Cr Compounds Research Articles

Storage modeling standard Cr(VI) solution based on comparison of time regression value with UV-Vis spectrophotometry

Chromium (Cr) compounds are found in nature in two forms, Cr (III) and Cr (VI). Analysis of Cr (VI) was determined using spectrophotometer UV-vis. A standard solution must be fresh as a standard that is usually not used repeatedly in the measurement. This study aims to determine whether the standard solution of Cr (VI) be used for a certain period until it must be disposed of. This idea is based on Cr (VI) compounds that were categorized as hazardous and toxic materials. In this study, the shelf life of standard Cr (VI) was carried out with controlled temperature and humidity in a refrigerator at 4 ℃ during the test period of two days. In this study, there was found that every hour of storage of standard Cr (VI) will observe a change in the gradient value of the regression. The model then compared with p-value resulted in only up to 7 hours of storage with a deviation of regression slope and intercept compared with initial time (T0–T7) is 0.0062 and 0.0019 which and its increases over time. From the result, it can be concluded that standard regression can be used as a model for determining the maximum storage time by comparing the regression values each time so that the seven hours storage time is the limit where the Cr (VI) that can no longer be used as a measurement standard. It concerned that standard regression could be used as a model for determining the maximum storage time by comparing the regression values each time. Keywords: Cr (VI), Modeling, Regression, Spectrophotometry UV-vis, T-Test

Reduced graphene oxide supported nanoscale zero-valent iron (nZVI/rGO) for in-situ remediation of Cr(VI)/nitrate-polluted aquifer

The compound pollution of nitrate and hexavalent chromium (Cr(VI)) in groundwater poses a serious risk to human health. Graphene oxide supported nanoscale zero-valent iron (rGO/nZVI) can effectively remediate Cr(VI) in groundwater. Xanthan gum is used as a good stabiliser and carrier to improve the stability of rGO/nZVI in aquifers. But the process and mechanism of in-situ simultaneous remediations of nitrate and Cr(VI) compound contamination by rGO/nZVI are still unclear. In this study, we investigated the process and mechanism of nitrate and Cr(VI) remediation using rGO/nZVI in simulated aquifers. The results show that rGO/nZVI has a good affinity for NO3−-N and Cr(VI), and the fitted maximum adsorption amounts of NO3−-N and Cr(VI) are 18.03 mg/g and 94.70 mg/g, respectively. There is a negative synergistic phenomenon between NO3−-N and Cr(VI), and Cr(VI) will preferentially occupy the active site of rGO/nZVI and inhibit NO3−-N removal. Xanthan gum-rGO/nZVI slurry injected into the aquifer can successfully form a stable reaction zone, which can continuously remove NO3−-N and Cr(VI) with high adsorption capacity of 8.88 mg/g and 61.06 mg/g at 96 h.

New CrOX (X = Cl, Br, I) monolayer with ultra-wide single spin states

The ultra-wide single spin states are of importance for ideal magnetic storage materials and spin injection sources. Here, a new type of CrOX (X = Cr, Br, I) monolayer has been revealed. We find that the basic constructive units for such new monolayers are four-coordinated, almost never being reported until now. More interestingly, they are half-metals and have an ultra-wide single spin channel in their electronic band structures. Monte Carlo simulations show that the Curie temperatures of three monolayers are relatively low, however they can be enhanced to exceed the liquid nitrogen temperature under strain or hole doping. The four-coordinated Cr compounds predicted here may open a new windows for exploring high spin-polarized half-metals.

A detoxification and value-added process for chromium ore processing residue (COPR) and Fe-C-bearing dust: Direct reduction-magnetic separation

Chromium ore processing residue (COPR), containing much virulent hexavalent chromium [Cr(VI)], is a by-product derived from chromate production. Fe-C-bearing dust from steel industry is very difficult to be utilized effectively because of its complex composition and unstable properties. The dust was co-processed with COPR by a direct reduction-magnetic separation process in this study. Through the strong reducing ability of solid carbon in Fe-C-bearing dust, the compounds of Cr and Fe were reduced to (Cr, Fe)7C3 alloy during the reduction roasting process and then selectively recovered by magnetic separation. In addition, the Pb and Zn compounds were reduced and volatilized into flue gas at high temperature. Under the optimal conditions, the results indicated that Cr-containing iron powder with 72.59 % Fe and 6.34 % Cr was obtained, and the recoveries of Fe and Cr were respectively 79.1 % and 76.9 %. The volatilization rates of Pb and Zn met 97.47 % and 99.95 %, respectively. The non-magnetic tailings were determined to be nontoxic and could be used as high-quality raw materials for building.

In Situ High-Temperature TEM Observation of Inconel Corrosion by Molten Chloride Salts with N2, O2, or H2O

In situ transmission electron microscopy (TEM) diffraction and imaging techniques are used to monitor and quantify corrosion of Inconel-625 by pure molten chloride salts (MgCl2 − NaCl − KCl) at 500 °C–800 °C in 1.0 atm inert N2 or pure O2, or by salts which are controllably hydrated in a high vacuum chamber. The isothermal corrosion rate R in inert N2 increases from 203 ± 30 μm year−1 at 700 °C to 463 ± 30 μm year−1 at 800 °C. An oxygen ambient causes a six-fold increase to R = 1261 ± 170 μm year−1 at 700 °C. Salt hydration dramatically accelerates corrosion to R> 3 × 105 μm year−1 at 700 °C while it leads to a more moderate R = 95 ± 20 and 486 ± 30 μm year−1 at 500 °C and 600 °C, respectively. These isothermal corrosion rates indicate that the molten chloride corrosion is significantly accelerated by salt hydration at temperatures above 600 °C, where corrosion is aggravated by increased generation and solubility of corrosive HCl gases. Hence, to reduce rate of corrosion it is important to both avoid incorporation of H2O into the system at each stage and ensure proper flushing of the system before increasing the temperature beyond 600 °C. Compositional analysis of the corroded cells indicate that corrosion in O2 ambient is dominated by oxidation of metals by O2 gas dissolved in the chloride melt, but corrosion in H2O ambients is caused by chlorination of metals by dissolved HCl gas and MgOH+ ions. So, to reduce rate of corrosion, steps should be taken to tailor chloride melt compositions that has low solubility for HCl and O2. All of our corroded samples exhibit passive-protective oxide layers of Cr, Mg, and Ni. In addition, distinct volatile compounds of Ni, Mo and Cr involving NiCl2, (Na,K)2MoO4 and CrO2(OH)2 are detected in N2, H2O, and O2 ambients, respectively. We believe that corrosion acceleration can be minimized by minimizing formation of volatile by-products or promoting reactions that could convert these volatile compounds to solid phases, as these volatile compounds led to destruction of protective oxide layers.

Peculiarities of adsorption of Cr (VI) ions on the surface of Chlorella vulgaris ZBS1 algae cells

Cr (VI) compounds are the most dangerous for human health and the environment, therefore, the study of their adsorption features is of great interest. A comprehensive study of the adsorption of Cr (VI) ions on the surface of Chlorella vulgaris ZBS1 algae cells was carried out evaluating the effect of the pH of the medium on the degree of removal of Cr (VI) ions from solutions and on the zeta potential of the cell surface was. The highest values of the degree of removal of Cr (VI) ions equal to 94.6–95.4% are achieved in the pH range of 1–2, being the result of the electrostatic attraction of HCrO4− groups to protonated amino groups of the cell surface and the possibility of reducing Cr (VI) ions to Cr (III) in an acidic medium, followed by the formation of Cr (III) ions of coordination bonds with amine and carboxyl groups of algae cells.The adsorption data were processed within the framework of Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. It was shown that the maximum Langmuir adsorption value was 74.63 mg/g. The values of the adsorption parameters 1/n and Kf in the Freundlich model were equal to 0.713 and 2.82 mg/g. In the Dubinin-Radushkevich model, the maximum adsorption capacity (qm) and free energy (E) were equal to 39.73 mg/g and 2.604 kJ/mol, respectively. Whereas, according to the Temkin model, the constant A was equal to 18.215 L/mg, and bT was equal to 0.023 kJ/mol. Taking into account the low values of free energy, it is concluded that adsorption is caused by non-covalent interactions.The study of adsorption kinetics showed that the adsorption of Cr (VI) ions on the surface of Chlorella vulgaris ZBS1 algae cells is described in the framework of the pseudo-second order model. The kinetic behavior of the process is discussed in the framework of the IPDM and ELM models. With increasing temperature, the constant of intraparticle diffusion of Cr (VI) ions decreases, which is explained with increasing of hydrophobic interactions between nonpolar sites of protein macromolecules and polysaccharides in the composition of algae cells. The increase in the adsorption of Cr (VI) ions at pH 8.62 in the temperature range of 298–353 K is justified by the shrinkage of the biosorbent volume, which leads to the blocking of a part of the anionic groups on the surface of algae cells. Therefore, the decrease in the electrostatic repulsion between the negatively charged surface of the adsorbent and Cr (VI) oxyanions is observed.

Assessing the fracture and fatigue resistance of nanostructured thin films

Fatigue failure through sustained loading of ductile materials manifests in irreversible motion of dislocations, followed by crack initiation and growth. This contrasts with the mechanisms associated with brittle ceramics, such as nanostructured physical vapor deposited thin films, where inhibited dislocation mobility typically leads to interface-controlled damage. Hence, understanding the fatigue response of thin films from a fundamental viewpoint – including altered atomic bonds, crystal structures, and deformation mechanisms – holds the key to improved durability of coated engineering components. Here, a novel method utilizing quasi-static and cyclic-bending of pre-notched, unstrained microcantilever beams coupled with in situ synchrotron X-ray diffraction is presented to study the fracture toughness and fatigue properties of thin films under various loading conditions. Investigating a model system of sputter-deposited Cr and Cr-based ceramic compounds (CrN, CrB2, and Cr2O3) demonstrates that the fatigue resistance of such thin films is limited by the inherent fracture toughness. In fact, cantilever cycling close to the critical stress intensity is sustained up to 107 load cycles on all materials, without inducing noticeable material damage, structural or stress-state changes. The observed variation in fracture toughness is put into context with linear-elastic fracture theory and complementary micro-pillar compression, thereby elucidating the wide range of values from as low as 1.6±0.2 MPa√m for Cr1.79O3 up to 4.3±0.3 MPa√m for Cr1.03B2, respectively. Moreover, possible mechanisms governing the elastic-plastic deformation response of all coatings, both in quasi-static and cyclic-loading conditions, are discussed. Our findings contribute key-insights into the underlying mechanisms dictating the damage tolerance of PVD coated components by relating fatigue strength limits to fundamental material properties.

Chemical sensitivity of the Kα X-ray emission of Ti and Cr compounds induced by 2 MeV protons

Kα x-ray emission induced by 2 MeV protons in thick Ti metal, TiO, Ti2O3, TiO2, MgTiO3, FeTiO3, TiC, TiN, TiB2, Cr metal, Cr2O3, CrO2, CrO3, K2Cr2O7 targets was measured using a wavelength dispersive spectrometer employing Johansson geometry to study chemical sensitivity of X-ray spectra. In the spectra the main Kα1 and Kα2 components as well as the KαL1 multiple ionization satellites were clearly resolved. The Kα1 and Kα2 peak positions and widths were extracted directly from the measured spectra in a consistent way. The results were compared with the existing data obtained by proton and photon induced ionization mechanisms, with the results of multiplet calculations, and with the observed chemical effects found in the related experimental Kβ spectra measured on the same Ti and Cr compounds at earlier times. The results obtained confirm linear correlations of the Kα1 first moments (M1) and the Kα center of gravity energy shifts with the central metal formal oxidation state, as well as between the Kα1 line widths and the Kα1 - Kβ1 M1 and/or centre of gravity energy shifts. The Kα energy shifts calculated by multiplet structure method for Cr compounds agreed with the experimentally obtained trends. Keywords: X-ray emission spectroscopy, High resolution X-ray spectra, Ti and Cr compounds, PIXE, Multiple ionization satellites.

Cornforth's and Corey-Suggs Cr(VI) compounds as efficient reagents for selective oxidation of certain polyols in aqueous KHSO4 medium –A kinetic and mechanistic approach

• Kinetics of oxidation of certain polyols have been studied by Cornforth's and Corey-Suggs Cr(VI) compounds viz., Pyridinium dichromate (PDC), and Pridinium chlorochromate (PCC). • Under mineral acid-free conditions in aqous KHSO 4 medium. • Reactions obeyed second order kinetics with a first order in [PCC] (or [PDC]) and [Alcohol], and rate of oxidaion accelerated by increaing [KHSO 4 ]. • On the basis of observed results plausible mechanism involvement of ((PyH)CrO 3 + ) spesies and polyol (ROH) in the rate determining step is proposed in he case of PDC oxidation. • In the case of PCC oxidaion, the slow step involved [(PyH)OCrO(OH)Cl) + ], and ROH to give corresponding carbonyl compounds as products. Cornforth's Pyridinium dichromate (PDC), and Corey-Suggs Pyridinium chlorochromate (PCC) were accomplished as efficient reagents for selective oxidation of certain polyols (ROH) in aqueous KHSO 4 medium at different temperatures. Kinetic study of these reactions depicted second order kinetics with a first order in [PCC] or[PDC] and [ROH] in aqueous bisulfate medium. A ten-fold increase in KHSO 4 concentration increased the observed rate constant (k′) by ten times showing first order dependence on [KHSO 4 ]. Added olefinic monomers did not affect the rate of oxidation, indicating the absence of free radical intermediates. On the basis of observed kinetic features, participation of ((PyH)CrO 3 + ) and polyol (ROH) in the rate determining step to give products in PDC path. In the case of PCC system, the slow step involved [(PyH)OCrO(OH)Cl) + ], and ROH to give products.

Simultaneous measurements of Cr, Cd, Hg and Pb species in ng L−1 levels by interfacing high performance liquid chromatography and inductively coupled plasma mass spectrometry

Toxicity, mobility, bioavailability and biofunctions of chromium, cadmium, mercury and lead are heavily dependent upon their specific chemical forms, leading to a high demand to metal speciation analysis rather than total quantification. Simultaneous speciation analysis of multiple metal(loid)s is attractive to a large sample capacity containing unstable analytes due to its economic and environmental advantages over the conventional single elemental strategies. In this work, an analytical method integrating online solid phase extraction into high performance liquid chromatography interfaced with inductively coupled plasma mass spectrometry (ICP-MS) to simultaneously preconcentrate and quantify Cr, Cd, Hg and Pb forms in pg L−1 levels in water was developed. Cr(III + VI), Cd(II), Hg(II), Pb(II), methylmercury (MeHg), ethylmercury (EtHg), and trimethyl (TML) and triethyl lead (TEL) were captured by the C18 adsorbent (equilibrated with 10 mL of 1.0 mM 2-hydroxyethanethiol at 10 mL min−1) and eluted by mobile phase (5.0 mM Cys at pH 2.0), then completely separated on the C18 column within 8.0 min and eventually determined by ICP-MS. Low limits of detection (0.001–0.007 ng L−1) and quantification (0.003–0.023 ng L−1), good relative standard deviations (<4%) and high enrichment factors (827–2656 folds) were obtained with good linearities. Three reference materials of total cadmium (GBW08602), total mercury (GBW08603) and total lead (GBW08601) in water were analyzed by the developed method to validate the accuracy with good agreement with certified values and satisfactory recoveries (92–100%). This method was proved feasible by the determination of Cr, Cd, Hg and Pb compounds in drinking water, river water, pond water and tap water.

Impact of Nano- and Micro-Sized Chromium(III) Particles on Cytotoxicity and Gene Expression Profiles Related to Genomic Stability in Human Keratinocytes and Alveolar Epithelial Cells.

Exposure to Cr(VI) compounds has been consistently associated with genotoxicity and carcinogenicity, whereas Cr(III) is far less toxic, due to its poor cellular uptake. However, contradictory results have been published in relation to particulate Cr2O3. The aim of the present study was to investigate whether Cr(III) particles exerted properties comparable to water soluble Cr(III) or to Cr(VI), including two nano-sized and one micro-sized particles. The morphology and size distribution were determined by TEM, while the oxidation state was analyzed by XPS. Chromium release was quantified via AAS, and colorimetrically differentiated between Cr(VI) and Cr(III). Furthermore, the toxicological fingerprints of the Cr2O3 particles were established using high-throughput RT-qPCR and then compared to water-soluble Cr(VI) and Cr(III) in A549 and HaCaT cells. Regarding the Cr2O3 particles, two out of three exerted only minor or no toxicity, and the gene expression profiles were comparable to Cr(III). However, one particle under investigation released considerable amounts of Cr(VI), and also resembled the toxicity profiles of Cr(VI); this was also evident in the altered gene expression related to DNA damage signaling, oxidative stress response, inflammation, and cell death pathways. Even though the highest toxicity was found in the case of the smallest particle, size did not appear to be the decisive parameter, but rather the purity of the Cr(III) particles with respect to Cr(VI) content.

The retention and speciation transformation mechanisms of chromium during bituminous coal combustion: Effects of inorganic minerals and combustion temperature

Coal combustion mainly releases chromium (Cr) as particulates and may oxidize Cr into toxic hexavalent forms. A series of combustion experiments combined with thermodynamic equilibrium calculations were used to study the speciation transformation behavior of Cr during the burning of a typical bituminous coal. Iron-bearing minerals and the combustion temperature were found to be vital for enriching Cr in ash and preventing Cr oxidation at high-temperature combustion process. During coal combustion, an increasing release trend of Cr versus the combustion temperature was observed. However, the degree of Cr oxidation didn't increase with the increased temperature. The fraction of Cr(VI) reached a maximum at 800°C, but gradually decreased as the combustion temperature rose to 1000°C. Further speciation study revealed that Cr was mostly presented in illite and pyrite in coal, which can be transformed into aluminosilicate glass and hematite. The ion-exchangeable, carbonate, and organic-bound Cr were easily released and also partly converted into less soluble residual form. At high combustion temperature (> 800°C), Fe2O3 exhibited a significant effect on Cr transformation and diminished the Cr(VI) ratios in coal ash. This was beneficial to the ash disposal or reutilization since Cr was retained as stable Cr (III) compounds in ash.

Bio-capture of Cr(VI) in a denitrification system: Electron competition, long-term performance, and microbial community evolution

Chromium is widely applied in industries as an important metal resource, but the discharge of Cr(VI) containing wastewater leads to the loss of chromium resources. This study proposed a bio-capture process of chromium in a denitrification system. The bio-capture potentiality was explored by investigating the electron competition between Cr(VI) and nitrogen compounds reduction, the long-term bio-capture performance, and the microbial community evolution. In the competition utilization of electron donors, both NO3--N and NO2--N took precedence over Cr(VI), and NO2--N reduction was proved to be the rate-limiting step. Under the optimum conditions of 20 mg/L NO3--N and 6 h HRT, 99.95% of 30 mg/L Cr(VI) could be reduced, and 220980 μg Cr/g MLSS was captured by the biofilm, which was fixed in intercellular as Cr(III). Microbiological analysis confirmed that the bio-reduction of Cr(VI) and NO3--N was mediated by synergistic interactions of a series of dominant bacteria, including genera Acidovorax, Thermomonas, and Microbacterium, which contained both the denitrification genes (narG, narZ, nxrA, and nirK) and chromate reduction genes (chrA and chrR). This study proved the feasibility of chromium bio-capture in denitrification systems and provided a new perspective for the Cr(VI) pollution treatment.

Study on physicochemical characteristics, solidification and utilisation of tannery sludge gasification ash

Gasification is an attractive method for tannery sludge (TS) disposal because of its advantages: volume reduction, stabilisation, harmlessness, and energy recovery. TS reduction ash (AR) and TS oxidation ash (AO), simulated from a downdraft fixed bed gasifier (DFBG) and an updraft fixed bed gasifier (UFBG), were investigated on their physicochemical characteristics, solidification behaviour, and value-added utilisation. Results showed that the main mineral matters in AR and AO consisted of Fe-oxids and Fe–Cr compounds, and the DFBG was more suitable for TS gasification than the UFBG because of the lower content of Cr(Ⅵ) in AR. With the addition of waste glass bottles (WGB), the ash fusion temperatures (AFTs) and leaching concentrations of heavy metals in AR and AO decreased significantly, and the heavy metals in AR and AO were successfully immobilised by the wrapping effect of the molten WGB. Moreover, gasification ash, as an auxiliary material for rock wool, reduced the AFTs and viscosity coefficient of the main chemical compositions in rock wool. With the addition of AR, the occurrence of Fe-containing compounds and the extremely low risk of leaching toxicity of heavy metals were observed. The maximum addition proportion of gasification ash was dependent on the maximum content of Fe2O3 allowed in the raw materials of rock wool, and its addition ratio must be below 15%.

Particulate hexavalent chromium alters microRNAs in human lung cells that target key carcinogenic pathways

Hexavalent chromium [Cr(VI)] is a global environmental pollutant and human lung carcinogen. However, the mechanisms of Cr(VI) carcinogenesis are not well defined. Cr(VI)-altered gene expression has been reported in the literature and is implicated in numerous mechanisms of Cr(VI) carcinogenesis. MicroRNAs (miRNAs) play a key role in controlling gene expression and are associated with carcinogenic mechanisms. To date no studies have evaluated global changes in miRNA expression in human cells after Cr(VI) exposure. We used RNA sequencing to evaluate how a particulate Cr(VI) compound (zinc chromate), the most potent form of Cr(VI), alters global miRNA expression after acute (24 h) or prolonged (72 and 120 h) exposure to 0.1, 0.2 and 0.3 μg/cm2 zinc chromate in an immortalized, non-cancerous human lung cell line (WTHBF-6). Particulate Cr(VI) significantly affected expression of miRNAs at all time points and concentrations tested. We also found the number of significantly downregulated miRNAs increased in a time- and concentration-dependent manner and many miRNAs were upregulated after 24 h exposure at the intermediate concentration tested. Pathway analyses of the differentially expressed miRNAs predicted miRNAs target pathways of Cr(VI) carcinogenesis in a time- and concentration-dependent manner. These data are the first to evaluate global changes in miRNA expression in human lung cells after Cr(VI) exposure and indicate miRNAs may play a key role in pathways of Cr(VI) carcinogenesis.

Simultaneous degradation of p-nitrophenol and reduction of Cr(VI) in one step using microwave atmospheric pressure plasma

Different physicochemical properties between Cr(VI) and phenolic compounds pose serious challenges for the effective treatment of co-contamination. This study developed an electrodeless high-flow microwave atmospheric plasma jet for the single-step simultaneous degradation of p-nitrophenol (PNP) and reduction of Cr(VI). Following a 15 min treatment with microwave atmospheric pressure plasma, the removal efficiency of Cr(VI) and PNP reached 97.5% and 93.6%, respectively, whereas that of total organic carbon reached 30.2%. Adding PNP to the solution significantly improved Cr(VI) reduction, whereas PNP degradation increased slightly with Cr(VI). The results indicate that the PNP intermediates significantly affected Cr(VI) reduction. Additionally, long-lived H2O2 and short-lived ·H aided the reduction of Cr(VI) during plasma treatment. The addition of hydroxyl scavengers during treatment implied that ·OH was largely responsible for PNP oxidation. High-performance liquid chromatography–mass spectroscopy (HPLC-MS) revealed that PNP intermediates, including p-nitrocatechol and 5-nitrobenzene-1,2,3-triol, function as Cr(VI) reductants. On the basis of the examined intermediate products, the potential PNP degradation pathway was investigated. The factors that could influence simultaneous dehgradation and reduction, including solution pH, gas velocity, and distance between the plasma outlet and the water surface were researched. Low pH supports Cr(VI) reduction, and the promotion of PNP for Cr(VI) reduction applies to all pH values. The degradation of PNP is insensitive to pH values with or without Cr(VI). The optimal gas velocity for PNP degradation and Cr(VI) reduction was revealed to be 6 L/min. The simultaneous removal of PNP and Cr(VI) benefits from a shorter distance between the plasma outlet and the water's surface.

Fabrication of a new magnetic CoFe2O4/ZrMCM-41 nanocomposite: Simple construction and application for fast reduction of Cr(IV) and nitroaromatic compounds

A new type of CoFe2O4/ZrMCM-41 nanocomposite was fabricated via sonochemical method and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and N2 adsorption desorption analyses. Different dosages of CoFe2O4 (10, 25 and 40 wt%) were deposited on the framework of ZrMCM-41 to design a series of magnetic nanocatalysts. SEM and EDX confirmed that the small-sized CoFe2O4 particles were uniformly distributed on the ZrMCM-41 framework. The magnetic CoFe2O4/ZrMCM-41 nanocomposite was used as a catalyst for the reduction of nitroaromatic compounds including 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), 4-nitroaniline(4-NA) and 2-nitroaniline (2-NA) and carcinogenic Cr(VI) at room temperature using NaBH4 as a reducing agent. The best performance observed for 100% reduction of 4-nitrophenol belongs to CoFe2O4/ZrMCM-41 25%, which occurs within 6 min, and the estimated rate constant is 0.97 min−1. In addition, the prepared CoFe2O4/ZrMCM-41 nanocomposites can be properly regenerated and reused for up to four cycles under an additional magnetic field without significant changes in its structure and activity. Therefore CoFe2O4/ZrMCM-41 nanocomposite could possibly be utilized for large scale applications.

Ftir Spectroscopy as a Convenient Tool for Detection and Identification of Airborne Cr(Vi) Compounds Arising from Arc Welding Fumes

Ftir Spectroscopy as a Convenient Tool for Detection and Identification of Airborne Cr(Vi) Compounds Arising from Arc Welding Fumes

Cornforth's and Corey-Suggs Cr(VI) Compounds as Efficient Reagents for Selective Oxidation of Certain Polyols in Aqueous KHSO &lt;sub&gt;4&lt;/sub&gt; Medium -A Kinetic and Mechanistic Approach

Cornforth's and Corey-Suggs Cr(VI) Compounds as Efficient Reagents for Selective Oxidation of Certain Polyols in Aqueous KHSO &lt;sub&gt;4&lt;/sub&gt; Medium -A Kinetic and Mechanistic Approach

Bacterial Journey of Micro- and Nano-adsorption mechanisms for Chromate Elimination: A Prospective Study

Chromium (VI) is extensively used in the leather and mining industries for various purposes. These industries release large volumes of untreated effluent containing a higher percentage of toxic Cr (VI) into the environment leading to adverse ecological and health problems. Cr (VI) compounds are recognized as highly carcinogenic, teratogenic and mutagenic to living organisms. Conventional approaches for chromate remediation are uneconomical or produce large quantities of toxic chemical wastes. Microbial remediation at the micro-and nano-scale provides a safe, flexible, inexpensive and eco-friendly strategy for the removal of chromate. This approach reduces the bioavailability of chromate ions to living organisms. It was perceived that the transformation and precipitation of Cr (VI) by microbial metabolic activities are very effective in this perspective. Biosorption is developing as an important integrated approach to treat industrial effluents containing higher amounts of Cr (VI) compounds. Microorganisms, for example, bacteria, fungi and algae used as biosorbents/ bio-materials for Cr (VI) removal have received great interest due to low cost, easy availability, high surface-to-volume ratio and rapid kinetics of adsorption and desorption. This review summarizes Cr (VI) remediation mechanisms by bacteria and integrates these microbes with nanotechnology such as carbon-nanotubes infused into calcium alginate, which considerably enhances the chromate reduction from an aqueous environment. Furthermore, it also discusses the significance of biomaterials and biosorption technology involved in chromate detoxification.