• Environmental Engineering Research
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• 제22권2호
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• pp.149-156
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• 2017

Chromium(III) recovery from tanning wastewater by means of adsorption on activated carbon and elution with sulfuric acid was studied. Tests were carried out at laboratory scale on an effluent of industrial origin. Initially, proteinaceous materials and fats were separated via sieving followed by ultrafiltration. The chemical composition of the sample thus precleansed was (in g/L): 1.09 chromium(III); 10.36 sulfate; 11.10 sodium; 9.57 chloride; 0.40 proteinaceous materials; and 0.20 fats. Adsorptions were made at 20, 30, and $40^{\circ}C$, establishing what temperature favored chromium(III) uptake. At $40^{\circ}C$, the maximum cation fixation was 40.2 mg/g, and the lowest content in an equilibrium solution was 3.9 mg/L. As regards sodium, chloride, and sulfate, the concentrations before and after the treatment were similar. Likewise, it was found that protons were also retained, modifying the pH of the liquid medium. Adsorption isotherms were analyzed using the Langmuir, Temkin, and Freundlich models. Finally, the extraction of the adsorbed tanning agent with sulfuric acid was evaluated. A recovery of 96.5% was achieved with 0.9 N at $70^{\circ}C$ (13.23 g/L $Cr^{3+}$; 42.98 g/L sulfate; and 0.40 g/L NaCl).

• 한국산업보건학회지
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• 제1권2호
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• pp.117-127
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• 1991

The exposure level of chromium and nickel for chrome and nickel plating workers were evaluated. Chromium and nickel concentrations in serum from 82 exposed workers and 66 controls, who were not exposed occupationally to metals, were analyzed by flameless atomic absorption spectrophotometry. The results were as follows : 1. The recovery percent of chromium and nickel concentrations in personal air samples were 95-108.2%, 88.0-107.7%, precisions (C.V., %) were 2.7-3.1%, 2.1-4.4%. respectively. 2. The recovery percent of chromium and nickel concentrations in serum were 93.6-106.4%, 91.3-107.9% and precisions (C.V. %) were 1.1-7.6%, 2.4-5.4% respectively. 3. The exposure level of chromium and nickel concentrations in the place of preparation process were $2.0{\pm}2.00{\mu}g/m^3$, chromplating were $35.7{\pm}53.07{\mu}g/m^3$, $2.8{\pm}3.42{\mu}g/m^3$, nickelplating were $4.6.0{\pm}5.8{\mu}g/m^3$, $18.62{\pm}4.41{\mu}g/m^3$, and covering were $2.9{\pm}2.02{\mu}g/m^3$, $1.1{\pm}0.47{\mu}g/m^3$ respectively. There were significant difference of concentrations for chromium and nickel in workplaces by groups statistically. 4. Chromium concentrations in serum of exposed group and control were $0.68{\pm}0.399{\mu}g/l$, $1.41{\pm}0.748{\mu}g/l$, respectively. There were significant difference of concentrations for chromium and nickel in serum by groups statistically. 5. Chromium and nickel concentrations in serum of exposed group were not significant by workplaces.

• 한국자원리싸이클링학회:학술대회논문집
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• 한국자원리싸이클링학회 1993년도 EARTH 발표논문초록
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• pp.25.3-26
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• 1993

• 한국산업보건학회지
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• 제1권2호
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• pp.214-220
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• 1991

As chromium in urine remains as oxychromic acid ions, chromium was extracted by using ion pair formed by anion exchanger trioctylamine. then after it is noted whether this TOA-MIBK method is effective or not for the chromium analysis by using flame method of Atomic absorption Spectrophotometric Analysis. The result is as following. 1. Effects of various acids on the extraction of Cr with MIBK including TOA are good in order $NHO_3$, $H_2SO_4$, HCl in distilled water sample and its proper concentration of HCl is 0.2 N. 2. For the analysis of urine sample, the best result can be achieved by following condition. After finished pretreatment adjusted to pH 6.5-7.5 by NaOH and again controlled pH 0.5-0.6 by HCl. 3. Though TOA concentration slightly affects the analytic value, best result is noted in 1-3% concentration. 4. Recovery rates of urine samples made by $0.3mg/l{\cdot}urine$, $0.6mg/l{\cdot}urine$, $0.9mg/l{\cdot}urine$ are shown from 96.7% to 104.8%. 5. Recovery rates of urine samples made by $0.01mg/l{\cdot}urine$, $10.03mg/{\cdot}urine$, $0.05mg/l{\cdot}urine$ are shown from 89.3% to 98.6%.

• 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).

• 자원리싸이클링
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• 제13권2호
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• pp.9-15
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• 2004

석유화학공정으로부터 폐기되는 폐산화철촉매를 이용하여 도금합성폐수중 크롬회수에 관한 연구를 회분식과 연속식으로 실시하였다. 도금합성제수 중 $CrO _{4}^{-2}$ 형태의 음이온으로 존재하는 6가 크롬은 폐산화철촉매의 등전점(pH 3.0)이하에서 폐촉매와 물리적 흡착을 한다. 한편, 6가 크롬은 pH 3.0 이상에서도 폐촉매의 수산화철과 산화환원반응에 의해 일부 환원되어 $Cr(OH)_3$로 침전한다. 컬럼을 이용한 크롬 연속회수실험에서 크롬합성폐수의 pH가 0.5∼2.0일 때 폐촉매의 크롬흡착량은 2.0∼2.3g/L이며, pH가 3.0에서는 1.5g/L이었다. 폐수 중 크롬농도가 50∼500mg/L로 높아질수록 폐촉매에 흡착한 크롬누적량은 1.29∼8.56g/L로 증가하지만, 유속이 30∼80 ml/mm으로 증가하여도 크롬 흡착누적량은 2.21∼2.49 mg/L로 거의 유사하였다.

• 한국산업보건학회지
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• 제6권2호
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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.

• 자원리싸이클링
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• 제1권1호
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• pp.23-28
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• 1992

용매추출법을 이용하여 스텐레스 산세폐액으로부터 산과 니켈 및 크롬 등의 유가금속을 효과적으로 회수하기 위한 처리공정을 개발하고자 하였다. 현재까지 일본, 스웨덴 및 캐나다 등에서 이와같은 폐산을 처리하기 위한 몇가지 기술이 개발된 바 있으나 이들 방법은 대부분 산의 회수만을 주목적으로 한 것이기 때문에 폐산에 함유된 금속성분이 수산화물 스러지로 그대로 폐기되는 결점을 지니고 있다. 본 실험은 질산 및 불산과 함께 금속성분인 니켈과 크롬을 회수하여 정제산을 산세공정에 재상용하는 한편 처리과정에서 발생하는 스러지양을 최소한으로 줄이고자 하는 목적에서 시도되었다. 질산과 불산의 혼산은 TBP를 추출재로 사용한 용매추출에 의해 효과적으로 회수할 수 있었으며 여기에서 나온 폐액은 중화침전에 의해 철분을 제거한 다음 최종적으로 D2EHPA를 추출제로 사용하여 니켈과 크롬을 분리회수 할수 있었다.

• 한국산업보건학회지
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• 제11권1호
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• pp.48-55
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• 2001

The purpose of this study was to evaluate the analytical accuracy and precision of microwave oven digestion/atomi absorption spectrophotometry (AAS) for analyzing airborne chromium collected on mixed cellulose ester membrane (M filter from the work environment, and to compare the accuracy and the precision with those of the National Institute for Occupational Safety and Health (NIOSH) Method #7024 hot plate digestion/AAS method. For this study, field air sample pairs were collected from a electroplating process, and spiked samples in a laboratory were prepared and using these samples. Two digestion methods were comp; and evaluated in terms of recovery rate and bias as indices of accuracy and coefficient of variation as a index of precision. The results and conclusions are as follows. In spiked samples, the accuracies (% mean recoveries) of hot plate/AAS and microwave oven/AAS method were 97.19%, 97.1%, respectively, and the precisions (pooled respectively, and the precisions (pooled coefficient of variance, $CV_{pooled}$) 6.93% and 3.88%, respectively. The biases of hot plate ani microwave oven methods were 4.56 - 14.7% and 2.22 - 7.42% respectively. There was no statistically significant difference between hot plate and microwave oven methods recovery rates of spiked samples (p>0,05). Also, no statistically significant difference was shown among the concentrations of air samples determined by two method (p>0.05). In conclusion, microwave oven/AAS method h excellent accuracy and precision, and advantages such as time-saving and simple procedure in comparison with the classical NIOSH method. Therefore, this method can be use widely to analyze airborne chromium collected on MCE filter from the work environments.

• 한국대기환경학회지
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• 제25권3호
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• pp.179-187
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• 2009

This paper describes the field evaluation of a sampling and analytical method for the quantity of airborne hexavalent chromium ($Cr^{6+}$) in the industrial areas, such as Sihwa and Banwol. Ambient measurements were performed by using the cellulose filter during the four seasons (October 2006 to June 2007). The determination of hexavalent chromium was carried out by ion chromatography. Performance validations, including method detection limit, relative standard deviation, and recovery percent, were also investigated. The mean concentrations of $Cr^{6+}$ in Sihwa and Banwol were 0.767 and 0.796 $ng/m^3$, respectively, which are similar to those of other foreign industrial areas. The seasonal variations of $Cr^{6+}$ levels were not quite different, which implies that the chromium was continuously emitted from the industrial sources throughout the year. The concentration variations between total chromium and $Cr^{6+}$ have also shown the similar pattern, suggesting that these components originate from the same sources. The concentration of $Cr^{6+}$ was found to be 0.7 to 2.4% of the total chromium. From these results, the approach using the cellulose filter may be suitable to collect $Cr^{6+}$ in the ambient air.