Ni Extraction Research Articles

Growth of tropical grasses in Oxisol contaminated by nickel

Soil pollution by heavy metals has increased worldwide and the search for plants that can be used to remediate polluted areas is an interesting alternative. The aim of this study was to evaluate the tolerance of tropical grasses to Ni and its availability for the Mehlich 1, DTPA, and USEPA 3051 and 3052 extraction methods in Ni-contaminated Oxisol. Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs ‘Aruana’ and ‘Tanzania’, Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster ‘Xaraes’ and ‘Marandu’, and Urochloa decumbens (Stapf) R.D. Webster ‘Basilisk’ were grown for 90 d in a Typic Hapludox (Oxisol) after adding 20, 40, and 120 mg Ni kg-1 to the soil. Tropical grasses showed a positive response to the application of Ni doses. The order of decreasing tolerance of tropical grasses to Ni in the soil was: ‘Basilisk’ > ‘Xaraes’ > ‘Marandu’ > ‘Aruana’ > ‘Tanzania’ based on the critical toxicity dose. Nickel concentration and accumulation increased with increasing soil Ni doses in all the tropical grasses. Mehlich 1, DTPA, USEPA 3051, and USEPA 3052 Ni extraction methods in the soil are efficient to diagnose Ni availability in tropical grasses.

The Use of Heap Bioleaching as a Pre-Treatment for Platinum Group Metal Leaching

Two samples, a Platreef flotation concentrate and coarse ore (<6 mm), were column bioleached at 65°C using a culture dominated by Metallosphaera hakonensis. Based on solution assays, extractions in excess of 90% Cu and Ni were achieved from the flotation concentrate, while from the coarse ore 96% Cu and 67% Ni extractions were achieved. The difference in extraction levels and leaching patterns despite identical conditions used for both samples is discussed, as is the performance of the samples during a follow-up leach step using cyanide to extract the PGMs in a separate column leach experiment. While the recovery of Pd and Au was excellent during these steps, recovery of Pt was limited to 35% after 45 days for the concentrate and 56% after 60 days for the whole ore material, primarily due to the presence of a refractory Pt mineral. Recovery from a concentrate without pre-treatment was substantially lower.

PGM converter matte mineral characteristics and effects on downstream processing

There is little in-depth study on the downstream processing characteristics of granulated PGM-containing converter matte, particularly related to grinding and liberation behavior closely associated with leaching, and also as a function of iron endpoint specific mineralogy. Moreover, there is limited physical property data available, such as hardness and breakage of converter matte mineral structures that allows for considering a possible dependence between the mineralogy and the downstream processing characteristics of converter matte. The aim of this study was to investigate a relationship between indentation hardness, breakage and the mineralogy of two different iron end point converter mattes namely Fe_0.15% and Fe_5.17%. This also allowed for a subsequent investigation to relate the mineralogy to the integrated downstream processing characteristics of granulated converter matte.A Nano-indentation tester was used to measure the indentation hardness of mineral structures. The indentation system also had the ability to test the breakage characteristics of the respective mineral structures by applying a preset load. Laboratory batch grinding tests were conducted at various specific energies with respect to granulated high and low iron mattes. A high resolution field-emission scanning electron microscope was utilized for mineralogical analysis. The perfect mixing ball mill model was subsequently used to assess the breakage rates of matte particles and minerals. A mineral liberation analyzer was used to investigate the liberation characteristics of mineral structures of interest.The investigations revealed that the minerals and associated boundaries showed relatively different indentation hardness. The indentation-induced breakage of nickel sulfide, copper sulfide and NiCu-alloy structures appeared preferential and related to the iron end point. The softest mineral was found to be copper sulfide, which exhibited the average indentation hardness of 1975 and 2978MPa within the low and high iron matte respectively. The increasingly harder minerals were nickel sulfide and NiCu-alloy in both low and high iron mattes with mean values around 5000MPa. The laboratory batch grinding of the converter mattes at specific energy inputs resulted in product size distributions correlated to the underlying mineralogy. Although the trends for the breakage rates was found to be similar for both mattes, the matte with Fe content of 5.17% exhibited higher breakage rates in the specific energy ranges from 5kWh/t to 25kWh/t. This indicated that the matte with 5.17% Fe produces finer product than that of the 0.15% Fe matte at the same energy level. Moreover, a higher degree of overall liberation was achieved for copper sulfide and NiCu-alloy present within the high iron matte particles compared to particles within the low iron matte. 40% of particles within the high iron matte are completely liberated at 5kWh/t specific energy, in contrast to about 20% within the low iron matte. However, Ni extraction achieved during leaching of minerals within the high iron matte was lower as opposed to minerals of the low iron matte. This was attributed to favorable Ni mineralization and chemistry of the low Fe matte which appears to be the most important driver for the downstream processing.

Extraction and environmental risk assessment of heavy metal in the municipal dewatered sludge using rhamnolipid treatment

ABSTRACTHeavy metal could lead to serious environmental risk to the ecosystem, destroy human health via the food chain. The heavy metal removal from sludge is an emergent issue. In this work, rhamnolipid, an environment-friendly material, was used to enhance heavy metal extraction from the sludge. The results showed that Cu, Zn, Cr, Pb, Ni, and Mn maximum extraction efficiencies were 35.10 ± 2.31%, 45.33 ± 3.24%, 27.58 ± 3.35%, 24.12 ± 3.51%, 43.31 ± 2.53% and 22.10 ± 2.11%, respectively; most of exchangeable and reducible fractions, and partly oxidizable and residual fractions have been extracted by the rhamnolipid solution. After treatment, IR values of heavy metals increased in the treated sludge, the IR values for Cu, Zn, Cr, Pb, Ni, and Mn were 0.24 ± 0.01, 0.25 ± 0.03, 0.21 ± 0.02, 0.32 ± 0.03, 0.22 ± 0.021 and 0.41 ± 0.03, respectively. MF values indicated that heavy metal mobility order was Zn>Ni>Cu>Mn>Cr>Pb in the treated sludge. According to the two risk assessment methods (risk assessment code, RAC and potential ecological risk index, PERI), the risk assessment of heavy metal was investigated in the after treatment sludge, which indicated that rhamnolipid could extract the mobility of heavy metal and lead to no or low risk to the ecosystem. Therefore, rhamnolipid was utilized to enhance heavy metal extraction from dewatered sludge in this study, which is a promising technique for heavy metal extraction from the dewatered sludge.

Separation of Ni and Co by D2EHPA in the Presence of Citrate Ion

Recycling processes for the recovery of metallic content from the electronic wastes are environmentally friendly and economical. This paper reports a method for the recovery and separation of Ni and Co from the sulfate solution by the use of D2EHPA. In this regard, the influence of citrate ion, as a carboxylate ligand, was examined in the separation conditions of Ni and Co via D2EHPA (a poor selective extractant for Ni and Co separation). It was found that the $$ \Delta {\text{pH}}_{0.5}^{\text{Ni-Co}} $$ (the difference between pH values corresponding to 50 pct extraction of metallic ion) increases to 1.5 at the citrate concentration of 0.05 M; this $$ \Delta {\text{pH}}_{0.5}^{\text{Ni-Co}} $$ value is much higher than that obtained in the absence of citrate ion (0.1). Fourier Transform Infrared Spectroscopy (FT-IR) indicated that the citrate ion is co-absorbed during the metallic ions absorption by D2EHPA meaning that the metal–organic complexes contain Co/Ni and citrate ion. Also, the stoichiometric coefficients of the Ni and Co extraction reaction were proposed by applying the slope analysis method.

Synergistic extraction of Co(II) over Ni(II) from chloride solutions by a mixture of Cyanex 301 and LIX 63

It is difficult to separate Co(II) and Ni(II) by extraction with single Cyanex 301 from acidic solution. The synergistic extraction of Co(II) over Ni(II) from aqueous chloride solutions was studied using a mixture of Cyanex 301 and LIX 63. A significant synergistic extraction of Co(II) with the synergistic enhancement factor of 191 was obtained by adding LIX 63 to Cyanex 301, while Ni(II) extraction was little affected. The highest separation factor of 10 was obtained at an optimum composition of the mixture. The extraction reactions with this mixture were proposed on the basis of slope analysis. The extracted species of Co(II) and Ni(II) was found to be Co(HA2)2·HB and Ni(HA2)2, respectively. Effective stripping of Co(II) and Ni(II) was attained by using different concentrations of HCl solution. It is feasible to apply this mixture for the separation of Co(II) and Ni(II) from the leach liquor of laterite ore.

Identification of the significant factors determining extractability of Ni and Cu after sulfation roasting of a PGM-bearing chromitite ore

Selective sulfation-roast-water leach process of a complex, chromite-rich Cu-Ni-PGM ore to dissolve water-soluble base metal sulfates contained therein was investigated as an alternative process to remove base metals prior to the extraction of precious metals. Ground run-of-mine ore (P80<75μm) was mixed with concentrated H2SO4 (sulfating agent) and Na2SO4 (dual catalyst and sulfating agent) to intensify atmospheric sulfation roast reaction in an unvented electric furnace (static roast under reducing conditions). The acquired calcine was water leached to extract the Ni and Cu sulfates. The roasting conditions were optimized using a Response Surface Methodology which included a Desirability Function Approach in order to maximize Cu and Ni extraction whilst limiting reagent consumption and suppressing Fe and Cr co-dissolution.It was possible to decompose the chromatic-ferritic structure and produce water-soluble metal species by roasting the ore containing 12.80g/t Pt, 15.20g/t Pd, 0.0646% Cu, 0.31% Ni, 13.60% Fe and 10.40% Cr. Approximately 90% Ni and 77% Cu were recovered after roasting at 550°C in closed atmosphere for 2h with 462kg/t H2SO4, 76.9kg/t Na2SO4 and by leaching at 80°C with 2wt% solid density for 24h. The raw ore, roasted mass and water-leach residue were characterized by fire assay and Tescan Integrated Mineral Analysis (TIMA GM Model). Pt+Pd grade has been upgraded from 28(raw ore) to 32.38g/t (water-leach residue).

Hunting for valuables from landfills and assessing their market opportunities A case study with Kudjape landfill in Estonia.

Landfill mining is an alternative technology that merges the ideas of material recycling and sustainable waste management. This paper reports a case study to estimate the value of landfilled materials and their respective market opportunities, based on a full-scale landfill mining project in Estonia. During the project, a dump site (Kudjape, Estonia) was excavated with the main objectives of extracting soil-like final cover material with the function of methane degradation. In total, about 57,777 m3 of waste was processed, particularly the uppermost 10-year layer of waste. Manual sorting was performed in four test pits to determine the detailed composition of wastes. 11,610 kg of waste was screened on site, resulting in fine (<40 mm) and coarse (>40 mm) fractions with the share of 54% and 46%, respectively. Some portion of the fine fraction was sieved further to obtain a very fine grained fraction of <10 mm and analyzed for its potential for metals recovery. The average chemical composition of the <10 mm soil-like fraction suggests that it offers opportunities for metal (Cr, Cu, Ni, Pb, and Zn) extraction and recovery. The findings from this study highlight the importance of implementing best available site-specific technologies for on-site separation up to 10 mm grain size, and the importance of developing and implementing innovative extraction methods for materials recovery from soil-like fractions.

Removal of nickel and vanadium from crude oil by using solvent extraction and electrochemical process

LLP Pavlodar Oil Chemistry Refinery crude oil contain high vanadium and nickel content, which containsmore than 23.09 g/t nickel and 58.59 g/t vanadium. In this study we used two types of metal removing methodssuch as solvent extraction and electrochemical process. The present research is conducted for comparativeanalysis of the deasphalting with organic solvents and electrochemical method. Maximum efficiency ofdeasphalting, with cyclohexane as the solvent, in Soxhlet extractor was 66.4% for nickel and 51.2% forvanadium content from crude oil. Percentage of Ni extraction reached maximum of approximately 20% byusing the electrochemical method in electrolysis cell, which was developed for this research. It consists of threesections: oil and protonating agent (EtOH) solution between two conducting membranes which divides it fromtwo capsules of 10% sulfuric acid and two graphite electrodes which cover all three parts in electrical circuit.Ions of metals’ pass through membranes and remain in acid solutions. The best result was obtained in 60minutes with ethanol to oil ratio of 1 to 3 respectively, current fits in to the range from 0.3A to 0.4A, voltagechanged from 12.8V to 17.3V.

Application of a selective dissolution protocol to quantify the terminal dissolution extents of pyrrhotite and pentlandite from pyrrhotite tailings

The recovery of valuable base metals from mining rejects presents an economical alternative to conventional hydrometallurgical processes. The reject of interest investigated in the present work is a nickeliferous, upgraded pyrrhotite tailings produced by Vale Base Metals in the Sudbury Basin of Ontario. A QEMSCAN™ analysis of the tailings showed a total Ni content of 1wt%, with 59% of the total Ni deported to pyrrhotite and 40% associated with pentlandite. The initial part of this study involved the development of a selective dissolution protocol to quantify the differential dissolution extents of the two Ni-bearing minerals. Application of this protocol to the pyrrhotite tailings sample showed that an acidity of 15wt% HCl, and a temperature of 80°C was adequate to selectively dissolve 96% of pyrrhotite from the tailings. Subsequently, an anoxic acidic leach of the tailings at pH1.5, and at 5% (w/v) solids loading showed minimal dissolution of Fe and Ni from pentlandite in tests with and without pH control. The extent of Ni dissolution was next evaluated as a function of pH during an oxic acid leach. The testing protocol involved leaching the tailings under two pH regimes: fixed and uncontrolled pH. The results showed that operation at a fixed pH increases the extent of Ni dissolution due to the higher concentration of the oxidant Fe(III) in solution. Finally, an oxic ferric leach showed that the terminal dissolution extents of pyrrhotite and pentlandite were comparable at 46% total Ni extraction.

Super-dry reforming of methane intensifies CO2 utilization via Le Chatelier's principle.

Efficient CO2 transformation from a waste product to a carbon source for chemicals and fuels will require reaction conditions that effect its reduction. We developed a "super-dry" CH4 reforming reaction for enhanced CO production from CH4 and CO2 We used Ni/MgAl2O4 as a CH4-reforming catalyst, Fe2O3/MgAl2O4 as a solid oxygen carrier, and CaO/Al2O3 as a CO2 sorbent. The isothermal coupling of these three different processes resulted in higher CO production as compared with that of conventional dry reforming, by avoiding back reactions with water. The reduction of iron oxide was intensified through CH4 conversion to syngas over Ni and CO2 extraction and storage as CaCO3 CO2 is then used for iron reoxidation and CO production, exploiting equilibrium shifts effected with inert gas sweeping (Le Chatelier's principle). Super-dry reforming uses up to three CO2 molecules per CH4 and offers a high CO space-time yield of 7.5 millimole CO per second per kilogram of iron at 1023 kelvin.

Co and Ni extraction and separation in segmented micro-flow using a coiled flow inverter

The segmented micro-flow extraction and separation of the adjacent elements of Co from Ni sulphate solution with Cyanex 272 is developed using a micro-scale coiled flow inverter (CFI). This is compared with the conventional batch extraction in parallel. Continuous operation of a process involving liquid-liquid extraction and then two-phase separation is achieved instantly. For the latter a micro-scale separator is used. Compared with batch extraction, the segmented micro-flow extraction process shows order-of-magnitude faster extraction times, higher extraction ability for Co, lower extraction for Ni, and then a better selectivity between Co and Ni at industrial-matching concentration. Regular columnar slugs are observed at low flow rates and found to be a Gaussian function of the flow rates. Matched in- and outlet flows indicates that extraction in micro-flow is dependent on mass transfer by molecular diffusion. Extraction efficiency is enhanced by the internal circulation flow generated within slugs. Additionally, the characteristic parameters, overall volumetric mass transfer coefficient kLα and overall mass transfer coefficient kL, are measured to determine the mass transfer performance. Compared with batch, much higher kLα of Co (0.26–0.017s−1) and smaller of Ni (0.053–0.013s−1) are investigated in CFI. Meanwhile, 4.5 times increasement of the kL value of Co to Ni is observed in CFI indicating the asynchronous extraction between Co and Ni.

Geogenic metal mobility in a coastal inlet impacted by cannery discharge, Magdalena Bay, Baja California Sur, Mexico

Magdalena Bay is an important habitat for marine organisms, some of which have been the subject of metal bioaccumulation studies. Cannery waste is discharged into the bay providing a plausible source of contamination but this study finds that some metals occur geogenically. Bay sediments and rocks (n=59) were analyzed for total metals and clustered (HCA) into two distinct groups with PCA indicating concentrations of Cr, Cu, Mn, and Ni influenced samples near ophiolite outcrops, which reported some metal concentrations exceeding averages in the crust by an order of magnitude (up to 4450ppm Cr and 1269ppm Ni). Metals at the cannery are rarely elevated above crustal averages except Zn (max. 160ppm), however, acid-extracted Zn was below recommended sediment quality guidelines in contrast to 80% of ophiolitic samples reporting Ni extractability exceeding such guidelines. This study raises awareness of geogenic metals when considering sources of contamination in marine environments.

Kinetics and statistical analysis of nickel leaching from spent catalyst in nitric acid solution

In this study, the kinetics of nitric acid leaching of a spent NiO–Al2O3 catalyst was investigated. The effect of leaching parameters such as reaction time (30–120min), temperature (25–65°C), stirring speed (500–1300min−1) and average particle size (63–300μm) on Ni extraction were determined by statistical analysis. The results obtained show that extraction of about 85% was achieved under the following conditions: average particle size 75μm, temperature 65°C, reaction time 120min, stirring speed 600min−1, nitric acid concentration 50% and solid/liquid ratio 1:3. The kinetics study indicates that diffusion through the product layer is the rate-controlling process during the reaction. The activation energy for the different particle size using a stochastic model was determined. Activation energy values from 13.07–25kJ/mol are consistent with that reported for mixed or intermediate-controlled processes. The linear relationship observed between the activation energy Ea and the inverse of the initial particle diameter suggest that the dissolution rate controlling step may shift from product layer diffusion to intermediate-controlled process by decreasing particle size.

Comparison of leaching and heavy liquid separation methods for low grade nickel lateritic ore

In this research, some tests such as atmospheric agitation leaching and gravity methods were performed using a low Ni grade lateritic sample taken from southern Iran. In these samples, Ni grade was 0.38% and the main minerals were serpentine, hematite and quartz. In this work, the response surface methodology was used to fit models to the experimental results. Hence, variables (temperature, sulphuric acid dosage and pulp density) were designed in central composite design method using DX7 software. Then, models for four results (Ni grade in leaching solution, and Ni, Mg and Fe extraction) were achieved, which could suggest that Ni and Mg extraction patterns are near to each other, while the Fe extraction pattern is different. Then, more physical tests (heavy liquid separation) were carried out to confirm the last results. In addition, the leaching experimental results were optimised and obtained under medium conditions at 4 h, 80°C, 2.59 N sulphuric acid and 200 g L− 1 pulp density; it is possible to extract >75% of Ni. However, under intensive conditions (especially ∼95°C), Ni extraction grows up.

Screening Bioleaching Systems and Operational Conditions for Optimal Ni Recovery from Dry Electroplating Sludge and Exploration of the Leaching Mechanisms Involved

ABSTRACTRecovery of valuable metals from electroplating sludge by bioleaching has attracted growing attention. However, extraction efficiency of metals was generally rather low even at a low pulp density of 1%–2% owing to failing to find the most suitable bioleaching system. In this work, high Ni recovery yield from electroplating nickel slag at a pulp density of 10% was attained by determining the best bioleaching process. The results showed the sulfur-A.t system exhibited the greatest extraction efficiency among the three bioleaching systems tested. The dissolved concentration of Ni and leaching efficiency reached 5400 mg/l and 90%, respectively, after 9 days of contact. Furthermore, 100% of Ni extraction was obtained at a pulp density of 10% by the sulfur-A.t system through optimizing operational conditions. Acid dissolution by biogenic H2SO4 was the dominating mechanism for Ni leaching in the sulfur-A.t system. However, other unknown leaching mechanisms also occurred which resulted in 19% Ni extraction. A direct contact between the sludge and cells was necessary for efficient Ni release by the sulfur-A.t system.

Heap and tank leaching of copper and nickel from a Platreef flotation concentrate using ammoniacal solutions

The technical feasibility of ammonia leaching of platinum group mineral (PGM)-bearing Platreef flotation concentrates was investigated as an alternative method for the recovery of base metals before precious metal recovery. The composition of the concentrate sample included 2·02% Cu and 3·17% Ni, mainly as chalcopyrite and pentlandite. A solution containing 4M NH4OH, 4M (NH4)2CO3, buffered in the pH range 9–10, was used as base case lixiviant in column and batch stirred tank reactor tests, around which the effects of total ammonia concentration and operating temperature were explored further. At optimal conditions nearly 100% Cu and Ni extraction were obtained in the batch stirred tank reactor, and 95% Cu and 60% Ni extraction was obtained in columns. The activation energy for chalcopyrite and pentlandite was 36 and 16 kJ mol− 1, respectively, in both reactors, indicating different reaction pathways for the two minerals. Gas-liquid mass transfer appears to be the limiting reaction step in columns much more than in tanks, and the degree of ammonia loss to air is significant. This initial test work indicates the feasibility of using ammonia leaching for this and similar materials as an alternative route to conventional smelting and refining before PGM recovery, but a number of technical challenges still need to be overcome.

Multi-element concentrations in plant parts and fluids of Malaysian nickel hyperaccumulator plants and some economic and ecological considerations.

Information about multi-elemental concentrations in different plant parts of tropical Ni hyperaccumulator species has the potential to provide insight into their unusual metabolism relative to a range of essential and non-essential elements, but this information is scant in the literature. As Ni hyperaccumulation, and possibly co-accumulation of other toxic elements, has been hypothesized to provide herbivore (insect) protection, there is a need to quantify a range of these elements in plant tissues and transport fluids to at least verify the possibility of this explanation. In this study, multiple elements were analyzed in a range of different plant parts and transport fluids from Ni hyperaccumulator species collected from Sabah (Malaysia). The results show preferential accumulation of Ni in leaves over woody parts, but the highest concentrations were found in the phloem tissue (up to 7.9 % in Rinorea bengalensis) and phloem sap (up to 16.9 % in Phyllanthus balgooyi), visible by a bright green coloration in the field fresh material. The amount of Ni contained in one mature R. bengalensis tree was calculated at 4.77 kg. The high Ni concentration in the flowers of Phyllanthus securinegoides could affect insect floral visitors and pollination. High concentrations of Ni in the seeds of this species also could supply the seedling with Ni and aid in herbivory protection during the first stages of development. Foliar Ca and Ni in P. cf. securinegoides and R. bengalensis are positively correlated. Low accumulation of Ca is desirable for phytomining but concentrations of Ca are high in most Ni hyperaccumulators examined, and this could have consequences for the economic viability of Ni extraction from bio ore if these species were to be used as 'metal crops'.

Evaluation of Cd(II) transport with imidazolium bromides bearing butyl and isobutyl groups as extractants from acidic iodide solutions by liquid–liquid solvent extraction

The aim of the paper is the selective extraction and stripping of Cd(II) from acidic iodide solutions containing Cd(II) and Ni(II) by liquid–liquid solvent extraction technique using synthesized and characterized imidazolium salts as carriers, which are 3-butyl-1-methyl-1H-imidazol-3-ium bromide (IM1), 1,3-dibutyl-1H-midazol-3-ium bromide (IM2), 3-isobutyl-1-methyl-1H-imidazol-3-ium bromide (IM3), 1,3-diisobutyl-1H-midazol-3-ium bromide (IM4), in dichloromethane. The important parameters affecting extraction and stripping behavior of Cd(II) were studied experimentally. Complex formation and its stoichiometric rate between IMs and CdI42− was explained with comparison of ATR-FTIR spectrums of pure and CdI42−(aq) loaded IMs and slope analysis. According to these evaluations, the adduct formation was confirmed as IM2CdI4(org). In the light of obtained results, the symmetric IMs substituting n-butyl group on nitrogen atoms have been determined as the best appropriate IMs to transport of Cd(II). Under optimum conditions, 99.24% of Cd(II) has been extracted from acidic iodide solution containing 500mg/L of Cd(II) and Ni(II). Ni(II) extraction percentages were observed as negligible throughout experiments. The extraction selectivity of Cd(II) over the other metal ion impurities has been identified in the order βCd/Ni>βCd/Co>βCd/Zn>βCdCu.

A Novel Viewpoint of Imidazolium Salts for Selective Extraction of Cobalt in the Presence of Nickel from Acidic Thiocyanate Solutions by Ionic-Liquid-Based Solvent-Extraction Technique

In this study, the selective extraction and stripping conditions of Co(II) from acidic thiocyanate solution containing Co(II) and Ni(II) by ionic-liquid-based solvent-extraction technique using symmetric and asymmetric imidazolium bromide salts substituting butyl and isobutyl groups were experimentally optimized. The molecular structure effect of imidazolium bromide salts (IMs) have been determined as main factor to extract Co(II). The executive parameters on stripping and extraction processes, such as IMs concentration, pH, thiocyanate concentration, stripping reagent type, and concentration, were experimentally investigated. Molecular variation of organometalic complex (adduct) consisting of IMs and Co-SCN, were illuminated by comparision of ATR-FTIR spectrums of pure and Co-SCN loaded IMs. Stoichiometric rates of the adduct was verified with slope analysis. In light of these examinations, Co(SCN)3− has been determined as prominent Co-SCN species in aqueous media. Symetric IMs were identified as more effective than asymmetric ones on selective separation of Co(II) from Ni(II). Under optimum conditions, 99.20% of Co(II) was extracted and 93.33% of Co(II) was recovered with higher separation factors especially in diluted solution, whereas, Ni(II) extractions were negligible. We have concluded that the separation power of this study is high in Co(II)/Ni(II) containing dilute solutions and it can be used in preconcentration purposes effectively.