Selective separation of copper with Lix 864 in a hollow fiber module

The transfer and separation of Cu(II), Co(II), Ni(II) and Zn(II) ions across a hollow fiber supported liquid membrane containing LIX 864 as the mobile carrier dissolved in kerosene solvent has been investigated. The flux and selectivity for copper has been studied as a function of the feed flow, the carrier concentration in the liquid membrane and the extraction solution acidity. A maximum copper recovery at 30% of LIX (v/v) in the diluent was obtained. The permeation experiments showed that at pH 2 in the extraction solution a highly selective separation of Cu over the other cations can be achieved. Increasing the acidity of the extraction solution copper selectivity decrease and the grade of recuperation sequence is Cu>Co>Ni>Zn. These results suggest that in selected situations, this membrane system can be competitive with the conventional liquid-liquid extraction process, in particular in leaching solutions with low metal concentration.     

A Study on the extraction of uranium(VI) from sulphate leach liquor using LIX63

The sulphate leach liquor obtained from the sulphuric acid leaching process of Egyptian monazite was treated using solvent extraction to recover U(VI) by LIX63. The influence of various basic variables such as pH, concentration of LIX63, temperature, different stripping agent, phase ratio and diluents was examined. Using 10% LIX63 with the aqueous solution at equilibrium pH 5.5 and a phase ratio A/O?=?1/1, a four-stage McCabe-Thiele plot was constructed, which showed 85.57% of U(VI) extraction. The thermodynamic data showed that the extraction process is exothermic with enthalpy change ΔH?=???43.866?kJ/mol, the stripping of U(VI) was quantitative using 4?M HNO₃. The stable complex UO₂(HSO₄)R_org formed during extraction which supports the cation exchange mechanism was confirmed by FTIR spectral analysis. Uranium cake was finally obtained from the strip solution by the addition of hydrogen peroxide and ammonium hydroxide as precipitating agents, and a workable flowsheet was then formulated.     

Solvent extraction of Ni(II) from sulfate solutions with LIX 84I: flow-sheet for the separation of Cu(II), Ni(II) and Zn(II).

This paper reports on solvent-extraction studies of Ni(II) from sulfate solutions with LIX 84I (2-hydroxy-5-nonylacetophenoneoxime) as the extractant. The extraction of metal depends on the equilibrium pH of the aqueous phase and the extractant concentration. The transfer of metal follows a cation exchange-type mechanism: Ni2+ + 2HA --> NiA2 + 2H+. Extraction varies with the nature of the diluents. Temperature has no effect on the extraction of metal. The extraction behavior of associated metals clearly demonstrates the application of LIX 84I as the extractant for the separation of Cu(II), Ni(II) and Zn(II). Based on the results, a flow sheet of the process was developed.     

Extraction of uranium and plutonium from oxalate bearing solutions using phosphonic acid: Solvent extraction, extraction chromatography and infrared studies

Solvent extraction and extraction chromatography studies of uranium and plutonium from oxalate supernatant solutions were carried out using 2-ethyl hexyl-2-ethyl hexyl phosphonic acid (PC88A). Based on the distribution data, it was inferred that both the uranium and plutonium could be recovered satisfactorily from such a solution. These studies were found to be useful in optimising the appropriate concentration of PC88A, HNO₃, oxalic acid and temperature to recover more than 90% of plutonium from the large volumes of oxalate bearing waste solutions. Spectral characteristics of the extractant and its complexing behavior with U(VI) was also studied using IR & FTIR.     

Determination of cyanides in electroplating solutions as Ni(CN)42– and analysis by capillary electrophoresis

A CE method was developed for the determination of total (free and weakly bound) cyanide in electroplating solutions based on the use of a cationic surfactant (TTAB) and complexation with Ni(II)-NH₃ solutions to Ni(CN)₄ ^2–. Both direct complexation and cyanide distillation combined with complexation were tested. Under optimized conditions, this method is time-saving compared to standard methods. Total cyanide determined by CE had detection limits (with respect to the initial sample concentration) of 0.5 μg/mL for direct complexation and 50 ng/mL for distillation combined with complexation. Total cyanide and cyanide not amenable by chlorination (CNAC) were determined in real samples from spent electroplating baths.     

The role of the solvent in equilibrium and kinetic aspects of metal chelate extractions

Equilibria and kinetics for the extraction of nickel(II) and copper(II) by 2-hydroxy-5-nonylbenzophenone oxime (LIX 65N) in seven organic solvent systems were studied in order to test the validity of several hypotheses related to the role of the solvent in equilibrium and kinetic aspects of metal chelate extraction. For the nickel—LIX 65N system, the extraction constant is essentially independent of the solvent system, whereas for the copper—LIX 65N system, the extraction constant is not independent of solvent; this indicates that while the stoichiometry of the nickel chelate remains the same in all solvents, that of copper does not. The observed rate constant for the nickel—LIX 65N extraction was found to vary inversely with the LIX 65N distribution constant as predicted from a mechanism involving slow formation of the 1:1 complex. The observed reaction rate constant for the copper—LIX 65N varied inversely with the square of the distribution constant, also in accordance with the previously postulated mechanism of the slow formation of the 2:1 copper complex. This study, therefore, unequivocally eliminates the interfacial mechanism in favor of the homogeneous chemical reaction mechanism for the extraction of metal ions by LIX 65N, as well as by other similar high-molecular-weight extractants.     

Determination of cyanides in electroplating solutions as Ni(CN)42– and analysis by capillary electrophoresis

A CE method was developed for the determination of total (free and weakly bound) cyanide in electroplating solutions based on the use of a cationic surfactant (TTAB) and complexation with Ni(II)-NH₃ solutions to Ni(CN)₄ ^2–. Both direct complexation and cyanide distillation combined with complexation were tested. Under optimized conditions, this method is time-saving compared to standard methods. Total cyanide determined by CE had detection limits (with respect to the initial sample concentration) of 0.5 μg/mL for direct complexation and 50 ng/mL for distillation combined with complexation. Total cyanide and cyanide not amenable by chlorination (CNAC) were determined in real samples from spent electroplating baths. Received: 5 February 1998 / Revised: 26 July 1998 / Accepted: 1 August 1998     

Recovery of uranium by polyurethane foam impregnated with 5,8-diethyl-7-hydroxy-6-dodecanone oxime

Sorption of uranium(VI) has been inbestigated using an open-cell plyurethane foam impregnated with 5,8-diethyl-7-hydroxy-6-dodecanone oxime (LIX 63). Above pH 4.5 more than 99% of uranium is sorbed onto the LIX 63 impregnated foam, and uranium can be desorbed with a dilute acid from the foam. The sorption capacity for uranium increases linearly with increasing concentration of impregnated LIX 63. Quantitative removal of uranium from salt solutions was accomplished.     

Preparation and solvent extraction of nickel complex of O,O'-dinonyldithiophosphate and its application to spectrophotometric determination of nickel in sediment samples

Nickel complex of O, O'-dinonyldithiophosphoric acid was prepared and characterised. Solvent extraction of nickel dinonyldithiophosphate [Ni(DNDTP)2] from acidic aqueous solutions into different organic phases was investigated and concentration of nickel was determined spectrophotometrically. A simple and selective spectrophotometric method was developed and applied to sediment samples.     

Studies on extraction of chromium (VI) from acidic solutions containing various metal ions by emulsion liquid membrane using Alamine 336 as extractant

The extraction of chromium (VI) ions from acidic solutions containing various metal ions by emulsion liquid membrane (ELM) was studied. Liquid membrane consists of a diluent, a surfactant, and an extractant. 0.5 M ammonium carbonate solution was used as stripping solution. Effects of acid concentration in feed solution, type and concentration of stripping solution, mixing speed, surfactant concentration, phase ratio and the influence of membrane characteristics were studied and optimum conditions were determined. Under the optimum conditions, extraction of chromium (VI) was tested and it was possible to selectively extract 99% of chromium from the acidic feed solution. This study also examined the effect of extractant concentration and acid type in the feed solution on the extraction of Cr (VI) ions and almost all of Cr (VI) from the acidic feed solution containing 500 mg/L from each of Co (II), Ni (II), Cd (II), Zn (II), and Cu (II) ions, and 100–500 mg/L Cr (VI) was extracted within 5–10 min.     

Deposition yield of nickel in alkaline bath for synthesizing Ni-63 beta source

Nickel (Ni) and Ni-63 films were synthesized by direct current electrodeposition. The composition of an alkaline electrolyte was ammonium citrate (25 g/l), hydrazine hydrate (25 g/l), and ammonium solution (25%) for adjusting the pH to 10. The acidic electrolyte at pH 4 was prepared using a full chloride bath. A higher deposition yield (92%) of the citrate electrolyte (pH 10) than 73% of acidic electrolyte (pH4) was measured using ICP. The deposition yield of radioactive Ni-63 in a citrate bath was also same as natural Ni in alkaline electrolyte. A newly prepared alkaline bath for the deposition of Ni-63 can be a solution for an extremely decreased radio-activity in the waste after plating.     

Electrochemical deposition of nickel from aqueous electrolytic baths prepared by dissolution of metallic powder

A new method of preparation of aqueous electrolyte baths for electrochemical deposition of nickel targets for medical accelerators is presented. It starts with fast dissolution of metallic Ni powder in a HNO₃-free solvent. Such obtained raw solution does not require additional treatment aimed to removal nitrates, such as the acid evaporation and Ni salt precipitation-dissolution. It is used directly for preparation of the nickel plating baths after dilution with water, setting up pH value and after possible addition of H₃BO₃. The pH of the baths ranges from alkaline to acidic. Deposition of 95% of ca. 50 mg of Ni dissolved in the bath takes ca. 3.5 h for the alkaline electrolyte while for the acidic solution it requires ca. 7 h. The Ni deposits obtained from the acidic bath are physically and chemically more stable and possess smoother and crack-free surfaces as compared to the coatings deposited from the alkaline bath. A method of estimation of concentration of H₂O₂ in the electrolytic bath is also proposed.

     

Process analysis of electroless nickel deposition baths using optical spectroscopies

Summary The analytical techniques of Vis-spectrophotometry and FTIR spectroscopy have been applied to the quantitative determination of important plating bath constituents of an electroless nickel-phosphorus electrolyte under realistic bath operation conditions. In combination with multivariate calibration methods (partial-least squares (PLS)- and principal component (PCR) regression) Ni²⁺, the reducing agent H₂PO ₂ ^– and its oxidation product HPO ₃ ^– could be directly determined even in the presence of other bath constituents like malic, lactic and adipic acids. For Ni²⁺, absorbance spectra in the 500–900 nm wavelength range were used to develop a PLS calibration model that allows to compensate matrix influences on the Ni²⁺ spectrum. PLS regression was carried out in the concentration range 0.5–6 g l^–1 Ni²⁺ with independently varying bath parameters (concentration of other bath constituents, pH and temperature). Evaluation of the model by predicting the concentrations of test samples which had been drawn from real process solutions of a Ni plating bath yielded a root-mean-squared error of 0.06 g l^–1. The metal concentration of the nickel electrolyte in a compact electroplating unit was monitored in-line by measuring spectra by means of a Vis-spectrometer adapted to the process via quartz glass fiber optical cables of 50 m length. A comparison of the in-line data with potentiometric off-line reference analyses showed good agreement of both data sets with a root mean-squared error of 0.15 g l^–1. The potential of FTIR spectroscopy for process analysis of plating bath solutions could be demonstrated by measuring off-line the concentrations of H₂PO ₂ ^– and HPO ₃ ^– . For these two components calibration samples containing all other main bath constituents were used to set up a PCR calibration model with IR spectra measured in the range from 850 to 1800 cm^–1 with an ATR trough technique. The data showed — within the error of the method of about 10% — generally a good accordance with the stoichiometry of the Ni²⁺/H₂PO ₂ ^– reduction process. The correlation of both parameters which was confirmed in these experiments could allow effective bath control with minimum analytical instrumentation, e.g. only a Vis-spectrophotometer.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Solvent extraction of metals using LIX26 extractant

Solvent extraction of some selected metals from an aqueous buffered solution by LIX26 extractant has been studied. The pH_1/2 values (at which 50% of metal ion is extracted) for extracting different metals by 1 v/v% LIX26 extractant in methyl isobutyl ketone have been obtained. The order of extraction of metals by LIX26 extractant as a function of pH_1/2 value is Pd(II)<Cu(II)<Sb(III)<Fe(II)<Co(II)<Zn(II)<Ni(II) <Pb(II)<Mn(II)<Cd(II).     

Toxicity assessment of nickel using Aspergillus niger and its removal from an industrial effluent

Chemical analysis of electroplating effluent revealed the presence of very high concentrations of nickel (393 ppm) in the effluent. Bioassay was carried out to test the toxicity of nickel chloride to Aspergillus niger. In contrast to 50% conidial inhibition at 1.7 mM nickel, hyphal extension was affected even at a lower concentration (0.4 mM), suggesting that hyphae are more sensitive than conidia to nickel. An increase in nickel concentration resulted in a proportionate decrease in the hyphal extension. Nickel (II)-resistant mutants of A. niger M1, M2, and M3, were obtained using direct selection, stepwise adaptation, and ultraviolet mutation techniques. Biosorption of Ni (II) by the mutant M3 was 50% more than that of its parent strain.     

Biosorption of Ni(II) from electroplating wastewater by modified (Eriobotrya japonica) loquat bark

Biosorption of nickel ions from aqueous solutions by modified loquat bark waste (MLB) has been investigated in a batch biosorption process. The biosorbent MLB was characterized by FTIR analysis. The extent of biosorption of Ni(II) ions was found to be dependent on solution pH, initial nickel ions concentration, biosorbent dose, contact time, and temperature. The experimental equilibrium biosorption data were analyzed by three widely used two-parameters Langmuir, Temkin and Freundlich isotherm models. Langmuir and Temkin isotherm models provided a better fit with the experimental data than Freundlich isotherm model by high correlation coefficients R². The maximum adsorption capacity was 27.548 mg/g of Ni(II) ions onto MLB. The thermodynamic analysis indicated that the biosorption behavior of nickel ions onto MLB biosorbent was an endothermic process, resulting in higher biosorption capacities at higher temperatures. The negative values of ΔG° (−5.84 kJ/mol) and positive values of ΔH° (13.33 kJ/mol) revealed that the biosorption process was spontaneous and endothermic. Kinetic studies showed that pseudo-second order described well the biosorption experimental data. The modified loquat bark (MLB) was successfully used for the biosorption of nickel ions from synthetic and industrial electroplating effluents.     

Studies on the applicability of artificial neural network (ANN) in emulsion liquid membranes

An artificial neural network (ANN) model of emulsion liquid membrane (ELM) process is proposed in the present study which is able to predict solute concentration in feed during extraction operation and ultimate % extraction at different initial solute concentration in feed phase, internal reagent concentration, treat ratio, volume fraction of internal aqueous phase in emulsion and time. Because of the complexity in generalization of the phenomenon of ELM process by any mathematical model, the neural network proves to be a very promising method for the purpose of process simulation. The network uses the back-propagation algorithm (BPA) for evaluating the connection strengths representing the correlations between inputs (initial solute concentration in feed phase, internal reagent concentration, treat ratio, volume fraction of internal aqueous phase in emulsion and time) and outputs (solute concentration in feed during extraction operation and % extraction). The network employed in the present study uses five input nodes corresponding to the operating variables and two output nodes corresponding to the measurement of the performance of the network (solute concentration in feed during extraction and % extraction). Batch experiments are performed for separation of nickel(II) from aqueous sulphate solution of initial concentration in the 200–100 mg/l ranges. The network employed in the present study uses two hidden layers of optimum number of nodes being thirty and twenty. A leaning rate of 0.3 and momentum factor of 0.4 is used. The model predicted results in good agreement with the experimental data and the average deviations for all the cases are found to be well within ±10%.     

LIX 84 as an extractant for throium(IV), uranium(VI) and molybdenum(VI)

The extraction order of Th(IV), U(VI) and Mo(VI) based on pH_0.5 values is Mo(VI)>U(VI)>Th(IV). Quantitative extraction has been observed for U(VI) by mixture of 10% (v/v) LIX 84 and 0.1M dibenzoylmethane at pH 4.2 and by mixture of 10% LIX 84 and 0.05M HTTA in the pH range 5.5–7.3 and for Mo(VI) by 10% LIX 84 from chloride media at pH 1.5. The order of extraction of Mo(VI) from 1N acid solutions is HCl>H₂SO₄>HNO₃>HClO₄ and extraction decreases very rapidly with increase in the concentration of HCl as compared to that from H₂SO₄, HNO₃ and HClO₄ acid solutions. The diluents C₆H₆, CCl₄ and CHCl₂ are found to be superior ton-butyl alcohol and isoamyl alcohol for extraction of Mo(VI). Influence of concentration of different anions on the extraction of U(VI) and Mo(VI) has been studied. Very little extraction has been observed in case of Th(IV) by LIX 84 or its mixtures with other chelating extractants or neutral donors.     

Separation and concentration of cobalt from ammoniacal solutions containing cobalt and nickel by emulsion liquid membranes using 5,7-dibromo-8-hydroxyquinoline (DBHQ)

The separation and concentration of cobalt from ammoniacal solutions containing nickel and cobalt by an emulsion liquid membranes (ELMs) using 5,7-dibromo-8-hydroxyquinoline as extractant has been presented. Membrane solution consists of a diluent (kerosene), a surfactant (Span 80), a modifier (tributylphosphate), and an extractant (DBHQ). Very dilute sulphuric solution containing EDTA as complexing agent, buffered at pH 5.0, has been used as a stripping solution. pH of ammoniacal feed solution containing cobalt and nickel was adjusted to 9.0 with hydrochloric acid. The important variables governing the permeation of cobalt have been studied. These variables are membrane composition, pH of the feed solution, cobalt and nickel concentrations of the feed solution, mixing speed, surfactant concentration, extractant concentration, EDTA concentration and pH of the stripping solution, and phase ratio. After the optimum conditions had been determined, it was possible to selectively extract 99.0% of cobalt from ammoniacal feed solution containing Co²⁺ and Ni²⁺ ions. The separation factors of cobalt with respect to nickel, based on initial feed concentration, have experimentally found to be of as high as 247.5 for about equimolar Co–Ni feed solutions.     

Preparation and Characterization of Nanostructured Ni-TiN Composite Films

Ni-TiN nanocomposite films were produced from a Ni plating bath containing TiN nanopar-ticles by using dc electroplating method. The structure and surface morphology of Ni-TiN composite coatings were analyzed by atom force microscope, X-ray diffraction, and trans-mission electron microscopy. Meanwhile, the anti-corrosion properties, hardness and ther-mostability of Ni-TiN nanocomposite films were also investigated and compared with the traditional polycrystalline Ni coatings. The results show that, compared with the tradi-tional polycrystalline Ni film, Ni-TiN nanocomposite coatings display much better corrosion resistance, higher film hardness, and thermal stability. In addition, the hardness of Ni-TiN nanocomposite coatings decreases slightly with the increase of electroplating current density,which may be due to the synergism of hydrogen evolution and faster nucleation/growth rate of nickel crystallites.