Relevant bibliographies by topics / Cr (VI) reduction

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  2. Dissertations / Theses
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Academic literature on the topic 'Cr (VI) reduction'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Cr (VI) reduction"

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Alexander, J., A. Mikalsen, and D. Ryberg. "MICROSOMAL REDUCTION OF Cr VI." Acta Pharmacologica et Toxicologica 59 (March 13, 2009): 267–69. http://dx.doi.org/10.1111/j.1600-0773.1986.tb02759.x.

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Standeven, Andrew M., and Karen E. Wetterhahn. "Chromium(VI) Toxicity: Uptake, Reduction, and DNA Damage." Journal of the American College of Toxicology 8, no. 7 (December 1989): 1275–83. http://dx.doi.org/10.3109/10915818909009118.

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Much recent data supports the “uptake-reduction” model explaining the carcinogenicity of chromium(VI) compounds and the lack of carcinogenicity of chromium(III) com pounds. Cr(VI) readily enters cells by diffusion through a nonspecific anion channel, whereas cells are relatively impermeable to Cr(III). Glutathione appears to facilitate Cr(VI) uptake by reducing Cr(VI) to Cr(III) after it enters the cell, presumably keeping intracellular Cr(VI) concentration low and allowing for further Cr(VI) uptake. Some other nonenzymatic factors, for example, ascorbate and riboflavin, as well as enzymes, such as cytochrome P-450, DT-diaphorase, and the mitochondrial electron transport chain complexes, are capable of reducing Cr(VI) in vitro, but their contribution in vivo is not clear. Cr(VI), once reduced intracellularly, produces various forms of DNA damage including DNA interstrand crosslinks, DNA-protein crosslinks, DNA strand breaks, and Cr-DNA adducts. The pathway of Cr(VI) metabolism in different tissues appears to influence the type of “reactive intermediates” produced, for example, Cr(V) and radical species, and thus the nature and extent of DNA damage. This DNA damage presumably accounts for observed functional changes in DNA replication and transcription which may be crucial to the carcinogenicity of chromium(VI) compounds.
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Tsigaridas, Kostas, Thomas Sawidis, and Afroditi Sivropoulou. "Cr(VI) reduction by bacteria species isolated from Cr(VI) polluted landfill." Current Opinion in Biotechnology 22 (September 2011): S57. http://dx.doi.org/10.1016/j.copbio.2011.05.156.

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Arias, Y. Meriah, and Bradley M. Tebo. "Cr(VI) Reduction by Sulfidogenic and Nonsulfidogenic Microbial Consortia." Applied and Environmental Microbiology 69, no. 3 (March 2003): 1847–53. http://dx.doi.org/10.1128/aem.69.3.1847-1853.2003.

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ABSTRACT In time course experiments, bacterial community compositions were compared between a sulfidogenic and two nonsulfidogenic Cr(VI)-reducing consortia enriched from metal-contaminated sediments. The consortia were subjected to 0 and 0.85 mM or 1.35 mM Cr(VI), and Cr(VI) reduction, growth, and denaturing gradient gel electrophoresis profiles of PCR products of small-subunit (16S) ribosomal genes were compared. Results showed that although Cr(VI) was completely reduced by the three consortia, Cr(VI) inhibited cell growth, with sulfate-reducing bacteria being particularly sensitive to Cr(VI) toxicity relative to other bacteria in the consortia.
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Thesai, Annadurai Sakthi, Rajalingam Sangeetha, Lakshmanan Ashokkumar, Ramachandran Palanivelan, Sundaram Rajakumar, and Pudukadu Munusamy Ayyasamy. "Evaluation of Cr(VI) Reducing Capability of Shewanella putrefaciens (MTTC8410) and Optimization of Operational Parameters." Journal of Pure and Applied Microbiology 14, no. 4 (December 15, 2020): 2715–27. http://dx.doi.org/10.22207/jpam.14.4.49.

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Bioremediation is an important technology to remediate the chromium (Cr) contaminated soil and water. In this study, Shewanella putrefaciens (MTTC8410) was used to investigate the influence of carbon concentration, pH, and temperature on reduction of hexavalent chromium [Cr(VI)] into trivalent chromium [Cr(III)]. The increased bacterial growth rate was significantly reduced the Cr(VI) concentration. In batch mode experiments, 1% starch recorded the highest reduction of Cr(VI) (90%) followed by 1% glucose (88% reduction) and a reduction of 77% was by 1% cellulose. By using various pH conditions the maximum Cr(VI) reduction was achieved at pH 7.0. In this experiment the maximum Cr(VI) reduction (75%) was observed at 35°C, followed by 30°C with 62% of Cr(VI) reduction. Bioreactor analysis revealed the highest reduction of Cr(VI) (88%) in unsterile tannery effluent. The significant levels of physico- chemical parameters were reduced in unsterile tannery effluent, as compared to the sterile tannery effluent. The experimental results revealed that the S. putrefaciens (MTTC8410) could be used as a potential bacterial strain for reduction of Cr(VI) from contaminated groundwater.
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Zhang, Jun Hui. "Characterization of a Rhizobium larrymoorei FJ Exhibiting High Level Cr(VI) Reduction Potential." Advanced Materials Research 356-360 (October 2011): 1009–14. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.1009.

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The investigation was conducted to evaluate mechanism of Cr(VI) resistance and reduction by a bacterial strain named FJ under different conditions. This strain, identified as a member of Rhizobium larrymoorei by analysis of its 16S rRNA gene sequence was previously isolated from a paddy soil contaminated by e-waste recycling. Good Cr(VI) reduction ability catalyzed by growing cells of R. larrymoorei FJ was observed in batch cultures conducted at different initial Cr(VI) concentrations. Up to 83.23% reduction was shown in LB medium supplemented with 2.50 mM Cr(VI). Cr(VI) was transformed to some soluble form of Cr(III) due to anaerobic respiration. Biosorption was also observed in the process of bioreduction. But only loosely cell-surface binding Cr(VI) was detected in cells grown in medium supplied with different concentrations of Cr(VI). Present of yeast or citrate could enhance Cr(VI) reduction of resting cells. However, Cr(VI) reduction by resting cells was only observed at Cr(VI) concentration lower than 0.25 mM. R. larrymoorei FJ exhibited a high efficiency of Cr(VI) reduction at temperatures from 28°C to 37°C and pH values from 6.0 to 7.0.
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Chen, Chiou-Pin, Kai-Wei Juang, and Dar-Yuan Lee. "Effects of liming on Cr(VI) reduction and Cr phytotoxicity in Cr(VI)-contaminated soils." Soil Science and Plant Nutrition 58, no. 1 (February 2012): 135–43. http://dx.doi.org/10.1080/00380768.2011.653673.

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Kourtev, Peter S., Cindy H. Nakatsu, and Allan Konopka. "Inhibition of Nitrate Reduction by Chromium(VI) in Anaerobic Soil Microcosms." Applied and Environmental Microbiology 75, no. 19 (August 14, 2009): 6249–57. http://dx.doi.org/10.1128/aem.00347-09.

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ABSTRACT Chromium is often found as a cocontaminant at sites polluted with organic compounds. For nitrate-respiring microbes, Cr(VI) may be not only directly toxic but may also specifically interfere with N reduction. In soil microcosms amended with organic electron donors, Cr(VI), and nitrate, bacteria oxidized added carbon, but relatively low doses of Cr(VI) caused a lag and then lower rates of CO2 accumulation. Cr(VI) strongly inhibited nitrate reduction; it occurred only after soluble Cr(VI) could not be detected. However, Cr(VI) additions did not eliminate Cr-sensitive populations; after a second dose of Cr(VI), bacterial activity was strongly inhibited. Differences in microbial community composition (assayed by PCR-denaturing gradient gel electrophoresis) driven by different organic substrates (glucose and protein) were smaller than when other electron acceptors had been used. However, the selection of bacterial phylotypes was modified by Cr(VI). Nine isolated clades of facultatively anaerobic Cr(VI)-resistant bacteria were closely related to cultivated members of the phylum Actinobacteria or Firmicutes. In Bacillus cereus GNCR-4, the nature of the electron donor (fermentable or nonfermentable) affected Cr(VI) resistance level and anaerobic nitrate metabolism. Our results indicate that carbon utilization and nitrate reduction in these soils were contingent upon the reduction of added Cr(VI). The amount of Cr(VI) required to inhibit nitrate reduction was 10-fold less than for aerobic catabolism of the same organic substrate. We speculate that the resistance level of a microbial process is directly related to the diversity of microbes capable of conducting it.
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Marsh, Tamara L., and Michael J. McInerney. "Relationship of Hydrogen Bioavailability to Chromate Reduction in Aquifer Sediments." Applied and Environmental Microbiology 67, no. 4 (April 1, 2001): 1517–21. http://dx.doi.org/10.1128/aem.67.4.1517-1521.2001.

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ABSTRACT Biological Cr(VI) reduction was studied in anaerobic sediments from an aquifer in Norman, Okla. Microcosms containing sediment and mineral medium were amended with various electron donors to determine those most important for biological Cr(VI) reduction. Cr(VI) (about 340 μM) was reduced with endogenous substrates (no donor), or acetate was added. The addition of formate, hydrogen, and glucose stimulated Cr(VI) reduction compared with reduction in unamended controls. From these sediments, an anaerobic Cr(VI)-utilizing enrichment was obtained that was dependent upon hydrogen for both growth and Cr(VI) reduction. No methane was produced by the enrichment, which reduced about 750 μM Cr(VI) in less than six days. The dissolved hydrogen concentration was used as an indicator of the terminal electron accepting process occurring in the sediments. Microcosms with sediments, groundwater, and chromate metabolized hydrogen to a concentration below the detection limits of the mercury vapor gas chromatograph. In microcosms without chromate, the hydrogen concentration was about 8 nM, a concentration comparable to that under methanogenic conditions. When these microcosms were amended with 500 μM Cr(VI), the dissolved hydrogen concentration quickly fell below the detection limits. These results showed that the hydrogen concentration under chromate-reducing conditions became very low, as low as that reported under nitrate- and manganese-reducing conditions, a result consistent with the free energy changes for these reactions. The utilization of formate, lactate, hydrogen, and glucose as electron donors for Cr(VI) reduction indicates that increasing the availability of hydrogen results in a greater capacity for Cr(VI) reduction. This conclusion is supported by the existence of an enrichment dependent upon hydrogen for growth and Cr(VI) reduction.
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Javaid, Mahwish, and Sikander Sultan. "Plant growth promotion traits and Cr (VI) reduction potentials of Cr (VI) resistantStreptomycesstrains." Journal of Basic Microbiology 53, no. 5 (June 26, 2012): 420–28. http://dx.doi.org/10.1002/jobm.201200032.

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Dissertations / Theses on the topic "Cr (VI) reduction"

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VanEngelen, Michael Robert. "Fe(III) and Cr(VI) reduction in alkaline media using Soap Lake alkaliphiles." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Summer2005/m%5Fvanengelen%5F081905.pdf.

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Dragana, Tamindžija. "Isolation and characterization of Cr(VI) tolerant soil bacteria." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=110336&source=NDLTD&language=en.

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In  this  study,  tolerance  of  soil  bacteria  to  hexavalent  chromium  (Cr(VI))  was  investigated.  First,  influence  of  high chromium levels of anthropogenic and geogenic origin on the  soil cultivable  bacterial community was examined. Next, a number  of  bacterial  strains  with  high  Cr(VI)  tolerance  were  isolated  from  diverse   environmental  samples  such  as  soil, sediment, water and waste material.  Strains were  identified  and  tested for  the  level of  Cr(VI) tolerance  and  the  ability toreduce toxic Cr(VI) to more innocuous Cr(III). Selected  Bacillus cereus  group strains  were further characterized  -  their morphological  and  biochemical  characteristics,  16S  rRNA  and  pycA  gene  sequences,  biofilm  formation  potential  and resistance to other heavy metals were determined. Also, more detailed study of their tolerance level and  Cr(VI) reduction was  conducted.  Strain  with  the highest  resistance  together  with the  control  chromate  sensitive  strain  were  analyzed  by STEM EDS for their cellular and endospore Cr content under different conditions. Results indicate Cr(VI) tolerant bacteria are  present  both  in  low  and  high  Cr  environments.  Majority  of  isolates  belonged  to  the  B.  cereus  group  indicating  its overall high tolerance to  Cr(VI). Certain strains exhibited high  tolerance and reduction  ability,  indicating their possibleusefulness  in practical  bioremediation  application.  STEM  EDS  analysis  of  Cr(VI)-sensitive  B.  subtilis  PY79  strain  and Cr(VI)-resistant  B. cereus  group strain  NCr1a revealed  significant differences in their response to Cr(VI)  and in  their  Cr cellular and endospore content.
U ovom radu ispitana je tolerantnost  zemljišnih  bakterija na šestovalentni hrom (Cr(VI)). Prvo, ispitan je uticaj visokog nivoa  hroma  antropogenog  i  geogenog  porekla  na  kultivabilnu  bakterijsku  zajednicu  zemljišta.  Dalje,  izolovani  su bakterijski sojevi sa visokom tolerancijom na Cr(VI) iz različitih sredinskih uzoraka   kao što su zemljište, sediment, voda i otpadni materijal. Sojevi su identifikovani i određen je nivo njihove Cr(VI) tolerancije i sposobnost redukcije toksičnog Cr(VI)  u  manje  toksični  Cr(III).  Odabrani  sojevi  Bacillus  cereus  grupe  su  dalje  karakterisani  –  određene  su  njihove morfološke i biohemijske karakteristike, 16S rDNK i  pycA  sekvence, potencijal formiranja biofilma i otpornost na druge teške  metale.  Takođe,  sprovedeno  je  detaljnije  ispitivanje  njihove  tolerancije  i  redukcije  Cr(VI).  Soj  sa  najvišom otpornošću  je  uporedo  sa  kontrolnim  osetljivim  sojem  analiziran  pomoću  STEM  EDS  na  sadržaj  hroma  u  ćelijama  I endosporama u različitim uslovima. Rezultati ukazuju da su bakterije tolerantne na Cr(VI) prisutne i u sredinama sa niskim i  sa  visokim  koncentracijama  hroma.  Većina  izolata  pripadala  je  B.  cereus  grupi  što  ukazuje  na njenu  uopšteno  visoku otpornost na Cr(VI). Pojedini sojevi su pokazali visoku otpornost i sposobnost  redukcije Cr(VI), što ukazuje na mogućnost njihove praktične primene u bioremedijaciji. STEM EDS analiza osetljivog B. subtilis PY79 soja i Cr(VI)- rezistentnog soja B.  cereus  grupe  NCr1a  otkrila  je  značajne  razlike  u  njihovom  odgovoru na  Cr(VI)  i  sadržaju  Cr  u njihovim  ćelijama  i endosporama.
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Al-Hakak, Alaa. "Degradation of naphthalene and concurrent reduction of Cr (VI) by Pseudomonas putida ATCC 17484." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30806.

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Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are often present together at contaminated sites. These sites are considered difficult to clean-up using bioremediation technologies because of the toxicity of heavy metals to microorganisms. Laboratory experiments were conducted to verify if biodegradation of a model PAH, naphthalene, could be sustained over a long time-period (weeks) in the presence of a common heavy metal contaminant, Cr (VI). Complete reduction of Cr (VI) at concentrations up to 6.3 mg/L was achieved by Pseudomonas putida ATCC 17484 in the presence of naphthalene that was continuously released from an immiscible organic liquid, 2,2,4,4,6,8,8-heptamethylnonane (HMN). The presence of Cr (VI) inhibited bacterial growth and reduced naphthalene biodegradation rates. Despite this the microorganisms were able to degrade significant masses of naphthalene, quantities much greater than those reported in earlier studies. The addition of 1,2-Naphthoquinone, a possible by-product of naphthalene degradation and an oxidizing agent, resulted in improved naphthalene biodegradation rates in the presence of Cr (VI).
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Sharma, Kanika. "Microbial Cr(VI) reduction role of electron donors, acceptors, and mechanisms, with special emphasis on Clostridium spp. /." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE0000608.

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Igboamalu, Tony E. "Kinetic studies of Cr(VI) reduction in an indigenous mixed culture of bacteria in the presence of As(III)." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/46240.

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An indigenous mixed culture of bacteria collected from a Wastewater Treatment Plant (Brits, North West Province, South Africa), biocatalytically reduced Cr(VI) in the presence of As(III). Both the reduced chromium (Cr(III)) and the oxidised arsenic (As(V)) readily form amorphous hydroxides that can be easily separated or precipitated from the aqueous phase as part of the treatment process. Treatment of Cr(VI) and As(III) before disposal of wastewater is critical since both compounds are known to be carcinogenic and mutagenic at very low concentrations, and acutely toxic at high concentrations. Batch experiments were conducted to evaluate the rate of Cr(VI) reduction under anaerobic condition in the presence of its co-contaminant As(III) typically found in the groundwater and mining effluent. Results showed near complete Cr(VI) reduction under initial Cr(VI) concentrations up to 70 mg/L in a batch amended with 20 mg/L As(III). However, increasing Cr(VI) concentrations up to 100 mg/L resulted in the inhibition of Cr(VI) reduction activity. Further investigation was conducted in a batch reactor amended with 70 mg/L Cr(VI) concentration at different As(III) concentrations ranging from 5-70 mg/L to evaluate the effect of varying As(III) concentration on Cr(VI) reduction efficiency. Results showed that Cr(VI) reduction efficiency increased as As(III) concentrations increased from 5-40 mg/L. However, further increase in As(III) concentration up to 50 mg/L resulted in incomplete Cr(VI) reduction and decrease in Cr(VI) reduction efficiency. These results suggest that the rate of Cr(VI) reduction depends on the redox reaction of As(III) and As(V) with Cr(VI). Moreover, the inhibitory effect observed at high Cr(VI) and As(III) concentration may also be attributed to the dual toxicity effect of Cr(VI) and As(III) on microbial cell. From the above batch kinetic studies lethal concentration of Cr(VI) and As(III) for these strains was evaluated and established. Initial evaluation of the bacteria using 16S rRNA partial sequence method showed that cells in the mixed culture comprised predominantly of the Gram-positive species: Staphylococcus sp., Enterobacter sp., and Bacillus sp. The biokinetic parameters of these strains were estimated using a non-competitive inhibition model with a computer programme for simulation of the Aquatic System “AQUASIM 2.0”. Microbial reduction of Cr(VI) in the presence of As(III) was further investigated in continuous-flow bioreactors (biofilm reactor) under varying Cr(VI) loading rates. The reactor achieved Cr(VI) removal efficiency of more than 96 % in the first three phases of continuous operation at lower Cr(VI) concentration ranging from 20-50 mg/L. However, 20 % decrease in Cr(VI) removal efficiency was observed as Cr(VI) concentration increase up to 100 mg/L. The reactor was able to recover from Cr(VI) and As(III) overloading phase after establishing the resilient nature of the microorganism. Similarly to the batch reactor studies the overall performance of the reactor also demonstrated that the presence of As(III) greatly enhance Cr(VI) reduction in a bioreactor. This was evident by near complete removal of Cr(VI) concentration up to 50 mg/L. The basic mass balance expressions on Cr(VI) along with the non-competitive inhibition model were used to estimate the biokinetic parameters in the continuous flow bioreactor system. Cr(VI) reduction efficiency along the longitudinal column was also evaluated in this study. Results showed that Cr(VI) efficiency increased as Cr(VI) concentration travels along the longitudinal column. Other important factors such as oxygen and pH during biological Cr(VI) reduction in the presence of As(III) oxidation were also evaluated.
Dissertation (MEng)--University of Pretoria, 2014.
tm2015
Chemical Engineering
MEng
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Agrawal, Sheela G. "Cr(VI) reduction by Fe(II)-dissolved organic matter complexes and the characterization of pore water dissolved organic matter from a coastal wetland in the Laurentian Great Lakes." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1230735368.

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Baronaitė, Sandra. "Vario (II) ir chromo (VI) jonų pašalinimas metaline geležimi iš vandeninių tirpalų." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090629_122147-11310.

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Šiame eksperimente buvo nagrinėjama pH įtaka Cr (VI) ir Cu (II) jonų pašalinimui iš vandeninių tirpalų, naudojant metalinę geležį Fe (0), kai tirpalų pH vertės buvo nuo 2 iki 6, purtymo procese, uždaruose ir atviruose induose. Kadangi Cr (VI) ir Cu (II) jonų koncentracijų sumažėjimas tirpale priklauso nuo geležies paviršiaus, tai labai svarbu ją tinkamai paruošti: išvalyti ir aktyvuoti. Maksimalus Cr (VI) jonų pašalinimo efektyvumas buvo esant pH vertei 2, o Cu (II) jonų atveju, kai pH vertė 4 uždaruose induose ir atviruose induose – chromo atveju pH 6, vario atveju, kai pH 4. Pašalinimo įvertinimui naudojamos kalibraciniės kreivės pagal kurias apskaičiuojamos likusiųjų jonų koncentracijos, matuojant tirpalų optinius tankius. Metodas yra pigus ir patikimas, nes pašalinima didelė dalis sunkiųjų metalų jonų.
The effects of pH on Cr (VI) and Cu (II) ions removal from solutions by Fe (0) was investigated by batch shaking process. Since the presence of ferrous iron in the solution is mainly responsible for Cr (VI) and Cu (II) reduction the surface of iron must be purified and activated. The maximum Cr (VI) removal efficiency was found at pH 2 and in Cu (II) case it was pH 4 without oxygen and in case with open jar it was for Cr (vi) removal pH 6 and for Cu (II) removal pH 4. Remained concentrations of Cu (II) and Cr (VI) ions were investigated using calibrated graphs and analysis of optical density. This study confirmed that this method is cheap because we can use wasted iron and effective of removing most of heavy metal ions from solutions.
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Agrawal, Sheela G. "Cr(VI) reduction by Fe(II)-dissolved organic complexes and the characterization of pore water dissolved organic matter from a coastal wetland in the Laurentian Great Lakes." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1230735368.

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Oh, Jungmin. "Preparation and application of conducting polymer-carbon nanotube composite." [Johnson City, Tenn. : East Tennessee State University], 2004. https://dc.etsu.edu/etd/960.

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Thesis (M.S.)--East Tennessee State University, 2004.
Title from electronic submission form. ETSU ETD database URN: etd-1110104-211520 Includes bibliographical references. Also available via Internet at the UMI web site.
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Camera, Adriana Simane. "Estudo da especiação do cromo no processo de adsorção por carvão ativado usando a espectroscopia de emissão de raios X K&#946." Universidade Estadual do Oeste do Parana, 2011. http://tede.unioeste.br:8080/tede/handle/tede/1896.

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Made available in DSpace on 2017-07-10T18:08:16Z (GMT). No. of bitstreams: 1 Adriana Simane Camera.pdf: 3567207 bytes, checksum: 8d7a8eda99ee4c4d490c232bcc95cfd2 (MD5) Previous issue date: 2011-02-25
Fundação Araucária
This work aims to study the reduction of hexavalent chromium to trivalent form through the adsorption process as assessed by the Kβ X-ray emission spectrometry. As adsorbent material activated carbon samples were used, while the resin Amberlite IR 120 was used as an indicator of the presence of Cr(III) in all solutions containing Cr(VI). Preliminar speciation tests were performed previously in solutions containing Cr(VI) in order to analyze the possible reduction to Cr(III) due to the effect of solution pH. A EDTA-based colorimetric speciation method of Cr(III) was applied. Preliminary kinetic Cr adsorption tests were performed at controlled temperature and agitation, achieving the equilibrium at 24 h for activated carbon. Batch single equilibrium Cr adsorption experiments using activated carbon and cation exchange resin materials as adsorbents and 8 mequiv.L-1 of Cr (III) and Cr(VI) ions as adsorvates were performed at pH 3.5 and under controlled temperature and agitation. Adsorbent and Cr reference material samples were pressed in pellets for spectrometric analysis. By using a high-resolution spectrometer of Johann type and a 6.1 keV monochromatic X-ray beam, Kβ X-ray emission spectra of Cr-treated adsorbent and reference material samples were registered by a Si detector, scanning the scattering X-ray by a spherycal bent analyzer around the Kβ1,3 spectral line of metallic chromium. The sample, spherical bent analyzer and detector system was positioned on the Rowland circle in order to scan in high resolution condition, focus the maximum back-scattered X-ray beam on the main detector and built Kβ X-ray emission spectra. As the incident monochromatic X-ray beam is a time-depending function, X-ray intensity that was registrated by detector was monitored and it was normalized to monitor-detector intensity. By setting measurement time of 2-4 h for Cr-treated adsorbent samples and 10-30 min for Cr reference material ones, a complete full scan of Kβ X-ray emission region was performed with enough statistic to observe the sattelite lines of chromium, which suffer a strong influence due to the oxidation state of metal ion and the chemical environment. The Cr-Kβ emission spectra were plotted on the basis of recorded X-ray intensity (y-axis) and spherical bent analyzer (SBA) position (x-axis), performing both the monitor-to-normalized intensity and the converted-to-energy SBA position. Besides this, scattered X-rays on matrix bulk and chromium absorption edge effect were systematically subtracted from Cr-Kβ emission spectra, applying pseudo-physical procedures and consequentely allowing enhancing the weaker sattellites lines of chromium. Main physical characteristic such as energy and intensity of main (Cr-Kβ1,3) and satellite lines (Cr-Kβ2,5 and Cr-Kβ ) for Cr-Kβ emission spectra of Cr treated-adsorbent samples were extracted by gaussian type peak fits and then compared with those of Cr reference materials, allowing to assign the oxidation state of chromium ions adsorbed on activated carbon surface and removed by an ion exchange process on cationic resin surface. In addition, no Cr(VI) reduction in acidic solutions was observed according to the EDTA-based colorimetric speciation result as well as with no presence of Cr(III)-Kβ spectral line pattern in Cr(VI) treated cationic resin samples. Based on Cr-Kβ spectral line analysis, the activated carbon samples treated with Cr(III) and Cr(VI) ions have shown the same spectral line pattern corresponding to the Cr(III) one. Thus, the reduction of Cr(VI) to Cr(III) has occurred by the adsorption process
Este trabalho visa estudar a redução do cromo hexavalente à forma trivalente através do processo de adsorção, avaliada pela espectrometria Kβ de emissão. Amostras de carvão ativado foram utilizados como material adsorvente, enquanto a resina Amberlite IR 120 foi usada como um indicador da presença de Cr(III) em todas as soluções contendo Cr(VI). Testes preliminares de especiação foram realizados em soluções contendo Cr(VI), a fim de analisar a possível redução para Cr(III) devido ao efeito do pH da solução. Foi aplicado o método de especiação colorimétrica de Cr(III), usando como complexante o EDTA. Testes preliminares da cinética de adsorção de íons de Cr foram realizados em batelada a temperatura e agitação controlada, alcançando o equilíbrio em 24 h para o carvão ativado. Foram realizados experimentos de adsorção de Cr utilizando carvão ativado e resina de troca catiônica materiais em soluções contendo 8 mequiv L-1 de Cr(III) e Cr(VI) em pH 3,5 e com temperatura e agitação controladas. Foram prensados, em forma de pastilhas, amostras de adsorventes tratados com Cr(III) e (VI), além de materiais de referência de Cr, para análise espectrométrica. Usando um espectrômetro de alta resolução do tipo de Johann e um feixe de raios X monocromático de 6,1 keV, foram registrados, por um detector de Si, espectros de emissão de raios-X Kβ de amostras de material adsorbente tratados com íons de Cr bem como de materiais de referência, fazendo para tanto a varredura em energia dos raios-X espalhados pela amostra em torno da linha espectral principal Kβ do cromo metálico. O conjunto amostra, analisador esfericamente curvado (SBA) e detector foi posicionado sobre um círculo de Rowland, a fim de obter, em condições de alta resolução, a focalização do feixe de raios X retro-espalhados no detector principal e permitindo a construção de espectros de emissão Kβ. Como a intensidade do feixe incidente de raios-X monocromático foi uma função dependente do tempo, a intensidade de raios-X registrada pelo detector foi monitorada e normalizada por aquela registrada pelo detector-monitor. Ao definir o tempo de medição de 2-4 h para amostras adsorvente tratadas com íons de Cr e 10-30 min para os compostos de referência de Cr, uma região completa do espectro de emissão de raios-X foi obtida com estatística suficiente para observar as linhas satélite dos íons de cromo, que sofrem uma forte influência devido ao estado de oxidação do íon metálico e do ambiente químico. Os espectros Kβ foram graficados em intensidade de raios-X contra a posição do analisador curvado (SBA), sendo sistematicamente normalizados a intensidade do detector-monitor e convertendo a posição do SBA em energia. Além disso, o fundo oriundo dos raios X espalhados na amostra e do efeito da borda de absorção do Cr foi subtraído de todos os espectros de emissão Cr-K, destacando assim as linhas satelites de cromo. As características físicas, como a energia e a intensidade, das linhas principais (Cr-Kβ1,3) e linhas satélite (Cr-Kβ2,5 e Cr-Kβ") foram extraídas dos espectros de emissão Cr-K das amostras tratadas com Cr e comparados com os dos materiais de referência, permitindo inferir o estado de oxidação do cromo adsorvido no carvão ativado e os que também foram removidos pela resina catiônica. Além disso, não foi observado a redução do Cr(VI) na solução, de acordo com a ausência das linhas espectrais de Cr(III) em amostras de resina catiônica tratadas com Cr(VI). Baseado na análise das linhas espectrais, as amostras de carvão ativado tratadas com Cr(III) e Cr(VI) têm mostrado o mesmo padrão de linhas espectrais correspondentes ao Cr(III) e portanto, a redução de Cr(VI) para Cr(III) ocorreu durante o processo de adsorção
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Book chapters on the topic "Cr (VI) reduction"

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Gennaro, Armando, and Christian Durante. "Environmentally Accepted Processes for Substitution and Reduction of Cr(VI)." In Encyclopedia of Applied Electrochemistry, 866–72. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4419-6996-5_116.

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Yoon, Jae Kyung, Eun Jung Shim, Jin Wook Ha, and Hyun Ku Joo. "Photocatalytic Cr(VI) Reduction by Anodized TiO2." In Eco-Materials Processing and Design IX, 221–24. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/0-87849-472-3.221.

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Du, ChangMing, and JianHua Yan. "Reduction and Removal of Cr(VI) from Aqueous Solution by Microplasma." In Advanced Topics in Science and Technology in China, 41–59. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-3656-9_4.

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He, Jiawei, Ling Ai, Yiyan Wang, Yuan Long, Chaoliang Wei, and Jingjing Zhan. "Carbothermal Synthesis of Aerosol-Based Iron-Carbon Nanocomposites for Adsorption and Reduction of Cr(VI)." In Nanoscale Zerovalent Iron Particles for Environmental Restoration, 495–510. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-95340-3_14.

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Magalhães, Fabiano, Márcio César Pereira, José Domingos Fabris, Sue Ellen Costa Bottrel, Alejandro Amaya, Nestor Mogliazza, and Rochel Montero Lago. "Hematite reaction with tar to produce carbon/iron composites for the reduction of Cr(VI) contaminant." In LACAME 2008, 43–48. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-10764-1_8.

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Quievryn, George, Margarida Goulart, Joseph Messer Zhitkovich, and Anatoly Zhitkovich. "Reduction of Cr (VI) by cysteine: Significance in human lymphocytes and formation of DNA damage in reactions with variable reduction rates." In Molecular Mechanisms of Metal Toxicity and Carcinogenesis, 107–18. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4615-0793-2_13.

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Zhang, Chuanlun, Shi Liu, John Logan, Raja Mazumder, and Tommy J. Phelps. "Enhancement of Fe(III), Co(III), and Cr(VI) Reduction at Elevated Temperatures and by a Thermophilic Bacteriumt." In Seventeenth Symposium on Biotechnology for Fuels and Chemicals, 923–32. Totowa, NJ: Humana Press, 1996. http://dx.doi.org/10.1007/978-1-4612-0223-3_87.

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Dey, Satarupa. "Role of Bacterial Chromate Reductase in Bioremediation of Chromium-Containing Wastes." In Recent Advancements in Bioremediation of Metal Contaminants, 72–96. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-4888-2.ch005.

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Chromium toxicity is a major environmental concern as it is the chief environmental pollutant released by paint, stainless steel, and mining industries. In nature, chromium exists in two stable valance states: Cr(VI) and Cr(III). Cr(VI) is highly toxic and soluble at neutral pH, whereas Cr(III) is insoluble at normal pH and is less toxic. Thus, it is essential to draw strategies for mitigation of Cr(VI), and microbial reduction of toxic Cr(VI) has been identified as a bioremediation technique not only to detoxify chromium but also to recover the non-toxic Cr(III) by physical means. Chromate reductase, the central enzyme involved in bioreduction of Cr(VI) to Cr(III) may be both intracellular as well as extracellular in nature. Most of the chromate reductase enzyme belongs to the oxidoreductase group such as nitroreductase, iron reductase, quinone reductase, hydrogenase, flavin reductase, as well as NAD(P)H-dependent reductase. Detailed analysis of the structure of the enzymes will help us in the suitable application of these enzymes in bioremediation of metal-contaminated wastes.
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N. Chirwa, Evans M., and Pulane E. "Biological Cr(VI) Reduction: Microbial Diversity, Kinetics and Biotechnological Solutions to Pollution." In Biodiversity. InTech, 2011. http://dx.doi.org/10.5772/24311.

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Rane, N., V. Nandre, S. Kshirsagar, S. Gaikwad, and K. Kodam. "Simultaneous oxidation of As(III) and reduction of Cr(VI) by Alcaligenes sp." In Environmental Arsenic in a Changing World, 514–15. CRC Press, 2019. http://dx.doi.org/10.1201/9781351046633-204.

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Conference papers on the topic "Cr (VI) reduction"

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Chrastný, Vladislav. "CR ISOTOPES AS A VALUABLE TRACER OF CR(VI) REDUCTION IN POLLUTED (GROUND)WATERS." In 44th International Academic Conference, Vienna. International Institute of Social and Economic Sciences, 2018. http://dx.doi.org/10.20472/iac.2018.044.012.

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Shi, Hongfei, Chuanbo Dai, Fang Liu, Weidong Wang, and Huaqiao Tan. "PHOTOCATALYTIC REDUCTION OF Cr (VI) by PMo12/TiO2 ELECTROSPUN NANOFIBER COMPOSITES." In International Conference on New Materials and Intelligent Manufacturing (ICNMIM). Volkson Press, 2018. http://dx.doi.org/10.26480/icnmim.01.2018.94.97.

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Li, Xiaoqin, Lei Lei, Chen Yang, and Wei-xian Zhang. "Reduction of Cr(VI) by Nanoscale Zero Valent Iron (nZVI): The Reaction Kinetics." In 2010 4th International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2010. http://dx.doi.org/10.1109/icbbe.2010.5515574.

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Wang, De-Jin, and Xi-Mei Zhou. "Comparative Study on Photocatalytic Reduction of Cr (VI) by TiO2 and Ce-TiO2." In 2008 2nd International Conference on Bioinformatics and Biomedical Engineering (ICBBE '08). IEEE, 2008. http://dx.doi.org/10.1109/icbbe.2008.607.

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NOVACK, A. M., F. V. HACKBARTH, B. A. MARINHO, G. S. DOS REIS, J. A. B. VALLE, A. A. ULSON DE SOUZA, V. J. P. VILAR, and S. M. A. G. SOUZA. "PHOTOCATALYTIC REDUCTION OF Cr(VI) USING DIFFERENT HYBRID MATERIALS: TITANIUM NANOSHEETS/POZZOLAN AND KAOLIN/POLYSILOXANES." In XXII Congresso Brasileiro de Engenharia Química. São Paulo: Editora Blucher, 2018. http://dx.doi.org/10.5151/cobeq2018-pt.0165.

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Liu, Yanxiang, Li Guo, Feng Wu, and Nansheng Deng. "Influence of Low Molecular Weight Organic Carboxylic Acids on Cr (VI) Photo-Reduction in Montmorillonite Suspensions." In 2009 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2009. http://dx.doi.org/10.1109/icbbe.2009.5162962.

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"Photo-catalytic reduction of hexavalent chromium (Cr(VI)) under visible light with Bi-Zn co-doped TiO2." In 8th International conference on Research in Engineering, Science and Technology. Acavent, 2018. http://dx.doi.org/10.33422/8rest.2018.11.50.

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Wang, Qi, Zhaohui Wang, Yi Zhang, Yanqing Cong, Jincai Zhao, and Peide Sun. "Application of N-F-Codoped TiO2 for the Photocatalytic Reduction of Cr(VI) under Visible Light Irradiation." In 2010 4th International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2010. http://dx.doi.org/10.1109/icbbe.2010.5515535.

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Li, Ying, Xiaoliang Liang, Hongping He, and Yuji Arai. "Remarkable Effect of Co Substitution in Magnetite on the Reduction Removal of Cr(VI) Coupled with Aqueous Fe(II)." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.1533.

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Nickson, Ian D., Colin Boxall, Angela Jackson, and Guy O. H. Whillock. "The Development of a Method for the Simultaneous Measurement of Cerium (IV) and Chromium (VI) Species in Nitric Acid Media." In ASME 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2009. http://dx.doi.org/10.1115/icem2009-16124.

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The corrosion of stainless steel in nitric acid media is a major concern for the nuclear industry. Several reprocessing schemes such as PUREX (Plutonium Uranium Reduction Extraction) and UREX (Uranium Reduction Extraction) utilise nitric acid media, and an understanding of the behaviour of key chemical species in these process streams is vital if their effect on associated corrosion reactions and their rates is to be accurately assessed and quantified. This will allow for more accurate prediction of the working lifetime of any stainless steel surface in contact with the process stream in question. Two such key species that are found in nuclear process streams are cerium as Ce(IV) and chromium as Cr(VI), both of which may act as corrosion accelerants. The redox chemistry of cerium and chromium in highly active liquor (HAL) will depend on nitrous acid concentration, temperature, acidity, total nitrate and possibly the influence of other dissolved species and hence an analytical technique for the on-line measurement of these quantities would be useful for lifetime prediction and corrosion prevention. As a result of this, a strategy for the simultaneous measurement of both Ce(IV) and Cr(VI) species in the presence of other ions typically found in process streams (such as Iron, Magnesium Neodymium and Aluminium) has been developed. The work presented will discuss the design and implementation of the electrochemical techniques that we have used in the development of this strategy and in the measurement of the species in question.
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Reports on the topic "Cr (VI) reduction"

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John F. Stolz. Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report. Office of Scientific and Technical Information (OSTI), June 2011. http://dx.doi.org/10.2172/1016122.

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Wang, Li, and Li Li. Scaling Effects of Cr(VI) Reduction Kinetics. The Role of Geochemical Heterogeneity. Office of Scientific and Technical Information (OSTI), October 2015. http://dx.doi.org/10.2172/1223847.

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Chakraborty, Romy, Eoin L. Brodie, Boris Faybishenko, Yvette M. Piceno, Lauren Tom, Swati Choudhuri, Harry R. Beller, et al. Microbial community changes during sustained Cr(VI) reduction at the 100H site in Hanford, WA. Office of Scientific and Technical Information (OSTI), May 2010. http://dx.doi.org/10.2172/985936.

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