Surface complexation of Pb(II) on amorphous iron oxide and manganese oxide: spectroscopic and time studies

Hydrous Fe and Mn oxides (HFO and HMO) are important sinks for heavy metals and Pb(II) is one of the more prevalent metal contaminants in the environment. In this work, Pb(II) sorption to HFO (Fe(2)O(3) x nH(2)O, n=1-3) and HMO (MnO(2)) surfaces has been studied with EXAFS: mononuclear bidentate surface complexes were observed on FeO(6) (MnO(6)) octahedra with PbO distance of 2.25-2.35 Angstrom and PbFe(Mn) distances of 3.29-3.36 (3.65-3.76) Angstrom. These surface complexes were invariant of pH 5 and 6, ionic strength 2.8 x 10(-3) to 1.5 x 10(-2), loading 2.03 x 10(-4) to 9.1 x 10(-3) mol Pb/g, and reaction time up to 21 months. EXAFS data at the Fe K-edge revealed that freshly precipitated HFO exhibits short-range order; the sorbed Pb(II) ions do not substitute for Fe but may inhibit crystallization of HFO. Pb(II) sorbed to HFO through a rapid initial uptake ( approximately 77%) followed by a slow intraparticle diffusion step ( approximately 23%) resulting in a surface diffusivity of 2.5 x 10(-15) cm(2)/s. Results from this study suggest that mechanistic investigations provide a solid basis for successful adsorption modeling and that inclusion of intraparticle surface diffusion may lead to improved geochemical transport depiction.     

Ni(II) complexation to amorphous hydrous ferric oxide: an X-ray absorption spectroscopy study

Ni(II) sorption onto iron oxides and in particular hydrous ferric oxide (HFO) is among the important processes impacting its distribution, mobility, and bioavailability in environment. To develop mechanistic models for Ni, extended X-ray absorption fine structure (EXAFS) analysis has been conducted on Ni(II) sorbed to HFO. Coprecipitation revealed the formation of the metastable alpha-Ni(OH)(2) at a Ni(II) loading of 3.5 x 10(-3) molg(-1). On the other hand, Ni(II) formed inner-sphere mononuclear bidentate complexes along edges of FeO(6) octahedra when sorbed to HFO surfaces with Ni-O distances of 2.05-2.07 A and Ni-Fe distances of 3.07-3.11 A. This surface complex was observed by EXAFS study over 2.8 x 10(-3) to 10(-1) ionic strength, pH from 6 to 7, a Ni(II) loading of 8 x 10(-4) to 8.1 x 10(-3) molg(-1) HFO, and reaction times from 4 hours to 8 months. The short- and long-range structure analyses suggest that the presence of Ni(II) inhibited transformation of the amorphous iron oxide into a more crystalline form. However, Ni(2+) was not observed to substitute for Fe(3+) in the oxide structure. This study systematically addresses Ni(II) adsorption mechanisms to amorphous iron oxide. The experimentally defined surface complexes can be used to constrain surface complexation modeling for improved prediction of metal distribution at the iron oxide/aqueous interface.     

Adsorption of barium(II) on montmorillonite: an EXAFS study

Migration of radioactive radium, ²²⁶Ra, in soil is an environmental concern, especially in areas adjacent to uranium processing facilities. Barium(II), as Ba²⁺, was used as a Ra analog and reacted with a Na-montmorillonite to obtain mechanistic insights into the interaction of Ra with soil matrices. The majority of sorbed Ba is associated with the permanently charged surface sites on the montmorillonite basal surface. This is indicated by the facts that (1) sorption of Ba(II) on montmorillonite is not highly sensitive to solution pH, although an increase of sorption was observed at higher pH values; and (2) displacement of sorbed Ba increased with increased NaNO₃ concentration. As demonstrated by EXAFS, a small fraction of Ba also adsorbed on the montmorillonite edge, forming an inner-sphere surface complex through sharing of oxygen atom(s) from deprotonated –OH group of the Al octahedral layer. The EXAFS measured distances between Ba and O at the first shell, and Ba and Al of the second shell are 2.7–2.8 and 3.7–3.9 Å, respectively, consistent with the results from geometry of a inner-sphere complex at the edge site. Results from bulk experiments and spectroscopic analysis suggest a co-existence of outer- and inner-sphere surface complexes for Ba sorbed to the montmorillonite surface.     

Adsorption of organic matter at mineral/water interfaces: 7. ATR-FTIR and quantum chemical study of lactate interactions with hematite nanoparticles

The interaction of the l-lactate ion ( l-CH3CH(OH)COO(-), lact(-1)) with hematite (alpha-Fe2O3) nanoparticles (average diameter 11 nm) in the presence of bulk water at pH 5 and 25 degrees C was examined using a combination of (1) macroscopic uptake measurements, (2) in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and (3) density functional theory modeling at the B3LYP/6-31+G* level. Uptake measurements indicate that increasing [ lact(-1)]aq results in an increase in lact(-1) uptake and a concomitant increase in Fe(III) release as a result of the dissolution of the hematite nanoparticles. The ATR-FTIR spectra of aqueous lact(-1) and lact(-1) adsorbed onto hematite nanoparticles at coverages ranging from 0.52 to 5.21 micromol/m2 showed significant differences in peak positions and shapes of carboxyl group stretches. On the basis of Gaussian fits of the spectra, we conclude that lact(-1) is present as both outer-sphere and inner-sphere complexes on the hematite nanoparticles. No significant dependence of the extent of lact(-1) adsorption on background electrolyte concentration was found, suggesting that the dominant adsorption mode for lact(-1) is inner sphere under these conditions. On the basis of quantum chemical modeling, we suggest that inner-sphere complexes of lact(-1) adsorbed on hematite nanoparticles occur dominantly as monodentate, mononuclear complexes with the hydroxyl functional group pointing away from the Fe(III) center.     

Sorption of selenite onto chlorite considering mineral dissolution

In this study we investigated the sorption of selenite (SeO₃ ^2?) onto chlorite as a function of Se(IV) concentration, pH, and ionic strength. The sorption isotherm of Se(IV) onto chlorite was successfully presented by both the Langmuir isotherm and Tempkin equation although the Langmuir isotherm is somewhat better than the Tempkin equation. The sorption of Se(IV) onto chlorite was maintained to be constant at an acidic pH region, while the sorption decreased with an increasing pH at neutral and alkaline pH regions. However, the Se(IV) sorption onto chlorite was independent of the ionic strength of NaClO₄ solution. The amount of Se(IV) sorbed onto chlorite was significantly low compared to those of iron oxides such as apatite, goethite, hematite, and magnetite because of the lower content of Fe. We also investigated the effect of Fe(II) ions dissolved from chlorite on the Se(IV) sorption as a function of contact time. The chemical oxidation states of selenium sorbed onto chlorite surface were identified using X-ray absorption near edge structure (XANES) at the Pohang synchrotron light source. The amount of Fe(II) dissolved was increased by the contact time of 28 days but decreased after 28–56 days although the amount of dissolved Fe(II) ions was significantly small. This decrease of the dissolved Fe(II) may be due to the formation of Fe-oxyhydroxides such as ferrihydrite. The results of XANES measurements also showed that the Se(IV) sorbed onto chlorite was not reduced into Se(0) or Se(-II) even in the presence of Fe(II) ions in the solution because of the low Fe content of the chlorite although the mechanism was not clearly understood.     

Inorganic Ligand Effects on Pb(II) Sorption to Goethite (alpha-FeOOH)

The effects of sulfate anions on the uptake of Pb(II) onto goethite were investigated at the molecular level using in situ Pb L(III)-EXAFS and ATR-FTIR spectroscopies. Macroscopic uptake data show that Pb uptake can be enhanced by at least 30% at pH 5 in the presence of 3.16 mM sulfate and that sulfate uptake at pH 7 can be enhanced by more than a factor of 3 in the presence of 1.0 mM Pb. Consistent with behavior in sulfate-free systems, Pb(II) forms inner-sphere complexes sharing either corners or edges with Fe(O,OH)(6) octahedra under all conditions studied. The relative fraction of corner-sharing complexes is, however, significantly enhanced in the presence of sulfate at pH 5, 6, and 7 (all conditions studied) and additional sulfate species with C(3v) or lower point symmetry were noted in the presence of Pb by ATR-FTIR. Drawing on bond valence and structural constraints developed in J. D. Ostergren et al. (2000, J. Colloid Interface Science 224, 000-000), these results indicate formation of Type A ternary complexes bonded to the surface through Pb that is bound as a bridging bidenate complex to two adjacent A-type (singly coordinated) surface oxygens (( identical withFe-O)(2)-Pb-OSO(3)). Copyright 2000 Academic Press.     

Synthesis,characterization and biological studies of some Co(II), Ni(II) and Cu(II) complexes derived from indole-3-carboxaldehyde and glycylglycine as Schiff base ligand

The Schiff base ligand derived from indole-3-carboxaldehyde(indal) and glycylglycine(glygly) were synthesized and characterized by elemental analysis, IR, electronic spectrum, ¹H NMR and mass spectrum. Co(II), Ni(II) and Cu(II)–indal-glygly Schiff base complexes were synthesized and characterized by elemental analysis, molar conductance, IR, electronic spectra, magnetic measurements, ESR, electrochemical studies, TGA, DSC analysis, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR spectral data show that the ligand is tridentate and the binding sites are azomethine nitrogen, peptide nitrogen and carboxylato oxygen atoms. Electronic spectral measurements indicate tetrahedral geometry for Co(II) and Ni(II) complexes and square planar geometry for Cu(II) complex. Magnetic measurements show weak ferromagnetic behaviour for Co(II) and Ni(II) complexes and paramagnetic behaviour for Cu(II) complex. ESR spectral data shows the ionic link between metal and the Schiff base ligand. The metal complexes are found to be stabilized in the unusual oxidation states of the metal ion during electrolysis. Thermal analysis of the complex indicates that the decomposition takes place in three steps. IR and thermal studies indicate that the fourth position would be occupied by a water molecule in complexes. XRD shows that the complexes have the crystallite size of 31, 40 and 67 nm, respectively. The surface morphology of the complexes was studied by SEM. The antimicrobial activity of the ligand and its complexes were screened by Kirby Bayer Disc Diffusion method. DNA cleavage studies were performed for metal–Schiff base complexes in presence of hydrogen peroxide as oxidant.     

Synthesis and spectroscopic studies of CoII, NiII, FeIII and ThIV complexes derived from 2,2'-dihydroxy-3,3'-di(carboxymethyl)-1,1'-binaphthyl

The synthesis of 2,2'-dihydroxy-3,3'-di(carboxymethyl)-1,1'-binaphthyl (H2L) and its novel metal complexes with Co(II), Ni(II), Fe(III) and Th(IV) salts are reported. The ligand and its metal complexes have been characterized on the basis of analytical, conductance, spectral (IR, UV-vis, 1H NMR, mass) and magnetic susceptibility measurements. The M?ssbauer spectrum of the Fe(III) complex indicates a low-spin octahedral geometry around the Fe(III) ion. The IR and 1H NMR spectral data show that the ligand behaves in a dibasic bidentate fashion coordinating to two metal atoms through the two deprotonated naphthyl OH groups and acts in a dibasic tetradentate manner using both carbonyl oxygen's and the deprotonated naphthyl OH groups coordinating to two metal ions. Thermal studies (TGA, DTA) confirm the presence of solvents either inside or outside the coordination sphere and support the mechanism of the decomposition process. The value of [alpha]D20 for the ligand has been determined in DMSO.     

An ATR-FTIR spectroscopic study of the competitive adsorption between oxalate and malonate at the water-goethite interface

The competitive adsorption between oxalate and malonate at the water-goethite interface was studied as a function of pH and total ligand concentrations by means of quantitative adsorption measurements and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The results obtained show that ATR-FTIR spectroscopy resolves the individual spectroscopic features of oxalate and malonate when adsorbed simultaneously at the water-goethite interface. The characteristic peaks of all four types of predominating surface complexes existing in the single ligand systems were identified, namely one inner sphere and one outer sphere surface complex for each ligand. The quantitative adsorption data showed that oxalate partially out-competes malonate at the water-goethite interface. Evaluation of the peak area variations as a function of pH indicated that the stronger oxalate adsorption can be ascribed to the more stable inner sphere surface complex of oxalate, which in turn is related to the oxalate five-member chelate ring structure yielding a more stable complex compared to the six-member ring of malonate.     

Competitive sorption of carbonate and arsenic to hematite: combined ATR-FTIR and batch experiments

The competitive sorption of carbonate and arsenic to hematite was investigated in closed-system batch experiments. The experimental conditions covered a pH range of 3-7, arsenate concentrations of 3-300 μM, and arsenite concentrations of 3-200 μM. Dissolved carbonate concentrations were varied by fixing the CO(2) partial pressure at 0.39 (atmospheric), 10, or 100 hPa. Sorption data were modeled with a one-site three plane model considering carbonate and arsenate surface complexes derived from ATR-FTIR spectroscopy analyses. Macroscopic sorption data revealed that in the pH range 3-7, carbonate was a weak competitor for both arsenite and arsenate. The competitive effect of carbonate increased with increasing CO(2) partial pressure and decreasing arsenic concentrations. For arsenate, sorption was reduced by carbonate only at slightly acidic to neutral pH values, whereas arsenite sorption was decreased across the entire pH range. ATR-FTIR spectra indicated the predominant formation of bidentate binuclear inner-sphere surface complexes for both sorbed arsenate and sorbed carbonate. Surface complexation modeling based on the dominant arsenate and carbonate surface complexes indicated by ATR-FTIR and assuming inner-sphere complexation of arsenite successfully described the macroscopic sorption data. Our results imply that in natural arsenic-contaminated systems where iron oxide minerals are important sorbents, dissolved carbonate may increase aqueous arsenite concentrations, but will affect dissolved arsenate concentrations only at neutral to alkaline pH and at very high CO(2) partial pressures.     

Coadsorption of Cu(II) and glyphosate at the water-goethite (alpha-FeOOH) interface: molecular structures from FTIR and EXAFS measurements

The coadsorption of Cu(II) and glyphosate (N-(phosphonomethyl)glycine, abbreviated to PMG) at the water-goethite interface was studied by means of batch adsorption experiments, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The system was investigated over the pH range 3--9 and at total concentrations of 0.9 micromol and 2.2 micromol Cu(II) and PMG per m(2) of goethite. The collective quantitative and spectroscopic results show that Cu(II) and PMG directly interact at the water-goethite interface to form ternary surface complexes. Two predominating complexes have been identified. At pH 4 the IR and CuK-edge EXAFS data indicate a molecular structure where the phosphonate group of PMG bonds monodentately to the surface in an inner sphere mode, while carboxylate and amine groups coordinate to Cu(II) to form a 5-membered chelate ring. Hence, at pH 4, Cu(II) and PMG form a ternary surface complex on goethite with the general structure goethite-PMG-Cu(II). At the highest pH investigated (pH 9), the carboxylate group is still coordinated to Cu(II) but the phosphonate group is present in a relatively free, non-coordinated and/or disordered state. Although the spectroscopic data are not conclusive they indicate the formation of ternary surface complexes with the molecular architecture goethite-Cu(II)-PMG at high pH.     

A theoretical and experimental study of lead substitution in calcium hydroxyapatite

Characterization of lead substitution for calcium in hydroxyapatite (CaHA) is carried out, using experimental techniques and Density Functional theoretical (DFT) analyses. Theoretical modeling is used to obtain information of the Pb chemical environment for occupancy at either Ca(I) or Ca(II) sites of CaHA. Effects of the larger ionic radius of Pb(+2) compared to Ca(+2) are apparent in embedded cluster calculations of local chemical bonding properties. DFT periodic planewave pseudopotential studies are used to provide first-principles predictions of local structural relaxation and site preference for Pb(x)Ca(10-x)HA over the composition range x< or = 6. General characteristics of the polycrystalline material are verified by X-ray diffraction and FTIR analysis, showing the presence of a single phase of CaHA structure. A short range structure around lead is proposed in order to interpret the Pb L-edge EXAFS spectrum of the solid solution Ca(6.6)Pb(3.4)HA. In this concentration we observe that lead mainly occupies Ca(II) sites; the EXAFS fit slightly favors Pb clustering, while theory indicates the importance of Pb-Pb avoidance on site (II).     

Lead(II) complex formation with glutathione

A structural investigation of complexes formed between the Pb(2+) ion and glutathione (GSH, denoted AH(3) in its triprotonated form), the most abundant nonprotein thiol in biological systems, was carried out for a series of aqueous solutions at pH 8.5 and C(Pb(2+)) = 10 mM and in the solid state. The Pb L(III)-edge extended X-ray absorption fine structure (EXAFS) oscillation for a solid compound with the empirical formula [Pb(AH(2))]ClO(4) was modeled with one Pb-S and two short Pb-O bond distances at 2.64 ± 0.04 and 2.28 ± 0.04 ?, respectively. In addition, Pb···Pb interactions at 4.15 ± 0.05 ? indicate dimeric species in a network where the thiolate group forms an asymmetrical bridge between two Pb(2+) ions. In aqueous solution at the mole ratio GSH/Pb(II) = 2.0 (C(Pb(2+)) = 10 mM, pH 8.5), lead(II) complexes with two thiolate ligands form, characterized by a ligand-to-metal charge-transfer band (LMCT) S(-) → Pb(2+) at 317 nm in the UV-vis spectrum and mean Pb-S and Pb-(N/O) bond distances of 2.65 ± 0.04 and 2.51 ± 0.04 ?, respectively, from a Pb L(III)-edge EXAFS spectrum. For solutions with higher mole ratios, GSH/Pb(II) ≥ 3.0, electrospray ionization mass spectroscopy spectra identified a triglutathionyllead(II) complex, for which Pb L(III)-edge EXAFS spectroscopy shows a mean Pb-S distance of 2.65 ± 0.04 ? in PbS(3) coordination, (207)Pb NMR spectroscopy displays a chemical shift of 2793 ppm, and in the UV-vis spectrum, an S(-) → Pb(2+) LMCT band appears at 335 nm. The complex persists at high excess of GSH and also at ～25 K in frozen glycerol (33%)/water glasses for GSH/Pb(II) mole ratios from 4.0 to 10 (C(Pb(2+)) = 10 mM) measured by Pb L(III)-edge EXAFS spectroscopy.     

Synthesis, structure, and properties of the Cu(II) coordination compounds with the pyruvic acid nicotinoyl and isonicotinoyl hydrazones

New coordination compounds of Cu(II) and hydrazones of nicotinic and isonicotinic acids have been prepared. The complexes isolated have been studied by elemental analysis, thermogravimetric analysis, magnetic susceptibility measurements, IR, diffuse reflectance, and EXAFS spectroscopy. The geometry of the compounds has been determined and the type of the ligands coordination has been revealed. Antibacterial activity of the complexes has been studied.     

The A-cluster in subunit beta of the acetyl-CoA decarbonylase/synthase complex from Methanosarcina thermophila: Ni and Fe K-edge XANES and EXAFS analyses

The acetyl-CoA decarbonylase/synthase (ACDS) complex catalyzes the cleavage of acetyl-CoA in methanogens that metabolize acetate to CO(2) and CH(4), and also carries out acetyl-CoA synthesis during growth on one-carbon substrates. The ACDS complex contains five subunits, among which beta possesses an Ni-Fe-S active-site metal cluster, the A-cluster, at which reaction with acetyl-CoA takes place, generating an acetyl-enzyme species poised for C-C bond cleavage. We have used Ni and Fe K fluorescence XANES and EXAFS analyses to characterize these metals in the ACDS beta subunit, expressed as a C-terminally shortened form. Fe XANES and EXAFS confirmed the presence of an [Fe(4)S(4)] cluster, with typical Fe-S and Fe-Fe distances of 2.3 and 2.7 A respectively. An Fe:Ni ratio of approximately 2:1 was found by Kalphabeta fluorescence analysis, indicating 2 Ni per [Fe(4)S(4)]. Ni XANES simulations were consistent with two distinct Ni sites in cluster A, and the observed spectrum could be modeled as the sum of separate square planar and tetrahedral Ni sites. Treatment of the beta subunit with Ti(3+) citrate resulted in shifts to lower energy, implying significant reduction of the [Fe(4)S(4)] center, along with conversion of a smaller fraction of Ni(II) to Ni(I). Reaction with CO in the presence of Ti(3+) citrate generated a unique Ni XANES spectrum, while effects on the Fe-edge were not very different from the reaction with Ti(3+) alone. Ni EXAFS revealed an average Ni coordination of 2.5 S at 2.19 A and 1.5 N/O at 1.89 A. A distinct feature at approximately 2.95 A most likely results from Ni-Ni interaction. The methanogen beta subunit A-cluster is proposed to consist of an [Fe(4)S(4)] cluster bridged to an Ni-Ni center with one Ni in square planar geometry coordinated by 2 S + 2 N and the other approximately tetrahedral with 3 S + 1 N/O ligands. The electronic consequences of two distinct Ni geometries are discussed.     

Solvation of Copper(II) Ions in Liquid Ammonia

X-ray absorption fine structure (XAFS) measurements have been performed at -50 degrees C on a 0.4 mol dm(-)(3) copper(II) nitrate solution in liquid ammonia. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to determine the coordination number and bond distances for the solvated copper(II) ion in solution. The equatorial ammonia nitrogens are located 2.00 ? from the copper and the axial nitrogen 2.19 ? from the copper. However, it was not possible from the EXAFS analysis alone to conclude whether there was one or two axial nitrogens. Therefore, X-ray absorption near-edge structure (XANES) spectroscopy was combined with discrete variational Xalpha (DV-Xalpha) molecular orbital calculations for a series of five- and six-coordinated models to determine the coordination number and the geometry. The experimental XANES spectrum was best reproduced by a model where the copper(II) ion is pentacoordinated in liquid ammonia in a square pyramidal geometry with the copper(II) ion lifted above the average nitrogen plane.     

Template synthesis and spectral characterization of some Schiff base complexes derived from quinoxaline-2-carboxaldehyde and L-histidine

New Schiff base complexes of Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) were synthesized by template condensation of quinoxaline-2-carboxaldehyde, L-histidine, and the metal compound, and were characterized by elemental analysis, fourier transform infrared spectroscopy, electronic spectra, conductance measurements, magnetic susceptibility measurements, ESR spectra, and thermal analysis. In all the complexes, the Schiff base coordinates through azomethine nitrogen, quinoxaline nitrogen, and carboxylato oxygen. The physicochemical and spectroscopic measurements reveal square planar geometry for the copper(II) complex, tetrahedral geometry for the manganese(II), cobalt(II), and zinc(II) complexes, and octahedral geometry for the iron(III) and nickel(II) complexes.     

Transformation of ferrihydrite in the presence or absence of trace Fe(II): The effect of preparation procedures of ferrihydrite

Two-line ferrihydrite was prepared by two different procedures. In procedure 1, which is widely used, ferrihydrite (named as ferrihydrite-1) was prepared by droping NaOH solution into Fe(III) solution. In procedure 2, which is rarely reported, ferrihydrite (named as ferrihydrite-2) was prepared by adding Fe(III) and NaOH solutions into a certain volume of water simultaneously. The results showed that mixing procedures of Fe(III) and alkaline were critical in the sub-microstructures and the conversion mechanisms of ferrihydrites in the presence or absence of trace Fe(II). The sub-microstructure of ferrihydrite-1 favored the mechanism of its dissolution re-crystallization and hematite nanoparticles with rough surface were obtained. The sub-microstructure of ferrihydrite-2 favored the solid state transformation from ferrihydrite to hematite and hematite nanoparticles with smooth surface were formed. These research results will be helpful for us to control the synthesis of hematite nanoparticles with different surface state.     

Electron paramagnetic resonance, optical absorption, IR and Raman spectral studies on pelecypod shell

Pelecypod shell originated from Kolleru lake of Andhra Pradesh is used in the present work. It contains Mn(II) and Fe(III) in traces. The EPR spectrum of the compound is due to Mn(II) which is in three independent sites. The three g values are evaluated with slight differences. The hyperfine component varies from 9.33 to 9.49mT. The zero field splitting parameter is also ranges from 43.8(1) to 44.1(1)mT. Using the covalence parameter the number of ligands around metal is estimated as 20. In EPR spectrum Fe(III) is identified. The optical absorption spectrum is attributed to Mn(II) in octahedral geometry. Further 10 Dq band is attributed to Fe(II) in the optical absorption spectrum. NIR spectral results are due to water fundamentals, whereas IR and Raman spectrum is due to carbonate ion fundamentals.     

Spectral investigations on melanterite mineral from France.

EPR, Optical and IR spectral studies on a naturally occurring mineral melanterite are carried out at room temperature. EPR studies indicate the presence of Cu(II) ion in tetragonally distorted octahedral site and hyperfine lines could not be resolved due to higher concentration of the paramagnetic impurity in the mineral. Optical absorption spectrum is a characteristic of Fe(II) and Cu(II) ions. Crystal field parameters are evaluated. IR spectrum confirms the presence of water and sulphate ions.