• Environmental Analysis Health and Toxicology
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• v.21 no.4 s.55
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• pp.357-363
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• 2006

Chromium compounds are widely used in diverse industries including pigment manufacturing, painting, metal plating and leather tanning. With the wide uses of chromium, various adverse effects of the compounds on the environment and human health have been reported. Among them, hexavalent chromium [Cr (VI)], which is a carcinogenic heavy metal, has been widely studies. Epidemiological investigations have shown that respiratory cancers had been found in workers who had been occupationally exposed to Cr (VI). In this study, cell toxicity and induction of reactive oxygen species (ROS) by Cr (VI) (1, 2, 4, $8{\mu}M$) in cultured human bronchial epithelial cells were investigated. Exposure of the cells to Cr (VI) led to cell death, ROS increase, and cytosolic caspase-3 activation. The ROS increase was related with the decreased level of GSH. Chromatin condensation and fragmentation were occurred by Cr (VI) when evaluated by DAPI staining or agarose gel electrophoresis of the extracted DNA. Expression of ROS related genes including glutathione S-transferase, heme oxygenase-1, metallothionein were significantly induced in Cr (VI) treated cells. This result suggests the toxicity in cultured cells by Cr (VI) was expressed through the apoptotic process with ROS induction.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.04a
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• pp.77-77
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• 2006

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.05a
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• pp.62-63
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• 2000

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.10a
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• pp.93-93
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• 2006

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.10a
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• pp.88-88
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• 2006

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.687-690
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• 2010

The objective of this study is to investigate the effect of aldehyde compounds and ploysulfide as accelerating agents on removal of heavy metals and CN in plating wastewater. As a results of the experiments, the removal efficiency of cyanide using the formaldehyde type of aldehydes was the highest at pH 9. Next types were sodium formaldehyde bisulfite addut> paraldehyde> paraformaldehyde. Also, optimum pH and dosage for treating the residual heavy metals by using polysulfide were pH 9 and 30 mg/L, respectively. The removal efficiencies of cyanide, chromium, zinc and copper were above 96.7% at optimum condition.

• Journal of the Korean institute of surface engineering
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• v.28 no.1
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• pp.23-33
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• 1995

AISI 304 stainless steel has high resistance to corrosion due to the presence of a self-healing chromium oxide film on the surface, which also accounts for the difficulty in plating. Surface cleaning of this alloy is of fundamental importance in gold plating since its effectiveness puts an upper limit on the quality of the final coating. The cleaning of AISI 304 stainless steel was investigated with elimination of artificial passive oxide film and degreasing of remaining buffing wax as stearic acid. The familiar cleaning methods i.e. ultrasonic cleaning, electro-cleaning and activation treatment were fabricated in this study. Activation treatment showed best cleaning efficiency for elimination of passive oxide film among these methods, which was also confirmed by AES (Auger electron spectrometer) analysis. However, the best condition of cleaning was obtained by combining these methods. Electrocleaning time, for degreasing the stearic acid layer, was decreased with increasing amount of added KCN.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.177-181
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• 2009

Compositional gradient CrNx coatings were fabricated using arc ion plating in Ar/$N_2$ gaseous mixture by gradually increasing $N_2$ flux rate from 0 to 120 SCCM. The effect of negative substrate bias on the film microstructure and mechanical properties were systematically investigated with XRD, GDOES, and SEM. The results show that substrate bias has an important influence on film growth and microstructure of gradient CrNx coatings. The coatings mainly crystallized in the mixture of hexagonal $Cr_{2}N$ and fcc CrN phases. By increasing substrate bias, film microstructure evolved from an apparent columnar structure to an equiaxed one. With increasing substrate bias, deposition rate first increased, and then decreased. The maximum of deposition rate was 15 nm/min obtained at a bias of -50V.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.1
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• pp.125-142
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• 1996

Bond strength of four different cements to dental casting alloys which were treated with #600 emery, tin-plating, and $50{\mu}m$ sandblasting were evaluated. The alloy specimens were Type III Gold alloy(Degulor C), Palladium-Silver alloy(Pors on 4), Nickel-Chromium(Rexillium III) alloy, which were embedded in acrylic resin disc. The specimens were treated with #600 emery and tin plating, #600 emery and sandblasting, then bonded using Fuji I, Ketac Cem(Glass ionomer cements), Poly F, Livcarbo(Polycarboxylate cements). The specimens were immersed in water for 24 hours and shear bond strengths were evaluated by Instron Machine. Tin plated, sandblasted, and debonded alloy surfaces were observed using scanning electron microscope. On the basis of this study, the following conclusions could be drawn. 1. In the tin plated alloy group, increase in bond strength of glass ionomer cements was statistically insignificant. 2. In the tin plated alloy group, increase in bond strength of polycarboxylate cements was statistically significant, except nickel-chromium alloy. 3. Sandblasted alloy group showed higher bond strength than that of tin-plated alloy group.

• Macromolecular Research
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• v.10 no.2
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• pp.103-107
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• 2002

High purity water soluble chitosans (WsCs) were employed as a flocculant to remove heavy metal ions from wastewater of industrial plating wastewater treatment complex. Their weight average molecular weights and polydispersities were 272,000~620,000 g/mol and 1.4~1.9 range, respectively and were readily soluble in water in the pH range of 3~11. Heavy metal ions such as chromium, iron and copper were removed well by WsCs. When WsCs was blended with either sodium N, N-diethyldithiocarbamate trihydrate (SDDC$_{T}$) or sodium salicylate (SSc), the removal efficiency was further increased primarily due to the excess amount of hydrophilic sulfonic and carboxylic groups. Especially, in the case of WsCs-SSc the remaining chromium and copper concentrations were 0.1 mg/L and 9.5 mg/L, which are 1/15 and 1/3 compared with that of pure WsCs, respectively. The former is within the acceptable limit, but the latter is not. Therefore, the effective copper flocculant remains to be studied.d.