Aliquat Research Articles

Model for Metal Extraction from Chloride Media with Basic Extractants: A Coordination Chemistry Approach

The metal extraction mechanism of basic extractants is typically described as an anion exchange process, but this mechanism does not correctly explain all observations. This paper introduces a novel model for the extraction of metals by basic extractants from chloride media supported by experimental data on methyltrioctylammonium chloride and Aliquat 336 chloride systems. This model relies on the hypothesis that the metal species least stabilized in the aqueous phase by hydration (i.e., the metal species with the lowest charge density) is extracted more efficiently than the more water stabilized species (i.e., species with higher charge densities). Once it is transferred to the organic phase, the extracted species can undergo further Lewis acid-base adduct formation reactions with the chloride anions available in the organic phase to form negatively charged chloro complexes, which than associate with the organic cations. Salting-out agents influence the extraction, most likely by decreasing the concentration of free water molecules, which destabilizes the metal complex in the aqueous phase. The evidence provided includes (1) the link between extraction and transition-metal speciation, (2) the trend in extraction efficiency as a function of the concentration of different salting-out agents, and (3) the behavior of HCl in the extraction system. The proposed extraction model better explains the experimental observations in comparison to the anion exchange model and allows the prediction of optimal conditions for metal extractions and separations a priori, by selecting the most suitable salting-out agent and its concentration.

Methyltrioctylammonium chloride mediated removal of lignin from sugarcane bagasse for themostable cellulase production

The present study was aimed to evaluate the Methyltrioctylammonium Chloride (IL) and Sodium hydroxide effect on sugarcane bagasse (SB) structure and its subsequent utilization to produce cellulase from a thermophilic bacterium Bacillus aestuarii UE25. The strain was isolated from a crocodile pond of Manghopir, Karachi. Ten different factors affecting IL pretreatment of SB and cellulase production by UE25 were evaluated by Plackett-Burman design and three significant factors were optimized by employing Box Behnken design. Under optimum conditions, the strain produced 118.4 IU mL−1 of EG and 75.01 IU mL−1 of BGL that corroborated well with the predicted values by the model. Scanning electron microscopy, gravimetric analysis, Fourier transform infrared spectroscopy and NMR of SB revealed removal of lignin, decrease in cellulose content and structural changes in the SB after pretreatment and fermentation. The data provide prospects of utilizing this IL in comparison to imidazolium based IL for pretreatment of biomass.

On the Selective Transport of Nutrients through Polymer Inclusion Membranes Based on Ionic Liquids

In the last few years, the use of ionic liquid-based membranes has gained importance in a wide variety of separation processes due to the unique properties of ionic liquids. The aim of this work is to analyze the transport of nutrients through polymer inclusion membranes based on different concentrations of methyltrioctylammonium chloride, in order to broaden the application range of these kinds of membranes. Calcium chloride (CaCl2) and sodium hydrogen phosphate (Na2HPO4) nutrients were used at the concentration of 1 g·L−1 in the feeding phase. The evolution of the concentration in the receiving phase over time (168 h) was monitored and the experimental data fitted to a diffusion-solution transport model. The results show very low permeation values for CaCl2. By contrast, in the case of Na2HPO4 the permeation values were higher and increase as the amount of ionic liquid in the membrane also increases. The surface of the membranes was characterized before and after being used in the separation process by scanning electron microscopy coupled to energy dispersive X-Ray spectroscopy (SEM–EDX) and elemental mapping analysis. The SEM–EDX images show that the polymer inclusion membranes studied are stable to aqueous solution contacting phases and therefore, they might be used for the selective transport of nutrients in separation processes.

Adsorption/Desorption Stability of TCMA-Modified Clay in Simulated Digestion Environment

The modified clay was used for organic compounds adsorption and removal. However, desorption of the organic molecules, used for clay modification, in the real internal digestion environment of the animals is the main concern. Therefore, in this study, the adsorption/desorption studies of tri-capryl methyl ammonium chloride (TCMA)-modified clay at different cation exchange capacity (CEC) were investigated either by washing or by exposure to electrolytic solutions. The results indicated that the TCMA adsorption reaches up to 3 times the CEC of this clay. Beyond the CEC, the adsorption is accomplished by hydrophobic interaction. It is also found that the washing of clay has no effect on desorption of TCMA. Furthermore, desorption studies with stomach electrolyte solutions showed no more than 2 mg/L desorption of TCMA at acidic and neutral pH values which indicates the suitability of the TCMA clay for mycotoxin removal.

Recoveries of Ru(III) and Co(II) by Solvent Extraction and Ion Exchange from Tungsten Carbide-Cobalt Scrap through a HCl Leaching Solution

The addition of ruthenium to tungsten carbide-cobalt hard metals improves their mechanical properties. Since ruthenium is a platinum group metal, the recovery of ruthenium together with cobalt from the scrap of hard metals is of great importance. In order to develop a recovery process of ruthenium and cobalt, separation experiments were performed from the synthetic HCl leaching solution of the scrap of hard metals. In this work, solvent extraction and ion exchange were employed to investigate the separation behavior of the two metal ions as a function of HCl concentration. Ru(III) was selectively extracted over Co(II) by Aliquat 336 (trioctyl methylammonium chloride) and Alamine 300 (tri-n-octyl amine) when HCl concentration was lower than 5 M. The highest separation factor between Ru(III) and Co(II) was obtained at 3 M HCl. The loaded Ru(III) was stripped from Aliquat 336 by dilute HCl solution. Only Ru(III) was loaded into the anion exchange resins employed in this work in the HCl concentration range from 1 to 9 M. The highest loading percentage of Ru(III) was obtained from 3 M HCl solution. The loading of Ru(III) into anion exchange resins followed Freundlich isotherm and the loading capacity of the resins were determined. The loaded Ru(III) was eluted by the mixture of HCl and thiourea. Compared to solvent extraction, ion exchange was found to be more efficient to separate Ru(III) and Co(II) from the HCl solution in terms of separation factor and the ease of operation.

Preconcentration and Determination of Chlorophenols in Wastewater with Dispersive Liquid–Liquid Microextraction Using Hydrophobic Deep Eutectic Solvents

Hydrophobic deep eutectic solvents (DESs) were synthesized and developed for the preconcentration of three chlorophenols from wastewater by dispersive liquid–liquid microextraction (DLLME). The analyte concentrations were determined by high-performance liquid chromatography (HPLC). The hydrophobic DESs were prepared with the combination of hydrogen bond donors of decanoic acid or octanoic acid with different hydrogen bond acceptors of quaternary ammonium salts of tetrabutylammonium chloride, tetraoctylammonium chloride, methyltrioctylammonium chloride, and tetraheptylammonium chloride). Following the study of the stability and characterization by Fourier transform infrared spectroscopy, the hydrophobic DESs were developed as extractants and employed for the removal of 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) from wastewater. Using hydrophobic DESs as the microextraction solvents, several key parameters were optimized, including the type and volume of the hydrophobic DES, pH, and time of the extraction procedure. Under the optimized conditions, good recoveries from 90.8% to 93.0% were obtained for the three chlorophenols. The limits of detection were less than 0.05 µg/mL with relative standard deviations between 1.8% and 3.1%. The method was applied for the isolation and determination of synthetic chlorophenols in wastewater.

Novel hydrophobic deep eutectic solvent for vortex assisted dispersive liquid-liquid micro-extraction of two auxins in water and fruit juice samples and determination by high performance liquid chromatography

A green, simple, sensitive, efficient and rapid method was developed based on application of a novel deep eutectic solvent in vortex-assisted dispersive liquid-liquid microextraction (VA-DES-DLLME) of two auxins (indole-3-acetic acid (IAA) and 1-naphthaleneacetic acid (NAA)) in water and fruit juice samples followed by high performance liquid chromatography determination. The novel hydrophobic deep eutectic solvent was readily prepared by mixing isoamyl alcohol as hydrogen bonding donor and trioctylmethylammonium chloride as hydrogen bonding acceptor at room temperature for 3 min. Affecting parameters on VA-DES-DLLME were investigated and optimized. Under the optimum conditions, good linearity (1.0–500 μg L−1, r2 ≥ 0.99) was obtained for the auxins. Limit of detection (LOD) was 0.2 and 0.3 μg L−1 for IAA and NAA, respectively. Moreover, repeatability (intra-day, n = 6) and reproducibility (inter-day, n = 3) of the method expressed as relative standard deviation (RSD) at 10 and 100 μg L−1 concentration levels were <8%. Finally, applicability of the developed method was evaluated by analyzing the auxins in water and fruit juice samples and satisfactory results were obtained (recovery ≥ 90%).

A Fast and Easy ATP-Based Approach Enables MIC Testing for Non-resuscitating VBNC Pathogens.

Many bacteria enter the viable but non-culturable (VBNC) state to maximize resources and increase their tolerance to harmful conditions to cope with environmental stress, which has been described for a plethora of important human and foodborne pathogens. VBNC pathogens can potentially present a serious risk to human health as they are invisible to routine microbiological culture-based methods. Of high importance is the increased tolerance to antibiotics or disinfectant measures while in the VBNC state. The greatest remaining challenge for such investigations is the lack of an appropriate, cost-effective multi-species screening method due to experimental constraints. In this study, we investigated if de novo ATP production of cells in the VBNC state is a suitable indicator for overall cell viability that can be utilized to determine the minimum ATP inhibitory concentration (MAIC) of antibiotics and other antimicrobials. To validate this approach, heat-stress time-kill experiments were performed with both culturable and VBNC cells. We developed a comprehensive experimental setup and demonstrated the applicability of this VBNC–MIC assay for testing the tolerance of 12 strains of 4 important bacterial species (Escherichia coli, Bacillus cereus, Pseudomonas aeruginosa, and Listeria monocytogenes) in the VBNC state to eight important antimicrobials including four different antibiotics. We confirmed that bacteria in the VBNC state were resistant to all tested antibiotics (ampicillin, imipenem, ciprofloxacin, and gentamicin) and additionally insensitive to disinfectants (benzalkonium chloride and trioctylmethylammonium chloride) and preservatives (bronopol and sodium azide). These data emphasize the need for further research regarding the characteristics of bacterial pathogens in the VBNC state and present the advantages and high-throughput capabilities of ATP determinations to investigate tolerance of VBNC pathogens to antimicrobials. The presented method should be helpful in order to identify appropriate countermeasures, treatments, or disinfectants when confronted with bacterial pathogens in the VBNC state.

First Report on a Solvent-Free Preparation of Polymer Inclusion Membranes with an Ionic Liquid.

A novel and environmentally-friendly procedure for the preparation of polymer inclusion membranes (PIMs) containing an ionic liquid is presented for the first time. Traditionally, PIMs are prepared by a solvent casting method with the use of harmful organic solvents. Here we report a new solvent-free procedure based on a thermal-compression technique which involve the melting of the components of the PIM and the application of a high pressure to the melted specimen to form a flat-sheet film. In our study, we have tested different polymers, such as two cellulose derivatives as well as two thermoplastic polymers, polyurethane (TPU) and poli ε-caprolactone (PCL). The ionic liquid (IL) trioctylmethylammonium chloride (Aliquat 336) has been used to produce PIMs with a fixed composition of 70% polymer–30% IL (w/w). Both TPU and PCL polymers provide successful membranes, which have been thoroughly characterized. PIMs based on the polymer PCL showed a high stability. To test whether the properties of the IL were affected by the preparation conditions, the extraction ability of Aliquat 336 was investigated for both PCL and TPU membranes in terms of Cr(VI) extraction. Satisfactory values (90% extraction) were obtained for both membranes tested, showing this novel procedure as a green alternative for the preparation of PIMs with ILs.

Effect of Ionic Liquid Surfactants on Coal Oxidation and Structure.

The effects of six ionic liquids with surfactant property (1-hydroxyethyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([HOEtMIm][NTf2]), 1-hydroxyethyl-3-methyl imidazolium tetrafluoroborate ([HOEtMIm][BF4]), 1-dodecyl-3- methyl imidazolium bromide ([C12MIm]Br), 1-tetradecyl-3- methyl imidazolium bromide ([C14MIm]Br), trioctyl methyl ammonium chloride ([N8,8,8,1])Cl, and tetraethyl ammonium chloride ([N2,2,2,2]Cl)) on the oxidation characteristics and functional groups of coal were studied by means of critical micelle concentration, surface tension, thermogravimetric analysis, temperature-programmed oxidation, and Fourier transform infrared spectroscopy (FTIR) measurements. The lower critical micelle concentration for the ionic liquids except the [N2,2,2,2]Cl suggests the favorable surface activity of these ionic liquids. The surface activities of [N8,8,8,1]Cl, [C14MIm]Br, [C12MIm]Br, and [HOEtMIm][NTf2] were high, while that of [N2,2,2,2]Cl was relatively lower. The thermal stabilities of [HOEtMIm][NTf2] and [HOEtMIm][BF4] were high, while those of [N8,8,8,1]Cl and [N2,2,2,2]Cl were lower. The oxidation activities of ionic liquid-mixed coals were weakened to different degrees except [N8,8,8,1]Cl-mixed coal, because of the poor thermal stability and decomposition of [N8,8,8,1]Cl accelerating the coal oxidation. The other five ionic liquids were suitable for inhibiting coal oxidation, particularly the [HOEtMIm][BF4] and [HOEtMIm][NTf2] with higher inhibition rate, longer inhibition time, and also better thermal stabilities. The activation energy results further confirmed such inhibition effect. The functional group results showed that treatment of ionic liquids on coal can change the contents of hydrogen bonds, aliphatic groups, and aromatic groups in coal. It was inferred that the [HOEtMIm][BF4], [HOEtMIm][NTf2], and [C14MIm]Br were more effectively to affect coal structure and decrease coal oxidation activity.

Polymer inclusion membranes based on CTA/PBAT blend containing Aliquat 336 as extractant for removal of Cr(VI): Efficiency, stability and selectivity

Cellulose triacetate (CTA) and poly(butylene adipate-co-terephthalate) (PBAT)-based polymer inclusion membranes (PIMs) containing ionic liquid (tricaprylmethylammonium chloride (Aliquat 336)) as the carrier extractant were obtained for the facilitated and selective transport of Cr(VI) ions. The composition of PIMs was optimized in terms of the CTA/PBAT ratio. The obtained membranes were investigated using different techniques in order to show the influence of the membrane composition and the ionic liquid presence on the PIM resulting properties. The infrared analysis confirmed the presence of the intermolecular interactions of the hydroxyl groups of CTA with the carboxyl groups of PBAT and of the negatively charged carboxyl groups of CTA with the positively charged ammonium groups of Aliquat 336. The water contact angle measurements highlighted that the Aliquat 336 and PBAT presence modified the membrane hydrophobic/hydrophilic character. Moreover, it was shown that PIM containing the equivalent content of CTA and PBAT (35/35 wt%/wt%) with 30 wt% of Aliquat 336 revealed the optimized composition and was used for the Cr(VI) ions transport measurements. It was found that this PIM transported >99% of Cr(VI) in only 6 h and accumulated <5% of Cr(VI) ions with a high initial flux. For the first time it is shown that the selective Cr(VI) transport through blend PIM with reduced extractant content and without plasticizer is more efficient compared to common PIMs. Besides, the stability of obtained blend PIMs was confirmed by carrying out continuous transport studies over a long period of time (>120 h).

Extraction of cobalt(ii) by methyltrioctylammonium chloride in nickel(ii)-containing chloride solution from spent lithium ion batteries.

Spent lithium batteries contain valuable metals such as cobalt, copper, nickel, lithium, etc. After pretreatment and recovery of copper, only cobalt, nickel and lithium were left in the acid solution. Since the chemical properties of cobalt and nickel are similar, separation of cobalt from a solution containing nickel is technically challenging. In this study, Co(ii) was separated from Ni(ii) by chelating Co(ii) with chlorine ions, Co(ii) was then extracted from the aforementioned chelating complexes by methyltrioctylammonium chloride (MTOAC). The effects of concentrations of chlorine ions in the aqueous phase ([Cl−]aq), MTOAC concentrations in organic phase ([MTOAC]org), ratios of organic phase to aqueous phase (O/A), and the initial aqueous pH on cobalt separation were studied. The results showed that [Cl−]aq had a significant impact on cobalt extraction efficiency with cobalt extraction efficiency increasing rapidly with the increase in [Cl−]aq. The effect of initial pH on cobalt extraction efficiency was not significant when it varied from 1 to 6. Under the condition of [Cl−]aq = 5.5 M, [MTOAC]org = 1.3 M, O/A = 1.5, and pH = 1.0, cobalt extraction efficiency reached the maximum of 98.23%, and nickel loss rate was only 0.86%. The stripping rate of cobalt from Co(ii)–MTOAC complexes using diluted hydrochloric acid was 99.95%. By XRD and XRF analysis, the recovered cobalt was in the form of cobalt chloride with the purity of cobalt produced reaching 97.7%. The mode of cobalt extraction was verified to be limited by chemical reaction and the kinetic equation for cobalt extraction was determined to be: R(Co) = 4.7 × 10−3[MTOAC](org)1.85[Co](aq)1.25.

A hydrophobic deep eutectic solvent based vortex-assisted liquid-liquid microextraction for the determination of formaldehyde from biological and indoor air samples by high performance liquid chromatography

Hydrophobic deep eutectic solvents (DESs) are a new class of green solvents, and their research and application are a brand new area. So far, only a few hydrophobic DESs have been reported as extraction solvents. In this paper, five kinds of hydrophobic DESs composed of trioctylmethylammonium chloride and hydroquinone, 4-phenylphenol or 4-cyanophenol are designed and prepared for the first time. Melting point / glass transition temperature and density are also determined for these DESs. Coupled with HPLC, these hydrophobic DESs have been used as extractants in vortex-assisted liquid-liquid microextraction for the selective enrichment and indirect determination of formaldehyde. The optimization of reaction and extraction conditions, such as pH value, reaction time and temperature, concentration of 2,4-dinitrophenylhydrazine, type and dosage of the extraction solvent, speed and time of vortex, salt addition and centrifugation time are investigated in detail. It is found that under the optimized experimental conditions, the calibration curve of this method is linear in the range of 1.0–200.0 μg L−1 with the linear correlation coefficient (r2) of 0.9994. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) are 0.2 μg L−1 and 1.0 μg L−1, and the intra-day and inter-day precision (RSD, n = 5) are 1.1% and 3.5%, respectively. The interference of some common coexisting ions and neutral molecules have been also tested. The proposed method has been successfully used for the determination of formaldehyde from biological and indoor air samples. The recovery of formaldehyde is in the range from 83.1% to 104.4%, and the relative standard deviation is lower than 5.9%. Furthermore, the analytical parameters of the proposed method have been compared with other extraction and microextraction methods.

Novel Aliquat-336 impregnated chitosan beads for the adsorptive removal of anionic azo dyes

In this study, novel Aliquat-336 impregnated chitosan conjugation beads (CS–AL) were synthesised through the reaction of amino groups of chitosan with tricaprylylmethylammonium chloride. The prepared CS-AL was characterised by XRD, FTIR, SEM, EDX and BET analyses. The FTIR analysis showed that the Aliquat-336 ionic liquid was successfully inserted into the chitosan beads structure. It was used as an efficient adsorbent for the fast removal of Methyl orange and Alizarin, as two anionic azo dye models. The optimum adsorbent dosage was 2 g/L with high adsorption behaviour in a wide pH range of 7–11. The adsorption kinetics of the studied dyes onto CS-AL was well described by the pseudo-second-order model. In addition, the adsorption equilibrium study showed that it was fitted by the Langmuir isotherm model. The CS-AL beads could be easily separated by filtration after the adsorption process. The adsorption property of prepared CS–AL conjugation beads suggested it as a novel adsorbent for wastewater treatment.

Adsorption of Bisphenol-A from aqueous solution using amberlite XAD-7 impregnated with aliquat 336: Batch, column, and design studies

Bisphenol-A (BPA) was removed from water solution using washed (WX7) and impregnated (IX7) Amberlite XAD-7 resin with Aliquat-336 (A336). 0.5 g (IX7-0.5) and 1 g (IX7-1) of A336 per g of WX7 were loaded on the resin. Characterization of prepared adsorbents was done by FTIR, FE-SEM, EDS, BET. Point of zero charge study was also conducted to find the point at which the surface of adsorbent became neutrally charged. Equilibrium and kinetic experiments in the batch mode were carried out to observe the influence of contact time, amount of adsorbent, the initial concentration of BPA, pH, temperature, and ionic strength of solution (NaCl and Na2SO4) on the adsorption. IX7-1 showed comparatively better removal efficiency than that of IX7-0.5 or WX7. 5 g L-1 was determined to be the optimum mass of adsorbent (WX7, IX7-0.5, and IX7-1). Equilibrium (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and kinetic (pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich) models were fitted to the experimental results. Used IX7-1 was regenerated up to 5 times, and showed almost the same removal and good reusability of impregnated resin even after 5th cycle. Studies in a fixed bed column were also done by changing the flow rate, the height of the bed, and initial BPA concentration to evaluate the performance of IX7-1. Models like Thomas, Adham Bohart, and BDST were used to predict the column behavior, and to estimate the parameters for the scale-up of the process. Finally, the economic analysis of prepared resin was done, and the cost of impregnated resin (IX7-1) was found to be $2.055/g.

A hydrophobic deep eutectic solvent mediated sol-gel coating of solid phase microextraction fiber for determination of toluene, ethylbenzene and o-xylene in water coupled with GC-FID

As a new type of green solvents, deep eutectic solvents (DESs) are attracting more and more attentions due to their unique properties and cheapness. However, most DESs reported previously were hydrophilic and thus limiting their applications in aqueous medium. In this study, a novel hydrophobic DES was prepared by mixing ethylparaben and methyl trioctyl ammonium chloride, and density, viscosity, and contact angle of the DES were determined to character its solvent characteristics. Then, this DES was used as an efficient additive of sol-gel sorbent coating of poly(dimethylsiloxane) (PDMS) fiber. It was found that the addition of hydrophobic DES could generate a lot of neat pores in the PDMS fiber surface, thus significantly improving the performance of PDMS fiber coating. The feasibility of PDMS-DES adopted for head space solid phase microextraction was evaluated by GC-FID for the extraction and determination of volatile organic compounds, such as toluene, ethylbenzene and o-xylene. Key parameters affecting the extraction efficiency were investigated systematically. Under optimal conditions, the linear range with PDMS-DES fiber lied between 10 and 1000 μg L−1, and the limit of detection (LOD) was in the range from 0.005 to 0.025 μg L−1. Compared with homemade PDMS fiber, the peak area of signal response for the PDMS-DES fiber was 3 times higher. At the same time, the LOD for the proposed method was much lower than the commercial 100 µm-PDMS fiber coating.

A hydrophobic deep eutectic solvent-based vortex-assisted dispersive liquid-liquid microextraction combined with HPLC for the determination of nitrite in water and biological samples.

In recent years, hydrophobic deep eutectic solvents as new generation of green solvents have attracted wide attention in liquid microextraction technique. In this article, four hydrophobic deep eutectic solvents composed of trioctylmethylammonium chloride and oleic acid were designed and prepared firstly. Combined with high-performance liquid chromatography, these deep eutectic solvents were used as an extraction solvent in vortex-assisted dispersive liquid-liquid microextraction for the selective enrichment and indirect determination of trace nitrite from real water and biological samples. This method is based on the diazotization-coupling reaction of nitrite with p-nitroaniline and diphenylamine in acidic water, and then the nitrite is quantified indirectly by measuring the obtained azo compounds. Some factors influencing the extraction efficiency, including the reaction and extraction conditions, were investigated. Under the optimized conditions, the method has a linear range of 1-300 μg/L with a correlation coefficient of 0.9924, limit of detection of 0.2 μg/L, limit of quantitation of 1 μg/L, intraday and interday relative standard deviations of 4.0 and 6.0%. This method was successfully applied in determination of nitrite from three environmental water and two biological samples with the recovery in the range of 90.5-115.2%. In addition, these results were well agreement with those obtained by the conventional Griess method.

Recovery of uranium and plutonium from pyrochemical salt matrix using supercritical fluid extraction

Pyrochemical reprocessing of spent nuclear fuel involves use of molten salts for the separation of actinides from fission products. Salt waste arising from this process contains residual actinides along with fission products. In the present study, extraction of residual uranium and plutonium from pyrochemical salt matrices was investigated using supercritical fluid extraction (SFE) technique. Supercritical carbon dioxide (SCCO2) containing various ligands was examined to recover actinides from salt matrix with minimum generation of secondary liquid waste. Influence of ligand, salt matrix, temperature, pressure, co-solvent and HNO3 concentration was examined for efficient recovery of actinides. Among the ligands employed in present study, SCCO2 containing trioctylmethylammonium chloride resulted in better recovery of actinides. The recovery of uranium from salt matrix was also demonstrated using semi-preparative scale SFE facility. This study is first of its kind for recovery of actinides from pyrochemical salts using SFE.

Extraction of Cr (VI) by pickering emulsion liquid membrane using amphiphilic silica nanowires (ASNWs) as a surfactant

Pickering emulsion is the replacement of surfactants with solid, often nano-sized particles. The particle-stabilized emulsions have good thermodynamic and kinetic stability. Pickering emulsion liquid membrane (PELM) was prepared using mahua oil as a diluent, aliquat 336 (Trioctyl methylammonium chloride) as a carrier and amphiphilic silica nanowires (ASNWs) (10–40 ml ethanol addition) as a surfactant. Sodium hydroxide (NaOH) was used as stripping phase in the concentration range from 0.1 to 0.5 M for the extraction of hexavalent chromium [Cr (VI)] from aqueous solution. The variety of edible and non-edible oils was investigated for the stability of water in oil emulsion. Factors that influence silica-stabilized Pickering emulsions are pH, agitation speed, stripping phase concentration, the volume ratio of membrane to stripping phase (M/S), initial feed concentration, treat ratio(feed to emulsion volume ratio) and surfactant concentration for better PELM stability. And also, the extraction efficiency of Cr (VI) was investigated using aliquat as a carrier. The physicochemical properties of ASNWs were studied using Scanning Electron Microscopy (SEM), Fourier Transforms Infrared Spectroscopy (FTIR) and Dynamic Light Scattering (DLS) techniques. At an optimum condition, 99.69% of Cr (VI) removal from aqueous solution was obtained.

Solvent Extraction of Rhodium from Chloride Solutions added Tin(II) with Amine Extractants

Chloride is one of the effective medium in which platinum group metals (PGMs) can be brought into a solution, thus chlorocomplexes are particularly important in the process chemistry of PGMs separations. Rh (III) chlorocomplexes are poorly extracted into organic solvents, which is due to the charge of the complex as well as those inert character in a solution, that is, formation of RhCl6-n(H2O)n(3-n) - (n=1-6) . The problem of solvent extraction of Rh from chloride solutions has not yet been solved and there is no effective industrial extractant for Rh. PGMs are traditionally separated from one another and the other metals by a complex series of selective precipitation techniques. These are generally inefficient in terms of the degree of separation achieved. Solvent extraction applied to refining process for PGMs offers several advantages over the traditional precipitation methods. Adding Sn (II) to a Rh (III) feed is a good procedure which can be used to make Rh react more easily to extraction, however, stripping of Rh from the loaded organic pahse is very difficult. In the present study, the extraction of Rh from hydrochloric acid solutions with tri-n-octylamine (TOA) and tri-octyl methyl ammonium chloride (TOMAC) were tested to clarify the effect of addition of Sn (II) on the extraction of Rh and stripping of Rh.