obtained at a pH of approximately 2.5 while leaving nickel and cobalt in the raffinate. A shrinking particle model which can enable, under certain conditions, evaluation of the extent of metal dissolution present in nickel–metal hydride batteries was developed. A proposed electrochemical recovery of nickel and cobalt is also briefly discussed. Copyright © 2004 Society of Chemical Industry     

Reclamation of nickel from spent nickel catalyst

Spent nickel catalyst containing an average 9.6% nickel was obtained locally from an oil hydrogenation industry. It was digested with 1–3N HCl, HNO₃, H₂SO₄ and mixtures thereof in one to three stages of durations ranging from one to three hr at 100°C using spent nickel catalyst to acid proportions of 1:3 to 1:8 (w/v). Nickel recoveries of over 94% were obtained when one part of spent catalyst was digested for three hr with six or more parts of 3N mixture of HCl and HNO₃ (3:1, v/v). Acid extracts of spent nickel catalyst obtained using HCl, H₂SO₄ and mixtures thereof were treated with NaOCl to convert their content of iron in the ferric form. The iron from the nickel extract was precipitated out in the form of ferric hydroxide at pH 6.0. Nickel from the iron-freed acid extracts was recovered at pH 8.5±0.5 as nickel hydroxide. Nickel formate was prepared by refluxing nickel hydroxide with 10% formic acid in about 6% excess to stoichiometric requirements for 30 min. The dried nickel formate was reduced in peanut oil at 230°C to 270°C for 0.25 to 2.75 hr. The reduction at 260°C on kieselguhr support, employing nickel formate:oil:support in ratio of 50:43:7, for two hr provided catalyst of maximum activity. The hydrogenation activity of the reclaimed catalyst, assessed by standard AOCS procedure, was greater than that of the parent catalyst. Presented at the AOCS Meeting in New Orleans, LA, in May 1987.     

Production of sintered high alumina refractories from Turkish bauxite ore

Abstract

Bauxite ore extracted from Seydis¸ehir-Konya in Turkey has been used for the production of sintered bauxite. The high iron and calcium in the bauxite were decreased to low levels by hydrochloric acid leaching. Temperature and acid concentration significantly affected the level of iron extraction from bauxite. The aluminium dissolution during acid leaching at 6M and below 70°C was ≤2%, and calcium dissolution was over 95%. XRD and XRF of leached bauxite revealed that the level of iron within the bauxite was decreased below 2% and that no significant TiO₂ or SiO₂ dissolved during leaching. XRD of leached bauxite sintered at 1400-1700°C for 4 h revealed only corundum (α -Al₂O₃) and mullite (3Al₂O₃.2SiO₂). SEM investigation showed that bauxite grains were in the form of large aggregates. The maximum bulk density obtained at 1700°C was low compared with commercial refractory bauxites and the leached bauxite therefore needed to be sintered for longer times at 1700°C or at higher temperatures.     

Kinetic Study of Spent Nickel Catalyst Dissolution in HCl and Aqua Regia Medium

The leaching kinetics of spent nickel oxide catalysts in HCl and aqua regia solution is described. The considered parameters affecting nickel recovery are particle size, reaction time, acid concentration, and reaction temperature. Nickel could be extracted with HCl by ～87.41 % and with aqua regia by ～81.01 % using a spent catalyst with 200 mesh particle size at a reaction temperature of 100 °C. The reaction time was 360 min and the concentrations of HCl and aqua regia were 37 % and 80 %, respectively. The leaching kinetics indicates that shrinking sphere and diffusion were the rate‐controlling processes during the reactions with HCl and aqua regia, respectively. The activation energies for HCl and aqua regia were determined as 24.04 and 19.03 kJ mol^–1, respectively.     

Esterification of high acidity vegetable oil catalyzed by tin-based catalysts with different sulfate contents: contribution of homogeneous catalysis

Biodiesel production costs can be significantly reduced by using nonrefined feedstock. Sulfated solid catalysts have been proposed for producing biodiesel from acid oils by esterification reactions. Nevertheless, leaching of sulfate species to the reaction medium may occur, but often it is not considered. In this article, a commercial tin sulfate (SnSO₄) was used as a catalyst for the esterification of a feedstock with high content of free fatty acid in order to assess the contribution of the homogeneous catalysis in different situations. SnSO₄ was calcined at different temperatures (300, 400, 500 and 700?°C) and converted into SnO₂ after calcination at temperatures higher than 300?°C. Homogeneous catalysis seems possible to occur with all of the catalysts, but it was clearly observed for the uncalcined catalyst (SnSO₄) and for that calcined at 300?°C (SnSO₄(300)). For these catalysts, an important leaching of the sulfate species was confirmed. Higher conversions were obtained with the uncalcined SnSO₄. Reactions at the same conditions using sulfuric acid as catalyst at concentrations of 0.1% were performed and confirmed conversions higher than 80%. Heterogeneous catalysis plays a significant role only with the catalyst that present the highest specific surface areas and acidity (SnSO₄(400)). As some small amount of sulfate species is retained in the structure or surface of the calcined catalysts (even after calcination at 700?°C), we cannot exclude the possibility that these species are also leached during reaction. Thus, a possible contamination of biodiesel through the use of sulfated catalysts cannot be ruled out.     

Recovery of nickel from spent catalyst from palm oil hydrogenation process using acidic solutions

In this study, recovery of nickel from spent catalyst from palm oil hydrogenation process is carried out via extractive leaching process using sulfuric and hydrochloric acids. The effects of acid concentration, solid-liquid ratio, temperature and digestion time on the recovery (acid dissolution) process are investigated. It is found that sulfuric acid is the better leaching solution as compared to hydrochloric acid for recovery (dissolution) of nickel from the spent catalyst. Results from speciation modelling using VMINTEQ further imply that nickel can form sulfate complexes which are more stable than chloride complexes at concentrations higher than 1 M. The optimum conditions for maximum recovery at 85% are achieved at 67% sulfuric acid concentration, digestion time of 140 min, solid-to-liquid ratio of 1:14 and reaction temperature of 80 °C. At solution temperatures higher than 80 °C, the percentage nickel extraction is reduced. The optimization study presented here is useful for spent catalyst generators in the palm oil industry intending to recover valuable metals which may assist in reducing palm oil processing costs.     

红土镍矿浸出液除杂制备氢氧化镍

以低品位硅镁型红土镍矿硫酸浸出液为原料,用黄钠铁矾[Na2Fe6(SO4)4(OH)12]除铁、NaF除镁、中和沉镍,考察了不同因素的影响。结果表明,添加4 mL/L双氧水对浸出液氧化预处理、用Na2SO4为除铁钠源、控制溶液pH为1.6?2.2、反应时间1.5 h的条件下,铁去除率达92.1%,镍损失率为6.7%,滤渣主相为Na2Fe6(SO4)4(OH)12;除铁后滤液用NaF除去镁离子,最优条件为搅拌速率300 r/min、溶液pH=5.5?6.0及NaF 用量25 g/L,镁去除率达90.9%,镍损失率为6.8%;除杂后净化液用中和水解法提镍,在室温下添加8 g/L NaOH为沉镍剂,中和沉镍提取率达95.1%,得到纯度99.5%的Ni(OH)2产品,镍的综合回收率为82.70%。     

Reactivation and Reuse of a Hydrotreating Spent Catalyst for Cyclohexene Conversion

A comparative study has been made on the efficiency of leaching, using different concentrations of oxidized oxalic acid, and thermally treating techniques to reactivate a Ni‐Mo‐spent hydrotreating catalyst. The reactivation of the treated catalysts was performed in a pulse microcatalytic reactor under atmospheric pressure of hydrogen and reaction temperatures ranging from 250 °C to 450 °C using cyclohexene as model hydrocarbon. The studies revealed that a decoking spent catalyst after leaching using a low concentration (2 %) enhanced its physical characteristics (surface area and average pore diameter) and catalytic activity towards maximum cyclohexene hydrogenation and hydroisomerization reactions at 300 °C and 350 °C, respectively.     

Recycling of nickel–metal hydride batteries. II: Electrochemical deposition of cobalt and nickel

A combination of hydrometallurgical and electrochemical processes has been developed for the separation and recovery of nickel and cobalt from cylindrical nickel–metal hydride rechargeable batteries. Leaching tests revealed that a 4 mol dm^?3 hydrochloric acid solution at 95 °C was suitable to dissolve all metals from the battery after 3 h dissolution. The rare earths were separated from the leaching solution by solvent extraction with 25% bis(2‐ethylhexyl)phosphoric acid (D2EHPA) in kerosene. The nickel and cobalt present in the aqueous phase were subjected to electrowinning. Galvanostatic tests on simulated aqueous solutions investigated the effect of current density, pH, and temperature with regard to current efficiency and deposit composition and morphology. The results indicated that achieving an Ni? Co composition with desirable properties was possible by varying the applied current density. Preferential cobalt deposition was observed at low current densities. Galvanostatic tests using solutions obtained from treatment of batteries revealed that the aqueous chloride phase, obtained from the extraction, was suitable for recovery of nickel and cobalt through simultaneous electrodeposition. Scanning electron micrography and X‐ray diffraction analysis gave detailed information of the morphology and the crystallographic orientation of the obtained deposits. Copyright © 2004 Society of Chemical Industry     

Kinetics of Silica Dissolution from Rice Husk Char

The effect of leaching time and temperature on the ash content of rice husk char and the resultant surface area development was investigated. Experiments on dissolution of rice husk char ash with 0.5 mol NaOH solution were conducted at 40°C, 60°C, 80°C and 95°C for different times up to 7200 s. The surface areas of the leached chars after drying were determined using Micromeritics 2200 surface area analyzer. The leaching data was analyzed using different models applicable for fluid‐solid non‐catalytic reactions. It was found that the data could be satisfactorily represented by diffusion‐controlled mechanism as well as modified shrinking core models. The activation energies were in the range of 41.75 to 51.25 kJ/mole. The surface areas of the leached chars were found to depend linearly on the percentage of ash content in the chars.     

Carbon nanotube growth at 420 °C using nickel/carbon composite thin films as catalyst supports

Nickel/carbon composite (Ni/C) thin films were used as catalyst supports for the growth of vertically aligned multiwalled carbon nanotubes (MWCNTs) at temperature as low as 420 °C. Nickel nanoparticles embedded within the carbon matrix of Ni/C films have served as catalysts for the synthesis of nanotubes by PECVD using acetylene/ammonia plasma. Two different nickel contents (40 at.% and 60 at.%) in the films were used. Analysis indicated a diffusion of nickel atoms in the form of nanoparticles to the film surface upon annealing. This diffusion depends on both annealing temperature and nickel concentration in the films and affects the MWCNT growth at low temperature. The MWCNT synthesis was tested at growth temperature ranging between 335 and 520 °C. The growth of MWCNTs at 420 °C was only achieved by using Ni/C films with a high nickel content (60 at.%). These MWCNTs did not present considerable loss in their growth rate and structural quality compared to MWCNTs grown on classical substrates (Ni catalysts deposited on TiN), at higher temperature (520–600 °C). The results suggest that carbon saturation at the surface and subsurface of nickel catalysts of the Ni/C films is responsible for the improvement of MWCNT growth at low temperature.     

Leaching of vanadium and other metals from Athabasca Oil Sands coke and coke ash

Flexicoker coke derived from Athabasca Oil Sands bitumen contains a number of heavy metals, including vanadium, nickel, iron and titanium, which are susceptible to extraction by hydrometallurgical procedures. The leaching behaviour has been studied as a function of pH, temperature and the presence of salts and redox agents. Greater than 50% extraction of the vanadium, iron and nickel can be achieved by acid leaches, but only about 20% of the titanium can be extracted. Weakly acidic leaches extract about 30% of the nickel content but no significant amounts of the other metals. If cokes derived from Athabasca Oil Sands bitumen by the flexicoking process or the conventional delayed-coker coking process are combusted at temperatures below 500 °C, the vanadium and nickel values in the residual ash are readily susceptible to acid leaching.     

从失活的油脂加氢催化剂中回收镍

采用酸浸后再氨络合的方法从废油脂加氢催化剂中回收镍，镍的回收率最高可达99%以上。酸浸前先在适当温度下焙烧废催化剂样品有利于镍的溶出。使用由盐酸与硫酸以适当比例构成的混酸比使用单一盐酸或硫酸更有利于镍的溶出。加氨时，采用反加方式比正加和并流方式所得镍的回收率高。     

Synthesis of high purity nickel oxide by a modified sol-gel method

Nickel oxide (NiO) powder was synthesized by a modified sol-gel method using nickel acetate, citric acid and ethylene glycol as precursors. The synthesized material was thermally annealed at 250?°C for 2?h (pre-calcination step) and at 800?°C for 1?h (calcination). Scanning electron microscopy shows formation of particles with sizes of up to 50?μm after pre-calcination and of ? 10?μm after calcination. Nickel, oxygen and carbon were detected by energy dispersive X-ray spectroscopy (EDS) in the pre-calcined material, while only Ni and O were found after the calcination process. X-ray photoelectron spectroscopy (XPS) indicates that the composition of the synthesized nickel oxide is close to stoichiometric. Raman and Fourier transform infrared spectra show only characteristic peaks of nickel oxide. The calcined particles have cubic crystalline structure of NiO as proved by X-ray diffraction (XRD). EDS, XPS, XRD, Raman and FTIR confirmed that high purity nickel oxide was obtained by the proposed low-cost and highly effective method.     

新型固定床Raney镍(Ⅱ)成型合金的浸取过程

以20%的拟薄水铝石为黏结剂制备新型固定床Raney镍催化剂,采用苯加氢为模型反应,研究了前驱物成型合金浸取条件对催化剂加氢活性的影响.实验结果表明,对于860℃焙烧2 h后的成型合金,以10%～20%的NaOH溶液在80～90℃浸取3～4 h可得到具有较高加氢活性的固定床Raney镍催化剂.浸取反应可在1～4 h内基本完成,浸取后催化剂表面出现微孔结构,具有较好的苯加氢活性和活性稳定性,可在120℃、0.5 MPa、空速2 h^-1的缓和条件下实现苯的完全转化.     

Nickel/Silber-Hydrierkatalysatoren und ihre Verwendung zur selektiven Härtung von Fetten

Nickel/Silver Catalysts and Their Application in Selective Hydrogenation of Fats Catalysts used for the hardening of fats are critically evaluated from the view-point of reaction mechanisms and kine-tics. Carrier catalysts composed of nickel and silver exhibit high selectivities, low rates of isomerization and unusual longevity. They can be removed completely from the hydrogenated fat by the usual operations. These catalysts, which do not have the drawbacks of copper-containing catalysts, can be used instead of the latter. Hydrogenation characteristics of the new catalysts depend upon their composition and mode of preparation. Two types of nickel/silver catalysts have been found suitable; Ni/Ag-carrier catalyst TR containing at least 10 parts of silver per 100 parts of nickel, which is reduced at 220°–290°C, and Ni/Ag-carrier catalyst HS containing 7 to 8 parts of silver per 100 parts of nickel, which is reduced at 350°–450°C. Both catalysts TR and HS are suitable for the production of stable edible fats, for example, from soybean oil or rapeseed oils derived from the new varieties of rape. Using the type TR catalyst, the linolenic acid content of an oil can be reduced to a level of less than 2% without an appreciable reduction in the content of linoleic acid. Thus, from soybean oil, after removing small amounts of solid glycerides, a cold-stable salad oil can be obtained which does not tend to flavour reversion. The second type of catalyst, HS, reduces also the content of linoleic acid thus yielding heat-stable products that are suitable as frying oils and liquid shortenings. Experimental conditions and results of commercial testing are described. Methods for the preparation and handling of the new catalysts as well as the composition and the properties of hydrogenated products are presented.     

Nano-indentation on nickel aluminate spinel and the influence of acid and alkaline attacks on the spinel surface

Nickel aluminate spinel phase was successfully sintered from the thermal reactions between nickel oxide and kaolinite or γ-alumina precursor, to simulate the stabilization mechanism of hazardous metal-bearing waste by ceramic matrix. The product phases were then tested using nano-indentation to obtain their nanohardness and Young's modulus, as a means to evaluate the properties of the product after incorporating the waste material. The results indicate the beneficial effect of forming aluminate spinel phase in the system due to its superior mechanical properties. A higher sintering temperature was found to enhance crystal growth in the spinel phase, together with its nanohardness and modulus. The minimum temperature for fabricating nickel aluminate spinel with a surface property comparable to ceramic materials was found to be 1200 °C, although the initiation of the spinel phase can be achieved at a lower temperature. Nano-indentation experiments performed on the spinel-containing samples leached by strong acid and alkaline solutions reveal the superiority of nickel aluminate spinel in resisting acid and alkaline attack and also suggest a reliable mechanism for hosting hazardous nickel in the crystal structure.