Potential benefit of surfactants in a hydrocarbon contaminated soil washing process: Fluorescence spectroscopy based assessment

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  • Journal of Hazardous Materials 219 220 (2012) 141 147

    Contents lists available at SciVerse ScienceDirect

    Journal of Hazardous Materials

    jou rn al h om epage: www.elsev ier .com

    Potenti on proces ss

    Amandina Environmenta , UKb School of Life

    a r t i c l

    Article history:Received 10 OReceived in reAccepted 26 MAvailable onlin

    Keywords:Soil washingHydrocarbon cFluorescenceSurfactantTween80

    tion tcentrhe efocarbtionst 1% (d 65%ion (9d sanemov

    in the soil washing sedimentation process, enhancing sludge/water volume separation by 10% over thewater only wash. In summary, uorescence spectroscopy proved an effective technique to compare TPHremoval efciencies as part of soil washing laboratory based treatability testing.

    2012 Elsevier B.V. All rights reserved.

    1. Introdu

    Soils conyaromatic techniques hand is a chowever, thimpede thegravel and in the ne taminants asurfactantscess.

    Many aring processcontaminanare in the monly. Contafractions suSpecically

    Corresponburgh EH14 4A

    E-mail add

    0304-3894/$ http://dx.doi.oction

    taminated with aromatic hydrocarbons, including pol-hydrocarbons (PAH) are often slow to remediate bysuch as bioremediation [1]. Soil washing, on the otheromparatively rapid soil remediation technique [24],e hydrophobic nature of aromatic hydrocarbons can

    effectiveness of the water only wash process to cleansand fractions and thereby concentrate contaminationsolid fractions [5]. Therefore, particularly where con-re coated or adsorbed onto gravel and sand fractions,

    are of potential interest to improve the cleaning pro-

    ticles researching the use of surfactants in the soil wash- refer to removal efciency as the ability to concentratets into the liquid phase (efuent) [6,7]; however, theseain based on soils consisting of a single (sand) fraction

    minant removal efciency in soils consisting of multiplech as gravel, sand, silt and clay are more complicated., contaminant removal efciency can be considered in

    ding author at: School of Life Sciences, Heriot-Watt University, Edin-S, Scotland, UK. Tel.: +44 0131 451 3974; fax: +44 0131 451 3009.ress: t.j.aspray@hw.ac.uk (T.J. Aspray).

    terms of the removal from a particular solid fraction or, the transferfrom the soil to the liquid efuent. Given that the objective of soilwashing is to recover the gravel and sand fractions, contaminantremoval efciency should address these fractions specically. Inaddition, as the silt and clay fractions are usually heavily contam-inated and often require disposal, it may be better to concentratecontamination in silt and clay rather than the liquid efuent. Assuch, surfactants which primarily enhance the desorption of con-taminants from gravel and sand fractions, without necessarilyincreasing contaminant water solubility are of interest.

    Numerous studies have assessed the potential of chemical sur-factants such as SDS, Brij 35 or Tween80 to improve removalefciency of contaminants in the soil washing process; the results ofwhich are that surfactants show varying contaminant removal ef-ciencies. With the relative performance of a particular surfactantsbeing soil specic, laboratory based treatability tests are benecialto decide the most appropriate surfactant for a specic soil andsite. For example, Surfacpol has been shown to be more effectivethan Tween80 or SDS in sand [8], whereas, Tween80 and Brij35 hadsimilar removal efciencies in a sandy loam soil [9].

    In addition to the choice of surfactant, many studies havefocused on dening optimal washing parameters for the surfac-tant, for example, the inuence of washing time, temperature, aswell as surfactant concentration [7,10]. In these previous articles,washing times varied from 5 min to 48 h; however, in order to have

    see front matter 2012 Elsevier B.V. All rights reserved.rg/10.1016/j.jhazmat.2012.03.071al benet of surfactants in a hydrocarbs: Fluorescence spectroscopy based asse

    e Uhmanna, Thomas J. Aspraya,b,

    l Reclamation Services Ltd, Westerhill Road, Bishopbriggs, Glasgow G64 2QH, ScotlandSciences, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, UK

    e i n f o

    ctober 2011vised form 3 March 2012arch 2012e 3 April 2012


    a b s t r a c t

    Soil washing is an ex situ soil remediamajor gravel and sand fractions, conaddition of surfactants can improve tcence spectroscopy to assess the hydrgas chromatography. Three wash solusoil: water, Sea Power 101 (SP101) athe gravel and sand was SP101 (54 anmoved contamination to the silt fractremoval efciency from the gravel anthan water wash). In addition to TPH r/ loc ate / jhazmat

    contaminated soil washingment

    reatment process. The purpose of soil washing is to clean theating contamination into the ne silt and clay fractions. Theciency of this method. Here we report the use of UV uores-on cleaning process as a rapid and cost effective alternative to

    were tested on a total petroleum hydrocarbon contaminatedv/v) and Tween80 at 0.5% (w/v). The most effective to wash

    improvement over the water only wash, respectively) which4% of contaminants). Tween80 appeared not to enhance TPHd fractions but did concentrate TPH in the efuent (95% moreal from gravel and sand, SP101 also showed potential benet

  • 142 A. Uhmann, T.J. Aspray / Journal of Hazardous Materials 219 220 (2012) 141 147

    a time-efcient treatability test and to mimic currently availablesoil washing plant, washing duration should last minutes ratherthan hours. Finally, articial ageing of pollution has also been stud-ied, although in reality, ageing of pollution is not a variable in soilwashing tresoils which

    In recensidered forBiosurfactaing microorsaliva) anddate, biosucompared removal efremoval thSDS [14,15excellent bconditions effective [1

    In additfractions, thave an inFlocculatingcess and soalso needs can reducefactants andchemical tyinvolving suprocesses.

    Finally, performancgravimetricphy in partiinterest as aretains a hi

    The aimfactants (thSea Power soil. Specifrom gravelcompared tciency was cost effectitreatability

    2. Materia

    2.1. Solutio

    The thre

    (1) Deionis(2) Sea Pow

    tant proconcentby ourscomparmicelle rescencBriey, orescenorder toand 384

    Table 1Soil characteristics.

    Moisture content 16.8%pH 6.2


    l omati


    een8entied o




    ionisric c

    Pow Poween8een8een


    istor oil ran b

    il wa

    each follo

    of fr 1 l oin wpasswash63lyze

    2.5. Pr


    Soil mixesolu


    c whole soil (mg/kg)283.85549.95

    c gravel only fraction (mg/kg)90.85


    0 at 0.5% (Tween80); a non-ionic surfactant (Fisherc, Loughborough, UK). The concentration was chosenn previous articles [8].

    tions were prepared in a 2.5 L container with deionised

    ns for occulation test

    tions were:

    ed water (hereafter referred to as water),hloride at 0.5% (v/v) (FeCl3); a occulating agent,er at 1% (v/v) (SP101),er at 1% (v/v) and ferric chloride at 0.5% (SP101&FeCl3),0 at 0.5% (w/v) (Tween80),0 at 0.5% (w/v) and ferric chloride at 0.5% (v/v)80&FeCl3).

    ically hydrocarbon contaminated soil was taken from aenery located in Ayrshire, Scotland, UK. Soil character-e found in Table 1.

    shing procedure

    wash solution, three replicate experiments were con-wing the stages below:

    esh soil, previously sieved through 8 mm, was mixedf wash solution and stirred for 20 min. A wash time ofas chosen based on previous reports [8]. This mixtureed through two sieves (3.35 mm and 63 m aperture)ed with an additional 500 ml of wash solution.m fraction was allowed to settle for 5 h (correspond-e where no signicant reduction in sediment height

    ). After which, the resulting supernatant was removed. soil fractions were oven-dried.e resulting solid fractions; gravel (>3.35 mm), sand

    and silt/clay (

  • A. Uhmann, T.J. Aspray / Journal of Hazardous Materials 219 220 (2012) 141 147 143

    Fig. 1. Peak loTween80 and

    The expeferent pa30 min, 130 min ona spectroter).

    2.6. Ultravi

    The petrngerprint concentratithe intensit[24].

    UVF speter (Gilden pwith 10 ml Loughboroushaker. ThePTFE lter.as soils. Iniand wastew(EEM) scanically, totalexcitation wstep of 5 nmwith the reand concenrelationshipcentration was consisttion range. necessary. TNewbury, M5 ppm (EDR

    3. Results

    3.1. Surfact

    Tween80Even thougare in diffetamination using the EMcarbon contTherefore, t

    Table 2Compensation factors for the surfactant inuence on TPH analysis.

    Tween80 SP101

    .005%5% C% C

    nsat5]. T

    tion ition tion e facthat nly umentfacton exrfactardizeactios whactio. By ct shpe re

    fect o

    Surfa TPHfor ta), w80 apgravereatehen

    ed tolity i

    soil poug

    und wt impiclescy, Tr parrmincicsh sns becation on the excitation emission matrix (EEM) map of TPH, PAH,SP101.

    riment lasted 3 h. During this time the evolution of dif-rameters was studied. At each chosen time (0, 10 min,

    h, 2 h and 3 h) the sludge height was taken, and fromwards, total suspended solids (TSS) was analyzed usingphotometer (Hach DR 2800 Portable Spectrophotome-

    olet uorescence (UVF) spectroscopy analysis

    oleum products have a specic location within the EEM[23,24]; but the peak can move in the map with theon [23]. However, within a specic calibration range,y can be used to nd the contaminant concentration