Decrease In Electron Density Research Articles

Topside ionospheric effects of the annular solar eclipse of 15th January 2010 as observed by DEMETER satellite

We present effects of the annular solar eclipse of 15th January 2010 on the topside ionosphere using the DEMETER satellite data. Measurements of the electron-ion density and electron temperature by the ISL (Instrument Sonde de Langmuir) and IAP (Instrument Analyseur de Plasma) instruments on board the DEMETER satellite during the eclipse time over the low latitude (±40) Indian ocean area are presented. We found the peak decrease in electron density to be about 35% and the peak decrease in ion density to be about 40% from the reference orbits at the altitude of the satellite (∼660km). Electron and ion temperatures were found to have decreased by 200–300K at the same altitude. Instead of simple decrease as in ion density, electron temperature showed a complex wave-like oscillation as the solar eclipse progressed. Electron density decreased to a minimum value before the maximum obscuration and starts to increase before passing through another minimum at the time of maximum obscuration. Both the minima are located at the ±10° geomagnetic latitude. Variations of electron and ion densities were found to follow the average solar illumination experienced by the satellite and its conjugate points at satellite altitude, while the electron temperature showed no such correlation.

Исследование реакции ионосферы на продукты горения топлива при работе двигателей транспортных грузовых кораблей серии «Прогресс» по данным Иркутского радара некогерентного рассеяния

The FSUE Central Research Institute of Machine Building (TsNIIMash), Rocket and Space Corporation “Energia”, and Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) jointly conducted the active space experiment “Radar-Progress” in 2007–2015. During this experiment, we used the Irkutsk Incoherent Scatter Radar to study space-time characteristics of ionospheric disturbances generated by exhaust products of “Progress” cargo spacecraft engines. As the basic effect during exhaust product injection we consider the formation of new centers for recombination of ambient ionospheric ions O+ on molecules of water and carbon dioxide. This produces an ionization “hole” in the region of injection. In nighttime conditions when the majority of experiments were performed, this hole was filled by hydrogen ions from the plasmasphere, thus the ion composition in the vicinity of the hole and incoherent scatter spectra were changed. For successful observation of the ionization hole dynamics, the critical factors are the degree of radar antenna diagram filling by exhaust products and the velocity of the thermospheric neutral wind, which makes exhaust gases move from the antenna diagram. These two factors lead to poor repeatability of successful experiments. Successful experiments recorded a decrease in electron density up to 35 % in the hole that existed for 30 min. The lifetime of the region with high concentration of H+ ions can be as long as one hour.

Nickel-macrocycle interaction in nickel(II) porphyrins and porphyrazines bearing alkylthio β-substituents: A combined DFT and XPS study

An electronic structure analysis of two nickel(II) tetrapyrrole complexes bearing β-alkylthio substituents, NiOMTP and NiOETPz, has been carried out through a combination of high-resolution XPS experiments and DFT calculations. The Ni 2p XPS spectra show a 0.5 eV shift to higher energy of the Ni 2p[Formula: see text] and Ni 2p[Formula: see text] binding energies on going from the porphyrin to the porphyrazine complex. This shift, which is well-reproduced by relativistic spin-orbit ZORA calculations, is indicative of a depletion of electron density on the central metal. Such a depletion of electron density is related to the macrocycle-induced changes in the metal-ligand interactions. In the porphyrazine complex both the ligand to metal [Formula: see text] donation and the metal to ligand [Formula: see text]-back donation increase. The latter increases slightly more than the former, however, leading to a decrease of electron density on the central metal.

Relics in galaxy clusters at high radio frequencies

We observed three radio relics in galaxy clusters and one radio relic candidate at 4.85 and 8.35 GHz in total emission and linearly polarized emission with the Effelsberg 100-m telescope and one radio relic candidate in X-rays with the Chandra telescope. The radio spectra of the integrated emission below 8.35 GHz can be well fitted by single power laws for all four relics. The flat spectra (spectral indices of 0.9 and 1.0) for the "Sausage" relic in cluster CIZA J2242+53 and the "Toothbrush" relic in cluster 1RXS 06+42 indicate that models describing the origin of relics have to include effects beyond the assumptions of diffuse shock acceleration. The spectra of the radio relics in ZwCl 0008+52 and in Abell 1612 are steep, as expected from weak shocks (Mach number $\approx 2.4$). We find polarization degrees of more than 50 % in the two prominent Mpc-sized radio relics, the Sausage and the Toothbrush. The high degree of polarization indicates that the magnetic field vectors are almost perfectly aligned along the relic structure. The polarization degrees correspond to Mach numbers of $>2.2$. Polarized emission is also detected in the radio relics in ZwCl 0008+52 and, for the first time, in Abell 1612. Abell 1612 shows a complex X-ray surface brightness distribution, indicating a recent major merger. No Faraday depolarization is detected between 4.85 GHz and 8.35 GHz, except for one component of the Toothbrush relic. Faraday depolarization between 1.38 GHz and 8.35 GHz varies with distance from the center of the host cluster 1RXS 06+42, which can be explained by a decrease in electron density and/or in strength of a turbulent magnetic field. Faraday rotation measures show large-scale gradients along the relics, which cannot be explained by variations in the Milky Way foreground. Large-scale regular fields appear to be present in intergalactic space around galaxy clusters.

Pd Nanoparticles Coupled to WO2.72 Nanorods for Enhanced Electrochemical Oxidation of Formic Acid.

We synthesize a new type of hybrid Pd/WO2.72 structure with 5 nm Pd nanoparticles (NPs) anchored on 50 × 5 nm WO2.72 nanorods. The strong Pd/WO2.72 coupling results in the lattice expansion of Pd from 0.23 to 0.27 nm and the decrease of Pd surface electron density. As a result, the Pd/WO2.72 shows much enhanced catalysis toward electrochemical oxidation of formic acid in 0.1 M HClO4; it has a mass activity of ∼1600 mA/mgPd in a broad potential range of 0.4-0.85 V (vs RHE) and shows no obvious activity loss after a 12 h chronoamperometry test at 0.4 V. Our work demonstrates an important strategy to enhance Pd NP catalyst efficiency for energy conversion reactions.

Wigner crystal phases in bilayer graphene

It is generally believed that a Wigner Crystal in single layer graphene can not form because the magnitudes of the Coulomb interaction and the kinetic energy scale similarly with decreasing electron density. However, this scaling argument does not hold for the low energy states in bilayer graphene. We consider the formation of a Wigner Crystal in weakly doped bilayer graphene with an energy gap opened by a perpendicular electric field. We argue that in this system the formation of the Wigner Crystal is not only possible, but different phases of the crystal with very peculiar properties may exist here depending on the system parameters.

Antibacterial Combination of Oleoresin from Copaifera multijuga Hayne and Biogenic Silver Nanoparticles Towards Streptococcus agalactiae.

Streptococcus agalactiae (group B Streptococcus - GBS) remains a leading cause of neonatal infections and an important cause of invasive infections in adults with underlying conditions. This study evaluated for the first time the effect of an oleoresin collected from Copaifera multijuga Hayne (copaiba oil) alone or in combination with silver nanoparticles produced by green synthesis using Fusarium oxysporum (AgNPbio) against planktonic and sessile cells of GBS isolated from colonized women. Copaiba oil showed a dose-dependent bactericidal activity against planktonic GBS strains, including those resistant to erythromycin and/or clindamycin. Scanning and transmission electron microscopy of GBS treated with copaiba oil revealed morphological and ultrastructural alterations, displaying disruption of the cell wall and decreased electron density due to leakage of cytoplasmic content. Copaiba oil also exhibited antibacterial activity against biofilms of GBS strains, inhibiting their formation as well as the viability of mature biofilms. In addition, the combination of copaiba oil with AgNPbio resulted in a synergistic effect against planktonic cells and biofilm formation, reducing the minimal inhibitory concentration values of both compounds. No hemolytic activity was detected for both compounds. These results indicate the potential of copaiba oil, alone or in combination with AgNPbio, for the development of new alternative strategies for controlling GBS infections.

Temperature and electron density in femtosecond filament-induced Cu plasma

Laser-induced breakdown spectroscopy (LIBS), which is also known as laser-induced plasma spectroscopy (LIPS), is a very promising spectral analysis technique for detecting elemental composition. The possibility of remote operation of LIBS is one of the properties, which expands the application scope of this technique. The remote LIBS technique is based on a long-range lens. With the increase of focusing distance, it is difficult to tightly focus laser pulse due to the diffraction limits. The size of focusing spot increases with focusing distance increasing. This will require extremely high laser energy. Femtosecond laser filamentation due to optical Kerr effect can be applied to the remote LIBS. During the filament propagation, the waist of laser beam is close to a constant value. The laser intensity inside the filament is about 1013 W/cm2 (intensity clamping). The intensity is sufficient to ablate sample and produce the plasma. It can overcome the influence of the diffraction limit in nanosecond LIBS. Although many researchers have studied the femtosecond geometrical focusing and femtosecond filamentation LIBSs, the spectral characteristics have not been completely understood. In this paper, we study the femtosecond laser filament-induced Cu plasma spectroscopy. Femtosecond laser system is an ultrafast Ti:sapphire amplifier (Coherent Libra). The full-width at the half maximum is 50 fs at a wavelength of 800 nm with a repetition rate of 1 kHz and its output energy is 3.5 mJ. A quartz lens with a focal length of 1 m is used to focus the laser to generate a filament channel. The spectral intensity of produced Cu plasma along the filament channel is measured by using the optical emission spectroscopy, and the distribution of Cu(I) intensity versus the distance between sample and focused lens is obtained. The results indicate that in a longer distance range along the filament, plasma spectroscopy has stronger emission due to the intensity clamping effect in femtosecond laser filamentation. In addition, we also calculate the plasma temperature and electron density by using the Boltzmann plot and the Stark broadening. The plasma temperature and electron density along the filament channel can be divided into three main regions: region 1) from 950 mm to 970 mm, in which the plasma temperature and electron density increase with the increase of distance; region 2) from 970 mm to 1030 mm, in which the change of plasma excitation temperature is opposite to the change of electron density; region 3) from 1030 mm to 1050 mm, in which the plasma temperature and electron density decrease with the increase of distance.

An analytical model of multi-component radio frequency capacitively coupled plasma and experimental validation

An analytical model describing the hydrogen added argon radio frequency capacitively coupled plasma is presented and its predictions are tested with the experimental results. In the analytical model, it is found that the rf current density, electron temperature and density, as well as the density of light ion in multi-component plasma collectively influence the normalized sheath thickness and potential. As for low pressure rf plasma, the sheath potential is the qualitative measure of the DC self bias, the change of DC self bias with hydrogen addition is predicted in this model. The values of electron density and temperature as a function of hydrogen content in the discharge is calculated on the basis of a homogeneous discharge model using the rms values of current and voltage as well as by rf compensated Langmuir probe at different experimental conditions. In the experiment with hydrogen added argon plasma, the rf power as well as the working pressures are varied. The presence of hydrogen in the argon discharge leads to the decrease of electron density and increase of electron temperature. The measured DC self bias for the hydrogen added argon plasma is found lower than the pristine argon plasma. This decrease of DC self bias with hydrogen addition is in accordance with predictions of the theoretical model.

Saturation effects of the lower ionosphere based on two‐dimensional HF heating model

AbstractThis paper presents a two‐dimensional (2‐D) theoretical model of the lower ionospheric heating by high‐frequency (HF) electromagnetic waves. Compared with the traditional one‐dimensional model, we develop the half‐power width of the heating beam into the theoretical formulations, which dictates the 2‐D distribution characteristics of electron temperature and density perturbations; we also introduce the Sodankylä Ion Chemistry (SIC) model. Based on this numerical model, the saturation effect of ionospheric electron temperature and density is investigated, and simulation is performed by heating at a wave frequency of 6 MHz. Results show that because of energy absorption, the electron temperature peaks at 74 km, and the relative increment of electron density peaks at 94 km in the height direction. Conversely, both the maximum perturbations of electron temperature and density appear on the beam center in the horizontal direction. Second, the saturation time of electron temperature initially increases slowly and then rapidly with increased height. Meanwhile, the saturation time of electron density decreases with increased height. In the horizontal aspect, both the saturation time of electron temperature and density are symmetrical at approximately the position of the beam center owing to the initial Gaussian distribution. Electron temperature far from the beam center results in a long saturation time. Conversely, with increased distance from the beam center, the saturation time of electron density decreases.

The Pt (II)⋅⋅⋅Cl Interactions: Nature and Strength

AbstractThe Pt (II)⋅⋅⋅Cl interactions between trans‐Pt (NH3)2X2/cis‐Pt (NH3)2X2 (X=OH, F, Cl, Br) and ClF were constructed and studied by Møller‐Plesset perturbation theory (MP2) method. The metal Pt (II)‐complex could act as the halogen bond acceptor, the Pt (II)⋅⋅⋅Cl interaction strength depends on the nature and the configuration of platinum (II) ligands: the metal halogen‐bonding interactions in trans‐Pt (OH)2(NH3)2⋅⋅⋅ClF/cis‐Pt (OH)2(NH3)2⋅⋅⋅ClF are obviously stronger than those in trans‐PtX2(NH3)2⋅⋅⋅ClF/cis‐PtX2(NH3)2⋅⋅⋅ClF (X=F, Cl, Br); the halogen bonds in cis‐complexes are somewhat stronger than those in respective trans‐complexes. This particular Pt (II)⋅⋅⋅Cl interactions is much stronger than hydrogen bond and has some degree of covalent character. For the Pt (II)⋅⋅⋅Cl interactions, the charge transfer between the related molecular orbitals of PtX2(NH3)2 and ClF are obvious, which is consistent with that the exchange energy contributes most to the total interaction energy. The stronger of the Pt (II)⋅⋅⋅Cl interactions, the more decreased electron density outside Pt (II) facing the chlorine atom, and the more increased electron density between Pt (II) and Cl, indicating that the polarization effect plays an important role in the formation of the Pt (II)⋅⋅⋅Cl interactions.

Ionospheric Effects of a Solar Eclipse of March 20, 2015 on Oblique Sounding Paths in the Eurasian Longitudinal Sector

The results of measuring HF signals on oblique chirp sounding paths in the Eurasian region during a solar eclipse of March 20, 2015 and the neighboring days are presented. The solar eclipse took place against the background of a strong magnetic storm. It was established that during the solar eclipse on oblique sounding paths of different length and orientation the decrease in the maximum observable frequency for the F mode (MOF-F) and the lowest observable frequency for the F mode (LOF-F) was 8–14% and 22–33%, respectively. During the eclipse, the signal amplitude increased by 3–5 dB. On the Lovozero—Nizhny Novgorod path in the maximum phase of the solar eclipse, the electron density decrease in the ionospheric E and F2 layers at the midpoint of the path reached 37% and 22%, respectively. According to the MOF and LOF variation measurements for various modes, the group delay time of radio signals, and the results of spectral analysis, it was found that in the eclipse there were wave disturbances with a period of 25 to 50 min. However, quasi-periodic variations of MOF-F and LOF-F having a a period of 50 to 80 min but which started before the eclipse were detected on some paths. Probably, in these cases, the variations were a result of the superposition of disturbances from two sources, namely, the magnetic storm and the solar eclipse.

Changes of NmF2 and hmF2 over Biak (1°S, 136°E) during total solar eclipse on March 9, 2016

Ionospheric responses to solar eclipse is interesting to learn. In this paper, we presented ionspheric F2 responses to total solar eclipse on March 9, 2016 over Indonesia from Biak station (-1 °; 136.0 °) which is within the obscuration 86.55%. The total solar eclipse over Biak occurred at 00:58 UT (09:58 local time) in F2 layer height of ionosphere (h ≈ 300 km). Observation of the ionospheric F2 over Biak during the total solar eclipse investigated using ionosonde with 15 minutes resolution. Ionization and recombination processes that occur in the ionosphere proceed by solar radiation. At the time of the ionosphere receives solar radiation, ionization process dominated in the F2 layer. Diurnal ionosphere parameters changed following the solar radiation. During the solar eclipse, the process of ionization in the F2 layer disturbed. Total solar eclipse on March 9, 2016 affected almost simultaneous decrease in maximum electron density (NmF2) ∼52% and increase hmF2 ∼24% at the elapsed time of totality observed from Biak Station.

Recent Advances in Numerical Simulation of Propagation of EM Waves in the Earth's Ionosphere

EM wave propagation in the magnetoactive terrestrial ionosphere was investigated by numerical methods, and associated software was developed. Two principal functions were realized: ray tracing and ionogram synthesis. For the first time, reference-standard models, including the International Reference Ionosphere (IRI) 2012, World Magnetic Model 2010, and World Geodetic System 1984, have been globally implemented for every component of the propagation medium, and fully manipulatable 3-D visualization was enabled in a study utilizing the bicharacteristic method. An assimilation model of the ionosphere was also used along with IRI. The focus was on the unveiling of multiskip long-range propagation effects. Effective numerical algorithms for solving the bicharacteristic system that allow rapid insight into an extremely large-scale EM problem and enable quasi-real-time operation were discussed. The simulation in the presence of abnormal locally increased or decreased electron density in the ionosphere of natural or artificial occurrence was considered. Experimental ionograms obtained by an ionosonde were compared to numerically synthesized ones.

First observations from the RISR-C incoherent scatter radar

First-light measurements from the Canadian face of the Resolute Bay Incoherent Scatter Radar (RISR-C) were taken in August of 2015. Data were taken for roughly 25 hours on both RISR-C and the North face of the Resolute Bay radar (RISR-N) in an 11-beam World Day mode. Overall, the measurements from the RISR-C radar are of high quality and consistent with results from the RISR-N radar. During the 25-hour period analyzed in this study, the ionosphere responded to changes in orientation of the Interplanetary Magnetic Field (IMF). During one particular event, a change from Bz negative to positive and By positive to negative caused the anti-sunward flow to stall, and a strong dawn-to-dusk flow, with decreased electron density and increased ion temperature, replaced it in the RISR-C field-of-view. Overall, it is clear that measurements from the RISR-C radar will complement and greatly expand the scope of ionospheric polar cap measurements.

Study of Non-Isothermal Crystallization of Polydioxanone and Analysis of Morphological Changes Occurring during Heating and Cooling Processes.

Non-isothermal crystallization kinetics of polydioxanone (PDO), a polymer with well-established applications as bioabsorbable monofilar suture, was investigated by Avrami, Mo, and isoconversional methodologies. Results showed Avrami exponents appearing in a relatively narrow range (i.e., between 3.76 and 2.77), which suggested a three-dimensional spherulitic growth and instantaneous nucleation at high cooling rates. The nucleation mechanism changed to sporadic at low rates, with both crystallization processes being detected in the differential scanning calorimetry (DSC) cooling traces. Formation of crystals was hindered as the material crystallized because of a decrease in the motion of molecular chains. Two secondary nucleation constants were derived from calorimetric data by applying the methodology proposed by Vyazovkin and Sbirrazzuoli through the estimation of effective activation energies. In fact, typical non-isothermal crystallization analysis based on the determination of crystal growth by optical microscopy allowed secondary nucleation constants of 3.07 × 105 K2 and 1.42 × 105 K2 to be estimated. Microstructure of sutures was characterized by a stacking of lamellae perpendicularly oriented to the fiber axis and the presence of interlamellar and interfibrillar amorphous regions. The latter became enhanced during heating treatments due to loss of partial chain orientation and decrease of electronic density. Degradation under various pH media revealed different macroscopic morphologies and even a distinct evolution of lamellar microstructure during subsequent heating treatments.

Diurnal evolution of the F region electron density local time gradient at low and middle latitudes resolved by the Swarm constellation

AbstractIn this study we have provided new insights into the local time gradient of F region electron density (ΔNe) derived from the lower pair of Swarm satellites flying side by side. Our result shows that the electron density (Ne) increase starts just at sunrise, around 06:00 LT, simultaneously at low and middle latitudes due to the increased photoionization. At equatorial latitudes the increase in electron density gets even steeper after 07:00 LT, and the steepest increase of electron density (about 3 · 1010 m−3 within 6 min) occurs around 09:00 LT. We suggest that the upward vertical plasma drift in connection with the buildup of the equatorial fountain effect plays a major role. We also found that the local time variations of the equatorial ionization anomaly (EIA) crest electron density during daytime are similar to the respective evolutions at the equator, but about 1–2 h delayed. We relate this delay to the response time between the equatorial electric field and the buildup of the plasma fountain. At equinox months a fast decrease of the F region electron density is seen at the EIA trough region during the prereversal enhancement, while an increase is found meanwhile at crest regions. Afterward, a fast decrease of the EIA crest electron density occurs between 19:00 and 23:00 LT, with seasonal dependence. The local time gradient between Swarm A and C shows also prominent longitudinal wave‐4 pattern around August months, and the phase of DE3 in ΔNe is found to be delayed by 6 h compared to that in Ne.

Time-resolved electron density and electron temperature measurements in nanosecond pulse discharges in helium

Thomson scattering is used to study temporal evolution of electron density and electron temperature in nanosecond pulse discharges in helium sustained in two different configurations, (i) diffuse filament discharge between two spherical electrodes, and (ii) surface discharge over plane quartz surface. In the diffuse filament discharge, the experimental results are compared with the predictions of a 2D plasma fluid model. Electron densities are put on an absolute scale using pure rotational Raman spectra in nitrogen, taken without the plasma, for calibration. In the diffuse filament discharge, electron density and electron temperature increase rapidly after breakdown, peaking at ne ≈ 3.5 · 1015 cm−3 and Te ≈ 4.0 eV. After the primary discharge pulse, both electron density and electron temperature decrease (to ne ~ 1014 cm−3 over ~1 µs and to Te ~ 0.5 eV over ~200 ns), with a brief transient rise produced by the secondary discharge pulse. At the present conditions, the dominant recombination mechanism is dissociative recombination of electrons with molecular ions, . In the afterglow, the electron temperature does not relax to gas temperature, due to superelastic collisions. Electron energy distribution functions (EEDFs) inferred from the Thomson scattering spectra are nearly Maxwellian, which is expected at high ionization fractions, when the shape of EEDF is controlled primarily by electron–electron collisions. The kinetic model predictions agree well with the temporal trends detected in the experiment, although peak electron temperature and electron density are overpredicted. Heavy species temperature predicted during the discharge and the early afterglow remains low and does not exceed T = 400 K, due to relatively slow quenching of metastable He* atoms in two-body and three-body processes. In the surface discharge, peak electron density and electron temperature are ne ≈ 3 · 1014 cm3 and Te ≈ 4.25 eV, attained after the surface ionization wave reaches the grounded electrode. The sensitivity of the present diagnostics is too low to measure electron density in the plasma during surface ionization wave propagation (estimated to be below ne ≈ 1013 cm−3). After peaking during the primary current pulse, the electron density decays due to dissociative recombination. Electron temperature decreases rapidly over ~150 ns after the primary current pulse rise, to Te ≈ 0.5 eV, followed by a much more gradual electron cooling between the primary and the secondary discharge pulses, due to superelastic collisions providing moderate electron heating in the afterglow.

Preparation of MnOx-loaded biochar for Pb2+ removal: Adsorption performance and possible mechanism

In order to increase Pb2+ adsorption capacity of biochar derived from rice husk, the present work explored a facile modification route based on the loading of manganese oxide (MnOx) nanoparticles. SEM, BET, TEM, FTIR and XPS analysis confirmed the successful loading of MnOx nanoparticles onto biochar. The maximum Pb2+ adsorption capacity for MnOx loaded biochar (MOLBC) with MnOx coverage of 40% was as high as 86.5mg g−1, while that for blank biochar was as low as 14.7mg g−1. Specific surface area as high as 340.0m2 g−1 was exhibited by 40%MOLBC, while the specific surface area of blank biochar was only 234.8m2 g−1. The MOLBC demonstrated relatively high adsorption capacity for Pb2+, due to the formation of MnOx sphere complexes especially monodentate, as well as oxygen complexes on biochar surface. Besides this, π-electron cloud system, decrease of electron density from π-band of graphenic nature carbon due to addition of -COOH and induced vacancy defect of graphenic basal plane created on biochar surface was also considered to play a key role in Pb2+ adsorption. The results suggested that MOLBC could be promisingly implemented as an environmentally friendly and inexpensive adsorbent for Pb2+ removal from wastewater.

Mechanism study of Cr(III) immobilization in the process of Cr(VI) removal by Huolinhe lignite

Lignite showed high capacity for reducing Cr(VI) to Cr(III) and hence removed Cr(VI) from aqueous solution, but the reduced Cr(III) cannot be released from adsorbent afterwards especially under acidic condition. In order to know why Cr(III) ions are immobilized within lignite adsorbent and how to recovery Cr species, the interaction of Cr(III) ions with lignite oxidized by Cr(VI) was studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The data obtained from these studies indicate that Cr(III) ions are bonded to oxygenic functional groups in lignite oxidized by Cr(VI) and electrons are delocalized over -O-Cr-O- domain. It is also revealed that the O atoms of C=O and C-O groups in the adsorbent matrix are bonded to Cr(III) ions along with the decrease of electron density, while the O atoms of O-C=O group are along with the increase of electron density. Based on these important structural information, we developed a method to treat Cr-loaded lignite further and to recover the Cr species.