Separation of Mercury(II) as Chloride from Zinc(II), Cadmium(II), Gold(III), and Thallium(III) by Extraction in High-Molecular-Weight Amines

Abstract

The extraction behavior of Zn(II), Cd(II), Hg(II), Au(III), and Tl(III) has been studied at different HCl molarities in some commercially available liquid anion exchangers. The effect of such variables as the type of amine, molarity of HCl, amine concentration, and organic diluent on extraction has been explored to suggest the best conditions of separation of Hg(II) from Zn(II), Cd(II), Au(III), and Tl(III).     

Ion-Exchange Behavior of Mercury(II) in Mixed Solvents: Separation from Zinc(ll), Cadmium(ll), Gold(lll), and Thallium(lll)

Abstract

Distribution coefficients of Zn(II), Cd(II), Au(III), Hg(II), T1(I), and Tl(III) between cation- and anion-exchangers Amberlite IR-120 and Amberlite IR-400, and aqueous solutions containing nitric or hydrochloric acid and organic solvents have been determined. The organic solvents were methanol, acetone, and tetrahydrofuran. The separation of Hg(II) from Zn(II), Cd(II), Au(III), and Tl(III) has been proposed in mixed solvents with high separation factors. Some of these separations have been actually performed using column method.     

Adsorption of Mercury(II), Lead(II), Cadmium(II) and Zinc(II) from Aqueous Solutions using Mercapto‐Modified Silica Particles

This article presents a novel systematic approach to the fabrication of highly functionalized, silica (SiO₂) nanoparticles used for the adsorption of heavy‐metal ions (Hg²⁺, Pb²⁺, Cd²⁺, Zn²⁺). Almost monodispersed silica (SiO₂) nanoparticles with narrow particle size distributions of around 85 ± 5 nm were formed using the Stöber process. The prepared SiO₂ nanoparticles were successfully surface‐treated during a one‐step procedure by the covalent attachment of mercaptopropyl groups onto the surfaces of the SiO₂ nanoparticles. A FTIR spectra analysis confirmed that the binding of the mercaptosilane molecules onto the surface of the silica nanoparticles mediated the Si–O–Si and –SH vibrations. TEM/EDXS micrographs indicated the almost monodispersed and spherical morphology of the prepared product with strong signals of Si and S, thus implying that the coating procedure involving the mercapto groups onto the silica surface had been successfully accomplished. The final results for the heavy‐metal (Hg²⁺, Pb²⁺, Cd²⁺, Zn²⁺) adsorption showed the strongest affinity within the following sequence Hg²⁺ (99.9%) > Pb²⁺ (55.9%) > Cd²⁺ (50.2%) > Zn²⁺ (4%). Adsorption equilibrium was achieved after 1 h for all the analyzed samples.     

Adsorption Thermodynamics and Kinetics of Mercury (II), Cadmium (II) and Lead (II) on Lignite

This study examines the adsorption thermodynamics and kinetics of heavy metal ions [(Hg (II), Cd (II), Pb (II)] on a demineralized lignite coal. The study also investigates the effects of process parameters like contact time, pH, concentration of metal ion, temperature and adsorbent mass on the extent of metal-ion adsorption from solution.The results of the kinetic studies show that the adsorption reaction is first order with respect to the metal cation solution concentration, with activation energies of 4.9, 8.2 and 9.1 kJ mol^–1 for Hg (II), Cd (II) and Pb (II), respectively. These low activation energy values indicate that the adsorption reaction is diffusion-controlled. The results of the thermodynamic investigations indicate that the adsorption reactions are spontaneous (ΔG°< 0), slightly exothermic (ΔH°< 0) and irreversible (ΔS°> 0).The results of the study further show that the adsorption process is pH, adsorbent mass and metal-ion concentration dependent. Adsorption increases with increase in these variables. Temperature has only a marginal effect on adsorption. The reasons for these observations have been suggested.     

Cobalt(II), Zinc(II) and Cadmium(II)-Squarate Complexes with N-Methylimidazole

Three M(II)-squarate complexes, [Co(sq)(H₂O)(Nmim)₄] (1), [Zn(μ_1,3-sq)(H₂O)₂ (Nmim)₂] _n (2) and [Cd(μ_1,3-sq)(H₂O)₂(Nmim)₂] _n (3) (sq = squarate, Nmim = N-methylimidazole) have been synthesized and characterized by elemental, spectral (IR and UV–Vis.) and thermal analyses. The molecular structures of the complexes have been investigated by single crystal X-ray diffraction technique. The squarate ligand acts as two different coordination modes as a monodentate (in 1) and bis(monodentate) (O ^1– O ³ ) bridging ligand (in 2, 3). The Co(II) atom has a distorted octahedral geometry with the basal plane comprised of three nitrogen atoms of Nmim ligands and a oxygen atom of squarate ligand. The axial position is occupied by a nitrogen atom of Nmim and one aqua ligand. The crystallographic analysis reveals that the crystal structures of 2 and 3 are one-dimensional linear chain polymers along the c and b axis, respectively. The configuration around each metal(II) ions are distorted octahedral geometry with two nitrogen atoms of trans-Nmim, two aqua ligands and two oxygen atoms of squarate-O¹,O³ ligand. These chains are held together by the C–H···π, π···π and hydrogen-bonding interactions, forming three-dimensional network.     

Foam Separation of Mercury(II) and Cadmium(II) from Aqueous Systems

Abstract

Mercury(II) and cadmium(II) were separated from aqueous systems by a number of batch-type precipitate flotation and adsorbing colloid flotation techniques. HgS, CdS, and Cd(OH)₂ were removed by precipitate flotation; Fe(OH)₃, Al(OH)₃, FeS, and CuS were used as adsorbing colloids. Sodium lauryl sulfate and hexadecyltrimethylammonium bromide (HTA) were used as collectors. Dependence of separation efficiency on pH and ionic strength was investigated. Floc foam flotation of both metals with CuS and HTA was found to be quite effective, resulting in residual Hg(II) levels as low as 5 ppb and residual Cd(II) levels as low as 20 ppb. Floc foam flotation of Cd(II) with FeS and HTA yielded residual Cd(II) levels as low as 10 ppb.     

Rapid Solvent Extraction of Indium(III) and Its Separation from Gallium(III) and Aluminum(III)

Abstract

Mesityl oxide (4-methyl-3-pentene-2-one) has been used extensively for the solvent extraction separation of several transition elements (l). In the present communication, solvent extraction behavior of indium (III) toward mesityl oxide as a function of HCl or HBr concentrations has been studied and a simple and rapid method for the solvent extraction separation of gallium, indium, and aluminum has been proposed.     

Solvent Extraction Separation of Chromium(VI), Iron(III), Cobalt(II), and Nickel(II) with Di-n-pentyl Sulfoxide

Abstract

Di-n-pentyl sulfoxide (DPSO) was employed for the solvent extraction separation of some transition metals from hydrochloric acid medium. It was found that chromium(VI) gets extracted at low acid concentrations (3 to 4.5 M), and iron(III) and cobalt(II) only above 5 M HCl. Nickel was not extracted at any of the test conditions. These transition metals were separated from one another by suitable choice of the extraction conditions.     

Mutual Influence of Iron(III) and Gold(III) as Macroconstituents in the Extraction Systems Forming Three Liquid Phases

Abstract

The extraction of a mixture of iron(III) and goId(III) by either pure or diluted (benzene as diluent) diisopropyl ether (IPE) from aqueous solutions of hydrochloric acid at 20°C was investigated. The dependence of metal extraction on the initial concentration of hydrochloric acid, iron(III), and IPE was studied under conditions of third phase formation. It was found that under certain conditions, gold(III) coextracted with iron(IH).     

Recovery and Separation of Lanthanum(III), Aluminum(III), Cobalt(II), and Nickel(II) from Misch Metal by Solvent Extraction Using Bis(2-ethylhexyl) phosphinic Acid

Abstract

This paper describes use of bis(2-ethylhexyl) phosphinic acid as a reagent for extraction and mutual separation of lanthanum(III), aluminum(II), cobalt(II), and nickel(II) in 1.0 mol/L sodium nitrate. The extraction and stripping behavior of the four metal ions has been investigated using the extractant in Solvesso #150 as a diluent. The mutual separation and recovery of the metal ions from their mixtures has been tested by multistage extraction with a conventional separator funnel. A set of separation schemes has also been proposed for a continuous countercurrent multistage extraction which is comprised of ten extraction stages, four scrubbing stages, and seven stripping stages. Lanthanum(III) and aluminum(III) are coextracted but separated by selective stripping into different concentrations of hydrochloric acid. Cobalt(II) can be extracted with the nickel(II)-preloaded extractant solution, whereas nickel(II) remains in the aqueous phase. The successful separation of these metal ions from a misch metal-simulated sample is presented.     

Solvent-Extraction Behavior of Cobalt(II), Nickel(II), Copper(II), and Palladium(II) with Tri-n-butylphosphate

Abstract

A systematic study of the extraction behavior of cobalt(II), nickel(II), copper(II), and palladium(II) with TBP from thiocyanate system in various ranges of acid concentrations has been performed. The thiocyanate medium leads to enhanced extractions in all these cases compared to those in the previously used chloride medium. For palladium, the chloride and nitrate systems have been critically examined. Sixty-two per cent extraction occurs from 4 M hydrochloric acid using 100% TBP in a single run and the extraction becomes quantitative (>99%) after four successive equilibrations. A simpler method has been proposed for rapid extraction of palladium(II) as the thiocyanate complex. Quantitative extraction occurs in the presence of 1.2% thiocyanate solution from 0.5 to 2 M hydrochloric acid (initial) up to pH 8.0. The extractable species of cobalt(II), nickel(II), copper(II), and palladium(II) from thiocyanate medium are probably similar and of the type [M(CNS)₄]^2? [K·TBP·3H₂O]₂ ⁺ (buffer solution) and [M(CNS)₄]^2? [H·TBP·3H₂O]⁺ ₂ (acid solution). A simple extraction scheme has been worked out for the separation of palladium(II) from iron(III), cobalt(II), nickel, manganese(II), copper(II), and platinum.     

Extraction and Preconcentration of Mercury(II) from Aqueous Solutions

Abstract

The extraction/preconcentration of mercury(II) from aqueous media using diphenyl-2-pyridylmethane (DPPM) in benzene has been studied. The factors influencing the extraction are optimized. An extractive preconcentration procedure has been proposed on the basis of its quantitative extraction in a single equilibration from 1 M hydrochloric acid solution containing 0.02 M potassium thiocyanate. Extracted mercury can be stripped almost completely into 10 M aqueous solutions of hydrochloric or perchloric acid. A mechanism has been proposed, and the extractable species is assumed to be HgCl_2—n (SCN) _n (DPPM)₂, where n = 1,2. Aqueous to organic volume ratios up to 100:1 can be used without loss of extraction efficiency, and the procedure can effectively be used in water pollution abatement studies.     

Selective Transport of Copper(I,II), Cadmium(II), and Zinc(II) Ions through a Supported Liquid Membrane Containing Bathocuproine,Neocuproine, or Bathophenanthroline

Abstract

Some selective transport systems for heavy metallic ions through a supported liquid membrane (SLM) containing a 2,2′-dipyridyl derivative ligand, 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline (bathocuproine), 2,9-dimethyl-1,10-phenanthro-line (neocuproine), or 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline), were investigated. The transport of copper(I, II), cadmium(II), zinc(II), lead(II), and cobalt(II) ions was accomplished with a halogen ion such as chloride, bromide, or iodide ion as a pairing ion species for any SLM. The ranking of the permeability of the metallic ions was Cu^+,2+, Zn²⁺, Cd²⁺ ? Pb²⁺, Co²⁺. When the oxidation-reduction potential gradient was used as a driving force for metallic ions, the transport of Cu⁺ ion was higher than those of Cd²⁺ and Zn²⁺ ions for any SLM containing bathocuproine, neocuproine, or bathophenanthroline. On the other hand, in the transport system which used the concentration gradient of pairing ion species, the permeability of the Cu²⁺ ion decreased whereas that of the Cd²⁺ ion increased. Moreover, it was found that the different selectivity for the transport of metallic ions is produced by using various pairing ion species.     

Indium(III)-hexacyanoferrate(III, II) as an inorganic material analogous to redox polymers for modification of electrode surfaces

Polynuclear indium(III)-hexacyanoferrate(III, II) films were prepared electrochemically on a glassy carbon substrate. The deposition was performed by cycling the potential between 0.85 and 0.0 V vs sce in a fresh 0.5 mM InCl₃/0.5 mM K₃Fe(CN)₆/0.5 M KCl mixture at pH 2. During the negative scans, the cationic In³⁺ species interact with the simultaneously generated anionic Fe(CN)⁴⁻₆ to yield sparingly soluble mixed-valent coatings on the electrode surfaces. Different thicknesses, typically corresponding to 1–100 nmol cm⁻², could be obtained by varying the cycling times. The modified electrode exhibits a single set of well-defined and highly reversible voltammetric peaks (related to the hexacyanoferrate redox transitions) in K⁺-containing electrolytes. Electrochemical charging is accompained by the cation motion, leading to the cation storage in the reduced state and its release upon oxidation. The results are consistent with high ionic conductivity of potassium in the film. Experiments in the other alkali metal electrolytes show that the cataion transport, necessary for the charge compensation during redox transitions, cannot be simply related to the size of a cation and the zeolitic structure of indium hexacyanoferrate.     

Extraction of Fe(III), Zn(II), and Mn(II) Using a System with a Green Solvent for Trioctylmethylammonium Thiocyanate

Theoretical Foundations of Chemical Engineering - An environmentally friendly solvent, namely, polypropylene glycol 425, has been proposed for the extraction of metal ions from chloride solutions...     

Extraction of Cu(II), Ni(II), and Al(III) with the Deep Eutectic Solvent D2EHPA/Menthol

Theoretical Foundations of Chemical Engineering - A new hydrophobic deep eutectic solvent (HDES) based on di(2-ethylhexyl)phosphoric acid and menthol has been proposed for the extraction of...     

Solvent Extraction Behavior and Mutual Separation of Some Bivalent Metal Ions Using Thiocarbohydrazide as the Complexing Agent

Abstract

Thiocarbohydrazide (NH₂. NH. CS. NH. NH₂) was used as a complexing agent for the solvent extraction separation of some bivalent metals. Separation of Cd from Co, Cu, and Pd, and of Pb from Ni and Pd was carried out using the effect of pH on their extractability. The separation of Cu from Zn and Hg, and of Pb from Zn and Cd was also carried out using various masking agents.     

Separation and concentration processes of solutions of Co(II), Ni(II), Cr(III), Fe(III) and Mn(II) by extraction with toluene-dissolved rosin

The extraction and stripping of Co(II), Ni(II), Cr(III) and Fe(III) from aqueous solutions by rosin dissolved in toluene has been investigated. Results obtained show that rosin is better extractant than abietic or n-lauric acids under comparable conditions. From these results, and the data of Mn(II) solvent extraction studied previously under the same conditions, a separation and concentration process for these five cations in aqueous solutions has been designed. Saturated solutions of Fe(III), Cr(III), Mn(II) and finally Co(II) and Ni(II) have been obtained successively by extraction and stripping, by addition of ammonium hydroxide to obtain the appropriate pH value, and by modifying adequately the organic phase/aqueous phase volume ratio.     

Water-soluble oxidized starch in complexation of Fe(III), Cu(II), Ni(II) and Zn(II) ions

The structure of the bromate-oxidized wheat starch (OS) contains partly opened glucose units with carbonyl and carboxyl groups at C2-, C3- or C6-positions. OS with a variable degree of oxidation (DO) was studied in alkaline conditions as a water-soluble complexing agent for Fe(III), Cu(II), Ni(II) and Zn(II) ions, which are common in various wastewaters. Complexation was studied by inductively coupled plasma-optical emission spectrometry (ICP–OES) in a single metal ion or multi-metal ion solutions. The DO affected the efficiency of the complexation with metal ions. OS with the high DO (carboxyl and carbonyl DO of 0.72 and 0.23, respectively) complexed and held Fe(III) or Zn(II) ions in a soluble form effectively in 0.5 mM single ion alkaline solution with the molar ratio of 0.65:1 of oxidized starch-to-metal ion (OS-to-M). The OS-to-M molar ratio of 1.3:1 was required to form a soluble complex with Cu(II) or Ni(II) ions. These complexes were thermally stable at the temperature range of 20–60 °C. OS with the low DO (carboxyl and carbonyl DO 0.47 and 0.17, respectively) complexed Zn(II) ions highly, Cu(II) and Ni(II) ions poorly and Fe(III) ions only partly. In the multi-metal ion solution of OS the solubility of these metal ions improved with the increasing DO of starch, which followed the same tendency as was observed in the single metal ion systems. The increased molar ratio of OS-to-M improved the complexation and solubility of the metal ions in all multi-metal ion series. As the soluble multi-metal ion complexes were reanalyzed after 7 days, all solutions had kept the high complexation and solubility of metal ions (ca. 90%). Complexation by OS did not show a selective binding of the ions in the multi-metal ion solution. It was concluded that the flexible, opened ring structure units of OS prevented the selective binding to metal ions but made the complexes highly stable. Titrimetric studies of OS–Fe(III) complexation showed that each anhydroglucose unit of OS had more than one coordination site and as the content of OS increased, the free sites coordinated to Fe(III) ions and formed cross-linked starch structures.