zeolites in a permeable reactive barrier (prb): one year of field experience in a refinery...
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Chemical Engineering Journal 178 (2011) 204 209
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Chemical Engineering Journal
jo u r n al hom epage: www.elsev ier .c
Zeolite Onrener es
Rodolfo V AuDanila Ga Department o Novab Department oc eni S.p.A., Re Departd Studies & Res e E. M
a r t i c l
Article history:Received 3 August 2011Received in revised form 14 October 2011Accepted 18 October 2011
Keywords:ZeoliteZSM-5MordeniteWater treatmeAdsorption pr
es ofreactive barrier (PRB) located under a coastal renery. The average organic contamination was 5 mg/L oftotal petroleum hydrocarbons, whose toxic constituents are aromatic (BTEX) and polynuclear aromatichydrocarbons (PAHs), and 5 mg/L of MTBE, specic gasoline additive, while the average concentrationsof more representative inorganic ions were: Na+, 8537 mg/L; Cl, 10,700 mg/L. The target of the entireprocess was: hydrocarbons, 350 g/L; MTBE, 10 g/L; and BTEX, 1, 15, 50 and 10 g/L, respectively.Two working tests of six months each were performed. In the rst phase two zeolite lters, constituted by
A permepermeable versely to tremoving cnatural movare favourain which thand then senormally ucontinuousimpermeab(gate), whilacross the want of the f
ZSM-5 (120 kg) and mordenite (150 kg), were used to treat water with a ow (Q) kept xed at 4 m3/d. Inthe second phase next each lter a new one of same material has been added to have a total of four lters,two of ZSM-5 (120 kg each) followed by two of mordenite (150 kg each), while the ow was doubled. Inboth tests the concentration of the organic contaminants in the outlet water remained constantly underthe limits. Between the two phases, the test was interrupted for six months for removing by backwashingthe inorganic and biological deposits formed on the lters. The performances of zeolites were evaluated onthe basis of the composition of both water sampled at the outlet of zeolite lters (by gas-chromatographicanalysis, GCMS) and contaminants adsorbed in the zeolite channels (by thermogravimetric analysis, TGAand GCMS).
2011 Elsevier B.V. All rights reserved.
able reactive barrier (PRB) consists essentially of adiaphragm of a reactive material, placed in situ trans-he ow of a polluted plume, capable of degrading orontaminants, transported by groundwater during itsement. This technology replaces, where the conditionsble, the conventional pump and treat technology,e plume is extracted from groundwater by pumpingnt to a dedicated water treatment. The congurationstilized in PRB technology are funnel and gate and
barrier. In the rst case the water is conveyed by anle diaphragm (funnel) to the permeable reactive zonee in the second one the reactive material is distributedidth of the contaminated groundwater plume. A vari-
unnel and gate consists of the drain and gate, where
ding author. Tel.: +39 0321447310; fax: +39 0321447506.ress: email@example.com (R. Bagatin).
a drain captures the portion of groundwater containing the plume,including the conveyance, and facilitates the test area, thus allow-ing a reduction of the extent of the barrier itself.
The key component in PRB technology is constituted by the reac-tive material, which should be selected on the basis of the natureof the contaminants to be removed and on the hydro-geologicalconditions of the site. Zero-valent iron (ZVI) is the most commonmaterial used in PRBs, followed by granulated activated carbon(GAC). Other examples of reactive materials include microorgan-isms, natural zeolites, peat, phosphates, limestone and amorphousferric oxide .
Depending on the nature of the material, the elimination of thecontaminants occurs by different processes such as degradation,adsorption or precipitation. In any case, the effectiveness of thematerials depends on their physicalchemical properties as well ason the nature of the compounds to be removed.
Particularly important is the problem related to the decon-tamination of groundwater from hydrocarbons, chlorinatedhydrocarbons and oxygenates (e.g. MethylTertButylEther, MTBE).For such kind of compounds the most widely used reactive
see front matter 2011 Elsevier B.V. All rights reserved.cej.2011.10.050s in a permeable reactive barrier (PRB):y groundwaterPart 1: The performanc
ignolaa, Roberto Bagatina,, Alessandra De Folly Dhisletti c, Roberto Millini c, Raffaello Sistod
f Environmental Technologies, eni S.p.A., Istituto eni Donegani, Via G. Fauser 4, I-28100f Chemistry, La Sapienza Universit di Roma, Piazzale A. Moro 5, I-00185 Roma, Italyning & Marketing Division, San Donato Milanese Research Center, Physical Chemistry earches Department, Renewable Energy & Environment Technologies, eni S.p.A. Piazzal
e i n f o a b s t r a c t
This paper describes the performancom/ locate /ce j
e year of eld experience in a
risb, Cristina Flegoc, Massimo Nalli c,
ment, Via F. Maritano 26, I-20097 S. Donato Milanese, Italyattei 1, I-00144 Roma, Italy
zeolites utilized for one year as adsorbents in a permeable
R. Vignola et al. / Chemical Engineering Journal 178 (2011) 204 209 205
materials seem to be ineffective. For instance, ZVI, used in PRBtechnology since the years 1990s, directly degrades several con-taminants, but appears to be ineffective on irreducible compoundssuch as 1,2-dichloroethane (1,2-DCA), chlorobenzenes as well ashydrocarboaged by ecoof contaminmetal ions.the physicainteractionspresent in gorganics tive in treatas oxygenatas vinyl chl
Removaticularly rechemical, pscarcely efflevels requwhether trefor its olfac
Surfactahighly effewastewater(with negattection) [6,7
This papPRB in drations of theow of watebeing remocrossed a ga drain anbelow the gwater ew by the passing the desreduced to the possiblity needed an existingment) was an adsorbendifferent clathe adsorptsecond zeofour lters treat a rangadvantagestaminant sewith salt aneffective capounds preHowever, story works,duration artiveness of selectively comparableSpecic zeoDCA and Valiphatic, has BTEX an
Table 1Main characteristics of zeolites utilized.
Characteristics ZSM-5 Mordenite
decoe barningformers cnite utedent
of remmpostratatedratioifferece ats, a als wf conthe mof th
litesterisoth cir hidersnite.lite sB fro
. 1 an, resptem s ou
ion, r doe. Sipte neth obes neet,honer wmenon is controlled by a vacuum chamber equipped with ahat provides both the emptying regular of the formed gase initial priming of the siphon. The piezometric fall to thedownstream is obtained by implementing a well for the col-
of the output in which the discharge is obtained through ans [2,3]. On the other hand, the use of GAC was encour-nomics and by the possibility of removing a wide rangeants, such as chlorinated solvents, hydrocarbons and
However, GAC presents several disadvantages due tolchemical characteristics of its surface: pore plugging,
with humic substances and inorganic ions, alwaysroundwater, adverse effect of pH on the adsorption of. Additionally, GAC has been shown to be slightly effec-ment of water containing very soluble compounds, suched organics, or low molecular weight compounds, suchoride (VC) .l of MTBE is challenging because this compound is par-calcitrant and different processing systems based onhysicalchemical and biological features proved to beective, particularly when considering the restrictiveired for this contaminant, such as 350 g/L in water,ated as a hydrocarbon, or still worse, the 2040 g/L
tory threshold.nt modied zeolites (SMZs) have been described asctive for the treatment of hydrocarbon-containing, although evidencing progressive surfactant releaseive impact both on economics and environmental pro-].
ging results have been reported also for siliceousic) zeolites .er illustrates the design of the industrial demo-scalein and gate conguration, according to the prescrip-
environmental plan of safety of the industrial site. Ther drained from an existing trench, or part of it, instead ofved by pump and treat processes outside the ground,ate formed by specic reactive zeolites, thus creatingd gate PRB conguration. The system was placed justround level, but higher than the groundwater table, sodue to a siphon structure whose operation is ensuredive hydraulic upstream downstream gradient. Dur-ign phase the sources of pressure losses have beena minimum and devices have been used to minimizee formation of gas that could put at risk the continu-for passive hydraulic operation. As drain of the PRB
trench was employed, while the gate (reactive ele-performed using two pairs of lters, each containingt material selected according to its specicity towardssses of contaminants present: a rst zeolite suited forion of aliphatic and light aromatic components and alite useful towards larger hydrocarbons and MTBE. Thecan be operated in series or in parallel and are sized toe of 4 to 8 m3/day (depending on conguration). The
of zeolite application concern with the organic con-lectivity, the rapid kinetics, the lack of interferencesd humic substances (also at tens g/L) and, mainly, thepacity in the removal of almost all the organic com-sent in groundwater of petrochemical and petrol sites.uch prerogatives were demonstrated only in labora-