Leachability of Lead by Incorporation of Treated and

REV.CHIM.(Bucharest)♦ 67♦ No. 4 ♦ 2016 http://www.revistadechimie.ro 673

Leachability of Lead by Incorporation of Treated and UntreatedSugarcane Bagasse in Solidification/stabilization Method

A comparative study

AESLINA ABDUL KADIR1,2*, ALI BENLAMOUDI1, IOAN GABRIEL SANDU2,3, MOHD MUSTAFA AL BAKRI ABDULLAH2,4,ANDREI VICTOR SANDU2,3*1 Department of Water and Environmental Engineering, Faculty of Civil and Environmental Engineering, University Tun HusseinOnn Malaysia, 86400 Parit Raja, Batu Pahat Johor, Malaysia2 Center of Excellence Geopolymer & Green Technology (CeGeoGTech), School of Material Engineering, Universiti MalaysiaPerlis (UniMAP), P. O. Box 77, d/a Pejabat Pos Besar, 01000 Kangar, Perlis Malaysia.3 Gheorghe Asachi Technical University of lasi, Faculty of Materials Science and Engineering, 71 D. Mangeron Blvd., 700050, lasi,Romania4 Faculty of Engineering Technology, Universiti Malaysia Perlis (UniMAP), P.O. Box 77, D/A PejabatPosBesar, Kangar, Perlis 01000,Malaysia

This paper presents the results of the treatment of lead contaminated soil by using the solidification/stabilization (S/S) method incorporated with sugarcane bagasse (SCB). A comparative study between theuse of SCB before and after hydrochloric acid treatment is studied. Moreover, testing tests like density, waterabsorption, compressive strength and TCLP are also conducted. The results have indicated that the treatmentof SCB is needed since it increases the UCS of the matrices, decreases the WA and decreases also thedensity of these matrices. In addition, this study improves the S/S method, by providing an alternative lowcost material and at the same time by offering a new friendly proposal method for sugarcane bagasseelimination.

Keywords: solidification/stabilization, lead, water absorption, leachability, sugarcane bagasse, compressivestrength, heavy metal, agricultural wastes

Industrial production leaves enormous quantities ofmineral wastes accompanied with toxic heavy metals likecadmium (Cd), copper (Cu), chromium (Cr), arsenic (As)and lead (Pb). These industries may include theelectroplating, power generation, ceramics industries,sewage water and mining activities. Pb generated fromsuch industries is considered very toxic, which may causeacute diseases such as restlessness, anaemia,neurological effects, nausea and adverse effects on bothmale and female reproductive functions as mentioned bythe Health Protection Agency [1].

To address these effects, many treatment methods havebeen implemented, among which the solidification/stabilization (S/S) has been proved as an effective methodwhen the lead impacts towards the environment could bereduced or even eliminated. The S/S method is basedmainly on cement and water to form matrices andencapsulate the lead inside them. These matrices shouldbe sufficiently stable to prevent the leachability of lead inface of the different meteorological factors. Nevertheless,one of the disadvantages of the S/S method is that thetoxicity is still inside the matrices, not destroyed norabsorbed. Other researchers have studied the leadelimination from the environment and proved that it couldbe absorbed by different agricultural wastes such assugarcane bagasse [2-5], rice husk [6], oil palm shell [7]and others. Around 140 billion metric tons of theseagricultural wastes are generated each year. This hugeamount, rather than being disposed to the landfill, it maybe reduced by its incorporation into heavy metals treatmentmethods so as to provide a sustainable solution for theenvironment.

* email: [email protected]; [email protected]

This paper studies the incorporation of one of theseagricultural wastes, which is the sugarcane bagasse (SCB)within solidified matrices as a sustainable solution toeliminate the heavy metals from the environment in oneside and minimize the huge quantity of SCB form theenvironment. Nevertheless, the main focus of this researchis the comparison between incorporation of treated anduntreated sugarcane bagasse where the variation of thedifferent characteristics have been studied. Therefore, theoutcome could determine the feasibility and theeffectiveness of the sugarcane bagasse treatment on itsincorporation into the solidification/stabilization matrices.

Experimental partMaterials and methodSynthetic soil preparation

The clay soil was collected from Research Center ofSoft Soil (RECESS) in UTHM campus, then, it was dried andgrinded to pass through the sieve of 300 µm. After that, itwas mixed with a precise quantity of Pb in order to imitatethe real contaminated soil. The Pb was generated fromthe lead nitrates (Pb(NO3)2), by dissolving an amount ofPb(NO3)2 calculated by the equation 1 in a volume of water,then, the solution was mixed to the clay. The targetconcentration of Pb was 1000 ppm. This percentage waschosen in order to test the worst case scenario of thecontaminated soil. The soil samples were put in closedcontainer to avoid any toxicity that might be caused by thePb.

(1)

whereas:m = weight of the solution required (g)

http://www.revistadechimie.ro REV.CHIM.(Bucharest)♦ 67♦ No. 4 ♦ 2016674

C = target concentration of Pb (ppm)ms = specimen final weight (g)n = molecular numberMs = solution molecular weight (g/mol)η = percentage purity chemical (%)Mm = metal atomic weight (g/mol)

Cement and WaterOrdinary Portland cement type II (CEM II) was mixed

with distilled water.

Sugarcane bagasse waste (SCB) SCB was collected as a waste from beside a small

shop of sugarcane juice in Parit Raja, Johor after the juicewas extracted. After that, the SCB was divided into twoparts A and B. Part A was used as it is. Part B was treated inan acidic solution in order to eliminate the maximum ofthe cellulose fibers and to liberate the lignin. This treatmentwas conducted because the presence of the solublesugars, even at low concentration (0.03-0.15 wt.%) incement may retard the setting time and the strength of thethis cement [5].

Firstly, 0.1M of HCl was prepared from the 37% HClavailable in the environmental laboratory in FKAAS, UTHMby using the equation 2. Then, this 0.1M of HCl was boiledwith the part B of SCB for 45 min on a hot-plate. Thisprocedure was repeated 3 to 4 times until the filtrate wasvirtually colorless. Both of part A and the residual productof part B was dried in the oven under a temperature of105°C for around 24 h in order to eliminate the moisturecontent, then, they were grinded separately to pass overthe sieve of 300µm (to eliminate the maximum fiber fromSCB) and kept separately in closed container. The choiceof this size is eliminate the maximum fiber from the SCB.

(2)

Where:V = volume required from the main HCl solution (L)n = molarity needed (mol)µ= percentage in mass of the main acid concentration

(%)d = density of the main solution (g/L)M = molar mass (g/mol)

Material characterization by X-ray fluorescence (XRF)In this study, the XRF was conducted on the cement,

the SCB (treated and untreated), and the contaminatedsoil. The results of the XRF test are The results of the XRFtest are in need as the preliminary assessment and werediscussed further in the results.

Pellet preparationFirstly, the pelettes were prepared in the ratio of sample

to wax powder equal 7:3. The role of the wax powder is tocohere the samples particles.

Each sample was well mixed with the wax powder,inserted into the base die and die barrel and compressedby using a plastic rod. Then, it was put into the compressiontool and turned clockwise until tight. After that, the gearwas swung until the pressure gauge reached about 15,then; it was left for 1 minute before removing the die basefrom the die barrel. Then, a black die cup was put underthe barrel, the die base was put into the compressionmachine and the plunger was turned until the pellet fell.After that, the pallet was removed from the black steelcup and was subjected to the XRF analysis.

XRF AnalysisThe XRF spectrometer is an x-ray instrument that works

on wavelength-dispersive spectroscopic principles. In thisstudy, the samples were subjected to the XRF analysis byS4 Pioneer, Bruker AXS machine on the SPECTRA Plusanalysis program, which generates the calculations of netintensities for the sample with the determination of thepeak positions automatically.

Samples preparationThe matrices were being formulated as follows: 2.5%

and 5% of SCB for 90% of soil samples; 7.5 and 3.75% ofSCB for 85% of soil samples and 10 and 15% of SCB for20% of soil samples. Table 1 shows the quantitativecomponents of the different samples. The amount of soilwere calculated in parallel with the other components.The weight of each sample was 130 g to avoid any wasteof the materials, and the quantity of each component wascalculated through its percentage in each sampleaccording to the table 1.

Samples confinementIn this project the water cement ratio (W/C) was ranged

between 0.35 and 0.5, depended on the added quantity ofSCB. After the amounts preparation of different componentsof the specimens have been done, they were blended withina mixer for a couple of minutes, then, solidified one by onein a cylindrical mold, with the dimensions of 38mm indiameter and 76mm in height (38mm x 76mm). Theconfinement was in 3 layers within the mold, and eachlayer was scratched to ensure that it was adhered with thesuccessive one. The solidified samples were extractedfrom the mold and wrapped with a cellophane cover, then,they were left cured for 7 days, 14 days and 28 days beforethey were passed into the physical and the mechanicaltests. The curing was under a room temperature within acontainer that contains water to regulate the moisturewithin it. The samples were labeled SxCySCBz, where xand y were the percentages of cement and SCB,respectively.

Table 1THE QUANTITATIVE

COMPONENTS OF THEDIFFERENT SAMPLES


Mechanical and physical testsThe mechanical and physical tests may give a partial

decision about the efficiency of the S/S method.

Unconfined compressive strength (UCS)This test was conducted in this study in order to evaluate

the strength of the mixture of the SCB with the cement athigher stress, as well as to imitate the disposalstandardization of the solidified samples.

The test has been carried out by using the GeocompLoadTrac II system. The specimens were extruded fromthe molds, leveled, measured for length and diameter,weighed and placed in the loading device so that it iscentered on the bottom platen. Then, they were subjectedto uniaxial compression test (UCT). The load was applied,until the sample’s failure [8]. Then, the UCS values wereobserved on the screen attached to the loading device,knowing that the results were being based on automaticcalculation of several parameters such as strain, averagecross-sectional area and deformation time.

Duplicate samples were tested for each condition andthe average results were reported and analyzed.

Water adsorption test (WA)The water adsorption test was conducted according to

ASTM [9]. The procedure involved the drying of thespecimen in the oven under a temperature of 105°C forcertain time until its weight were constant, this weightwas recorded. Then, the specimen was immersed indistilled water until saturation and weighted again afterexcess water on their surfaces was wiped off using a drycloth. The water absorption percentage was estimated asthe percentage of the ratio between the difference of thedry and wet specimen and the dry specimen (eq. 3).

(3)

Where:W = water adsorption percentage,Sw = weight of the wet sample,Sd = weight of the dry sample.

Density testFor this test, the densities values were calculated by

dividing the masse over the volume of the cylindrical

samples since all the parameters (Diameter, Length andweight) were determined. The densities values wereexpressed in (g/cm3).

Leaching testToxicity Characteristic Leaching Procedure (TCLP)

In order to simulate the mobility of the compounds inthe landfill areas, this test was conducted by crushing 100gof the solidified/stabilized sample to pass a 9 mm sieve.The samples were extracted according to USEPA Method1311, and the extractions were carried out with 20:1 liquidto solid ratio in an acetate solution at pH 2.88 ± 0.05, in 2Lbottles and to be rotary agitated at 30 rpm for 18 h usingthe rotary system [12]. After the sample was extracted inthe acetic fluid, the solid and liquid phases were separatedby filtration through 0.45 mm pore size membrane filters.The pH was measured and the extract was digested(acidified to 2%HNO3) prior to analysis for metals usingthe atomic absorption spectroscopy (AAS). Then, the Pbquantity in the solutions obtained was compared with theregulatory limit by the USEPA, which is 5 ppm. The resultof this test together with the previous result of the UCS testshould give the final decision about the efficiency of themethod.

.Results and discussionsSugarcane Bagasse (SCB)

Table 2 and table 3 show percentages of the differentcomponents of untreated and treated sugarcane bagasserespectively. Silicate (SiO2) and potassium oxide (K2O) arepresented on major quantities for the untreated SCB whichare 1.57 and 1.52%, while iron oxide (Fe2O3), silicate,aluminum oxide (Al2O3) and chlorine (Cl) on the other handare presented in major quantities for treated SCB, whichare 3.16, 1.15 and 3.23% respectively. The lowconcentration of these elements may indicate that SCBcontains very low pozzolanic characteristics. Due to thismatter, SCB could not be a replacement for the cement.Then again , the increase of Cl in the second table is simplydue to HCl treatment of SCB whilst the increase of SiO2,Fe2O3 and Al2O3 may refer to the increase of the pozzolaniccharacteristics of SCB after treatment, even thecorrespondent percentages are quite low comparing tothe cement components.

.

Table 2PERCENTAGES OF THE DIFFERENT

COMPONENTSOF UNTREATED SUGARCANE BAGASSE


DensityFigure 1 shows density values of the incorporation of

treated and untreated SCB within the matrices. It ispresented that the densities values of incorporation ofuntreated SCB are lower than those for the incorporated oftreated SCB. This difference, which is increased with theincrease of the SCB percentages in the matrices is due tothe decrease in volume of SCB after treatment with HCl,because the treatment has the role to eliminate themaximum of cellulosic fibers as mentioned by Janusa [5].And as known that the density is the ratio between themass and the volume, so, the more volume, the less densityand vice versa.

Water absorption (WA)Figure 2 shows the change of water absorption in

function of SCB added. The results demonstrated that theWA increases with the increase of SCB percentages. Inaddition, it is presented that the highest WA value is 54.4%for 7.5% of untreated SCB and 38.9% for 10% of treatedSCB. These high amounts of WA may also due to the abilityof SCB as fibrous agricultural waste to absorb water, maylead to the destruction of the matrices if the cement is notas sufficient to maintain the matrices in their solidifiedforms.

Table 3PERCENTAGES OF THE DIFFERENT

COMPONENTS OF TREATED SUGARCANE BAGASSE

Moreover, in almost all the samples, it is observed thatthe matrices that contain treated SCB absorb less watercompared to those contain untreated SCB. This result isinterpreted with the role of SCB treatment in the eliminationof nature fiber as mentioned by Alamri and Low [11], whoargued that the nature fiber may absorb more water, thus,the treatment of SCB may decrease the quantity of waterabsorption. The result obtained is also supported by Kimand Seo [12] who mentioned that the amount of waterabsorption is due to the hydrophilic nature of cellulose fibers,these cellulose fibers have a central hollow region whichallows much more water to be absorbed via the capillaryeffect. In addition to that, the WA may have a role in thesolidification of the matrices and the increase of strength,this relationship was also described in the compressivestrength part.

Unified Compressive Strength (UCS) Figure 3, figure 4 and figure 5 show the results of the

UCS test for incorporation of untreated and treated SCB for7, 14 and 28 days, respectively.

It is observed that the UCS values decrease clearly in allthe samples with the increase of untreated SCBpercentages, even at low percentage. In this case, themaximum UCS obtained was 1648 kPa and 1833 kPa for

Fig. 2. Water absorption for samples after 28curing days

Fig. 1. Density of samples incorporatedwith SCB after 28 Curing days


Fig. 3. UCS after 7 curing days

treated and untreated SCB respectively for 15% cementwith 5% SCB. The reduction in the results is due to the lowpozzolanic characteristics of SCB as shown in its propertiespreviously.

The results show also that the UCS values for theincorporation of untreated SCB do not fit to the landfilldisposal limit (340 kPa) for almost all the samples, only forits 5% combination with 15% of cement where the UCSwas 380 kPa, 528 kPa and 1648 kPa for 7, 14 and 28 days,respectively.

Nevertheless, for treated SCB, its incorporation showsmuch greater values of UCS compared to thoseincorporated with untreated SCB, and comply with thelandfill disposal limit for all the samples. In this case, thelowest strength obtained was 345 kPa on blending 10% ofSCB with 10% of cement for only 7 curing days. This resultis refer to the change in properties of SCB after treatmentand the increase of the pozzolanic characteristics asdescribed in the XRF results. Thus, the treatment of SCB isneeded before blending the samples in order to achievethe strength requirement for disposing the solid waste inthe landfill.

Leaching testToxicity characteristic Leaching Procedure (TCLP)

Table 4 shows the TCLP results of the incorporation ofuntreated SCB. It was observed that the Pb was detectedat very low concentration for almost all the samples whichwere below 5 ppm, except for the sample of 5% SCB with5% cement, where the concentration exceeded thethreshold and was detected at 6.95 ppm.

By referring to UCS results, it was observed that the fourthand the sixth samples that correspond to the highest UCSvalues, which were 963 kPa and 1648 kPa, respectivelyshowed minimal leaching of Pb which were 0.40 and 0.15ppm, respectively. Otherwise, the lowest UCS value whichwas 296 kPa for the first sample showed the highestleaching of Pb. Moreover, the same table (table 4) showsthat the more quantity of cement in samples correspondsto the less leached Pb, and vice versa. All these results areexplained by the role of cement and strength of samples inmaintaining the Pb and prevent it to leach out the matrices[13-17].

Table 5 shows the leachability of Pb after incorporationof treated SCB. The results were very near in values tothose correspond to the incorporation of untreated SCB.




Table 4TCLP RESULTS OF THE INCORPORATION OF

UNTREATED SCB

Therefore, the results are subjected to the sameexplanation.

The result obtained for both table 4 and table 5 areexplained by the formation of Pb(OH)2, which is insoluble,thus, the Pb was captured within the matrices, and wasprevented to be leached out. Equation 4 explains thechemical reaction within the matrices, which may beensured by XRD analysis in future works:

Pb(NO3)2 +CaO+3H2O = Pb(OH)2+2HNO3+Ca(OH)2 (4)

ConclusionsThe results showed that the incorporation of SCB without

treatment into the solidification matrix decreases itsstrength, so that it cannot fit to the landfill disposal limit. Inthis case, the SCB should be very minimal in order tomaintain the UCS of the matrices. In fact, the treatment ofSCB increases the UCS of the matrices, decreases the WAand decreases also the density of these matrices, and thisis due to the increase in pozzolanic characteristics of SCBafter treatment. Due to this matter, the treatment of theagricultural waste is needed in order to improve themechanical and the physical properties for the matricesand increase the efficiency of the S/S method. This researchimproves also that the simple treatment of SCB with thehydrochloride acid is an easy and effective method thatcan improve the properties of this agricultural waste forthe usage in solid waste treatment.

Overall, this study improves the S/S method by providingan alternative low cost material and at the same time byoffering a new friendly proposal method for sugarcanebagasse elimination.

Acknowledgments: The authors want to thank the University of TunHussein Onn Malaysia (UTHM) laboratories for the facilities to achievethis work.

Table 5TCLP RESULTS OF THE

INCORPORATION OF TREATED SCB

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Manuscript received: 26.11.2015

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Leachability of Lead by Incorporation of Treated and