Showing papers on "Chromium published in 2013"
TL;DR: The chemical/biological remediation processes for Cr(VI) and their efficiency have been summarised in some detail and the interaction of chromium with various microbial/bacterial strains isolated and their reduction capacity towards Cr( VI) are also discussed.
841 citations
TL;DR: This work has demonstrated an on-off fluorescent CD probe for detecting Cr(VI) based on the inner filter effect (IFE) because the absorption bands of Cr(IV) fully covered the emission and excitation bands of CDs.
Abstract: Chromium(VI) [Cr(VI)] is considered as a severe environmental pollutant, due to its highly toxic and carcinogenic properties. Therefore, low cost, highly sensitive sensors for the determination of Cr(VI) are highly demanded. It is well-known that highly luminescent carbon dots (CDs) have been successfully applied as fluorescent nanosensors for pH, ions, and molecular substances. In the present work, we have demonstrated an on–off fluorescent CD probe for detecting Cr(VI) based on the inner filter effect (IFE) because the absorption bands of Cr(IV) fully covered the emission and excitation bands of CDs. This CD-based nanosensor provides obvious advantages of simplicity, convenience, rapid response, high selectivity, and sensitivity, which have potential application for the detection of Cr(VI) in the environmental industry. In addition, because Cr(VI) can be reduced to low valent chromium species easily by reductant, resulting in the elimination of the IFE and recovery of CD fluorescence, the CD–Cr(VI) mixt...
673 citations
TL;DR: The utilization of waste tires (hard-to-dispose waste) as a precursor in the production of activated carbons (pollution-cleaning adsorbent) and it was found that the adsorption process is pH dependent.
Abstract: Because of the continuous production of large amount of waste tires, the disposal of waste tires represents a major environmental issue throughout the world. This paper reports the utilization of waste tires (hard-to-dispose waste) as a precursor in the production of activated carbons (pollution-cleaning adsorbent). In the preparation of activated carbon (AC), waste rubber tire (WRT) was thermally treated and activated. The tire-derived activated carbon was characterized by means of scanning electron microscope, energy-dispersive X-ray spectroscopy, FTIR spectrophotometer, and X-ray diffraction. In the IR spectrum, a number of bands centred at about 3409, 2350, 1710, 1650, and 1300–1000 cm−1 prove the present of hydroxyl and carboxyl groups on the surface of AC in addition to C═C double bonds. The developed AC was tested and evaluated as potential adsorbent removal of chromium (III). Experimental parameters, such as contact time, initial concentration, adsorbent dosage and pH were optimized. A rapid uptake of chromium ions was observed and the equilibrium is achieved in 1 h. It was also found that the adsorption process is pH dependent. This work adds to the global discussion of the cost-effective utilization of waste rubber tires for waste water treatment.
368 citations
TL;DR: In this article, the catalytic performance of the metal-organic framework Cr-MIL-101 in solvent-free coupling of CO2 and epoxides to produce cyclic carbonates has been explored at both high-pressure (100 ǫ CO2) and low pressure (8 ǔ CO2), in the temperature range of 25-120 c.
248 citations
TL;DR: In this paper, a simple route for the fabrication of manganese dioxide/iron oxide/acid oxidized multi-walled carbon nanotube magnetic nanocomposites (MnO2/Fe3O4/o-MWCNTs) was presented.
218 citations
TL;DR: The resulting composites were investigated in the reduction of Cr(VI) to Cr(III) using formic acid, showing that the Pt and Pd catalysts were active with the Pt nanoparticles immobilized in MOF exhibiting the best performance.
195 citations
TL;DR: The newly designed N-doped porous carbon with magnetic nanoparticles formed in situ (RHC-mag-CN) demonstrated a very quick adsorption property for the removal of Cr(VI), and shows perfect magnetic separation performance from aqueous solution.
188 citations
TL;DR: In this article, the authors describe the chromium removal in aqueous solution by nanoscale zero-valent iron (nZVI)-Fe3O4 nanocomposites, which were prepared by a novel in situ reduction method.
169 citations
TL;DR: In this article, a noble-metal-free Cu-Cr catalyst was successfully synthesized by a modified co-precipitation method using the cheap metal nitrates, and the physical properties of the resulting Cu-cr catalysts were studied by XRD (X-ray diffraction), EDX (Energy-dispersive X-ray), TEM (Transmission electron microscopy) and XPS (Xray photoelectron spectroscopy) to reveal their influence on the catalytic performance.
167 citations
TL;DR: The present finding suggests that the bioinoculant effectively reduced the toxicity of hexavalent chromium to chickpea plants and concurrently enhanced the biological and chemical characteristics of chickPEa, when grown in chromium treated soils.
165 citations
TL;DR: FT-IR analysis reveals that the polyphenolic compounds present in the leaf extracts of Eucalyptus globules may be responsible for the reduction and stabilization of the ZVNI.
TL;DR: It is demonstrated that R-nZVI has the potential to become an effective agent for treating wastewater containing Cr(VI) and Cr(III), and it was found that nZVI loads, resin dose, pH value and initial concentration of Cr( VI) were all important factors.
TL;DR: A novel method based on target-induced fluorescence quenching of glutathione-stabilized gold nanoclusters, with its simplicity, low cost, high selectivity and sensitivity, could be used as a promising tool for chromium analysis in environmental water samples.
TL;DR: A new method using NaOH-NaNO3 binary melts to treat vanadium slag is proposed in this article, where vanadium and chromium can be simultaneously extracted in the leaching processes.
Abstract: A new method using NaOH-NaNO3 binary melts to treat vanadium slag is proposed. Vanadium and chromium can be simultaneously extracted in the leaching processes. Under the optimum reaction conditions, the recovery of vanadium and chromium can reach 93.7% and 88.2% in 6 h, respectively. The kinetics investigation indicates that the decomposition of vanadium slag is controlled by mass transfer in product layer. During the reaction, NaOH is believed to provide basic media and facilitate the dissolution of acidic oxides. NaNO3 decomposes to produce a large amount of active oxygen species, such as O, O-2(2-),and O2-. NaOH intensifies the decomposition of NaNO3 to NaNO2, but inhibits further decomposition of NaNO2. NaNO3 can be regenerated by oxidation of NaNO2 using oxygen at high temperature. The apparent activation energy of NaNO2 oxidation in the temperature ranging from 350 to 450 degrees C is 105.5 kJ/mol. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 541-552, 2013
TL;DR: In this paper, a method for the removal of arsenic and chromium contaminants from water by using ionically modified magnetic nanoparticles (PPhSi-MNPs) was described.
TL;DR: In this article, a review of Cr-free Fe-based HTS catalysts is presented, focusing on the roles and functions of non-chromium promoters in the catalysts.
TL;DR: Both proteins induced an enhanced extent of released iron, chromium, nickel and manganese, whereas both proteins reduced the corrosion resistance of SS, with the reverse situation for iron metal (reduced corrosion rates and reduced metal release in the presence of proteins).
Abstract: Implantation using stainless steels (SS) is an example where an understanding of protein-induced metal release from SS is important when assessing potential toxicological risks. Here, the protein-induced metal release was investigated for austenitic (AISI 304, 310, and 316L), ferritic (AISI 430), and duplex (AISI 2205) grades in a phosphate buffered saline (PBS, pH 7.4) solution containing either bovine serum albumin (BSA) or lysozyme (LSZ). The results show that both BSA and LSZ induce a significant enrichment of chromium in the surface oxide of all stainless steel grades. Both proteins induced an enhanced extent of released iron, chromium, nickel and manganese, very significant in the case of BSA (up to 40-fold increase), whereas both proteins reduced the corrosion resistance of SS, with the reverse situation for iron metal (reduced corrosion rates and reduced metal release in the presence of proteins). A full monolayer coverage is necessary to induce the effects observed.
TL;DR: The findings demonstrate the feasibility for the coconversion of As(III) and Cr(VI) in AMD and real-world constraints to this strategy for environmental remediation.
Abstract: Arsenic and chromium are often abundant constituents of acid mine drainage (AMD) and are most harmful as arsenite (As(III)) and hexavalent (Cr(VI)). To simultaneously change their oxidation state f...
TL;DR: In this article, three duplex stainless steel weldments were produced by changing the chromium element to study the correlation between the pitting corrosion characteristics and the component ratio of the dual phase.
TL;DR: Three additional M-Cr complexes have been isolated, where the iron site is systematically replaced with other first-row transition metals (Mn, Co, or Ni), while the chromium site is kept invariant, characterized by X-ray crystallography.
Abstract: In the field of metal–metal bonding, the occurrence of stable, multiple bonds between different transition metals is uncommon, and is largely unknown for different first-row metals. Adding to a rec...
TL;DR: In this article, the influence of alloyed chromium on atmospheric corrosion resistance (ACR) of weathering steels in simulated industrial atmosphere was investigated, by determining the relative corrosion rate after periodic immersion wet/dry cyclic corrosion for 72h.
TL;DR: Low-toxicity chromium(II) chloride catalyzes at 25 °C within minutes the coupling reactions of various (hetero)arylmagnesium reagents with N-heterocyclic halides, aromatic halogenated ketones or imines, and alkenyl iodides.
Abstract: Low-toxicity chromium(II) chloride catalyzes at 25 °C within minutes the coupling reactions of various (hetero)arylmagnesium reagents with N-heterocyclic halides, aromatic halogenated ketones or imines, and alkenyl iodides. Remarkably, much lower amounts of homo-coupling side products are obtained compared to related iron, cobalt, or manganese cross-couplings.
TL;DR: This study demonstrates a simple and efficient method of generating catalytically active MOF materials for environmental detoxification as well as defensive applications.
Abstract: Porous materials based on chromium(III) terephthalate metal organic frameworks (MOF) MIL-101(Cr) and their complexes with dialkylaminopyridines (DAAP) were synthesized via a DAAP-MOF complexation, and tested for hydrolytic degradation of organophosphorous esters such as diethyl 4-nitrophenyl phosphate (paraoxon). Elemental analysis, TGA, XRD, FT-IR, TEM, SEM, and nitrogen adsorption measurements indicated that the DAAP units were incorporated into MIL-101 pores by complexation, keeping the parent framework intact. The DAAP-MOF enabled facile paraoxon hydrolysis in water/acetonitrile mixtures under ambient conditions (100% conversion after 24 h at pH 10). The MOF-DAAP complexes showed synergistic effects, being 7-fold and 47-fold more active than the parent MIL-101 or DAAP materials, respectively. The high hydrolysis reaction turnover was realized by simultaneous action of the Lewis acid Cr(III) center of the MOF as well as the electron-rich nucleophile, DAAP. This study demonstrates a simple and efficient...
TL;DR: Pani-Pd and PANI are recommended for future sensor applications for chromium detection at low pH and PPY and PANi-NW were found to be highly sensitive with respect to pH and Cr(VI) initial concentration.
TL;DR: In this paper, Ndoped and N-F co-doped TiO2 catalysts were tested for the photocatalytic reduction of Cr(VI) in the presence of oxalate ions.
Abstract: N-doped and N–F co-doped TiO2 catalysts were prepared via a sol–gel method using NH4Cl and NH4F as N and N–F dopant precursors, respectively, having Ti:N and/or F molar ratios of 1:1, 1:2 and 1:3. The catalysts were tested for the photocatalytic reduction of Cr(VI) in the presence of oxalate ions. XRD analysis showed the formation of TiO2 anatase phase in all cases. UV–vis DRS spectra showed that both N–F and N-doping resulted in a decrease in the band gap energy (Eg), at the values of 2.81 eV and 3.01 eV, respectively. Thus, N–F doped TiO2 showed enhanced absorption at visible wavelengths. The structure and photodynamics of the TiO2 catalysts was investigated in detail by electron paramagnetic resonance (EPR) spectroscopy. The EPR data showed that: [i] NO centers, Nb and O2- radicals were formed. In addition, lattice Ti3+ ions were detected in N–F co-doped solids; [ii] the Nb and Ti3+ species were photoactive, while the NO species were non-photoactive. The photocatalytic efficiency for Cr(VI) reduction in the presence of oxalate ions, followed the trend TNF1 > TN1 > TNF2 > TN3 > TN2 > TNF3. Importantly, an apparent correlation between the catalytic efficiency and the concentration of Nb species was revealed by EPR. The location of Nb in the crystal lattice of TiO2 has been assessed also by measuring their microwave saturation parameters P1/2. Electron capturing by O2 and subsequent generation of O2- was favored for N-doped catalysts. In contrast, in N–F co-doped catalysts, O2 could not compete efficiently with Cr(VI) for the photogenerated electrons in energy states below the conduction band of TiO2, resulting in higher reduction efficiency for these catalysts.
TL;DR: In this paper, the performance of the Co1Cr2 catalyst with a Co/Cr molar ratio of 1:2 was evaluated on methane combustion with a space velocity of 36,000h −1.
TL;DR: In this paper, a facile and novel method for the removal of toxic chromium based on the appealing interaction between exfoliated graphene oxide (EGO), trioctylamine (TOA) and Cr(VI) is reported.
TL;DR: In this article, a simple voltammetric technique for quantification of the chromium(VI) is presented, which is based on the direct linear sweep voltammmetric reduction of Cr(VI), without any accumulation stage, or any complexing agent.
Abstract: Chromium(VI) should be monitored and controlled in the environment, since it is introduced into the environment from several sources and it is both toxic and carcinogenic being harmful to the health of human and also animals. A simple voltammetric technique for quantification of the chromium(VI) is presented in this paper. The technique is based on the direct linear sweep voltammetric reduction of Cr(VI) on a gold plated carbon based composite electrode, without any accumulation stage, or any complexing agent. The effect of supporting electrolyte matrix, pH and also scan rate is investigated. The effect chloride ions interference is also investigated. The calibration curve for chromium(VI) detection using the proposed method shows linearity from 20 μg/L to 2000 μg/L with a detection limit of 4.4 μg/L achieved without any accumulation or pre-concentration process. The method was also successfully used for determination of Cr(V) in river sample water, where recovery of 96% was achieved.
TL;DR: In this article, an electrospinning method was used to synthesize alumina nanofibers for adsorbent removal of chromium(VI) and fluoride ions from an aqueous system.
Abstract: In this study, we have synthesized alumina nanofibers by using an electrospinning method. The obtained alumina nanofibers were used as adsorbents for the removal of chromium(VI) and fluoride ions from an aqueous system. The morphology and size of the obtained nanofibers were characterized by scanning electron microscopy and transmission electron microscopy analytical techniques. The X-ray diffraction study of the nanofibers indicated the formation of pure and crystalline α-alumina. The effects of the pH, adsorbent dose, contact time, and initial concentration of the adsorbate on the alumina nanofiber surface have been studied. The optimum pH values for maximum removal of chromium(VI) and fluoride on the alumina nanofiber surface were found to be pH 5 and 7, respectively. The experimental data obtained from the adsorption studies by alumina nanofibers were analyzed by the Langmuir and Freundlich equation using a linearized correlation coefficient at room temperature. The Freundlich isotherm was found to fi...
TL;DR: In this article, a batch adsorption procedure was used to test the suitability of the fruit peel dust as an adsorbent for hexavalent chromium (reduction-coupled adaption) and the effect of different conditions, for example contact time, sorbate concentration, solution pH, and temperature, on sorption were investigated.
Abstract: The objective of this study was to assess the uptake of hexavalent chromium from aqueous solutions by mosambi (Citrus limetta) peel dust. A batch adsorption procedure was used to test the suitability of the fruit peel dust as an adsorbent for hexavalent chromium (reduction-coupled adsorption). The effect of different conditions, for example contact time, sorbate concentration, solution pH, and temperature, on sorption were investigated, and maximum uptake of hexavalent chromium from contaminated water was 250 mg g−1 at pH 2.0 and 40 °C. Hexavalent chromium uptake from contaminated water followed a pseudo-first-order rate expression. ΔG
0, ΔH
0, and ΔS
0 were evaluated and it was concluded that sorption was feasible, spontaneous, and endothermic in nature. The process is in good agreement with the Langmuir isotherm. The nature of possible adsorbent–metal ion interactions was examined by use of FTIR spectroscopy. This revealed the involvement in chromium binding of –OH, –NH, C=O, and C–O groups on the cell surfaces. This study indicated that mosambi peel can be used as an effective and environmentally friendly biosorbent for treatment of hexavalent chromium-containing contaminated water. Hexavalent chromium compounds are more toxic than trivalent chromium because of their high water solubility and mobility. Mosambi (Citrus limetta) peel effectively removes hexavalent chromium from contaminated water by reducing it to trivalent chromium.