No abstract

The identification and characterization of carbonaceous materials (CMs) that control hydrophobic organic chemical (HOC) sorption is essential to predict the fate and transport of HOCs in soils and sediments. The objectives of this paper are to determine the types of CMs that control HOC sorption in the oxidized and reduced zones of a glacially deposited groundwater sediment in central Illinois, with a special emphasis on the roles of kerogen and black carbon. After collection, the sediments were treated to obtain fractions of the sediment samples enriched in different types of CMs (e.g., humic acid, kerogen, black carbon), and selected fractions were subject to quantitative petrographic analysis. The original sediments and their enrichment fractions were evaluated for their ability to sorb trichloroethene (TCE), a common groundwater pollutant. Isotherm results and mass fractions of CM enrichments were used to calculate sorption contributions of different CMs. The results indicate that CMs in the heavy fractions dominate sorption because of their greater mass. Black carbon mass fractions of total CMs in the reduced sediments were calculated and used to estimate the sorption contribution of these materials. Results indicate that in the reduced sediments, black carbon may sequester as much as 32% of the sorbed TCE mass, butthat kerogen and humin are the dominant sorption environments. Organic carbon normalized sorption coefficients (K(oc)) were compared to literature values. Values for the central Illinois sediments are relatively large and in the range of values determined for materials high in kerogen and humin. This work demonstrates the advantage of using both sequential chemical treatment and petrographic analysis to analyze the sorption contributions of different CMs in natural soils and sediments, and the importance of sorption to natural geopolymers in groundwater sediments not impacted by anthropogenic sources of black carbon.

To better understand sorption, separation methods are needed to enrich soils and sediments in one or more types of carbonaceous materials (CM), especially in fine grain materials where physical separation is not possible. We evaluated a series of chemical and thermal treatment methods by applying them to four different CMs prepared in our laboratory: a humic acid (HA), a char, a soot, and a heat-treated soot (HN-soot). Before and after each treatment step, CM properties were evaluated including aqueous phase sorption with trichloroethene (TCE). Results indicate that treatment with hydrofluoric (HF) and hydrochloric acid (HCI) to remove silicate minerals, and with trifluoroacetic acid (TFA) to remove easily hydrolyzable organic matter, has relatively little effect on the humic acid mass (<19% change) and TCE sorption to this material. Subsequent treatment with NaOH to extract fulvic and humic acids results in almost complete removal of the humic acid mass (>92%) and has little to no effect on the masses of the char and two soots (<8% change) and TCE sorption to these materials. Treatment with acid dichromate to remove kerogen and humin also has little effect on masses of the char and soots (<16% change), but TCE sorption to these materials is significantly altered (by >10x in some cases), and there is strong evidence of surface oxidation based on X-ray photoelectron and diffuse reflectance Fourier transform infrared spectroscopy results. The last step, thermal treatment, which targets char removal, also destroys >96% of the soots pretreated with acid dichromate. However, when thermal treatment is applied to the original soots, <32% of these materials are destroyed. Thermal oxidation also affects sorption to one of the soots (by approximately 2x at low concentration), and surface oxidation is evident. These results suggest that treatment with HCl, HCl/HF, TFA, and NaOH can be applied to soils and sediments to obtain CM enrichment fractions for sorption evaluation, but that acid dichromate and heat treatment may not be appropriate for these purposes.

Metal organic frameworks (MOFs) have been suggested as promising materials for application in the degradation of chemical warfare agents, with the majority of studies to date focusing on nerve agents. One of the most prominent MOFs used in the detoxification of nerve agents is UiO-66, which is of interest as a future nerve agent decontaminant. However, blister agents, which constitute one of the most toxic and highly reactive categories of chemical agents, are yet to be examined as gas-phase decontamination targets using MOF structures. In this study, a novel type of UiO-66 with a smaller particle size, namely, UiO-66S, was used as a decontaminant for the blister agent simulant, 2-chloroethyl ethyl sulfide (2-CEES). The gas-phase chemical adsorption and decomposition of 2-CEES were demonstrated for the first time, with an estimated t 1/2 of 1.34 h. This value is the highest reported value for an MOF in gas-phase reaction conditions. The obtained nontoxic degradation products were identified, and the reaction mechanism was studied using density functional theory calculations. Furthermore, the synthesized UiO-66S catalyst also exhibits superior catalytic ability toward nerve agent simulants (diisopropyl fluorophosphate).The results of the study provide a firm basis for the use of UiO-66S as a future decontaminant for both nerve and blister agents.

Abstracts − This study evaluated the environmental impacts of a soil washing (SW) process, especially, we compared the on-site and off-site remediation of TPH-contaminated soil using green and sustainable remediation (GSR) tool. To assess relative contribution of each stage on environmental footprints in the entire soil washing process, we classified the process into four major stages: site foundation (stage I), excavation (stage II), separation & washing (stage III), and wastewater treatment (stage IV). In on-site SW process, the relative contribution of CO 2 emissions and energy consumption were 87.1% and 80.4%, respectively in stage I, and in off-site SW process, the relative contribution of CO 2 emissions and energy consumption were 82.7% and 80.5%, respectively in stage II. In conclusion, the major factor contributing environmental impact in the SW process were consumable materials including steel and stainless steel for washing equipment in on-site treatment and fuel consumption for transportation of soil in off-site treatment.Key words: Environmental Impact, On/off Site Soil Washing, CO 2 Emissions, Energy Consumption, Green and Sustainable Remediation (GSR) †To whom correspondence should be addressed. E-mail: kbaek@jbnu.ac.kr ‡ 이 논문은 KAIST 양지원 교수님의 정년을 기념하여 투고되었습니다.This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Various methods to degrade explosives efficiently in natural soil and water that include trinitrotoluene (TNT) have been studied. In this study, TNT in water was degraded by reduction with palladium (Pd) catalyst impregnated onto alumina (henceforth Pd-Al catalyst) and formic acid. The degradation of TNT was faster when the temperature of water was high, and the initial TNT concentration, pH, and ion concentration in water were low. The amounts of Pd-Al catalyst and formic acid were also important for TNT degradation in water. According to the experimental results, the degradation constant of TNT with unit mass of Pd-Al catalyst was 8.37 min -1 g -1 . The degradation constant of TNT was higher than the results of previous studies which used zero valent iron. 2,6-diamino-4-nitrotoluene and 2-amino-4,6-dinitrotoluene were detected as by-products of TNT degradation showing that TNT was reduced. The by-products of TNT were also completely degraded after reaction when both Pd-Al catalyst and formic acid existed. Even though there are several challenges of Pd-Al catalyst (e.g., deactivation, poisoning, leaching, etc.), the results of this study show that TNT degradation by Pd-Al catalyst and formic acid is a promising technique to remediate explosive contaminated water and soil.

No abstract

No abstract