• 한국산업보건학회지
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• 제4권2호
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• pp.189-197
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• 1994

Analytic methods for Cr(VI) level in industrial hygienic field were suggested by the National Institute for Occupational Safety and Health(NIOSH method 7600, 7604). There were growing needs for measurement of Cr(III) and Cr(VI) levels simultaneously. Two analytical methods were suggested to determine Cr(III) and Cr(VI) levels simultaneously. The one is method by using reversed phase high peformance liquid chromatography(HPLC) and the other is by using ion exchange HPLC. The purpose of this work was to evaluate the usefulness of these two analytic methods. For the difference of ionic charges of Cr(III)-ethylendiamine tetraacetic acid(EDTA) chelate and $CrO_4{^-2}$, we could detect them simultaneously by ion exchange HPLC. Also, we attempted to determine the levels of Cr(III) and Cr(VI) chelated with sodium diethyldithiocarbamate(NaDDTC) by using reversed phase HPLC. The confirmation of Cr(III) and Cr(VI) were checked by fraction collector and nameless atomic absorption spectrometer. The optimal conditions for the formation of Cr(III)-EDTA chelate were two hours incubation period with pH 5. Cr(III)-EDTA and Cr(VI) in EDTA solution were successfully separated by anion exchange column using $Na_2CO_3/NaOH$ mixture as mobile phase. Peaks of Cr(III)-EDTA and Cr(VI) in EDTA were identified at 5 minutes and 7 minutes of retention time respectively by the ion exchange HPLC. The formation of Cr(III)-NaDDTC and Cr(VI)-NaDDTC chelates were twelve hours incubation period. Cr(III)-NaDDTC and Cr(VI)-NaDDTC chelates were separated by reversed phase column using methanol and water mixture as mobile phase. Peaks of Cr(VI)NaDDTC and Cr(III)-NaDDTC chelates were identified at 13 minutes and 26 minutes of retention time respectively by the reversed phase HPLC. Due to reduction of Cr(VI) to Cr(III), it seems to be not suitable for simultaneous determination of Cr(III)-NaDDTC and Cr(VI)-NaDDTC chelates by reversed phase HPLS. Simultaneos determination of Cr(III) and Cr(VI) by ion exchange HPLC was more accurate and simple method.

• Advances in environmental research
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• 제4권3호
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• pp.197-210
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• 2015

Hexavalent chromium [Cr (VI)] adsorption on lateritic soil and lateritic soil blended with black cotton (BC) soil, marine clay and bentonite clay were studied in the laboratory using batch adsorption techniques. In the present investigation the natural laterite soil was blended with 10%, 20% and 30% BC soil, marine clay and bentonite clay separately. The interactions on test soils have been studied with respect to the linear, Freundlich and Langmuir isotherms. The linear isotherm parameter, Freundlich and Langmuir isotherm parameters were determined from the batch adsorption tests. The adsorption of Cr (VI) on natural laterite soil and blended laterite soil was determined using double beam spectrophotometer. The distribution coefficients obtained were 1.251, 1.359 and 2.622 L/kg for lateritic soil blended with 10%, 20% and 30% BC soil; 5.396, 12.973 and 48.641 L/kg for lateritic soil blended with marine clay and 5.093, 8.148 and 12.179 L/kg for lateritic soil blended with bentonite clay respectively. The experimental data fitted well to the Langmuir model as observed from the higher value of correlation coefficient. Soil pH and iron content in soil(s) has greater influence on Cr (VI) adsorption. From the study it is concluded that laterite soil can be blended with clayey soils for removing Cr (VI) by adsorption.

• 한국산업보건학회지
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• 제25권1호
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• pp.89-94
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• 2015

Objectives: The objective of this study was to determine characteristics of workers' exposures to airborne total and hexavalent chromium by job title in electroplating processes. Methods: Total Cr was determined through a modified method based on NIOSH Method 7024. Airborne hexavalent Cr, Cr(VI), was sampled and extracted according to NIOSH Method 7600 and analyzed at 520 nm using an ion chromatograph/visible detector. Results: The geometric mean(GM) of total Cr concentrations from all factories was $11.2{\mu}g/m^3$(GSD=4.9). The GM of Cr(VI) concentrations from all factories was $2.84{\mu}g/m$ (GSD=5.2), and the concentrations among factories were significantly different (p<0.05). The Cr(VI) levels were lower than total Cr levels. Total Cr exposure levels were highest among buffing workers ($21.6{\mu}g/m^3$), but Cr(VI) levels were highest among plating workers($4.15{\mu}g/m^3$). The concentrations of Cr(VI) and total Cr from plating tasks was highly correlated(r=0.91). Conclusions: In the electroplating industry, plating workers were mainly exposed to Cr(VI), but others were not. Oxidation-reduction states of Cr and job titles should be considered in the exposure or risk assessments of chrome electroplating factories.

• 한국암석학회:학술대회논문집
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• 한국암석학회 1999년도 춘계학술대회
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• pp.25-29
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• 1999

Manganese (Mn) oxides in soils and sediments differ in structure and composition. The influence of that diversity on the chromium (Cr) oxidation is the subject of this report. Oxidation of Cr(III) to Cr(VI) by coarse clay size Mn oxides (synthetic pyrolusite and natural lithiophorite, todorokite, and bimessite) was studied. Chromium oxidation by Mn oxides was initially fast and followed by a slow reaction. More Cr was oxidized by the Mn oxides at lower pH and higher initial Cr(III) concentration in solution. Birnessite had the highest chromium oxidation capacity per unit external surface area (COCUESA) and lithiophorite had the lowest COCUESA. The kinetics of Cr oxidation and COCUESA of Mn oixdes were apparently controlled by reactivity of surface Mn, mineralogy, and solution properties (pH and Cr(III) concentration).

• 대한화학회지
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• 제30권5호
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• pp.423-432
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• 1986

폐수 중의 6가크롬을 음이온 교환체인 aliquat-336(tri-caprylmethyl ammonium chloride)으로 이온쌍을 형성시켜 유기용매인 p-xylene으로 추출하여 원자흡수분광도법으로 정량하는 방법에 대하여 조사 검토하였다. Toluene을 용매로 사용하여 유기물을 제거한 폐수 100ml를 취하여 염산으로 pH 0.5 되게 산성화시킨 다음 aliquat-336을 0.01M되게 녹인 p-xylene 20ml로 6가크롬을 추출하였다. 표준물첨가법에 의해 air-acetylene 불꽃에서 용매중에 추출된 6가크롬을 정량하였다. Al(III), Fe(III), Cr(III)이온들은 6가크롬의 추출 및 흡광도 측정에 방해 하지 않았으며, Fe(III)이온이 6가크롬을 3가크롬으로 환원시키기 때문이다. 또한 유기물이 존재하면 6가크롬의 흡광도를 감소시키므로 이런 방해유기물을 toluene으로 추출 제거하였다. 최적 조건으로 분석한 결과는 96%이상의 회수율을 보여 주었고 이는 미량 분석에서 정확한 방법이라 할 수 있고, 상대평균편차가 3.95%로서 재현성도 비교적 좋았다.

• 한국산업보건학회지
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• 제7권2호
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• pp.223-232
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• 1997

The accuracy and precision of a modified method of NIOSH Method 7600 and EPA method 218.6 was determined for analyzing hexavalent chromium, Cr(VI), collected on PVC filter from workplace air. The method was designed to extract from Cr(VI) on PVC filter with a alkali solution, 2% NaOH/3% $Na_2CO_3$, and to analyze it using ion chromatography/visible absorbance detection(IC/VAD). The results and conclusion are as the following. 1. The peak of Cr(VI) was separated sharply on chromatogram and was linearly related with Cr(VI) concentration in sloution. The correlation coefficient was 0.9999 in a calibration curve. The limit of detection was 0.25 $0.25{\mu}g/sample$. 2. The accuracy(% recovery) was 93.3% in a set of sample($9-50{\mu}g$) stored for a day, and 100.1%($10-60{\mu}g$) in another set of samples stored for 2 hours. It is assumed that the difference in recovery by storage time was due to reduction of Cr(VI) to Cr(III). 3. The precision(coefficient of variation, CV) of the method was 0.015 in spiked samples with Cr(VI) standard solution, and 0.010 in spiked samples with plating solution from a chrome electroplating factory. The overall CV in all types of samples was 0.0013. 4. The Cr(VI) was stable in 2% NaOH/3% $Na_2CO_3$ at least for 10 hours. In conclusion, the IC/VAD method is appropriate for determining low-level Cr(VI) in workplace air containing various interferences.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1997년도 제15회 KOSCO SYMPOSIUM 논문집
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• pp.61-68
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• 1997

The morphology and size distribution of chromium oxides and the concentration measurement of atomic arsenic have been studied in laminar diffusion flames. Nitrogen was added to vary flame temperatures in hydrogen flames. Ethene flames were used in order to investigate the potential for interaction between the soot aerosol that is formed in these flames and the chromium aerosol. Two sources of chromium compounds were introduced: chromium nitrate and chromium hexacarbonyl. A detailed investigation of the morphology was carried out by scanning electron microscopy (SEM). The amounts of Cr(VI) and total Cr were determined by a spectrophotometric method and by X-ray fluorescence spectrometry, respectively. Also, LIF was used for the measurement of atomic arsenic, which was excited at 197.2 nm and was detected at 249.6 nm. Results showed that the morphology of the particles varied with the flame temperature and with the chromium source. The particles were characterized by porous structures, cenospheres and agglomerated dense particles when chromium nitrate solution was added to the flames. At low to moderate temperatures, porous sintered cenospheric structures were formed, in some cases with a blow hole. At higher temperatures, an agglomerated cluster which was composed of loosely sintered submicron particles was observed. It was also found that the emission of Cr(VI) from the undiluted $H_2$ flame was more than 10 times larger than in the 50% $H_2$ / 50% $N_2$ flame on a mass basis. Single point LIF measurement of atomic arsenic indicated that arsenic exist only in the low temperature, fuel rich region.

• Journal of Microbiology and Biotechnology
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• 제31권11호
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• pp.1519-1525
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• 2021

Hexavalent chromium (Cr(VI)) is recognized to be carcinogenic and toxic and registered as a contaminant in many drinking water regulations. It occurs naturally and is also produced by industrial processes. The reduction of Cr(VI) to Cr(III) has been a central topic for chromium remediation since Cr(III) is less toxic and less mobile. In this study, fermentative Fe(III)-reducing bacterial strains (Cellu-2a, Cellu-5a, and Cellu-5b) were isolated from a groundwater sample and were phylogenetically related to species of Cellulomonas by 16S rRNA gene analysis. One selected strain, Cellu-2a showed its capacity of reduction of both soluble iron (ferric citrate) and solid iron (hydrous ferric oxide, HFO), as well as aqueous Cr(VI). The strain Cellu-2a was able to reduce 15 μM Cr(VI) directly with glucose or sucrose as a sole carbon source under the anaerobic condition and indirectly with one of the substrates and HFO in the same incubations. The heterogeneous reduction of Cr(VI) by the surface-associated reduced iron from HFO by Cellu-2a likely assisted the Cr(VI) reduction. Fermentative features such as large-scale cell growth may impose advantages on the application of bacterial Cr(VI) reduction over anaerobic respiratory reduction.

• 한국환경보건학회지
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• 제29권2호
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• pp.69-76
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• 2003

Hexavalent chromium may reduce on polyvinyl chloride (PVC) filter during sampling and storage of sample. Recently, new or modified filters for preventing Cr(VI) from the reduction has been introduced. Thus, this study was performed to compare the reduction behaviors of Cr(VI) on several sampling filters and to find the most appropriate filter for airborne Cr(VI) sampling in plating operation. The results were as follows. 1. There were statistically significant differences among PVC, polytetrafluoroethylene (PTFE). glass fiber (GF) and polyvinylidene fluoride (PVDF) filters in recovery rates of spiked Cr(VI) samples by storage time(p<0.05). There was no significant difference between PVC and PTFE filters(p>0.05). The PVC and PTFE filters showed higher recoveries than GF and PVDF filters(p<0.05). 2. The quartz fiber(QF) filter treated with an alkali solution(2% NaOH/3% Na$_2$CO$_3$, 1% NaOH) showed a significantly higher recovery of Cr(VI) by storage time than other filters(GF and QF filter)(p<0.05). There was no difference in recovery of Cr(VI) between alkali-treated and untreated GF it filters(p>0.05). But the QF filters treated with two alkali solution showed a significantly higher recovery than the untreated QF filter(p<0.05). There was no significant difference in recovery of Cr(VI) between QF filters treated with 1% NaOH and 2% NaOH/3% Na$_2$CO$_3$(p>0.05). In conclusion, treatment of QF fillers with alkali solution was most effective in protecting from the reduction of Cr(VI).

• Environmental Engineering Research
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• 제22권1호
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• pp.95-107
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• 2017

Adsorption equilibrium and kinetic behavior of two toxic heavy metals hexavalent chromium [Cr(VI)] and mercury [Hg(II)] on mustard oil cake (MOC) was studied. Isotherm of total chromium was of concave type (S1 type) suggesting cooperative adsorption. Total chromium adsorption followed BET isotherm model. Isotherm of Hg(II) was of L3 type with monolayer followed by multilayer formation due to blockage of pores of MOC at lower concentration of Hg(II). Combined BET-Langmuir and BET-Freundlich models were appropriate to predict Hg(II) adsorption data on MOC. Boyd's model confirmed that external mass transfer was rate limiting step for both total chromium and Hg(II) adsorptions with average diffusivity of $1.09{\times}10^{-16}$ and $0.97m^2/sec$, respectively. Desorption was more than 60% with Hg(II), but poor with chromium. The optimum pH for adsorptions of total chromium and Hg(II) were 2-3 and 5, respectively. At strong acidic pH, Cr(VI) was adsorbed by ion exchange mechanism and after adsorption reduced to Cr(III) and remained on MOC surface. Hg(II) removal was achieved by complexation of $HgCl_2$ with deprotonated amine ($-NH_2$) and carboxyl (COO-) groups of MOC.