solar energy volume 83 issue 8 2009 [doi 10.1016%2fj.solener.2009.03.013] a. navarro; i. cañadas;...

8/11/2019 Solar Energy Volume 83 Issue 8 2009 [Doi 10.1016%2Fj.solener.2009.03.013] a. Navarro; I. Caadas; D. Martinez; J. Rodriguez; J.L. Mendoza -- Applicatio

1/10

Application of solar thermal desorption to remediationof mercury-contaminated soils

A. Navarro a, * , I. Can adas b , D. Martinez b , J. Rodriguez b , J.L. Mendoza a

a Department of Fluid Mechanics, Polytechnic University of Catalonia (UPC), ETSEIT, Colon 11, 08222 Terrassa, Barcelona, Spainb Plataforma Solar de Almer a (PSA), Solar Platform of Almeria-CIEMAT, P.O. Box 22, Tabernas, E-04200 Almeria, Spain

Received 24 November 2008; received in revised form 19 January 2009; accepted 11 March 2009Available online 8 April 2009

Communicated by: Associate Editor Gion Calzaferri

Abstract

Solar thermal desorption at temperatures up to 500 C is an innovative technology applied to the removal of mercury and arsenicfrom soil polluted by mining operations. As the soil is heated in a low and high-temperature solar system, the pollutant vapor pressurerises, producing mass transfer to the gas phase, which is then extracted by vacuum pumps and blower systems.

In the UPC low-temperature experiments, removal of mercury from the polluted soil was as much as 76%. The experimental resultsshow that volatilization of mercury is only signicant when the temperature is above approximately 130 C, which agrees with the pre-dominant mercury solid phases detected. PSA middle-temperature experiments, showed that when soil and mine waste samples wereheated to 400500 C, mercury elimination was signicant (41.387%). However, the results from heating to 320 C or below 300 C,indicated little or negligible removal, possibly, because the uid dynamics in the uidized-bed module and the presence of cinnabarand pyrite rich-Hg as dominant mineral phases.

These results show the potential for efficiently removing mercury and other pollutants from solid matrices (soil, waste, etc.) at lowtemperatures.

2009 Elsevier Ltd. All rights reserved.

Keywords: Solar energy; Desorption; Mercury; Soil contamination; Mine wastes

1. Introduction

Mercury is the most hazardous metal for human healthand the environment due to its ability to bioaccumulate, itstoxic effects, and the possibility of aqueous mobilization in

concentrations over the maximum levels allowed by mostdrinking water standards. Most human exposure to inor-ganic mercury is from Hg 0 vapor, derived from industriessuch as AuAg mining and chlor-alkali plants ( Fitzgeraldand Lamborg, 2005 ), although the main mercury-relatedhuman health concern is exposure to the highly neurotoxicorganomercury compound, monomethylmercury ( Fitzger-ald and Lamborg, 2005 ).

The release of mercury into the environment in Hg min-ing areas is generally associated with the abandonment of mine waste, which is mainly composed of calcines (wasteoriginated in the metallurgy of Hg) and mining wastesimpoundments, which contain waste rock and low-grade

stockpiles (Gray, 2003; Rytuba, 2003; Higueras et al.,2003; Ferna ndez-Martnez et al., 2006; Qiu et al., 2006;Navarro et al., 2006 ). Mercury has mainly been extractedfrom cinnabar (HgS), although the following are also mer-cury phase materials: livingstonite (HgSb 4S8), corderoite(Hg 3S2Cl2), metacinnabar (cubic HgS), schuetteite(Hg 3(SO4)O2), montroydite (HgO), calomel (Hg 2Cl2), tie-mannite (HgSe) and kleinite ( 4[Hg2NCl] Hg[SO4,Cl] H 2O).The main process for extracting mercury from cinnabar isto roast the ore at 500600 C, which releases Hg0. Thus,when the temperature reaches to 600800 C, the mercury

0038-092X/$ - see front matter 2009 Elsevier Ltd. All rights reserved.

doi:10.1016/j.solener.2009.03.013

* Corresponding author. Tel.: +34 937398151; fax: +34 7398101.E-mail address: [email protected] (A. Navarro).

www.elsevier.com/locate/solener

Available online at www.sciencedirect.com

Solar Energy 83 (2009) 14051414
mailto:[email protected]:[email protected]


2/10

compounds would be converted into gaseous mercurywhich could be recovered. Table 1 shows desorption tem-peratures and their ranking for some mercury compounds(Biester et al., 1997; Gaona, 2005 ).

Some treatments processes, such as stabilization/solidi-cation, thermal desorption, vitrication, soil ushing and

soil washing have been used for mercury-contaminated soilremediation ( Troxler et al., 1997; ITRC, 1998; EPA, 2003;Chang and Yen, 2006 ). The thermal desorption treatmentis, usually, an ex situ remedial technology which convertsmercurial compounds into the volatile mercury, and hasbeen considered as a preferred technology, due of moresafety and less emission of treating substance ( Chang andYen, 2006 ). However, the major disadvantages are highcapital costs and effectiveness only at rather high mercuryconcentrations ( Kucharski et al., 2005 ).

Several mercury thermal desorption experiments havedemonstrated the feasibility of mercury removal at temper-atures between 127 and 600 C (Matsuyama et al., 1999;Chang and Yen, 2006; Kunkel et al., 2006 ). Experimentalremediation of mercury-polluted soils by low-temperaturethermal desorption has also shown mercury removal of over 99% in sand (Kunkel et al., 2006 ) and the volatiliza-tion of at least 99% of mercuric sulde from polluted soil(Matsuyama et al., 1999 ).

Therefore, solar thermal desorption, using solar energyas the primary energy source in a low-to-medium-tempera-ture solar furnace may be an option for soil treatment. Theuse of solar energy in these environmental applications isnew, although the natural mobilization of mercury fromsoil by incident solar radiation is well-known ( Gustin

et al., 2002). Moreover, the majority of the experiencesbased on the application of solar energy do not use solarradiation in thermal desorption processes ( Funken et al.,1999; Flamant et al., 1999; Steinfeld and Palumbo, 2001;Nakamura et al., 2000; Effelsberg and Barbknecht, 1991;Effelsberg et al., 1992; Kaneko et al., 2004).

The main objective of this research was to evaluate thepotential of solar thermal desorption (STD) for removalof mercury from mining contaminated soils. A low-temper-ature laboratory system was designed and used to evaluatethe effectiveness of STD, and a middle-temperature solarfurnace was used to evaluate the application of a uid-ized-bed reactor in thermal desorption.

2. Materials and methods

2.1. Characterization of soil and mine waste

Samples of soils and mine waste were collected in theValle del Azogue and Bayarque mines (SE, Spain). The

Valle del Azogue mine was the principal mercury minein the Betic Ranges from approximately 18731890 andthe ore is composed of stibnite, cinnabar, As minerals(realgar and orpiment), sphalerite, siderite, chalcopyrite,pyrite, quartz, calcite and baryte ( Navarro et al., 2006 ).Other mineral phases detected ( Mendoza et al., 2005 )include metacinnabar (HgS), SeHgS, tiemannite (HgSe),corderoite (Hg 3S2Cl2), shakhovite (Hg 4SbO 5(OH) 3) andschuetteite (Hg 3(SO4)O2). The Bayarque mine is locatednear the valley of the Almanzora River and the town of the same name. Its underground mines were exploiteduntil approximately 1973. The mineralogy mainly consistsof cinnabar, malachite, azurite, hematites, galena, goe-thite, siderite, chalcopyrite, bornite, chalcosine, covelliteand uorite.

Approximately 1.5-kg samples of mine waste and soilwere manually extracted and crushed to 10 mesh in a jawcrusher, quartered, and pulverized in an agate mortar,rehomogenized and repacked in plastic bags. Soil sampleswere taken from a depth of approximately 00.25 m andwere sent to Actlabs (Ontario, Canada) with other minesamples. Au, Ag, As, Ba, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe,Hf, Hg, Ir, La, Lu, Na, Ni, Nd, Rb, Sb, Sc, Se, Sm, Sn,Sr, Ta, Th, Tb, U, W, Y and Yb were quantitatively ana-lyzed by instrumental neutron activation analysis (INAA)

and Mo, Cu, Pb, Zn, Ag, Ni, Mn, Sr, Cd, Bi, V, Ca, P,Mg, Tl, Al, K, Y and Be were analyzed by inductively cou-pled plasma emission spectroscopy (ICP-OES). The ther-mal treated samples were analyzed in the same way. Theaccuracy of analytical data may be evaluated around10%, because the heterogeneity of solid samples.

The mine waste samples were studied using transmittedand reected light microscopy, X-ray diffraction (XRD)and scanning electron microscopy (SEM) with an attachedenergy dispersive X-ray spectroscopy system (EDS) at theElectronic Microscopy Laboratory of the UniversitatAuto noma de Barcelona.

Hg phases were determined by solid-phase-Hg-thermo-desorption (SPTD), based on the specic thermal desorp-tion or decomposition of Hg compounds from solids at dif-ferent temperatures ( Biester and Scholz, 1997; Navarroet al., 2006). Mercury thermo-desorption curves weredetermined by means of an in-house apparatus, consistingof an electronically controlled heating unit and an Hgdetection unit. Measurements were carried out at a heatingrate of 0.5 C/s and nitrogen-gas ow of 300 mL/min. Thelowest level of detection under the given conditions is in therange of 4050 ng if all Hg is released within a single peak(Biester and Scholz, 1997). Results are depicted as Hgthermo-desorption curves (Hg-TDC) which show the

release of Hg(0) versus temperature.

Table 1Desorption temperatures of different mercury phases.

Phase Desorption temperature of phase Hg ( C)

Hg 0


3/10

2.2. Furnaces

In this study, two systems of solar thermal desorption,an experimental low-temperature solar furnace (LT-UPC)and a middle-temperature solar furnace (MT-PSA), wereused to treat mercury-polluted soil and mine waste from

the Valle del Azogue and Bayarque mines.Besides, since the use of activated-carbon is effective inmercury vapor adsorption ( Spiric and Hraste, 1999; Kara-tza et al., 2000; Vitolo and Seggiani, 2002; Li et al., 2002;Lee et al., 2002; Meij et al., 2002; Lee and Park, 2003 ),an activated-carbon lter was used in the treatment of gas-eous mercury compounds.

2.2.1. Low-temperature solar furnace (LT-UPC)The experiments were done in a low-ux-density, low-

temperature solar furnace, which consists of ve elements:a solar reector, a glass furnace (or reactor), a uid-coolingsystem, an Hg gas adsorption system, and a vacuum pumpwhich mobilizes ambient air from the glass furnace to theactivated-carbon lter ( Fig. 1a). The system has a collector

and rotating base which allows seasonal adjustment to thesolar position. The glass furnace is a high-temperature-resistant glass ask that is connected to a thermometer tomeasure the temperature inside it. An air-cooled coil gas-cooling system lowers the temperature in case it shouldexceed 400 C, before the gas enters the carbon lter.

Finally, a vacuum pump generates the extraction ow-rateof Hg-polluted gases.The treatment procedure consists of placing the polluted

soil sample in the furnace, turning the reector northwardand directing the center of sunlight reected by the collec-tor onto the base of the glass furnace. When it is ready, thevacuum pump is put into operation to start up extractionof the polluted gas. The temperature is measured at 10-min intervals for 24 h. When the sample has cooled, it istaken out of the furnace, packed and sent to be analyzedfor Hg content, metals and rare earth elements.

2.2.2. Middle-temperature solar furnace (MT-PSA)A uidized-bed reactor design by CIEMAT and

CENIM-CSIC was used to test the feasibility of high-tem-

Fig. 1. (a) Scheme of operation of the low-temperature solar furnace (LT-UPC). (b) Scheme of operation of the middle-temperature solar furnace (MT-

PSA). SC: system cooling, F CA : activated-carbon lter.

A. Navarro et al./ Solar Energy 83 (2009) 14051414 1407


4/10

perature solar desorption in the Plataforma Solar deAlmer a (PSA) Solar Furnace ( Fig. 1b). This system hastwo main parts, the PSA Solar Furnace facility, and thesolar uidized-bed module connected to an Hg gas collec-tion system with a nal activated-carbon adsorption bed(Fig. 2).

The PSA Solar Furnace consists of a at heliostat, aparabolic dish, and a louvered ux shutter. The GM140at-surface heliostat, which reects the solar radiation ontothe parabolic dish, has a 140-m 2 reective area, with 93%reectivity. It tracks the sun continuously, and is controlledby a remote system connected to a computer. The uxshutter, which regulates how much solar radiation arrivesat the uidized-bed, is 11.5 m wide and 11.2 m high, andconsists of 30 slats arranged in two columns in the modulewall. The concentrator or parabolic dish consists of 89spherical sandwich-type facets, with a total reecting areaof 98.5 m2 and reectivity of 94%. The concentrator dishis the main component of the solar furnace. It concentratesincident light from the heliostat, multiplying the radiantenergy in the focal zone, to a peak ux of 300 W/cm 2

and total power of 68 kw ( Monterreal, 2005 ).The uidized-bed reactor, with indirect solar heating

and open volumetric receiver, is a new device developedby CENIM and CIEMAT for installation in the PSA SolarFurnace. Fig. 2 shows a schematic diagram of the modularuidized-bed installed in the test assembly (Can adas et al.,2006).

The uidized-bed module consists of an indirectly-heated solar uidized-bed reactor, with two independentcircuits, one for heating, through which air from the absor-

ber module is forced by a blower located at the end of thetest assembly, and another for the uidized ow (com-pressed air or gas). All the equipment is insulated to mini-mize heat loss. The surface temperature of the absorbermodule is measured by a pyrometer ( Ballestrn et al., 2008).

The soil samples are inserted in the uidized-bed cham-ber for treatment. The uidized-bed operates at a ow-rate

of 50 L/min. As shown in Fig. 2, the uidized-bed cylindri-cal chamber is 1 m high and 20 cm in diameter. The conicalbase is connected by the uidized ow circuit to a pump/aircompressor that generates the uidizing air ow. Thischamber is heated up by another outer module heated bythe absorber. At the top of the uidized-bed chamber,

the Hg gas collector system is connected to a cooling sys-tem that lowers the Hg gas temperature to below 400 C.The treatment procedure for each sample consists of

placing a soil sample in the uidized-bed chamber, sealingthe cover and connecting it to the gas recovery system. Theheliostat controller automatically directs the solar radia-tion onto the concentrator dish, which in turn beams theconcentrated solar rays onto a focal point located on theoptical axis. The absorber module in the focal zone, isgradually heated by concentrated solar radiation as theshutter is gradually opened to the reference temperatureof 400 C, and this temperature is maintained for approxi-mately 30 min.

During the treatment, a blower forces air through theabsorber module, where it is heated, and part of the energyin this air is transferred into the uidized-bed chamberthrough its steel walls, heating it, and then preheating theair or gas that uidizes the bed as it passes through the coilbehind it. When this has been accomplished, the digitaldata is saved. At the end of the experiment, when the sam-ple is cold, it is taken out to be analyzed. The main differ-ence between the LT-UPC and the MT-PSA furnaces, wasin the operation system, thus the low-temperature furnaceis static, while the middle-temperature furnace is a uid-ized-bed reactor.

3. Results and discussion

3.1. Geochemistry of soils and mine waste

The mean concentrations of mercury and other metalsin the soil and mine waste samples from the Valle del Azo-

Fig. 2. Schematic drawing of the uidized-bed module in the Solar Platform Almer a (MT-PSA).

1408 A. Navarro et al./ Solar Energy 83 (2009) 14051414


5/10

gue and Bayarque mines is shown in Table 2 . The totalmercury concentration in waste from the Valle del Azoguemine varies between 1 and 4000 mg/kg, and at the Bayar-que mine between 33 and 4600 mg/kg. In the waste samplesfrom the Valle del Azogue and Bayarque mines, the aver-age is 649.1 mg/kg and 1247.7 mg/kg, respectively. Total

mercury in surface soil from the Valle del Azogue rangedfrom 1.0 to 2300 ppm, concentrations which are belowthose detected near the Almade n mine (Higueras et al.,2003, 2006). Due to the mining activities, along with theimpact of high Ag, As, Pg, Sb and Zn, plants in most of the area have disappeared or are severely affected by thevery high mercury and metal content found in them ( Vila-devall et al., 1999).

Hg-thermo-desorption curves (Hg-TDC) found for min-ing wastes, soils and calcine samples showed predominantrelease of Hg in two temperature ranges: 200250 C and300330 C (Fig. 3). The rst temperature range wasassigned to release Hg from the soil matrix componentsbased on the Hg-TDCs of standard materials ( Biesterand Scholz, 1997 ). Thus, we assume that most Hg in thecalcine material is bound to mineral components mainlyby iron oxides, which were formed when the cinnabar-bear-ing ore was being roasted. It has been suggested in earlierstudies, that Hg 0 formed during thermal breakdown of cin-nabar is re-condensed during cooling of the material andadsorbed to dehydrated iron oxide surfaces ( Biester et al.,1999). Sample B01, which was taken directly from theBayarque mine furnace outlet shows the matrix-boundHg mainly formed during roasting. In addition to matrix-bound Hg, some calcine samples contain at least traces of

cinnabar. This could be explained by incomplete break-down of cinnabar ore during the roasting process.The second temperature range was assigned to Hg

release from cinnabar, which was the predominant mineralHg-phase in contaminated soils ( Fig. 3b) and miningwastes (host rock and low-grade stockpiles). Cinnabarand a possible Hg sulfate were also detected in several sam-

ples (Navarro et al., 2006 ). No free metallic Hg, which istypically released at temperatures below 100 C (Biesterand Scholz, 1997 ), was found in any of the samples studied.

Mercury phase characterization by soil sample X-rayshowed cinnabar (HgS), corderoite (Hg 3S2Cl2), mercurydichloride (I) (Hg 4O2Cl2), hypercinnabar (HgS), laffittite

(AgHgAsS 3), metacinnabar ((Hg)S), shakhovite (Hg 4SbO5(OH) 3), schuetteite (Hg 3(SO4)O2) and tiemannite (HgSe).The proportionally predominant phase is cinnabar, whichis concordant with the SPTD analyses.

3.2. Thermal desorption experiments

The low-temperature experiments (LT-UPC) were con-ducted under global radiation at least 30 W/m 2 and nomore than 300 W/m 2. The variation in temperature andglobal radiation, the time, and the duration of some testsmay be observed in Fig. 4. Peak temperatures of 280 Cwere reached. The temperature ranges and average temper-ature are shown in Table 3 .

Mercury removal efficiency in the soil and waste samplesis up to 76% and was negligible in samples A01 to A04(Table 3 ). The experimental results show that mercury vol-atilization is only signicant when the temperature is aboveapproximately 130 C, which is in agreement with the dom-inant solid phases of mercury: cinnabar and Hg 0 bound tothe solid matrix. Both phases have a volatilization temper-ature of 300330 C and 200250 C, respectively. The lowHg removal in the samples A01 to A04 may be associatedto their mineralogical characteristics, since these sampleswere mining wastes and soils with a great percentage of cin-

nabar and pyrite. The volatilization of Hg from cinnabarparticles needs a mean temperature above 300 C, approx-imately, and the mean temperature of the LT-UPC exper-iment reached, only, 91130 C. The greater Hg-removalwas reached in the sample A06, which showed high con-tents of volatile-Hg-phase minerals, such as calomel andkuzminite ( Navarro et al., 2009 ). In the samples M04 to

Table 2Concentrations of metals in mine waste and soils in the Valle del Azogue mine. Values in mg/kg except Ba (%). NIL ( ): The Netherlands soil interventionvalues ( ): indicative level of contamination ( ): soils and mine wastes. NCD: non-polluted soils.

As Ba Cd Cr Cu Hg Pb Se Sb Sr Zn

Valle del Azogue mineWastesMean 526.1 6.0 5.7 70.5 47.5 649.1 901.6 4325.6 945.3 2631.0Min 12.9 0.07


6/10

M07, Hg is associated to mineral compounds matrix, andpossibly derived from the atmospheric deposition of Hg 0

evaded from old roasting plant emissions. Moreover, thevacuum pumping system used in this experiment, whichcarried atmospheric air from the glass furnace, showed agreat effectiveness, moving high amounts of gaseous Hgto activated-carbon lter.

In the middle-temperature experiments (MT-PSA) theglobal radiation was approximately 900 W/m 2 (Fig. 5) withan exposure time of between 75 and 315 min ( Table 5 ).Based on the results of the heating tests, when soil andwaste were heated to 400500 C, mercury removal was sig-

nicant. However, when heated to 320 C or below 300 C,

there is little or negligible removal of mercury ( Table 4 ).Thus, in mercury removal in Samples M02, M03, M05and M07 was between 41.3 and 87.0%, when heated to overapproximately 400 C, (Table 4 ), whereas removal fromSamples B02 and AZ21 was only between 12.1 and36.3%, because the furnace temperature was just over300 C. Mercury removed was negligible in Samples A01to A05, Az22 and B01, possibly because of the low temper-atures reached, the short experiment exposure time and thepresence of signicative amounts of cinnabar and Hg-richpyrite in these samples. Thus, in sample A02, which washeated up to 479 C, there may have been no removal

due to its mineralogical nature. In fact, in sample A02, a

B01 - furnace calcine

0

200

400

600

800

1000

1200

1400

1600

1800

0 100 200 300 400 500 600 700

C

E x t

i n k t i o n

0

20

40

60

80

100

120

140

160

180

200

B0102

B0101

B02 - alluvial soil

0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600 700

C

E x t

i n k t i o n

0

10

20

30

40

50

60

70

80

90

100

B0202

B0201

a

b

Fig. 3. Examples of mercury thermo-desorption curves. The two curves in each graphic represent a SPTD experience on the same material. (a) Calcinesample B01 which shows Hg0 matrix-bound dominant. (b) Soil sample B02 which shows cinnabar as dominant phase mineral.

1410 A. Navarro et al./ Solar Energy 83 (2009) 14051414


7/10

large percentage of mercury may be encapsulated in pyrite,which has a high volatilization temperature ( Table 1 ). Thepossible presence of HgSO 4 or HgO (Sample A03), com-pounds releasing Hg at above 400 C, may also explainthe absence of mercury removal in some samples. Anotherfactor that may determine the efficiency of mercuryremoval in the uidized-bed experience is the velocity of the solid particles inside the furnace. Thus, the terminalvelocity of material particles calculated from Stokes equa-tion was comprised between 0.16 m/s (silty particles) and4.15 m/s (sandy particles). Since entry velocity of particleswas 2.65 m/s, the silty particles, possibly, move to theupper part of the furnace, accumulating in the lter. There-fore, the transport of dominant ne particles inside the u-idized-bed furnace and the consequent low efficiency in the

heat and mass transport together with the lter-block for-mation may also explain the low Hg-removal of MT-PSAexperiences, despite the high-temperature reached. In allthe samples treated in the MT-PSA experiences, the bestresults were obtained with samples that present dominant

Hg0

bound to the solid matrix (Az21, M02 to M07), exceptthe sample B02, which is coincident with the LT-UPCresults.

As content shows this metalloid was removed in heatingtests in the same samples which have signicant mercurydesorption, except for Sample M07, and Samples B01and AZ22 ( Table 5 ). As removal was between 5.5 and77.3%, indicating the feasibility of As desorption fromthe polluted soil and mine waste. These results show thatmore mercury and arsenic is removed by heating whenoperating temperatures are over 400 C, although mercuryremoval may differ depending on the minerals containing itand exposure time. Results also suggest that mercury con-tained in cinnabar and pyrite is not efficiently removed bydesorption caused by the solar treatment in the experimen-tal conditions, although removal may be complete athigher temperatures (500600 C).

4. Conclusions

This article reports the rst time a solar thermal concen-trated facility has been used for remediation of mercury-contaminated soils. Two different concentrated facilitieswere employed with satisfactory results in different temper-ature ranges.

Sample A03

0

50

100

150

200

250

300

13:33 13:48 14:02 14:16 14:31 14:45 15:00 15:14 15:28 15:43 15:57 16:12 16:26 16:40 16:55

Time

T e m p e r a t u r e

C

0

100

200

300

400

500

600

700

800

900

1000

R a d

i a t i o n

W / m 2

T 170506

R 170506

Fig. 4. Temperatures and global radiations of some tests from low-temperature experiments (LT-UPC): T indicates temperature of DDMMYY and Rindicates the global radiation of DDMMYY.

Table 3Data tests made in a solar furnace LT-UPC.

Sample Initial Hg(mg/kg)

Final Hg(mg/kg)

%Desorption

T (mean)( C)

Operationtemperatures( C)

A01 530 506 4.5 128.0 45145A02 1000 >1000 91.0 38125A03 210 >200 113.0 55165A04 540 >500 130.9 65187A06 600 176 70.6 129.2 80168M04 4000 2800 30.0 203.3 68247M05 50 12 76.0 213.0 110280M06 399 240 39.8 168.5 128197M07 23 12 47.8 131.2 88149

A. Navarro et al. / Solar Energy 83 (2009) 14051414 1411


8/10

The SPTD determinations showed two different temper-ature ranges in which Hg was released from the samples,200250 C and 300330 C. From previous interpretation,the rst Hg release peak indicates Hg released from thematrix, whereas the second peak at higher temperaturesindicates presence of cinnabar ( Biester and Scholz, 1997;Navarro et al., 2006 ). The rst release of Hg was typically

found for calcinated samples, where cinnabar was brokendown, but some Hg is re-adsorbed onto the calcinatedmaterial during cooling. The second peak release is domi-nant in the mining wastes and soils.

The low-temperature experiments (LT-UPC) showedup to 76% mercury removal efficiency in soil and minewaste samples. Experimental results indicate that volatili-zation of mercury is only signicant when the temperatureis above approximately 130 C, which is in agreementwith the predominant mercury solid phases (Hg 0 boundto solid matrix in samples A06 and M04 to M07). Themiddle-temperature experiments (MT-PSA) showed thatwhen soil and mine waste were heated to 400500 C,mercury removal was signicant. However, the resultsfrom heating to 320 C or below 300 C, show little ornegligible removal of mercury, mainly, in the sampleswith signicative amounts of cinnabar and Hg-rich pyrite.The As solar desorption tests showed that between 5.5and 77.3% of this metalloid was removed, indicating thefeasibility of As desorption from polluted soil and minewaste.

The thermal desorption technique was successfullyapplied to polluted samples from the Valle del Azogueand Bayarque mines, and was demonstrated to be an alter-native method for decontaminating hazardous waste sites

where mercury is present because of its volatility.

Sample B01T

0

100

200

300

400

500

600

700

800

900

1000

14:51 15:06 15:21 15:36 15:51 16:06

TIME

R a d

i a t i o n

W / m 2 ; T e m p e r a t u r e

C

0

10

20

30

40

50

60

70

80

90

100

P e r c e n

t a g e

T f urn ace Rad iat io n sh ut ter

Fig. 5. Temperatures, global radiations at percentage of shutter opening in B01 sample test in the middle-temperature solar furnace in PSA.

Table 4Results of Hg elimination from the experiments in the middle-temperaturesolar furnace (MT-PSA).

Sample InitialHg(mg/kg)

FinalHg(mg/kg)

%Desorption

Expositiontime (min)

Temperature( C)

A01 530 >500 174 23332A02 1000 >1000 156 57479

A03 210 >200 159 24309A04 540 >500 115 20337Az21 330 290 12.1 101 100315Az22 1 >1 79 93318M02 450 200 55.6 129 20485M03 470 60.9 87.0 315 38482M05 50 9.48 81.0 185 29502M07 23 13.5 41.3 214 55359B02 33 21 36.3 90 25320B01 66 >60 75 70326A05 400 >400 90 70347

Table 5Results of As elimination from the experiments in the middle-temperature

solar furnace (MT-PSA).Sample Initial As (mg/kg) Final As (mg/kg) Desorption (%)

A01 300 >300 A02 620 >600 A03 184 199 A04 680 >700 A05 320 >300 B01 9.6 7 27.0AZ22 12.9 7 45.7B02 20.8 13 37.5AZ21 448 423 5.5M02 296 67 77.3M03 1610 578 64.0M05 129 114 11.6

M07 233 297

1412 A. Navarro et al. / Solar Energy 83 (2009) 14051414


9/10

Acknowledgements

This work was funded by The Spanish Ministry of Sci-ence and Technology (project REN2003-09247-C04-03and ENE2006-13267-C05-01/ALT) in collaboration withthe PSA-CIEMAT (Centro de Investigaciones Energe ticas,

Mediombientales y Tecnologicas), and the 20032004Technical and Scientic Infrastructure Program (FEDERCIEM-E008). The authors wish to thank Dr. Ursula Kelmand Mo nica Uribe for ray X analyses and their interpreta-tion, to Alfonso Vazquez and Bernardo Ferna ndez of theCENIM-CSIC for their participation in the design anddevelopment of the uidized-bed, and nally to the PSAFurnace personnel, especially Jose Galindo, for their tech-nical support in this project.

References

Ballestrn, J., Can adas, I., Rodrguez, J., 2008. Testing a Solar-BlindPyrometer, 14th SolarPACES International Symposium on Concen-trated Solar Power and Chemical Energy Technologies. Las Vegas,USA.

Biester, H., Scholz, C., 1997. Determination of mercury phases incontaminated soils Hg-pyrolysis versus sequential extractions.Environment Science Technology 31, 233239.

Biester, H., Hess, A., Mu ller, G., 1997. Investigations on differentmercury-phases in soils of a Hg-mining area by a temperature-controlled-pyrolysis technique. In: Reuther, R. (Ed.), EnvironmentalScience. Geochemical Approaches for the Environmental Engineeringof Metals. Springer, Heidelberg, pp. 3343.

Biester, H., Gosar, M., Mu ller, G., 1999. Mercury speciation in tailings of the idrija mercury mine. Journal of Geochemical Exploration 65, 195 204.

Can adas, I., Te llez, F., Rodrguez, J., Martnez, D. 2006. SOLARPRO: asurvey of feasible high temperature industrial applications of concen-trated solar energy. In: Proceedings of 13th International Symposiumon Concentrated Solar Power and Chemical Energy Technologies.ISBN: 84-7834-519-1. Seville, Spain.

Chang, T.C., Yen, J.H., 2006. On-site mercury-contaminated soilsremediation by using thermal desorption technology. Journal of Hazardous Materials 128, 208217.

Effelsberg, H., Barbknecht, B., 1991. The use of thermal solar energy totreat waste materials. Part 1. In: Becker, M., Funken, K.H., Schneider,G. (Eds.), . In: Solar Thermal Energy Utilization, vol. 5. SpringerVerlag, Berlin, pp. 413482.

Effelsberg, H., Kirchner, E., Barbknecht, B., 1992. The use of thermalsolar energy to treat waste materials. Part 2. In: Becker, M., Funken,K.H., Schneider, G. (Eds.), . In: In Solar Thermal Energy Utilization,vol. 6. Springer Verlag, Berlin, pp. 239326.

EPA, 2003. Evaluation of Chemically Bonded Phosphate Ceramics forMercury Stabilization of a Mixed Synthetic Waste. EPA/600/R-03/113, p. 70.

Ferna ndez-Martnez, R., Loredo, L., Ordonez, A., Rucandio, M.I.,2006. Physicochemical characterization and mercury speciation of particle-size soil fractions from an abandoned mining area inMieres, Asturias (Spain). Environmental Pollution 142 (2), 217 226.

Fitzgerald, W.F., Lamborg, C.H., 2005. Geochemistry of mercury in theenvironment. In: Lollar, B.S. (Ed.), . In: Environmental Geochemistry,Treatise on Geochemistry, vol. 9. Elsevier-Pergamon, Oxford, pp. 107 148.

Flamant, G., Ferriere, A., Laplaze, D., Monty, C., 1999. Solar processingof materials: opportunities and new frontiers. Solar Energy 66 (2),

117132.

Funken, K.H., Pohlmann, B., Lu pfert, E., Dominik, R., 1999. Applicationof concentrated solar radiation to high temperature detoxication andrecycling processes of hazardous wastes. Solar Energy 65, 2531.

Gaona, X. 2005. El mercurio como contaminante global: Desarrollo demetodolog as para su determinacio n en suelos contaminados yestrategias para la reduccion de su liberacion al medio ambiente.Thesis PhD, Universidad Autonoma de Barcelona, Departamento deQumica, Unidad de Qumica Anal tica, p. 138.

Gray, J.E., 2003. Leaching, transport, and methylation of mercury in andaround abandoned mercury mines in the Humboldt River basin andsurrounding areas, Nevada. US Geological Survey Bulletin 2210-C, 15.

Gustin, M.S., Biester, H., Kim, C.S., 2002. Investigation of the light-enhanced emission of mercury from naturally enriched substrates.Atmospheric Environment 36, 32413254.

Higueras, P., Oyarzun, R., Biester, H., Lillo, J., Lorenzo, S., 2003. A rstinsight into mercury distribution and speciation in soils from theAlmade n mining district, Spain. Journal of Geochemical Exploration80, 95104.

Higueras, P., Oyarzun, R., Lillo, J., Sa nchez-Herna ndez, J.C., Molina,J.A., Esbri, J.M., Lorenzo, S., 2006. The Almade n district (Spain):anatomy of one of the worlds largest Hg-contaminated sites. Scienceof the Total Environment 356, 112124.

ITRC, 1998. Technical guidelines for on-site thermal desorption of solidmedia and low level mixed waste contaminated with mercury and/orhazardous chlorinated organics. Interstate Technology and RegulatoryCooperation Work Group, p. 68.

Kaneko, H., Kodama, T., Gokon, N., Tamaura, Y., Lovegrove, K.,Luzzi, A., 2004. Decomposition of Zn-ferrite for O 2 generation byconcentrated solar radiation. Solar Energy 76, 317322.

Karatza, D., Lancia, A., Musmarra, D., Zucchini, C., 2000. Study of mercury absorption and desorption on sulfur impregnated carbon.Experimental Thermal and Fluid Science 21, 150155.

Kucharski, R., Zielonka, U., Sas-Nowosielska, A., Kuperberg, J.M.,Worsztynowicz, A., Szdzuj, J., 2005. A method of mercury removalfrom topsoil using low-thermal application. Environmental Monitor-ing and Assessment 104, 341351.

Kunkel, A.M., Seibert, J.J., Elliot, L.J., Ricci, K., Lynn, E.K., Pope, G.A.,2006. Remediation of elemental mercury using in situ thermaldesorption (ISTD). Environmental Science & Technology 40, 2384 2389.

Lee, S.H., Park, Y., 2003. Gas-phase mercury removal by carbon-basedsorbents. Fuel Processing Technology 84, 187206.

Lee, S.H., Rhim, Y., Park, Y., 2002. Preparation of novel sorbents for gas-phase mercury removal. Carbon Science 3 (4), 187191.

Li, Y.H., Lee, C.W., Gullet, B.K., 2002. The effect of activated carbonsurface moisture on low temperature mercury adsorption. Carbon 40,6572.

Matsuyama, A., Iwasaki, H., Higaki, K., Yabuta, H., Sano, T., Akagi, H.,1999. Basic study on the remediation technology of mercury com-pound-contaminated soil by low-temperature thermal treatment. In:Ebingahus, R. (Ed.), Mercury Contaminated Sites. Springer-Verlag,Berlin, pp. 421440.

Meij, R., Vredenbregt, L.H.J., te Winkel, H., 2002. The fate and behaviorof mercury in coal-red power plants. Air & Waste ManagementAssociation 52, 912917.

Mendoza, J.L., Navarro, A., Viladevall, M., Dome `nech, L.M., 2005.Caracterizacio n y tratamiento termico de suelos contaminados pormercurio. SIAGA, tomo II, Sevilla, pp. 10771088.

Monterreal, R. 2005. Preliminar Analysis of Irradiance DistributionShutter-100%. PSA-CIEMAT internal document.

Nakamura, T., Senior, C.L., Burns, E.G., Bell, M.D., 2000. Solar-powered soil vapor extraction for removal of dense nonaqueous phaseorganics from soil. Journal of Environmental Science and Health 35,795816.

Navarro, A., Biester, H., Mendoza, J.L., Cardellach, E., 2006.Mercury speciation and mobilization in polluted soils of the Valledel Azogue Hg mine (SE, Spain). Environmental Geology 49,

10891101.

A. Navarro et al./ Solar Energy 83 (2009) 14051414 1413


10/10

solar energy volume 83 issue 8 2009 [doi 10.1016%2fj.solener.2009.03.013] a. navarro; i. cañadas;...

Documents