An optical fluorescence quenching sensor based on functionally modified iron-doped carbon nanoparticles was designed for the selective and sensitive Cr(VI) ion detection. Multifunctional iron-doped carbon nanoparticles were enclosed in the scaffolds of a promising stable nanocarrier system called hyperbranched polyglycerol (HPG), which has been fluorescently modified with 1-pyrene butyric acid using the Steglich esterification procedure. The therapeutic and diagnostic capabilities were boosted when these nanoparticles were enclosed in the fluorescently modified dendritic structure, HPG. Iron-doped carbon nanoparticles coupled with fluorescently modified hyperbranched polyglycerol can be used as a sensor for metal ions and can then be used to successfully remove them from a sample. Moreover, the synthesised nanoparticles demonstrated promising antimicrobial efficacy against bacteria and fungi. These results are also discussed in detail.

By polymerizing acrylonitrile in the presence of ammonium persulfate as an initiator and Pterocladia capillacea-activated carbon (P-AC) as a filler, a composite material polyacrylonitrile/Pterocladia capillacea-activated carbon (PAN/P- AC) was developed. By reacting hydroxylamine with the composite's nitrile groups, the prepared composite was functionalized by amidoximation. FTIR spectrometry, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET) analysis were all applied to thoroughly characterize the fabricated adsorbent. For the treatment of Cr(VI) ions from synthetic solutions, the adsorption properties of amidoximated polyacrylonitrile/Pterocladia capillacea-activated carbon (PAO/P-AC) were investigated. The pH effect, uptake kinetics, adsorption isotherms, and thermodynamics studies were used to characterize adsorption properties. As a kinetic model analysis, the data confirmed that the pseudo-second-order rate equation matched well the adsorption process. With coefficients of determination (R2) of 0.9998, the Tempkin isotherm model had the lowest error, suggesting that it is the best fitted model to describe this adsorption mechanism. Thermodynamic parameters demonstrated that Cr(VI) adsorption was endothermic.

In the automotive industry, the platinum titanium anodes (Pt/Ti anode) play a significant role in electroplating of chromium coating on the vehicle’s shock absorber piston rod. In this paper, the structure of Pt/Ti anode was designed to obtain high quality and save time for the electroplating process. The structure of anode was designed in 2D & 3D modeling and analyzed by CATIA and ABAQUS program, respectively. The structural modeling of the anode was analyzed and carried out using a finite element method (FEM) by applied various loads. The manufacture anodes were installed in an electroplating bath in order to test the efficiency of chromium coating on shock absorber piston rod and safety of anode structure. The results presented indicate that the structural analysis is safe after applied loads due to the allowable stress is higher than the maximum equivalent stress about 4 times, and the chromium coating test obtained high-efficiency results.

Heavy metals resulted from the increase of human industrial activity are introduced into the environment through rainfall and wastewater, and have harmful effects on inhabitants. In this study, we investigated biological responses such as survival rate, growth rate, emergence rate and sex ratio, and morphological effects of mentum deformity in Chironomus plumosus, an indicator organism to evaluate pollutions on aquatic ecosystem. The survival rate of C. plumosus showed time- and dose-dependent decrease after chromium and copper exposures. Growth rate decreased at 4th day after chromium exposure and significantly reduced at exposure to relatively high concentration (copper 1000 mg L-1) for all exposure times. In addition, we observed that the emergence rate by exposure to copper 1000 mg L-1 was significantly lower than that of the control group. The imbalance of sex ratios showed at relatively low concentrations (chromium 10 and 50 mg L-1) with the high proportion of female and at the relative high concentration (copper 1000 mg L-1) with the high proportion of male. Furthermore, the morphological mentum deformities of C. plumosus observed in the exposed group according to chromium and copper exposure. These results suggest that the heavy metal exposure in environment may influence biosynthetic and morphological stresses of benthic invertebrate C. plumosus, and aquatic midge C. plumosus are potential indicators for toxicity assessment of heavy metals such as chromium and copper.

For diamond/metal composites it is better to use diamond particles coated with metal carbide because of improved wettability between the diamond particles and the matrix. In this study, the coating of diamond particles with a chromium carbide layer is investigated. On heating diamond and chromium powders at 800~900 oC in molten salts of LiCl, KCl, CaCl2, the diamond particles are coated with Cr7C3. The surfaces of the diamond powders are analyzed using X-ray diffraction and scanning electron microscopy. The average thickness of the Cr7C3 coating layers is calculated from the result of the particle size analysis. By using the molten salt method, the Cr7C3 coating layer is uniformly formed on the diamond particles at a relatively low temperature at which the graphitization of the diamond particles is avoided. Treatment temperatures are lower than those in the previously proposed methods. The coated layer is thickened with an increase in heating temperature up to 900 oC. The coating reaction of the diamond particles with chromium carbide is much more rapid in LiCl-KCl-CaCl2 molten salts than with the molten salts of KCl-CaCl2.

Crystal structure of the L12 type (Al,X)3Ti alloy (X = Cr,Cu) is analyzed by X-ray diffractometry and the nonuniform strain behavior at high temperature is investigated. The lattice constants for the L12 type (Al,X)3Ti alloys decrease in the order of the atomic number of the substituted atom X, and the hardness tends to increase. In a compressive test at around 473K for Al67.5Ti25Cr7.5, Al65Ti25Cr10 and Al62.5Ti25Cu12.5 alloys, it is found that the stress-strain curves showed serration, and deformation rate dependence appeared. It is assumed that the generation of serration is due to dynamic strain aging caused by the diffusion of solute atoms. As a result, activation energy of 60-95 kJ/mol is obtained. This process does not require direct involvement. In order to investigate the generation of serrations in detail, compression tests are carried out under various conditions. As a result, in the strain rate range of this experiment, serration is found to occur after 470K at a certain critical strain. The critical strain increases as the strain rate increases at constant temperature, and the critical strain tends to decrease as temperature rises under constant strain rate. This tendency is common to all alloys produced. In the case of this alloy system, the serration at around 473K corresponds to the case in which the dislocation velocity is faster than the diffusion rate of interstitial solute atoms at low temperature.

본 연구는 넙치 치어 (평균 체장 13.3±1.6 cm, 평균 체중 25.6±3.7 g)를 수중 6가크롬에 10일간 0, 0.5,1.0, 2.0 mg L-1 의 농도로 노출시켜 독성영향 판단하기 위해 수행되었다. 넙치 hemoglobin과 hematocrit와 같은 혈액학적 성상은 수중 크롬노출에 의해 유의적으로 감소하였다. 혈장 무기성분인 calcium과 magnesium은 크롬노출에 의해 유의적인 변화는 나타나지 않았다. 혈장 무기성분인 glucose와 cholesterol과 같은 1.0 mg L-1 이상의 크롬노출에 의해 유의적으로 증가하였지만, total protein은 유의적인 변화는 나타나지 않았다. 혈장 효소성분인 AST, ALT, ALP는 크롬노출에 의해 유의적인 증가가 나타났다. 본 실험의 결과는 수중 크롬노출은 넙치의 혈액 및 혈장성분에 유의적인 변화를 유발하며, 이러한 지표 의 변화는 수중 크롬노출의 독성영향을 판단하는 주요한 지표가 될 것이다.

The objective of this study is the removal of chromium from tannery wastewater by electrosorption on carbon prepared from lignocellulosic natural residue "peach stones' thermally treated. The followed steps for obtaining coal in chronological order were: cleaning, drying, crushing and finally its carbonization at 900°C. The characterization of the carbon material resulted in properties comparable to those of many coals industrially manufactured. The study of the dynamic adsorption of chromium on the obtained material resulted in a low removal rate (33.7%) without applied potential. The application of negative potentials of -0.7 V and -1.4 increases the adsorption of chromium up to 90% and 96% respectively. Whereas a positive potential of +1.4V allows desorption of the contaminant of 138%.

Nanoporous carbon structures were synthesized by pyrolysis of grass as carbon precursor. The synthesized carbon has high surface area and pore volume. The carbon products were acid functionalized and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, transmission electron microscopy, and Energy Dispersive X-ray microanalysis. Acid functionalized nanoporous carbon was explored for use in removal of toxic Cr(VI) ions from aqueous media. An adsorption study was done as a function of initial concentration, pH, contact time, temperature, and interfering ions. The experimental equilibrium data fits well to Langmuir isotherm model with maximum monolayer adsorption capacity of 35.335 mg/g. The results indicated that removal obeys a pseudo-second-order kinetic model, and that equilibrium was reached in 10 min. A desorption study was done using NaOH. The results of the present study imply that acid functionalized nanoporous carbon synthesized from grass is an efficient, renewable, cost-effective adsorbent material for removal of hexavalent chromium due to its faster removal rate and reusability.

With the stabilization of Korea’s industrialization, it has become interested in the efficient use of rare metals, climate change and industrial environment and safety etc. It is thus making efforts to implement economic policies that address such issues. Therefore it is necessary to understand the demand, supply and use of metal materials. Since 2010, the Korean government has developed the integrated material flow methodology and has been trying to examine the demand, supply and use of metal materials. In 2013, the Korean government surveyed the material flow of chromium. Material flow analysis and environment emission of chromium were investigated 8 steps; (1) raw material, (2) first process, (3) Intermediate product, (4) End product, (5) Use/accumulation, (6) Collection, (7) Recycling, (8) Disposal. Chromium was used for stainless steel, alloy steel, coated sheets, refractory material and coating materials. Recycling was done mainly in use of stainless steel scrap. To ensure efficient use of chromium, process improvement is required to reduce the scrap in the intermediate product stage. In the process of producing of the products using chromium, it was confirmed that chromium was exposed to the environment. It requires more attention and protection against environment emission of chromium.

This study was conducted to investigate the effects of Chromium-Methionine (Cr-Met) chelate feeding for different durations on growth and carcass characteristics in the late fattening stage of Holstein steers. Nine Holstein steers were randomly assigned to three dietary treatments (3 head per treatment) including Non Cr-Met chelate feeding (NCM, av. BW of 433.3 kg), Cr-Met chelate feeding for 2 months (2CM, av. BW of 459.6 kg), and Cr-Met chelate feeding for 4 months (4CM, av. BW of 490.0 kg), respectively. The feeding amount of Cr-Met chelate to an animal was limited to 400 ppb/day. Dry matter intake showed no differences among all the treatments (p>0.05). Average daily gain was also higher in the animals fed Cr-Met chelate diets than NCM (p<0.05). Carcass weights were also observed to be higher in Cr-Met chelate feeding treatments, especially in 4CM compared with other treatments (p<0.05). Although no significant differences were observed on back fat thickness and rib eye area(p<0.05), but 4CM showed much higher effects than NCM and 2CM. Marbling score meat color, fat color, texture, and maturity were not affected by treatments (p>0.05). The variations in meat quality were smaller in 4CM compared to other treatments. 4CM showed higher total and net income than other treatments (p<0.05). Therefore, the current study concluded that Cr-Met chelate supplementation for 4 months could increase daily gain, carcass characteristics, and profitability of Holstein steers in the late fattening stage.

말똥성게 (Hemicentrotus pulcherrimus)의 생식세포 및 pluteus 유생을 이용하여 중금속인 Arsenic (As)와 Chromium (Cr)이 정상 수정률 및 배아 발생률에 미치는 독성 영향을 조사하였다. H. pulcherrimus의 수정률 및 배아 발생률에 미치는 As와 Cr의 독성은 6.25, 12.5, 25, 50, 100 ppb의 농도에서 조사하였다. 0.5 M KCl 용액을 이용하여 방란 및 방정을 유도하였고, 정상 수정률 및 배아발생률은 수정 후 각각 10분 및 64시간째 관찰하였다. As와 Cr을 첨가하지 않은 대조구에서 정상 수정률과 배아 발생률은 각각 94%와 93% 이상을 나타냈다. 이들 중금속 첨가에 의해 수정률은 아무런 변화가 나타나지 않았지만 배아 발생률은 농도 의존적 감소하는 것으로 나타났으며, As의 첨가에 의해 배아 발생률은 6.25 ppb에서 유의적으로 감소하였으며 (P⁄0.01), Cr의 경우는 25 ppb에서 유의적인 감소를 나타냈다 (P⁄0.05). H. pulcherrimus의 정상 배아 발생률에 대한 LOEC는 As의 경우는 6.25 ppb를 Cr은 25 ppb를 나타냈다. 이들 연구결과로 해양생태계 내에서 As가 6.25 ppb, Cr이 25 ppb를 초과하는 농도일 때는 H. pulcherrimus와 같은 무척추동물의 정상부화율은 급격히 감소할 것으로 판단된다. 본 연구결과를 바탕으로, H. pulcherrimus의 정상 배아 발생률을 이용한 생물학적 평가방법은 중금속과 같은 유해물질에 대한 해양생태계의 영향을 판단하기 위한 시험방법으로 유용하게 이용될 수 있을 것으로 판단된다.