• Environmental Engineering Research
• /
• v.10 no.6
• /
• pp.294-305
• /
• 2005

The effectiveness of fly ash-, quicklime-, and quicklime-fly ash-based stabilization/solidification(S/S) in chromium(Cr) contaminated soils was investigated using modified semi-dynamic leaching tests. Artificial soil samples composed of kaolinite or montmorillonite contaminated with chromium nitrate(4000 mg $Cr^{3+}\;kg^{-1}$ of solid) were prepared and then subjected to S/S treatment using quicklime, fly ash, or quick lime-fly ash. The effectiveness of the treatment was evaluated by assessing the cumulative fraction of leached $Cr^{3+}$ as well as, by computing the effective diffusivity ($D_e$) and the leachability index (LX) of the treated samples. The reduction in $Cr^{3+}$ release for the untreated samples was more pronounced in the presence of montmorillonite, which was attributed to sorption. Treatment with quicklime, fly ash, or quick lime-fly ash was significantly effective in reducing $Cr^{3+}$ release most probably due to the formation of pozzolanic reaction products and $Cr(OH)_3$ precipitation. The most effective treatment was observed in montmorillonite-sand soil samples treated with quicklime-fly ash (99.8% removal). The mean $D_e$ decreased significantly and the mean LX was greater than 9 for all treated samples, indicating that the treated soils were acceptable for "controlled utilization". The mechanism controlling $Cr^{3+}$ leaching from all treated samples during the first 5 days appeared to be diffusion.

• Asian-Australasian Journal of Animal Sciences
• /
• v.14 no.8
• /
• pp.1164-1169
• /
• 2001

A five-week trial was conducted to evaluate the effect of organic chromium from different sources on growth performance, immune response and serum parameters of weaned pigs. One hundred and eighty Tianjin white pigs weaned at $35{\pm}1$ days of age, were allotted to three treatments with six replicates and10 pigs per pen. Pigs were fed corn-soybean-whey-fishmeal basal diets with either no supplemental Cr, $200{\mu}g/kg$ Cr as chromium picolinate (CrPi), or $200{\mu}g/kg$ Cr as chromium yeast (Cr-yeast). To assess humoral immune response, all pigs were immunized with swine fever virus on day 21 and two pigs from each pen were immunized with pure albumin on day 14. Cell-mediated immunity was measured by determining the double skinfold thickness (DST) of two pigs from each pen before and 24h after stimulation with phytohemagglutinin (PHA) on day 28. The results indicated that: (1) diets with Cr-yeast increased average daily gain (ADG, p<0.05) and tended to increase average daily feed intake (ADFI, p<0.10). Diets with CrPi did not increase ADG and ADFI (p>0.05). (2) Dietary CrPi or Cr-yeast supplementation did not affect blood urea nitrogen, glucose, or cholesterol (p>0.05), but blood urea nitrogen in CrPi and Cr-yeast supplemented groups and blood glucose in the Cr-yeast supplemented group were significantly influenced by sampling days (p<0.05). (3) Serum proteins (TP, ALB, and GLB) were influenced by sampling days (p<0.05), but not by dietary Cr treatment (p>0.10). (4) There were no significant differences among treatments in the titers of albumin antibody and swine fever virus antibody (p>0.05) or DST before and after PHA stimulation (p>0.05), indicating that organic chromium has no significant effect on the immune function of weaning pigs. Therefore, these results agree with other research that the effects of supplemental Cr are variable in weanling pigs.

• Journal of the Korean institute of surface engineering
• /
• v.52 no.3
• /
• pp.111-116
• /
• 2019

Chromium was coated on a steel substrate by the Cr(III) electroplating method, and corroded at $500-900^{\circ}C$ for 5 h in $N_2/0.1%H_2S-mixed$ gas to study the high-temperature corrosion behavior of the Cr(III) coating in the highly corrosive $H_2S-environment$. The coating consisted of (C, O)-supersaturated, nodular chromium grains with microcracks. Corrosion was dominated by oxidation owing to thermodynamic stability of oxides compared to sulfides and nitrides. Corrosion initially led to formation of the thin $Cr_2O_3$ layer, below which (S, O)-dissolved, thin, porous region developed. As corrosion progressed, a $Fe_2Cr_2O_4$ layer formed below the $Cr_2O_3$ layer. The coating displayed relatively good corrosion resistance due to formation of the $Cr_2O_3$ scale and progressive sealing of microcracks.

• Journal of Sericultural and Entomological Science
• /
• v.38 no.1
• /
• pp.25-30
• /
• 1996

The adsorption mechanism of Chromium(VI) uptake in silk fibroin fibers was discussed. The adsorption equilbrium of Chromium(VI) is significantly influenced by the initial adsorption rate and it showed 52% of the equilibrium uptake. The Chromium(VI) uptake by silk fibroin in increased with the acidic range of pH, which react upon Chromium(VI) oxidations. The enthalpy change in the Chromium(VI) on the temperatures, $\Delta$H, was found to be 39.7 KJ.mol-1, It means that the Chromium(VI) adsorption proceeds via a certain complex chemical reaction and the Chromium complex was found to be coordinated with carbonyl group of amides from the result of infrared spectra. The chroming of silk fibroin fibers in moderated in the conditions of 5$0^{\circ}C$, pH 2.4, and 3 hours, which prevent from the loss of physical properties. The equilibrium adsorption is attained at 5 X 10-3M of Chromium(VI) solutions.

• Journal of Microbiology and Biotechnology
• /
• v.12 no.1
• /
• pp.137-141
• /
• 2002

Anabaena variabilis ATCC 29413 grew in chromium (Cr) containing Chu-10 (basal) and nitrate-supplemented media, and the growth of the organism in $100{\mu}M$ chromium was found to be 50% of that in control medium. The growth in nitrate $({NO_3}^-)$ supplemented cultures was better as compared to cultures grown in basal medium. Free cells from basal and nitrate-supplemented media removed 5.2 and 7.4 nmol of chromium $mg^{-1}$protein in 8 h, respectively, from the medium containing $30{\mu}M$ chromium. The efficiency of chromium removal increased 7-fold in imidazole buffer (0.2 M, pH 7.0). A cell density equivalent to $100{\mu}g$ protein $ml^{-1}$ was found to be optimum for maximum Cr removal. Entrapment of cells in calcium-alginate beads did not affect the rate of Cr uptake by the cells. The efficiency of the laboratory-scale continuous flow bioreactor $(12.5{\times}2cm)$ loaded with alginate-immobilized cells (10 mg protein) and fed with $30{\mu}M$ chromium solution was compared at different flow rates. The efficiency of the bioreactor varied with flow rates. In terms of percent removal of Cr from influent, a flow rate of 0.1 ml $min^{-1}$ was found to be optimum for 6 h (54% Cr removal efficiency). Maximum amount of Cr (883 nmol) was removed by the cells in 3 h at a flow rate of 0.5 ml $min^{-1}$. The potential use of A. variabilis in removing Cr from industrial effluents is discussed.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.6
• /
• pp.855-862
• /
• 2006

Hexavalent chromium ($Cr^{6+}$) is a highly harmful pollutant, which can be detoxified and precipitated through reduction to $Cr^{3+}$. Bacillus megaterium TKW3 previously isolated from chromium-contaminated marine sediments was capable of reducing $Cr^{6+}$ in concomitance with metalloids ($Se^{4+}$, $Se^{6+}$, and $As^{5+}$). Notwithstanding approximately 50% inhibition, it was the first report of simultaneous bacterial reduction of $Cr^{6+}$ and $Se^{4+}$ (to elemental Se). No significant difference was observed among electron donors (glucose, maltose, and mannitol) on $Cr^{6+}$ reduction by B. megaterium TKW3. The reduction was constitutive and determined to be non-plasmid mediated. Peptide mass fingerprints (PMF) revealed a novel aerobic membrane-associated reductase with $Cr^{6+}$-induced expression and specific reductive activity (in nmol $Cr^{6+}$/mg protein/min) of 0.220 as compared with 0.087 of the soluble protein fraction. Respiratory inhibitor $NaN_3$ did not interfere with the reductase activity. Transmission electron microscopy with energy dispersive X-ray (TEM-EDX) analysis confirmed the aggregation of reduced chromium along the intracellular membrane region. Future identification of the N-terminal amino acid sequence of this reductase will facilitate purification and understanding of its enzymatic action.

• The Korea Journal of Herbology
• /
• v.21 no.1
• /
• pp.101-107
• /
• 2006

Objectives : It is well known that hexavalent chromium has toxic effect on normal cells. Recently, toxic effect of hexavalent chromium is diminished by the some extracts derived from herbs or plants. But, the toxic or protective mechanism of hexavalent chromium is well unknown. This study was performed to examine the protective effect of poncirin against $Na_2Cr_2O_7$-induced cytotoxicity on NIH3T3 fibroblasts. Methods : The protective effect of the cytotoxicity induced by $Na_2Cr_2O_7$ was measured by the cell viability after NIH3T3 fibroblasts were cultured with or without $Na_2Cr_2O_7$ for 48 hours. Antitoxic effects of poncirin on the cytotoxicity induced by $Na_2Cr_2O_7$ were examined by colorimetric assays such as MTT or XTT assay. Results : $Na_2Cr_2O_7$ decreased cell viability by the decreased absorbance in MTT or XTT assay, but, the poncirin increased cell viability which was decreased by $Na_2Cr_2O_7$-induced cytotoxicity on NIH3T3 fibroblasts. Conclusion : These results suggest that $Na_2Cr_2O_7$ showed cytotoxicity effect on NIH3T3 fibroblasts by the decrease of cell viavility, and poncirin was effective in the protection of $Na_2Cr_2O_7$-induced cytotoxicity in these cultures.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.9
• /
• pp.3437-3442
• /
• 2011

An on-line flow injection analysis with dual pre-concentration method was developed to determine the ultra trace tri and hexavalent chromium in water. In this system, the cation and anion pre-concentration columns were combined with a 10-port injection valve and then used to separate and concentrate Cr (III) and Cr (VI) selectively. The two species of concentrated chromium were sequentially eluted and determined by using HCl-KCl buffer of pH 1.8 as an eluent. Cr (III) was oxidized by hydrogen peroxide to Cr (VI). It was detected spectrophotometrically at 548 nm by complexation with DPC (diphenylcarbazide). Several factors such as concentration of $H_2O_2$, DPC and coil length in reaction condition were optimized. The linear range for Cr (III) and Cr (VI) was 0.1-50 ${\mu}g$/L. The limit of detections ($3{\sigma}$) of Cr (III) and Cr (VI) were 52 ng/L and 44 ng/L under the optimized FIA system, and their recoveries 98% and 103%, respectively. This method was applied to analyze contamination level of chromium species in tap water, groundwater and bottled water.

• Environmental Analysis Health and Toxicology
• /
• v.18 no.3
• /
• pp.165-174
• /
• 2003

Cr (Ⅵ) - containing compounds are well-established carcinogens, although the mechanism for chromium - induced carcinogenesis is still not well understood. The reduction of Cr (Ⅵ) to its lower oxidation states, par ticularly Cr (V) and Cr (IV), is an important step for the production of chromium-mediated reactive oxygen species (ROS). The persistent oxidative stress during the reduction process may play a key role in the mechanism of Cr (Ⅵ) -induced carcinogenesis. This paper summarizes recent studies on (1) the reduction of Cr (Ⅵ) to Cr (III) occur by a multiplicity of mechanisms depending on the nature of reducing agents including ascorbate, diol-and thiol-containing molecules, certain flavoenzymes, cell organelles, intact cells, and whole animals; (2) free-radical production with emphasis on hydroxy radical generation via Fenton or Haber-Weiss type reactions; and (3) free radical - induced cellular damage, such at DNA strand breaks, hydroxylation of 2'-deoxyguanosine, and activation of nuclear transcription factor kB.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.9
• /
• pp.1395-1402
• /
• 2005

The reaction of cis-[Cr([14]-decane)$(OH)_2]^+$ ([14]-decane = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-teraazacyclotetradecane) with auxiliary ligands {$L_a$ = acetylacetonate (acac), oxalate (ox) or malonate (mal)} leads to a new cis-[Cr([14]-decane)(acac)]$(ClO_4)_2{\cdot}(1/2)H_2O\;(1),\;cis-[Cr([14]-decane)(ox)]ClO_4{\cdot}(1/2)H_2O\;(2)\;or\;cis-[Cr([14]-decane)(mal)]ClO_4{\cdot}(1/4)H_2O\;(3)$. These complexes have been characterized by a combination of elemental analysis, conductivity, IR and Vis spectroscopy, mass spectrometry, and X-ray crystallography. Analysis of the crystal structure of cis-[Cr([14]-decane)(acac)]$(ClO_4)_2{\cdot}(1/2)H_2O$ reveals that central chromium(III) has a distorted octahedral coordination environment and two acetylacetonate-oxygen atoms are bonded to the chromium(III) ion in the cis positions. The angle $N_{axial}-Cr-N_{axial}$ deviates by $11^{\circ}$ from the ideal value of $180^{\circ}$ for a perfect octahedron. The bond angle O-Cr-O between the chromium(III) ion and the two acetylacetonate-oxygen atoms is close to $90^{\circ}$. The bond lengths of Cr-O between the chromium and the acetylacetonate-oxygen atoms are 1.950(3) and 1.954(2) $\AA$. They are shorter than those between chromium and nitrogen atoms of the macrocycle. The IR spectra of 1, 2 and 3 display bands at 1560 {ν (C=O)}, 1710 {${\nu}_{as}$(OCO)} and 1660 $cm^{-1}$ {${\nu}_{as}$(OCO)} attributed to the acac, ox and mal auxiliary ligands stretching vibrations, respectively.