Investigation of removal of Cr(VI), Mo(VI), W(VI), V(IV), and V(V) oxy-ions from industrial waste-waters by adsorption and electrosorption at high-area carbon cloth

Adsorption and electrosorption of Cr(VI), Mo(VI), W(VI), V(IV), and V(V) ions from water samples at low concentration were studied at high-area C-cloth electrodes. The concentrations of ions in the solution were monitored using in situ UV spectroscopy. All the investigated ions, except V(IV), showed better adsorption in acidic media. Positive polarization of the C-cloth caused increased adsorption of Cr(VI), Mo(VI), and V(V) ions. When previously adsorbed, Mo(VI) and V(V) ions were shown to be largely desorbable by negative polarization of the C-cloth. Since V(IV) does not become adsorbed significantly at the C-cloth in acidic media, the method provides an interesting means for separation of V(V) and V(IV) species in solution.     

Micro-determination of As(V), V(V), Mo(VI), W(VI) in the presence of Cu(II), Ni(II) and Zn(II)

A rapid procedure is described for the separation and determination of 0.025 mg to 1.0 mg quantities of As(V), V(V), Mo(VI) and W(VI) from small quantities of Cu(II), Ni(II), and Zn(II) using silica gel as the selective sorbent for the cations. The individual anionic components, which remain in the supernatant solution after separation from the cations, are determined by colorimetric methods. The complete recovery of As(V) in supernatant solution has also been tested radiometrically using⁷⁶As as the radioactive indicator. The sorbed cations after extraction with dilute hydrochloric acid are determined by EDTA titrations.     

Photometric determination of trace uranium(VI), phosphorus(V), arsenic(V), and vanadium(V) in saturated aqueous solutions of poorly soluble compounds

A procedure for extraction-photometric determination of uranium(VI) was developed and procedures for the determination of phosphorus(V), arsenic(V), and vanadium(V) were modernized. The solubility of some poorly soluble uranium compounds in aqueous solutions was determined. Deceased.     

Processing of Precipitates of Hydrated Tantalum(V), Niobium(V), and Titanium(IV) Oxides in Loparite Technology

Conditions were studied for the dissolution in HF of hydrated tantalum(V), niobium(V), and titanium(IV) oxides, which are formed by acid decomposition of loparite, and also for the selective extraction of Ta(V) with octanol from the resulting fluotitanic solutions.     

Determination of Nb(V), V(V), Co(II), Fe(III), Ni(II), Ru(III) and Pd(II) as their 4-(5-nitro-2-pyridylazo) resorcinol chelates by reversed-phase high performance liquid chromatography

This paper reports the separation and determination of Nb(V), V(V), Co(II), Fe(III), Ni(II), Ru(III) and Pd(II) by reversed-phase HPLC using the new reagent, 4-(5-nitro-2-pyridylazo) resorcinol (5-NO₂-PAR) as a precolumn derivatization reagent. On a C₁₈ column, the seven metal chelates can be separated quantitatively with methanol/water (5248, v/v) containing 15 mmol/l pH 5.0 acetate buffer and 10 mmol/l tetrabutylammonium bromide (TBA·Br). The detection limits for Nb(V), V(V), Co(II), Fe(III), Ni(II), Ru(III) and Pd(II) are 0.65 ppb, 0.94 ppb, 0.10 ppb, 0.15 ppb, 0.18 ppb, 3.02 ppb and 2.35 ppb, respectively when the ratio of signal to noise (S/N) is 3. This method is simple and rapid, and has been used in the analysis of rain and liquor with satisfactory results.     

Adsorption characteristics of As(V), Se(IV), and V(V) onto activated alumina: effects of pH, surface loading, and ionic strength

Arsenic, selenium, and vanadium are major anionic elements of concern in drinking water. This research investigated the adsorption characteristics of As(V), Se(IV), and V(V) onto a commercial activated alumina (AA) under different pH, surface loading, and ionic strength conditions using batch systems. The results indicated that the adsorption of these elements was significantly affected by pH and the surface loading. However, ionic strength generally did not impact their adsorption, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. A speciation-based adsorption model was used to simulate the adsorption of As(V), Se(IV), and V(V) by activated alumina and to determine the adsorption constants of different element species. This model can satisfactorily predict the adsorption of these elements in a broad pH range from 1.5 to 12 and a wide surface loading range from 1.0 to 50 mg/g activated alumina for different sorbent concentrations, using the same set of adsorption constants.     

EPR study of dithiophosphate,dithiocarbamate, and xanthate complexes of Cr(V), Mo(V), and W(V)

Liquid and frozen solutions of diethyl dithiophosphate, diethyl dithiocarbamate, and butyl xanthate complexes of Cr(V), Mo(V) and W(V) were studied by the EPR method in the temperature range from 293–77dg K. The spin-Hamiltonian parameters were determined. Conclusions were drawn about the structure of these complexes and about the bond character within the complexes. A multiplicity of the hyperfine splitting constants from Cr⁵³, Mo^95,97, and W¹⁸³ to the constant of additional hyperfine splitting from the p³¹ isotope is observed in diethyl phosphate complexes.     

Efficiency and application of poly(acryldinitrophenylamidrazone-dinitroacrylphenylhydrazine) chelating fiber for pre-concentrating and separating trace Au(III), Ru(III), In(III), Bi(III), Zr(IV), V(V), Ga(III) and Ti(IV) from solution samples

Poly(acryldinitrophenylamidrazone-dinitroacrylphenylhydrazine) chelating fiber was synthesized from polyacrylonitrile fiber and used for enrichment and separation for traces of Au(III), Ru(III), In(III), Bi(III), Zr(IV), V(V), Ga(III) and Ti(IV) ions from solution samples. The acidity, rate, re-use, capacity and interference on the adsorption of ions on the chelating fiber as well as the conditions of desorption of these ions from the chelating fiber were investigated by means of inductively coupled plasma optical emission spectrometry. The results show that 10-100 ngml(-1) of Au(III), Ru(III), In(III), Bi(III), Zr(IV), V(V), Ga(III) and Ti(IV) ions can be quantitatively enriched by the chelating fiber at a 2 mlmin(-1) of flow rate in the range pH 4-5, and desorbed quantitatively with 20 ml of 5 M HCl for In(III), Bi(III), Zr(IV), V(V), Ga(III), Ti(IV) and 20 ml of 4 M HCl+2% CS(NH(2))(2) solution for Au(III), Ru(III) (with recovery>95%). 50- to 500- fold excesses of Fe(III), Al(III), Mg(II), Mn(II), Ca(II), Cu(II), Ni(II) ions cause little interference in the concentration and determination of analyzed ions. When the fiber was reused for 8 times, the recoveries of the above ions enriched by the fiber were still over 87%. The relative standard deviations (RSDs) for the enrichment and determination of 10 ngml(-1) Au, Ru, In, Bi, Ga and 1 ngml(-1) Zr, V, Ti were lower than 3.0%. The results obtained for these ions in real solution samples by this method were basically in agreement with the given values with average errors of less than 6.3%. FT-IR spectra show that existence of NNCNHNH, OCNHNH and NO(2) functional groups are verified in chelating fiber, and Au(III) or Ru(III) is mainly combined with nitrogen (or oxygen) of the groups to form a chelate complex.     

Separation of the Oxyanions of Re(VII), Mo(VI), Cr(VI), W(VI), and V(V) from a Multicomponent Solution at pH 6 by foam Fractionation

Abstract

An experimental investigation is presented of the foam separation of the oxyanions of Re(VII), Mo(VI), Cr(VI), W(VI), and V(V). The pH 6.0, multicomponent aqueous solutions are 1.0 × 10 ^?6 M in each metal. The effect of chloride competition with the metal oxyanions for the cationic surfactant is determined with NaCl concentrations up to 0.3 M. With proper NaCl concentration adjustments, V(V) can be separated completely from the other four metals, and Re(VII) and Mo(VI) from the other three. Pulsed surfactant dosage is investigated for 1.0 × 10 ^?6 M Mo(VI) solutions at pH 6.0 and 3.1.     

Determination of arsenic(III), arsenic(V), antimony(III), antimony(V), selenium(IV) and selenium(VI) by extraction with ammonium pyrrolidinedithiocarbamate—methyl isobutyl ketone and electrothermal atomic absorption spectrometry

The solution conditions and other parameters affecting the ammonium pyrrolidine-dithiocarbamate—methyl isobutyl ketone extraction system for graphite-furnace atomic absorption spectrometric determination of As(III), As(V), Sb(III), Sb(V), Se(IV) and Se(VI) were studied in detail. The solution conditions for the single or simultaneous extraction of As(III), Sb(III) and Se(IV) were not critical. Arsenic(V) and Se(VI) were not extracted over the entire range of pH and acidity studied. Antimony(V) was extracted only in the acidity range 0.3—1.0 M HCl. Simultaneous extraction of total arsenic and total antimony was possible after reduction of As(V) with thiosulphate. Interference studies are also reported.     

Synthesis and Characterization of Six-Coordinate Nitrido Complexes of Vanadium(V), Chromium(V), and Manganese(V). Isolation of a Dinuclear, Mixed-Valent &mgr;-Nitrido Chromium(III)/Chromium(V) Species

Photolysis of a series of octahedral monoazido complexes of the type [LM(III)(didentate ligand)(N(3))](n)(+)X(n) of vanadium(III), chromium(III), and manganese(III) in the solid state or in solution yields quantitatively the corresponding six-coordinate nitrido complexes [LM(V)(didentate ligand)(N)](n)(+)X(n) and 1 equiv of dinitrogen. L represents the macrocycle 1,4,7-triazacyclononane or its N-methylated derivative (L'), the didentate ligands are pentane-2,4-dionate (acac), 2,2,6,6-tetramethylheptane-3,5-dionate (tacac), picolinate (pic), phenanthroline (phen), and oxalate (ox), and X(-) represents perchlorate or hexafluorophosphate. The following nitrido complexes were prepared: [LV(V)(N)(acac)](ClO(4)) (6), [LCr(V)(N)(acac)](ClO(4)) (13), [LCr(V)(N)(tacac)](ClO(4)) (14), [LCr(V)(N)(pic)](ClO(4)) (15), [LCr(V)(N)(phen)](ClO(4))(2) (16), [LCr(V)(N)(ox)] (19), [L'Mn(V)(N)(acac)]PF(6) (21). Photolysis of [LCr(III)(N(3))(ox)] (17) in the solid state produces the &mgr;-nitrido-bridged mixed-valent species [L(2)Cr(2)(ox)(2)(&mgr;-N)](N(3)) (18). The structures of the precursor complex [L'Mn(acac)(N(3))]BPh(4) (20), of 13, and of [L'Mn(V)(N)(acac)]BPh(4) (21) have been determined by X-ray crystallography. Complex 13 crystallizes in the orthorhombic space group Pnma, with cell constants a = 27.187(5) ?, b = 9.228(2) ?, c = 7.070(1) ?, V = 1773.7(6) ?(3), and Z = 4; complex 20 crystallizes in the triclinic space group P&onemacr; with a = 14.769(5) ?, b = 16.83(1) ?, c = 16.96(1) ?, alpha = 108.19(5) degrees, beta = 105.06(4) degrees, gamma = 99.78(4) degrees, V = 3719(2) ?(3), and Z = 4; and complex 21 crystallizes in the monoclinic space group P2(1)/n with a = 10.443(3) ?, b = 16.035(4) ?, c = 21.463(5) ?, beta = 95.76(1) degrees, V = 3575.9(14) ?(3), and Z = 4. The Cr(V)&tbd1;N and Mn(V)&tbd1;N distances are short at 1.575(9) and 1.518(4) ?, respectively, and indicate a metal-to-nitrogen triple bond.     

Determination of V(V), Nb(V), and Ta(V) with 2-(2-Thiazolylazo)-5-diethylaminophenol by Reversed-Phase High Performance Liquid Chromatography

The simultaneous determination of vanadium, niobium, and tantalum by reversed-phase high performance liquid chromatography (HPLC) with 2-(2-thiazolylazo)-5-diethylaminophenol (TADAP) as the precolumn chelating reagent has been established. Optimum conditions for the separation, such as the methanol content, the addition of tartaric acid, pH, and the concentration of acetate buffer, were investigated. The metal chelates were eluted in 8 min with a mobile phase of methanol–water (55/45, v/v) containing tartaric acid (0.1%, m/v) and acetate buffer (pH 3.5, 10 mmol/liter) on an ODS column at 568 nm. The detection limits (signal-to-noise RATIO = 3) for V(V), Nb(V), and Ta(V) were 0.16, 0.32, and 1.77 ng/ml, respectively. The proposed method was applied to the analyses of a reference of mineral and synthetic samples. The result was in accord with the certified value, and the recoveries were 98.9–101.8%.     

Differential pulse polarography of germanium(IV), tin(IV), arsenic(V), antimony(V), selenium(IV) and tellurium(VI) at the static mercury drop electrode in catechol—perchlorate media

The differential pulse polarography of Ge(IV), Sn(IV), As(V), Sb(V), Se(IV) and Te(VI) has been investigated in perchlorate media containing catechol using a static mercury drop electrode. Under optimum conditions, Ge(IV), Sn(IV), As(V), and Sb(V) undergo reduction to yield well-defined peaks; detection limits of 82 ppb, 28 ppb, 4 ppm, and 25 ppb, respectively, have been calculated. Few electrolytes are known for which these ions exhibit a quantitatively useful polarographic response. While Se(IV) and Te(VI) may be detected at levels of 115 ppb and 17 ppb, respectively, addition of catechol does not enhance the peak current relative to that observed in simple perchlorate solutions, as was the case for the other ions studied. The determination of germanium, arsenic and antimony in samples is described.     

Determination of distribution ratios of Zr(IV), Co(II), Sb(V) and Nb(V) using polyaniline in acid solutions

Journal of Radioanalytical and Nuclear Chemistry - In this work, we report the distribution ratios of Zr(IV), Co(II), Sb(V) and Nb(V) using polyaniline in HCl, HF, oxalic acid and...     

Molecular Mechanics Calculations on Chelates of Titanium(IV), Vanadium(IV/V), Copper(II), Nickel(II), Molybdenum(IV/V), Rhenium(IV/V) and Tin(IV) with Di- and Tridentate Ligands Using the New Extensible Systematic Force Field (ESFF)—An Empirical Study

Force field calculations were performed on a series of 27 transition metal complexes of titanium(IV), vanadium(IV/V), copper(II), nickel(II), molybdenum(IV/V), rhenium(IV/V), and tin(IV) with a broad variety of di- or tridentate ligands in order to find a reliable scheme for determining the molecular structure of such chelates with the new Extensible Systematic Force Field (ESFF). A good agreement between theoretical results and experimental data was achieved. In some cases an unspecific fitting of the force field was necessary.     

Adsorption of Pb(II), Cu(II), Cd(II), Zn(II), Ni(II), Fe(II), and As(V) on bacterially produced metal sulfides

The adsorption of Pb(II), Cu(II), Cd(II), Zn(II), Ni(II), Fe(II) and As(V) onto bacterially produced metal sulfide (BPMS) material was investigated using a batch equilibrium method. It was found that the sulfide material had adsorptive properties comparable with those of other adsorbents with respect to the specific uptake of a range of metals and, the levels to which dissolved metal concentrations in solution can be reduced. The percentage of adsorption increased with increasing pH and adsorbent dose, but decreased with increasing initial dissolved metal concentration. The pH of the solution was the most important parameter controlling adsorption of Cd(II), Cu(II), Fe(II), Ni(II), Pb(II), Zn(II), and As(V) by BPMS. The adsorption data were successfully modeled using the Langmuir adsorption isotherm. Desorption experiments showed that the reversibility of adsorption was low, suggesting high-affinity adsorption governed by chemisorption. The mechanism of adsorption for the divalent metals was thought to be the formation of strong, inner-sphere complexes involving surface hydroxyl groups. However, the mechanism for the adsorption of As(V) by BPMS appears to be distinct from that of surface hydroxyl exchange. These results have important implications to the management of metal sulfide sludge produced by bacterial sulfate reduction.     

Simultaneous determination of inorganic As(III), As(V), Sb(III), Sb(V), and Se(IV) species in natural waters by APDC/MIBK-NAA

A solvent extraction preconcentration as well as separation method involving ammonium pyrrolinedithiocarbamate (APDC) and 4-methyl-2-pentanone (MIBK) in conjunction with neutron activation analysis (NAA) was developed for the simultaneous measurement of low levels of inorganic arsenic, antimony and selenium species in natural waters. Several critical factors affecting the APDC/MIBK-NAA method were studied in detail including the selection of chelating agent, solvent, aqueous pH for the extraction of six species as well as a few organoarsenic species as representatives for organic species, the stability of the complexes in organic phase, phase volume ratios for extraction and back-extraction steps, and the reduction of the species from higher to lower oxidation state. The detection limits for arsenic, antimony and selenium were found to be as low as 0.026, 0.010 and 0.12 μg L^?1, respectively. Trace amounts of As(III), As(V), Sb(III), Sb(V), and Se(IV) in different types of natural water sample and two water certified reference materials were measured using the APDC/MIBK-NAA method.     

Electrometric titrations of Cr(VI), Mn(IV), V(V), Co(III) and U(VI) with a standard iron(II) solution in alkaline media containing hexitols

Direct and indirect potentiometric, bipotentiometric and biamperometric titrations with a standard iron(II) solution are described for some inorganic compounds in alkaline media containing hexitols (mannitol, dulcitol and sorbitol). The optimal conditions for titrations based on the Cr(VI) → Cr(III), Mn(IV) → Mn(III) → Mn(II), V(V) → V(IV), Co(III) → Co(II) and U(VI) → U(IV) systems are discussed. Of the hexitols studied, sorbitol has the greatest effect on the value of the redox potential of the Fe(III)/Fe(II) system; the E_f° value is about —1.10 V vs. SCE.     

Determination of V(V), Nb(V) and Ta(V) as their 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol chelates by reversed-phase HPLC

This paper reports the separation and determination of V(V), Nb(V) and Ta(V) by RP-HPLC using 5-Br-PADAP as a precolumn derivatizing reagent. On C(18) column, the three metal chelates can be separated on a baseline in 9 min with the mobile phase of methanol-water (59:41, v/v) containing tartaric acid (0.2%) and acetate buffer (pH 3.5, 10 mM). The detection limits of V(V), Nb(V) and Ta(V) are 0.13 ppb, 0.22 ppb and 1.79 ppb, respectively when S/N is 3. This method is simple and rapid, and has been used in mineral analysis with satisfactory results.     

Structural considerations and reactivity of peroxocomplexes of V(V), Mo(VI) and W(VI)

In this perspective we will discuss recent results on structural aspects of peroxocomplexes of transition metals having the d(0) configuration (V(V), Mo(VI), W(VI)), and show how these may be related to the reactivity of these species in both chemical and biological systems. In addition, we will consider the relevance of structural properties to their involvement as important intermediates in industrial and enzymatic catalysis. These will be related to the behaviour of peroxocomplexes of other diamagnetic transition metals, such as those with d(8) (Pd(II), Pt(II)) configurations.