• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.85-92
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• 1999

The complete catalytic oxidation of vinyl chloride was investigated over chromium oxide supported ${\gamma}$-alumina using a fixed bed micro-reactor at temperature between 240 and $300^{\circ}C$ and concentration between 600 and 3500 ppm. The oxidation of vinyl chloride was nonlinear in the concentration of vinyl chloride and zeroth order in the concentration of oxygen. The addition of HCl and $H_2O$ as products to the feed stream didn't influence the conversion of vinyl chloride. Several kinetic rate model were tested to describe the data over the range of condition investigated, and developed a model which provide the best correlation of experimental data. The resulting model of kinetic rate was derived by assuming that the reacting occurred via adsorption and subsequent decomposition of the vinyl chloride onto the oxygen covered chromium oxide surface, with the reaction being inhibited by the adsorption of vinyl chloride. The percent standard deviation between the predicted and experimental was about 5.2%, and the activation energy was 18.9 kcal/mol.

• Carbon letters
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• v.8 no.4
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• pp.280-284
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• 2007

Samples of active carbon of $1150\;m^2/g$ surface area were impregnated with ammoniacal salts of copper, chromium and silver, with and without triethylenediamine. The samples of impregnated carbon were aged at $50^{\circ}C$, with and without 90% RH (relative humidity), for a little more than one year and chemically evaluated periodically. Initially copper (II) and chromium (VI) reduced very fast in the samples in humid atmosphere to the extent of 30% and 60% respectively in four months. These values were found to be unaffected by the presence of triethylenediamine (TEDA) indicating that the chemical did not retard the reduction process of chromium (VI) and copper (II). However, in the absence of humidity the reduction of the impregnants was significantly less (10-12%, w/w) in four months. It was quite evident; therefore, that the moisture was mainly responsible for the reduction of chromium (VI) and copper (II) species in impregnated carbons. The prolonged ageing of the samples with and without triethylenediamme after four months with and without humid atmosphere showed that the extent of reduction of chromium (VI) was very low, i.e. 5-10% and of copper (II) was 2-25%. Silver is not reduced due to carbon, as it remained unchanged in concentration on storage. The impregnated carbon samples (100 g) without triethylenediamine, which were aged at room temperature for 5 years in absence of humidity and unaged when evaluated against cyanogen chloride (CNCl) at a concentration of 4 mg/L and airflow rate of 30 lpm showed a high degree of protection (80- 110 minutes).

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.11
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• pp.1628-1633
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• 2005

Three hundred and twenty four one day old mixed sex broiler chicks were assigned at random into 9 treatment groups. The experimental design was a 3${\times}$3 factorial arrangement. During the starter period (week 1-3), chicks were fed ad libitum. A cornsoybean meal based diet contained 23% crude protein, 3,200 kcal/kg metabolizable energy (NRC, 1994), and supplemented with organic or inorganic forms of chromium. Two organic chromium products, chromium yeast (Cr-Yeast from Alltech Biotechnology Corporation Limited) and chromium picolinate (Cr-Pic) were supplemented at the rate of 200, 400 and 800 ppb. One inorganic product, chromium chloride, was supplemented at the rate of 200, 400 and 800 ppb. During the finishing period (week 4-7), the corn-soybean meal based diet contained 20% crude protein, 3,200 kcal/kg metabolizable energy (NRC, 1994), and the same levels of chromium as in the starter period were added. No significant difference was observed among treatment groups in average daily gain, feed intake, body weight gain, feed conversion ratio and mortality. The carcass percentage of broilers receiving 200 and 400 ppb organic chromium (Cr-Yeast or Cr-Pic) was significantly increased (p<0.01). In addition, the supplementation of organic chromium reduced (p<0.05) breast meat fat content but increased breast meat protein content. The addition of chromium in the diet had no effect on boneless breast, skinless boneless breast, boneless leg, skinless boneless leg but reduced percentage of sirloin muscle. Total cholesterol and triglycerides were reduced by organic Cr supplementation. Supplementation with 200 and 400 ppb of both Cr-Yeast and Cr-Pic showed the lowest total cholesterol. The effects of type of Cr on HDL and LDL were variable, however, LDL increased with increasing level of Cr supplementation. This trial indicates that organic chromium tended to improve growth performances and carcass composition, reduced total cholesterol and triglycerides. The optimum level of organic chromium supplementation was at 200 ppb.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.2
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• pp.292-300
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• 1996

Hexavalent chromium($Cr^{+6}$) compounds are considered to be particularly hazardous, primarily because of the associated risk of allergic reaction and cancer. The analytic method of hexavalent chromium such as the s-diphenylcarba-zide(DPC) method and all ether previously used methods are often made uncertain due to significant interferences from organic components. This report can provide a technique for the more rapid and simple determination of total hexavalent chromium. than other currently using methods. The s-diphenylcarbazide method proposed by the U.S. National Institute for Occupational Safety and Health has low recovery rate(15.67 - 48.20%) due to interference, iron chloride and nickel chloride. A microwave oven technique has high recovery rate(about 70%) of insoluble hexavalent chromium. For the difference of ionic charges of $Cr^{+3}$-ethylenediamine tetraacetic acid(EDTA) chelate and $CrO_4{^{-2}}$, we could detect them simultaneously by ion exchanged high performance liquid chromatography. The confirmation of $Cr^{+3}$ and $Cr^{+6}$ were checked by fraction collector and flameless atomic absorption spectrometer. We observed that the small amount of hexavalent chromium is converted to trivalent chromium due to enhancement of chromium reduction by $Fe^{+3}$ or $Ni^{+2}$. As a result of this study, on the analysis of insoluble hexavalent chromium with microwave oven was used for, it may be better and more precise analysis after pretreatment by 2% NaOH-3% $Na_2CO_3$ and then analysis UV-spectrophotometer. It should be done for various studies on insoluble hexavalent chromium on the basis work environmental monitoring so called welding, painting etc.

• The Journal of Advanced Prosthodontics
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• v.9 no.2
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• pp.118-123
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• 2017

PURPOSE. To investigate the effect of non-thermal atmospheric pressure plasma (NTAPP) treatment on shear bond strength (SBS) between resin cement and colored zirconia made with metal chlorides. MATERIALS AND METHODS. 60 zirconia specimens were divided into 3 groups using coloring liquid. Each group was divided again into 2 sub-groups using plasma treatment; the experimental group was treated with plasma, and the control group was untreated. The sub-groups were: N (non-colored), C (0.1 wt% aqueous chromium chloride solution), M (0.1 wt% aqueous molybdenum chloride solution), NP (non-colored with plasma), CP (0.1 wt% aqueous chromium chloride solution with plasma), and MP (0.1 wt% aqueous molybdenum chloride solution with plasma). Composite resin cylinders were bonded to zirconia specimens with MDP-based resin cement, and SBS was measured using a universal testing machine. All data was analyzed statistically using a 2-way ANOVA test and a Tukey test. RESULTS. SBS significantly increased when specimens were treated with NTAPP regardless of coloring (P<.001). Colored zirconia containing molybdenum showed the highest value of SBS, regardless of NTAPP. The molybdenum group showed the highest SBS, whereas the chromium group showed the lowest. CONCLUSION. NTAPP may increase the SBS of colored zirconia and resin cement. The NTAPP effect on SBS is not influenced by the presence of zirconia coloring.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.1
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• pp.43-63
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• 2022

The aim of this review is to communicate some essential knowledge of the underlying mechanism of the corrosion of structural containment alloys during molten salt reactor operation in the context of prospective online monitoring in future MSR installations. The formation of metal halide species and the progression of their concentration in the molten salt do reflect containment corrosion, tracing the depletion of alloying metals at the alloy salt interface will assure safe conditions during reactor operation. Even though the progress of alloying metal halides concentrations in the molten salt do strongly understate actual corrosion rates, their prospective 1^st order kinetics followed by near-linearly increase is attributed to homogeneous matrix corrosion. The service life of the structural containment alloy is derived from homogeneous matrix corrosion and near-surface void formation but less so from intergranular cracking (IGC) and pitting corrosion. Online monitoring of corrosion species is of particular interest for molten chloride systems since besides the expected formation of chromium chloride species CrCl₂ and CrCl₃, other metal chloride species such as FeCl₂, FeCl₃, MoCl₂, MnCl₂ and NiCl₂ will form, depending on the selected structural alloy. The metal chloride concentrations should follow, after an incubation period of about 10,000 hours, a linear projection with a positive slope and a steady increase of < 1 ppm per day. During the incubation period, metal concentration show 1^st order kinetics and increasing linearly with time^1/2. Ideally, a linear increase reflects homogeneous matrix corrosion, while a sharp increase in the metal chloride concentration could set a warning flag for potential material failure within the projected service life, e.g. as result of intergranular cracking or pitting corrosion. Continuous monitoring of metal chloride concentrations can therefore provide direct information about the mechanism of the ongoing corrosion scenario and offer valuable information for a timely warning of prospective material failure.

• Journal of the Korean institute of surface engineering
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• v.49 no.1
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• pp.62-68
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• 2016

A chromium-free Ce-based conversion coating formed by immersion in a solution containing cerium chloride and nitric acid on AZ31 magnesium alloy has been studied. The effects of acid pickling on the morphology and the corrosion resistance of the cerium conversion coating were investigated. The corrosion resistance of the conversion coating prepared on AZ31 Mg alloy after organic acid pickling was better than that of inorganic acid pickling. The morphology of the conversion-coated layer was observed using optical microscope and SEM. Results show that the conversion coatings are relatively uniform and continuous, with thickness 1.0 to $1.1{\mu}m$. The main elements of the conversion coating of AZ31 Mg alloy are Mg, O, Al, Ce and Zn by EDS analysis. The electrochemical polarization results showed that the Ce-based conversion coating could reduce the corrosion activity of the AZ31 Mg alloy substrates in the presence of chloride ions.

• Nuclear Engineering and Technology
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• v.32 no.6
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• pp.531-536
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• 2000

The extraction of precious metals from aqueous solutions is performed by using a photoredox reaction with a Q-switched Nd:YAG laser. The metallic silver was efficiently precipitated and extracted from the silver nitrate solution by laser photolysis. An optimum reaction condition for silver extraction was determined by adjusting various experimental factors such as type of reducing agent, type of acids and reaction time. The composition of the reaction product was analyzed and it was identified as metallic silver, not other molecular types. The photoreaction of chromium(III) chloride in an acidic aqueous solution was also investigated. The 355 nm laser light was better suited for the reaction of silver nitrate as well as chromium(III) chloride in an acidic solution compared to the 532 nm light.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.58-66
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• 1999

The catalytic oxidation of vinyl chloride was investigated over $CrO_x$ impregnated on $Al_2O_3$ at temperature between 200 and $400^{\circ}C$. The major carbonaceous products were CO and $CO_2$, and the selectivity of $CO_2$ was gradually increased with increasing reaction temperature, while that of CO was dropped consequently. This suggests that CO is the first product which is further oxidized to $CO_2$ in the oxidation of vinyl chloride over $CrO_x/Al_2O_3$. The addition of HCl in the feed didn't affect the conversion of vinyl chloride, but the selectivity of $CO_2$ decreased by adding HCl. It implies that HCl inhibits, the complete oxidation of vinyl chloride to $CO_2$. When oxidizing vinyl chloride in dry air, significant amounts of $Cl_2$ were observed, while no $Cl_2$ was detected in the humid condition. The activities of several catalysts including various precious metals and other transition metal oxides were measured, it was found that the catalytic activity of 12% $CrO_x/Al_2O_3$ was higher than other catalysts except 1% $Pt/Al_2O_3$. The reaction rate of 12% $CrO_x/Al_2O_3$ was 1.2 times lower than that of 1% Pt/alumina, but it was 3 to 8 times more active than other catalysts for vinyl chloride oxidation at $275^{\circ}C$.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.10
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• pp.1414-1419
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• 2009

The study was conducted to evaluate the effects of trivalent chromium from different sources on growth, carcass composition, and serum parameters in finishing pigs. Ninety-six crossbred pigs with an initial average body weight of 65.57${\pm}$1.05 kg were blocked by body weight and randomly assigned to four treatments with three replicates. Pigs were offered one of four diets including a control diet or the control diet supplemented with 200 ${\mu}g/kg$ chromium from either chromium chloride ($CrCl_{3}$), chromium picolinate (CrPic) or chromium nanocomposite (CrNano) for 40 days. After completion of the feeding trial, eight pigs from each treatment were selected to collect blood samples, and slaughtered to measure carcass composition. The results showed that supplemental chromium had no significant effect on growth performance, while CrNano increased carcass lean proportion and loin Longissimus muscle area (p<0.05), and decreased carcass fat proportion and 10th rib backfat depth (p<0.05). CrPic supplementation also resulted in lower fat proportion and larger Longissimus muscle area (p<0.05). The addition of Cr from CrNano or CrPic decreased serum glucose (p<0.05) and increased concentrations of total protein and free fat acid in serum (p<0.05). Serum urea nitrogen, triglyceride and cholesterol were decreased (p<0.05), and serum high density lipoprotein and lipase activity were increased (p<0.05) with the supplementation of CrNano. Serum insulin was decreased (p<0.05) by supplemental Cr from CrNano or CrPic, and serum insulin-like growth factor I was increased significantly in the CrNano treated group. These results suggest that chromium nanocomposite has higher efficacy on carcass composition in pigs compared to the traditional chromium sources.