Ethanol washing of PAH-contaminated soil and Fenton oxidation of washing solution

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<ul><li><p>AbstractAs a means to remediate soil contaminated by polycyclicaromatic hydrocarbons, we investigated a combined pro-cess involving ethanol washing followed by a Fenton oxi-dation reaction. Artificial loamy soil was contaminated withvarious representative polycyclic aromatic hydrocarbons(i.e., fluorene, anthracene, pyrene, benzo(b)fluoranthene, orbenzo(a)pyrene) at concentrations ten times higher thanregulatory soil standards of The Netherlands or Canada,and then washed four times in ethanol, which reduced theconcentration of polycyclic aromatic hydrocarbon contam-ination to below the regulatory standard. Fenton oxidationof ethanol solutions containing anthracene, benzo(a)py-rene, pyrene, acenaphthylene, acenaphthene, benz(a)an-thracene, benzo(j)fluoranthene, or indeno(1,2,3-cd)pyreneshowed a removal efficiency of 73.3%99.0%; by contrast,solutions containing naphthalene, fluorene, fluoranthene,phenanthrene, or benzo(b)fluoranthene showed a removalefficiency of 9.6%27.6%. Since each of the nonremediatedpolycyclic aromatic hydrocarbons, excluding benzo(b)fluo-ranthene, are easily biodegradable, these results indicatethat the proposed treatment can be successfully applied topolycyclic aromatic hydrocarbon-contaminated soil thatdoes not contain high concentrations of benzo(b)fluo-ranthene. The main reaction products resulting from Fenton oxidation of ethanol solutions containinganthracene or benz(a)anthracene were anthraquinon orbenz(a)anthracene-7,12-dione, respectively; while 1,8-naphthalic anhydride was produced by solutions of ace-naphthylene and acenaphthene, and 9-fluorenone by a flu-orene solution.</p><p>Key words PAH-contaminated soil Ethanol soil washing Fenton oxidation Reaction product identification</p><p>Introduction</p><p>Polycyclic aromatic hydrocarbons (PAHs), which containmore than two benzene rings, are refractory organic com-pounds commonly produced by incomplete combustion of fossil fuels.1 Some PAHs with more than four benzene rings have accumulated in soil due to their strong microbialresistance.2</p><p>Clean-up processes for PAH-contaminated soil havebeen studied extensively over the last two decades, most ofthem being bioremediation processes based on microbialdegradation.39 Unfortunately, however, these processes are not only time-consuming, but are of limited value; theyhave almost no degradational effect on four-ring or greaterPAHs.2</p><p>With the aim of developing a means to accelerate PAH decomposition prior to microbial degradation, achemicalbiological treatment has been applied, i.e., anadvanced oxidative process with Fentons reagent,10,11</p><p>although practical application is difficult owing to the highcosts of the chemicals required.</p><p>Soil washing has been applied to PAH- and heavy metal-contaminated soil because of its simplicity, low capital andoperating costs, easy maintenance requirements, and rela-tively good removal efficiency. On the other hand, furthertreatment of the washing solution (i.e., water, surfactant,and solvent) is needed; hence, this is only a partial remedy.</p><p>According to a U.S. EPA report, highly PAH-contaminated soil (301400mgPAH/kg) was washed andbiodegraded by the Biogenesis system.12 Compressed air-hot water (90C) was used in this system, and a re-moval efficiency of 65%73% was obtained. After aerobicbiodegradation of the washed water, the total PAH removalefficiency was 85%88%. In spite of long-term biodegrada-tion (120 days), the treated soil could not meet the soil stan-dards of The Netherlands or Canada. Table 1 shows the soilstandards of The Netherlands and Canada.</p><p>In the process of Fenton treatment, a Fenton reactionproduces an OH radical (HO) in such a way that oxidationof refractory organics and an organic radical occurs.13,14</p><p>J Mater Cycles Waste Manag (2000) 2:2430 Springer-Verlag 2000</p><p>Byung-Dae Lee Masaaki Hosomi</p><p>Ethanol washing of PAH-contaminated soil and Fenton oxidation of washingsolution</p><p>Received: June 9, 1998 / Accepted: March 24, 1999</p><p>ORIGINAL ARTICLE</p><p>B.-D. Lee (*) M. HosomiDepartment of Chemical Engineering, Tokyo University ofAgriculture and Technology, 2-24-16 Naka, Koganei, Tokyo 184-8588,JapanTel. +81-42-388-7070; Fax +81-42-381-4201e-mail:</p><p>Used Mac Distiller 5.0.x Job OptionsThis report was created automatically with help of the Adobe Acrobat Distiller addition "Distiller Secrets v1.0.5" from IMPRESSED GmbH.You can download this startup file for Distiller versions 4.0.5 and 5.0.x for free from</p><p>GENERAL ----------------------------------------File Options: Compatibility: PDF 1.2 Optimize For Fast Web View: Yes Embed Thumbnails: Yes Auto-Rotate Pages: No Distill From Page: 1 Distill To Page: All Pages Binding: Left Resolution: [ 600 600 ] dpi Paper Size: [ 595 785 ] Point</p><p>COMPRESSION ----------------------------------------Color Images: Downsampling: Yes Downsample Type: Bicubic Downsampling Downsample Resolution: 150 dpi Downsampling For Images Above: 225 dpi Compression: Yes Automatic Selection of Compression Type: Yes JPEG Quality: Medium Bits Per Pixel: As Original BitGrayscale Images: Downsampling: Yes Downsample Type: Bicubic Downsampling Downsample Resolution: 150 dpi Downsampling For Images Above: 225 dpi Compression: Yes Automatic Selection of Compression Type: Yes JPEG Quality: Medium Bits Per Pixel: As Original BitMonochrome Images: Downsampling: Yes Downsample Type: Bicubic Downsampling Downsample Resolution: 600 dpi Downsampling For Images Above: 900 dpi Compression: Yes Compression Type: CCITT CCITT Group: 4 Anti-Alias To Gray: No</p><p> Compress Text and Line Art: Yes</p><p>FONTS ---------------------------------------- Embed All Fonts: Yes Subset Embedded Fonts: No When Embedding Fails: Warn and ContinueEmbedding: Always Embed: [ ] Never Embed: [ ]</p><p>COLOR ----------------------------------------Color Management Policies: Color Conversion Strategy: Convert All Colors to sRGB Intent: DefaultWorking Spaces: Grayscale ICC Profile: RGB ICC Profile: sRGB IEC61966-2.1 CMYK ICC Profile: U.S. Web Coated (SWOP) v2Device-Dependent Data: Preserve Overprint Settings: Yes Preserve Under Color Removal and Black Generation: Yes Transfer Functions: Apply Preserve Halftone Information: Yes</p><p>ADVANCED ----------------------------------------Options: Use and No Allow PostScript File To Override Job Options: Yes Preserve Level 2 copypage Semantics: Yes Save Portable Job Ticket Inside PDF File: No Illustrator Overprint Mode: Yes Convert Gradients To Smooth Shades: No ASCII Format: NoDocument Structuring Conventions (DSC): Process DSC Comments: No</p><p>OTHERS ---------------------------------------- Distiller Core Version: 5000 Use ZIP Compression: Yes Deactivate Optimization: No Image Memory: 524288 Byte Anti-Alias Color Images: No Anti-Alias Grayscale Images: No Convert Images (&lt; 257 Colors) To Indexed Color Space: Yes sRGB ICC Profile: sRGB IEC61966-2.1</p><p>END OF REPORT ----------------------------------------</p><p>IMPRESSED GmbHBahrenfelder Chaussee 4922761 Hamburg, GermanyTel. +49 40 897189-0Fax +49 40 897189-71Email: info@impressed.deWeb:</p><p>Adobe Acrobat Distiller 5.0.x Job Option File</p><p> /ColorImageDownsampleType /Bicubic /GrayImageDict &gt; /CalCMYKProfile (U.S. Web Coated (SWOP) v2) /ParseDSCComments false /PreserveEPSInfo false /MonoImageDepth -1 /AutoFilterGrayImages true /SubsetFonts false /GrayACSImageDict &gt; /ColorImageFilter /DCTEncode /AutoRotatePages /None /PreserveCopyPage true /EncodeMonoImages true /ASCII85EncodePages false /PreserveOPIComments false /NeverEmbed [ ] /ColorImageDict &gt; /AntiAliasGrayImages false /GrayImageDepth -1 /CannotEmbedFontPolicy /Warning /EndPage -1 /TransferFunctionInfo /Apply /CalRGBProfile (sRGB IEC61966-2.1) /EncodeColorImages true /EncodeGrayImages true /ColorACSImageDict &gt; /Optimize true /ParseDSCCommentsForDocInfo false /GrayImageDownsampleThreshold 1.5 /MonoImageDownsampleThreshold 1.5 /AutoPositionEPSFiles false /GrayImageResolution 150 /AutoFilterColorImages true /AlwaysEmbed [ ] /ImageMemory 524288 /OPM 1 /DefaultRenderingIntent /Default /EmbedAllFonts true /StartPage 1 /DownsampleGrayImages true /AntiAliasColorImages false /ConvertImagesToIndexed true /PreserveHalftoneInfo true /CompressPages true /Binding /Left&gt;&gt; setdistillerparams&gt; setpagedevice</p></li><li><p>25</p><p>With the above treatment history of PAH-contaminatedsoil in mind, we now describe a new, combined ethanol-washing/Fenton-oxidation process which is used for thispurpose. That is, we report on the applicability of ethanolwashing of artificial soil contaminated with represen-tative PAHs, and also on further degradation treatment ofPAH-containing washing solutions by a Fenton oxidationprocess. In addition, for various PAHs we identify the mainoxidation product generated in the Fenton reaction inethanol.</p><p>Methods</p><p>Materials</p><p>The following materials were used for PAHs: special grade naphthalene (NAP) (95%, Waco); acenaphthylene(ACEL) (98%, AccuStandard); acenaphthene (ACE)(97%, Aldrich); fluorene (FLU) (95%, Waco); fluoranthene(FLUT) (95%, Waco); 9-fluorenone (FLUO) (99%, Waco);phenanthrene (PHE) (98%, Aldrich); anthracene (ANT)(99%, Aldrich); anthraquinone (ANTQU) (97%, Aldrich);pyrene (PYN) (98%, Waco); benz(a)anthracene (BAA)(99%, Aldrich); benz(a)anthracene-7,12-dione (BAADI)(97%, Aldrich); benzo(b)fluoranthene (BBFT) (99%,Aldrich); benzo(j)fluoranthene (BJFT) (98%, AccuStan-dard); benzo(a)pyrene (BAP) (97%,Aldrich); indeno(1,2,3-cd)pyrene (INDE) (98%, AccuStandard); 1,8-naphthalicanhydride (NAPAN) (purity unknown, Aldrich). ForFenton oxidation reagents, the following were used: H2SO4(95%, Waco); NaOH (97%, Waco); FeSO47H2O (99%,Waco); H2O2 (30%, Waco); ethanol (99.5%, Kokusan). Forthe GCMS and HPLC analyses, dichloromethane (99.5%,Kokusan), acetonitrile (99.8%, Kokusan), and water (HPLCgrade) were used. Table 2 summarizes the chemical prop-erties of PAHs.15</p><p>As simulated soil, we used a loamy soil, namely akadama,which is representative of Japanese soil and has the follow-ing properties: mesh size No. 1020; organic carbon content1.6%; base-exchange capacity 17meq/100g soil. Soil pH was6.5 and was measured by following the standard methodsfor the examination of soil: 25ml water or 1N of KCl solu-tion was added to 10g soil [i.e., 1 :2.5 (soil :water or KClsolution)], and then the pH of the water or KCl solution wasmeasured by a pH meter.16</p><p>Artificially contaminated soil</p><p>After being prepared in individual Teflon bottles, the loamysoil was artificially contaminated by FLUT (50mg/kg soil), ANT (50mg/kg soil), PYN (100mg/kg soil), BBFT (10mg/kg soil), or BAP (10mg/kg soil). The concentrationsof these contaminants were ten times higher than thoseallowed under the soil standards. Briefly, 6ml of ethylacetate (50mg FLUT, ANT, or PYN/l; or 10mg BBFT orBAP/l) was added to 6g of soil, after which the mixture wasagitated reciprocally without capping at 100r.p.m. for 24hto evaporate the ethyl acetate.</p><p>Ethanol washing of PAH-contaminated soil</p><p>All washing was done at 30C. We first added 18ml freshethanol and washed and agitated (200r.p.m.) 6g of eachPAH-contaminated soil for 24h, and then removed 12ml of the supernatant. The remaining soil was washed again inthe same way after adding 12ml of fresh ethanol. This was repeated two more times (for a total of four washings).For similarly prepared controls, we substituted 12ml ofdichloromethane for ethanol. Each supernatant was ana-lyzed by HPLC to determine the PAH concentration.</p><p>Fenton oxidation of PAHs in ethanol</p><p>We performed Fenton oxidation of ethanol solutions con-taining NAP, ACEL, ACE, FLU, FLUT, PHE, ANT, BAA,PYN, BBFT, BJFT, BAP, or INDE. That is, a solution com-bining ethanol (10ml) with each prepared PAH (150mg/l)was added to teflon bottles and the pH was adjusted to 3.5by adding 1M H2SO4 or NaOH prior to adding 0.5M Fe2+</p><p>(2.7ml) and 30% H2O2 (4ml). After a variety of timeperiods, the reaction was terminated by adding four to eightdrops of concentrated H2SO4 to lower the pH to less than1.0. All of the Fenton oxidation experiments were con-ducted in the dark at 30C.</p><p>Analysis</p><p>It is noted that the pH values cited in this paper were notexactly the same as those found in pure water because weused a normal pH meter (Yokogawa, model pH82) whileadjusting the pH in ethanol solution containing at least 15%or 30% water (i.e., 2.7ml of 0.5M Fe2+ and/or 4ml of 30%H2O2 solution added to 10ml of ethanol). After Fenton oxi-dation, samples were filtered through a 0.22-mm hydropho-bic membrane filter (Durapore, Millipore) and subjected to HPLC analysis. For the GCMS analysis, to allow forliquidliquid extraction (i.e., ethanol/dichloromethane), weadded 10ml of dichloromethane followed by reciprocal agitation (200r.p.m.) at 30C for 1 day and filtration througha 0.22-mm hydrophilic membrane filter (Durapore,Millipore). Table 3 summarizes the GCMS analysis conditions.</p><p>Table 1. Soil standards of The Netherlands and Canada for residentialareas</p><p>PAH Soil standards (mg/kg soil)</p><p>Fluoranthene (FLUT) 5a</p><p>Anthracene (ANT) 5a</p><p>Pyrene (PYN) 10a</p><p>Benzo(b)fluoranthene (BBFT) 1b</p><p>Benzo(a)pyrene (BAP) 1b</p><p>a The Netherlandsb Canada</p></li><li><p>26</p><p>Table 2. Chemical properties of PAHs</p><p>PAH Molecular Boiling Log Kow Vapor pressureweight point (C) (mmHg)</p><p>Naphthalene (NAP)</p><p>128.1 218 3.36 2.30 10-1</p><p>Acenaphthylene (ACEL)</p><p>154.2 279 3.92 1.55 10-3</p><p>Acenaphthene (ACE)</p><p>152.2 280 4.05 NDa</p><p>Fluorene (FLU)</p><p>166.2 298 4.12 1.00 10-3</p><p>Fluoranthene (FLUT)</p><p>202.3 384 5.22 1.00 10-2</p><p>Phenanthrene (PHE)</p><p>178.2 340 4.52 6.80 10-4</p><p>Anthracene (ANT)</p><p>178.2 400 4.45 1.95 10-4</p><p>Pyrene (PYN)</p><p>202.3 393 5.18 6.85 10-7</p><p>Benz(a)anthracene (BAA)</p><p>228.3 438 5.61 5.00 10-9</p><p>Benzo(b)fluoranthene (BBFT)</p><p>252.3 480 6.35 ND</p><p>Benzo(j)fluoranthene (BJFT)</p><p>252.3 480 ND ND</p><p>Benzo(a)pyrene (BAP)</p><p>252.3 495 5.99 5.49 10-9</p><p>Indeno(1,2,3-cd)pyrene (INDE)</p><p>276.3 ND 6.58 1.00 10-10</p><p>ND: no data available</p></li><li><p>27</p><p>The concentrations of PAHs and their reaction productsafter Fenton oxidation were measured by isocratic HPLC(CCPE, Tosoh) with reverse phase separation (SupelcosilLC-PAH, 15cm 4.6mm i.d.) at 254nm and 25C. Themobile phase was optimized at 80% acetonitrile and 20%HPLC-grade water. Fenton oxidation products were alsoconfirmed by GCMS with electron impact and chemicalionization capability (5890-2, Hewlett Packard) and a dataacquisition system (Model 138,Wiley) equipped with a silicacapillary column (DB-5HT, 30m 0.25mm 0.1mm, J&amp;WScientific). All analyses were performed in quintuplicate (n = 5). The data shown in the results indicate a 95% confi-dence interval. We determined the main reaction productsof PAH in ethanol produced by Fenton oxidation.</p><p>Results and discussion...</p></li></ul>


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