Byung-Dae Lee

Prediction of Fenton oxidation positions in polycyclic aromatic hydrocarbons by Frontier electron density.

Five recalcitrant polycyclic aromatic hydrocarbons (PAHs) in ethanol were subjected to Fenton oxidation, and following GC-MS identification of respective oxidation products, their oxidation positions were compared to those predicted by Frontier electron density. Quinone forms of oxidation products were identified in each PAH. With the exception of fluorene, oxidation positions of quinone forms of products of acenaphthylene, anthracene, benz(a)anthracene, and benzo(a)pyrene corresponded with predicted positions in which Frontier electron density was high. From these results, it appears that determining the Frontier electron density of a PAH is a promising method for predicting the Fenton oxidation position.

A hybrid Fenton oxidation–microbial treatment for soil highly contaminated with benz(a)anthracene

In order to mitigate the strong microbial resistance of benz(a)anthracene [B(a)A] in soil, a hybrid treatment of Fenton oxidation followed microbial culture was carried out. Based on optimal Fenton oxidation. i.e., 1.0 ml of ethanol, 0.2 ml of 0.5 M Fe2+, and 0.3 ml of 30% H2O2 per 1 g of 500 mg B(a)A/kg soil, about 43% of B(a)A-7,12-dione was generated during oxidation of 97% B(a)A. When the comparative biodegradability between B(a)A-contaminated soil and B(a)A-contaminated soil after Fenton oxidation was examined, it was found that 98% of B(a)A-7,12-dione degraded after 63 d in comparison with only 12% of B(a)A over the same period; results demonstrating that Fenton oxidation enhances biodegradability of B(a)A through B(a)A-7,12-dione.

Fenton oxidation of ethanol-washed distillation-concentrated benzo(a)pyrene : Reaction product identification and biodegradability

After multiple ethanol washings followed by distillation, concentrated benzo(a)pyrene (B(a)P) in ethanol (approximately 85 mg L(-1)) was treated by Fenton oxidation, where > 99.8% of B(a)P was removed under a pseudo-first-order reaction. GC-MS and HPLC analysis identified B(a)P-1,6-, -3,6-, and -6,12-dione as Fenton oxidation products; all of which are known to have lower toxicity than B(a)P. Microbial resistance experiments demonstrated that B(a)P-1.6-, -3.6-, and -6,12-dione are more easily degraded than B(a)P. These results indicate that the proposed treatment can be effectively applied to remediate B(a)P-contaminated soil.

Photocatalytic degradation of gaseous perchloroethylene: products and pathway.

Batch photocatalytic degradation of 1000-ppm gaseous perchloroethylene (PCE) was conducted with UV irradiation such that nearly 100% was decomposed within 10 min. The main intermediate and final product were identified as trichloroacetylchloride (TCAC) and hydrogen chloride (HCl), respectively, and minor ones as dichloroacetic acid (DCAC), monochloroacetic acid (MCAC), carbon tetrachloride, chloroform, and phosgene. More than 90% of Cl- equivalent, i.e., the sum of the chlorine number in PCE, intermediates, and HCl, was compensated for during the time of PCE degradation; a result indicating that no other major chlorinated intermediates are present during the time of PCE degradation. In a similar experiment, 500 ppm of gaseous TCAC degraded into HCl within 3 h without producing DCAC or MCAC, where like PCE, more than 90% of Cl- equivalent, i.e., the sum of the chlorine number in TCAC and HCl, was compensated for during time of TCAC degradation. Accordingly, gaseous PCE is concluded to predominantly follow a degradation pathway of PCE --> TCAC --> HCl.

Characteristics of pharmaceuticals removal in the sewage treatment process

AbstractThis study was designed to analyze pharmaceuticals removal using biological sewage and wastewater treatment processes. Since pharmaceutical removal efficiency in a bioreactor was very low, it was determined that removing pharmaceuticals using biological treatment alone is very difficult. Thus, it attempted to identify the pharmaceutical removal characteristics with main physical and chemical processes such as coagulation sedimentation, ozonation, activated carbon treatment, and chlorine disinfection process as targets. The removal efficiency by coagulation and sedimentation turned out to be highest in atenolol with 16%. Other substances exhibited low removal rates regardless of coagulant dosage. Results of the batch test in which 30 mg/L of ozone was injected stepwise showed that diclofenac and trimethoprim showed a 95% removal rate at an ozone concentration of 5 mg/L, while iopromide with the lowest processing efficiency exhibited a 90% removal rate at a high ozone concentration of 30 mg/L. The s...

Evaluation of ethanol washing on dioxins-polluted soil and sediment based on adsorption relationships.

Abstract Multi‐stage ethanol washing on dioxins‐polluted soil and sediment were performed. The results indicated the existence of limit washing concentration (LWC), where no more dioxins were removed from the soil or the sediment by further washing. In each stage, dioxins concentration in the soil, sediment and ethanol could be described satisfactory by the Freundlich equation. The Freundlich capacity factor, Kef correlated with the LWC which was estimated to be ca. 1000 pmol g−1 in the case of soil, and about 150 pmol g−1 in the case of sediment. Organic contents in the soil and sediment affected the Freundlich intensity parameter, n−1 but not Kf. A model, which enables the calculation of removal efficiency of PCDD/DFs at each stage using Kf, n, and initial PCDD/DFs concentration, is presented.

Elucidation of the dechlorination pathway of 1,2,3,4-TCDD through atomic charge calculation

AbstractThe atomic charge of 1,2,3,4-TCDD as a model compound of dioxin using the Gaussian 03 program was compared with the radical dechlorination decomposition pathway reported in the literature. In the case of the atomic charge, the chlorine combined at the position of the carbon with a large negative charge value was found to have been dissociated first. Among the atomic charges, the CHelpG charge had the best agreement with the dechlorination degradation results in the literature. Based on the results, it is suggested that the radical dechlorination decomposition pathway of organic chlorinated compounds, including dioxins, can be predicted through atomic charge calculation.

Cleanup of Fluorene-Contaminated Soil by Continuous Chemical and Biological Treatment

We describe a method for effectively pretreating soil highly that has been contaminated with fluorene ( 120 mg/kg soil), i.e., we apply Fenton oxidation in which ethanol is added to increase fluorene removal. To obtain maximum fluorene removal efficiency, a minimum of 1.0 ml of ethanol, 0.35 ml of , and 0.2 ml of 0.5M was needed per 1 g of fluorene-contaminated soil. Under optimal Fenton oxidation conditions, 13% of 9-fluorene was generated during Fenton oxidation of 43% fluorene. The biodegradability of 9-fluorenone was subsequently confirmed to be much more rapid than that of fluorene, i.e., biodegradability of 96% versus 35% over 31 days. These results demonstrate that the proposed treatment method can be effectively applied to remove fluorene prior to disposal at industrial waste sites.

Prediction of Radical Reaction Positions in PAHs by Semi-Empirical Calculation

Abstract Each four polycyclic aromatic hydrocarbons (PAHs) was reacted with OH radical at 1.5 Å distance by CAChe MOPAC 2000 program. These results were compared to those reported experimental results. Reaction positions of all four PAHs corresponded with predicted positions in which ⊿ E(HOMO-LUMO) was approximately 4.7. Finally oxygen of OH radical combined with PAH and quinone form of products were produced. These results indicate that the proposed determining the ⊿ E(HOMO-LUMO) can be effectively applied to predict reaction position of recalcitrant compounds such as dioxins, PCBs, POPs, and etc.Key Words :HOMO, LUMO, PAHs, Radical reaction position 1. 서 론 1) 다환방향족탄화수소류(Polycyclic Aromatic Hydro- carbons, PAHs)는 벤젠 고리가 2개인 나프탈렌부터 벤젠 고리가 5개인 벤조에이피렌, 벤젠 고리가 6개인 benzo[ghi]perylene 까지 다양하나, US EPA에서 16 종류의 PAH에 대해 우선적으로 지정하여 관리하고 있다. PAHs에 의해 오염된 매체(토양이나 식품 등)의 경우 한 종류의 PAH에 의해 오염된 경우는 드물고 몇 종류의 PAHs가 혼재되어 있는 경우가 대부분이다. * Corresponding Author : Byung-Dae Lee, Department of Health, Uiduk University, Gyeongbuk 780-713, KoreaPhone: +82-54-760-1702E-mail: bdlee@uu.ac.krPAHs는 높은 발암성, 난분해성, 생물농축성 등으로 인해 PAHs의 환경 중 거동, 처리 기술 등에 관해 20세기 초반부터 지금 까지 많은 연구가 이루어져 왔다(Mekenyan 등, 1994; Government of Canada, 1994; Phillips, 1983). 환경 중에 존재하는 PAHs의 대부분은 다이옥신처럼 불완전한 연소에 의해 생성되고 일부는 산불 등과 같은 자연적인 요인에 의해서 발생하기도 한다(Warman, 1985; Smith, 1984; Talat 등, 1996). PAHs의 처리방법으로 생물학적 처리방법이 가장 경제적이고 환경친화적인 방법이기는 하나 PAHs의 난분해성 때문에 많은 처리시간이 소요되고 처리효율이 낮은 단점이 있다(Joshi와 Lee, 1996) 최근에는 이러한 생물학적 처리의 단점을 극복한 물리적 처리(Cookson, 1996), 화학적 처리(Watts, 1992), 소각처리