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Journal of Environmental Management 118 (2013) 205e210

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Journal of Environmental Management

journal homepage: www.elsevier .com/locate/ jenvman

Reuse of solid petroleum waste in the manufacture of porcelainstoneware tile

B.C.A. Pinheiro, J.N.F. Holanda*

Northern Fluminense State University, Laboratory of Advanced Materials, Group of Ceramic Materials, 28013-602 Campos dos Goytacazes, RJ, Brazil

a r t i c l e i n f o

Article history:Received 2 August 2012Received in revised form18 December 2012Accepted 27 December 2012Available online 28 February 2013

Keywords:Solid petroleum wastePorcelain stoneware tileReuseManagement

* Corresponding author. Tel.: þ55 22 2731 6108; faE-mail address: holanda@uenf.br (J.N.F. Holanda).

0301-4797/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.jenvman.2012.12.043

a b s t r a c t

This study investigates the incorporation of solid petroleum waste as raw material into a porcelainstoneware tile body, in replacement to natural kaolin material by up to 5 wt.%. Tile formulations con-taining solid petroleum waste were pressed and fired at 1240 �C by using a fast-firing cycle. The tilepieces were tested to determine their properties (linear shrinkage, water absorption, apparent density,and flexural strength), sintered microstructure, and leaching toxicity. The results therefore indicated thatthe growing addition of solid petroleum waste into tile formulations leads to a decrease of linearshrinkage, apparent density, and flexural strength, and to an increase of water absorption of the pro-duced tile materials. It was also found that the replacement of kaolin with solid petroleum waste, in therange up to 2.5 wt.%, allows the production of porcelain stoneware tile (group BIa, ISO 13006 standard).All concentrations of Ag, As, Ba, Cd, Cr (total), Hg, and Pb of the fired porcelain stoneware tile pieces inthe leachate comply with the current regulatory limits. These results indicate that the solid petroleumwaste could be used for high-quality porcelain stoneware tile production, thus giving rise to a newpossibility for an environmentally friendly management of this abundant waste.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

A large part of Brazilian demand for petroleum is covered by theextraction of crude oil in offshore platforms that producemore than85% of the local oil. Considering that, in 2010, Brazil produced about2million barrels of crude oil daily, the country’s petroleum industrygenerates large amounts of waste in the form of an oily sludge, andthe levels of such a waste are expected to continuously increase.The oily sludge from the petroleum industry is considered a haz-ardous waste material due to the presence of high amount of hy-drocarbons (oil) and traces of heavy elements (Curran, 1992; Saikiaet al., 2002; Sengupta et al., 2002; Elektorowicz and Habibi, 2005).Currently, most of the oily sludge produced in Brazil has beentreated with bentonite clay, resulting in a powdery waste materialreferred hereafter as solid petroleum waste. The disposal of solidpetroleum waste in sanitary landfills has already been tried(Pinheiro, 2009). However, such option presents environmentaland economic disadvantages: 1) the oil content has to be <1%(Andrade et al., 2009); 2) the high cost of petroleumwaste disposalin the landfill sites; 3) the landfills are quickly reaching their fullcapacity; and 4) the landfill sites of urban solid wastes usually

x: þ55 22 2724 1632.

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refuse to accept hazardous industrial wastes. Thus, given the urgentneed to find alternatives to this hazardous petroleum waste dis-posal, its reuse appears as an option that meets current economicaland environmental standards.

Due to the fact that ceramic industry uses huge amounts ofnatural rawmaterials, there is an obvious interest in solid wastes asa source of low-cost raw material. Porcelain stoneware tiles arelow-porosity materials that show a high technical performance. Ineconomical terms, the porcelain stoneware tile is considered thetile material world market leader. The main raw materials used inthe manufacture of porcelain stoneware tiles are kaolin, ball clays,feldspars, and quartz. Porcelain stoneware tile formulations alsocan contain talc, dolomite, calcite, wollastonite, and pigments inminor amounts (Dondi et al., 1999; Barba et al., 2002). Each com-ponent within the body provides different contributions to the finalproperties. Porcelain stoneware tiles are produced via powdertechnology: raw material preparation, dry uniaxial pressing, dry-ing, and single fast-firing cycles (<60 min cold-to-cold) at max-imum temperatures between 1180 and 1250 �C.

A literature review (Meejoda et al., 1993; Saikia et al., 2000; Tahaet al., 2001; Souza and Holanda, 2004; Acchar et al., 2009; Pinheiroand Holanda, 2009; Souza et al., 2011) showed that the reuse ofsolid petroleum waste in the manufacture of porcelain stonewaretiles has not yet been investigated. The aim of this study is toinvestigate the possibility of introducing solid petroleumwaste into

Fig. 1. X-ray diffraction patterns of the tile formulations.

Table 2Chemical compositions (wt.%) of the solid petroleumwaste and porcelain stonewaretile formulations.

Oxides Waste B0W B1W B2W B3W

SiO2 41.73 65.06 64.97 64.88 64.69Al2O3 10.93 22.49 22.21 21.92 21.35

B.C.A. Pinheiro, J.N.F. Holanda / Journal of Environmental Management 118 (2013) 205e210206

a porcelain stoneware tile body as a partial replacement for tradi-tional non-renewable kaolin material.

2. Materials and methods

A typical porcelain stoneware tile formulation and a solid pe-troleum waste in form of granular powder were selected as rawmaterials. The solid petroleum waste sample was collected in theBrazilian oil company located in south-eastern Brazil (Macaé-RJ).The mineralogical composition of said solid petroleum waste hasbeen published elsewhere (Souza et al., 2011). Selected mixturescontaining 0, 1.25, 2.5, and 5 wt.% waste were prepared (Table 1).The standard batch of porcelain stoneware tile used as a referenceconsisted of 40.0 wt.% kaolin, 47.5 wt.% Na-feldspar, and 12.5 wt.%quartz (Pinheiro et al., 2010). In this study, kaolin was partiallyreplaced with increasing amounts of solid petroleum waste.

The raw materials were dried at 110 �C and dry-ground andmixed using a laboratory mill, and then passed through a 325 mesh(45 mm ASTM) sieve. The tile formulations (Table 1) were mixed,homogenized, and granulated via dry process. The moisture con-tent (moisture mass/dry mass) was adjusted to 7%.

The chemical compositions of the solid petroleum waste andporcelain stoneware tile formulations were determined by X-rayfluorescence. X-ray diffraction analysis was performed using Co-Karadiation and 1.5� (2q) min�1 scanning speed in a conventionaldifffractometer (URD 65; Seifert). Crystalline phases were identifiedby comparing the intensities and positions of the Bragg peaks tothose listed in the JCPDS data files. The grain-size distribution of thetile powder was determined by sieving according to the NBR 7181standard (ABNT, 1984). Differential thermal analysis (DTA) of thetile sample was performed within the 25e1200 �C temperaturerange, by using a heating rate of 10 �C/min under air atmosphere.

The powders were pressed into test bars measuring(11.50� 2.54 cm2) under a load of 50 MPa, and then dried at 110 �C.The porcelain stoneware tile pieces were fast-fired at 1240 �C ina laboratory fast-firing kiln (FSQC e 1300/3; Maitec) for a total of60 min including cooling. The temperature and fast-firing cycleused in this study were chosen to simulate an actual firing processused in the ceramic tile industry.

Linear shrinkage values upon drying and firing were evaluatedfrom the length variation of the rectangular specimens (ASTM,1997). Water absorption values were determined from weight dif-ferences between the as-fired and water saturated samples(immersed in boiling water for 2 h) (ASTM, 1994a). The apparentdensity was determined by the Archimedes method (ASTM,1994a).The flexural strength of fired tile pieces was determined with thethree-point bending test (model 1125, Instron) at a loading rate of0.5 mm/min (ASTM, 1994b).

Microstructure characterization of fractured surfaces was car-ried out by scanning electron microscopy (DSM 962; Zeiss) viasecondary electron images (SEI), at 15 kV, after gold-coated. Thecrystalline phases after firing were identified via X-ray diffractionanalysis.

The pollution potential of porcelain stoneware tile pieces fired at1240 �C was determined by leaching (acetic acid buffer solution(0.5 M) at pH 5.0 for 18 h) according to NBR 10005 Brazilian

Table 1The proportions of the blends for the formulations (wt.%).

Formulation Kaolin Petroleum waste Na-feldspar Quartz

B0W 40.00 0.00 47.50 12.50B1W 38.75 1.25 47.50 12.50B2W 37.50 2.50 47.50 12.50B3W 35.00 5.00 47.50 12.50

standard (ABNT, 2004a). The concentrations of potentially toxicmetals present in the leaching extract were determined. Then, saidconcentrations obtained were compared to the maximum con-centrations of elements predicted by NBR 10004 Brazilian standard(ABNT, 2004b).

3. Results and discussion

The XRD patterns of the tile formulations are shown in Fig. 1.The following crystalline phases were identified: kaolinite(Al2O3$2SiO2$2H2O), quartz (SiO2), albite (NaAlSi3O8), barite(BaSO4), calcite (CaCO3), calcium sulfate (CaSO4$2H2O), montmor-illonite [(Al1.67Na0.33Mg0.33)(Si2O5)2(OH)2], and hematite (Fe2O3). Inaddition, only small differences in the intensity of diffraction peakscan be observed with the incorporation of solid petroleum wasteinto tile formulations.

The chemical compositions and loss on ignition of the wastesample and tile formulations are presented in Table 2. The solid pe-troleumwaste is constitutedmainlyof SiO2, followedbyAl2O3, Fe2O3,CaO,MgO, and BaO (minor amounts of Ti, Na, K, P, and Sr oxides). Theloss on ignition of waste sample is high, around 18.74 wt.%. SiO2,Al2O3, and Na2O are the major components in the tile formulations,which correspond to about 90.83e92.35%. It may be noted that thefluxing agent amount (Na2Oþ K2Oþ CaOþMgOþ Fe2O3) increaseswith the solid petroleumwaste addition. These results are consistentwith the XRD patterns shown in Fig. 1. The loss on ignition alsoincreased (5.79e6.03%) with the solid petroleum waste addition.This behavior can be mainly attributed to the presence of oil (hy-drocarbons), montmorillonite, calcite, and calcium sulfate in thesolid petroleumwaste (Souza et al., 2011). Thus, the replacement of

Fe2O3 7.63 0.16 0.25 0.34 0.53TiO2 0.52 0.01 0.02 0.03 0.04Na2O 0.44 4.80 4.80 4.80 4.79K2O 0.95 1.50 1.49 1.48 1.45CaO 7.76 0.20 0.30 0.39 0.58MgO 5.87 0.07 0.14 0.21 0.36BaO 5.03 e 0.06 0.13 0.25SrO 0.29 e e 0.01 0.01LoIþ at 1000 �C 18.74 5.79 5.85 5.91 6.03

LoIþ e loss on ignition.

Table 3Grain-size distribution of granulated powder (B2Wformulation).

Grain size, mm % in mass

<45 20.5045 64.4075 1.84104 2.92150 4.57250 5.70420 0.07>420 0.00

Table 4Results of the leaching tests of the tile pieces fired at 1240 �C (mg/l).

Element B0W B2W Regulatory limits

Ag 0.01 <0.01 5.0As <0.01 <0.01 1.0Ba 0.25 4.89 70.0Cd <0.01 <0.01 0.5Cr (total) 0.015 0.012 5.0Hg <0.001 <0.001 0.1Pb 0.069 0.081 1.0

B.C.A. Pinheiro, J.N.F. Holanda / Journal of Environmental Management 118 (2013) 205e210 207

kaolinwith solid petroleumwaste into porcelain stoneware tile bodymodifies its chemical andmineralogical compositions. Such a changemay influence the sintering behavior of the porcelain stoneware tilebody under examination.

The grain-size distribution of the granulated powder (for-mulation B2W) produced by the dry process is shown in Table 3. Asmay be observed, the granulated powder presented largest fractionin the grain-size range of 45 mm. This behavior was observed for alltile formulations containing solid petroleum waste. Thus, all stud-ied formulations are within the grain range that is appropriate toobtain a good reactivity during firing of the powders produced withthe dry process.

The DTA curve of B2W formulation is shown in Fig. 2. Twoendothermic events are seen in the DTA curve within the 43.2 �Cand 532.9 �C temperature ranges, respectively. The first endother-mic event at 43.2 �C is associated to the removal of physicallyadsorbed water on the ceramic body particles. The second is veri-fied around 532.9 �C, and occurs due to the dehydroxylation ofkaolinite, subsequently converted into metakaolinite. The endo-thermic events related to polymorphic transformation of aeb quartz and volatization of oil (hydrocarbons) should have beenprobably overlapped. The exothermic peak around 1001 �C herebydisclosed is mainly attributed to the disruption of the silicate latticeto form new crystalline phases from metakaolinite (Brindley andNakahira, 1959; Chen et al., 2000).

The technological properties of the porcelain stoneware tilepieces in the dried state at 110 �C have been determined. The resultsdisclosed no significant differences in the drying shrinkage (0.03e0.07%) of the green pieces, regardless of the added solid petroleumwaste amount. In the dried state, it is suggested to obtain a value oflinear shrinkage between 0 and 0.3%, in order to avoid cracks, fis-sures, and warpage (Dondi, 2003). Thus, the linear shrinkage valuesfor all porcelain stoneware tile pieces satisfy the recommendedlimits. The results demonstrate that no significant differences(1.89e1.91 g/cm3) in the drying density of the tile pieces were

Fig. 2. DTA curve for the formulation B2W.

observed. The flexural strength of the dried pieces lies between3.25 and 3.86 MPa, which is within the limits for industrial pro-duction of porcelain stoneware tiles, which requires values above2.5 MPa.

The results of the leaching tests with porcelain stoneware tilepieces fired at 1240 �C are shown in Table 4. The maximum con-centration values accepted by the Brazilian standard for leachingextract are also presented. It was found that the fired tile piecesleached concentrations of silver (Ag), arsenic (As), barium (Ba),cadmium (Cd), total chromium (Cr), mercury (Hg), and lead (Pb)below the current Brazilian regulatory limits. The low leachingcharacteristics of porcelain stoneware tiles can be attributed to theeffective stabilization of these heavy metals on the sintered glassymatrix. These results indicate that the produced porcelain stone-ware tile pieces could be considered as non-hazardous materials.Thus, the new porcelain stoneware tiles produced with solid pe-troleum waste can be reputed as an environmentally friendly tilematerial, being likely to be used at civil construction.

XRD patterns of the fired pieces for the B0W and B3W formu-lations are presented in Fig. 3. The crystalline phases found in B0Wformulation (Fig. 3a) were mullite and quartz. These phases are inaccordance with the SiO2eAl2O3eNa2O phase diagram (Osburn,1960). More specifically, they comply with the silica albite mullitetriangle of compatibility and the primary phase field of mullite. Thephase transformations involved in the porcelain stoneware tilebody (formulation B0W) during the firing process can be describedas follows (Brindley and Nakahira, 1959; Chen et al., 2000; Barbaet al., 2002). At w450 to 600 �C, kaolinite is transformed intoamorphous metakaolinite. At 573 �C, aeb quartz inversion of freesilica occurs. At w950 �C, the silicate lattice totally collapses, fol-lowed by a reorganization of the metakaolinite structure and for-mation of amorphous silica. In addition, a spinel structure isformed, and then quickly transformed intomullite. The onset of thesintering (initial melting) is expected to occur in the ternaryeutectic, around 1068 �C. At about 1200 �C, some content of quartzis transformed into cristobalite. Finally, the viscous liquid phaseformed is cooled to glass. Tile pieces containing solid petroleumwaste (formulation B3W) showed a quite different phase evolution

Fig. 3. XRD patterns of the tile pieces fired at 1240 �C: a) B0W; and b) B3W. Q e quartz,M e mullite, B e barite, H e hematite, and S e anhydrite calcium sulfate.

B.C.A. Pinheiro, J.N.F. Holanda / Journal of Environmental Management 118 (2013) 205e210208

(Fig. 3b). The following crystalline phases were found: mullite,quartz, barite, hematite, and anhydrite calcium sulfate. Thus, thereplacement of kaolin with solid petroleum waste changes thecomposition of the crystalline phases contained in the porcelainstoneware tile pieces.

SEM micrographs of fracture surfaces of B0W, B2W, and B3Wformulations fired at 1240 �C were compared to each other inFig. 4aec. They show the typical sequence of densification behavior

Fig. 4. SEM micrographs of the fracture surfaces of the tile pieces: a) B0W; b) B2W;and c) B3W.

of porcelain stoneware tiles, with an increased solid petroleumwaste amount. The microstructure of B0W formulation (Fig. 4a) isfound to be very homogeneous, with a smooth fracture surface. Thetile pieces presented an advanced sintering stage, in which theappearance of a structure with few open pores and signs of highvitrification can be observed. As indicated by the XRD analysis(Fig. 3), it encompasses the mullite, quartz, and glassy phases. B2Wformulation (Fig. 4b) had a sintered microstructure very similar tothat of waste-free tile pieces. However, the microstructure of theB3W formulation (Fig. 4c) differs from that of the reference sample.A more porous fractured surface can be observed. This effect sug-gests an evolution of gas in the structure of the sintered tile pieces.In fact, the combustion of the organic fraction of solid petroleumwaste contributes to generate pores in the fired tile structure. Itimplies, therefore, that additions of high petroleumwaste amountsinto porcelain stoneware tile body cause changes in the texture andporosity of the fired pieces.

The linear shrinkage of the tile pieces fired at 1240 �C is shownin Fig. 5. The pieces exhibited linear shrinkage values within the3.75e8.17% range, which is in accordance with the safe limits forindustrial production of porcelain stoneware tiles (Dondi, 2003).The linear shrinkage of tile pieces containing solid petroleumwastewas lower than that of the waste-free tile pieces (B0W for-mulation). This finding is substantiated by the incorporation ofquartz particles of solid petroleum waste into tile formulations. Inaddition, the volatization of hydrocarbons from such waste gener-ates pores in the fired structure.

The apparent density of the fired tiles pieces is shown in Fig. 6,which evidences that the apparent density presented differentbehaviors with solid petroleumwaste addition. For additions up to2.5 wt.%, the apparent density presented only a slight variationwithin the dispersion limits. Above 2.5 wt.%, however, the apparentdensity decreases sharply. This means that the replacement ofkaolin with solid petroleum waste is limited. The incorporation ofhigher amounts of solid petroleum waste can result in lower den-sification rate, formation of closed porosity, and structure expan-sion. This behavior is consistent with the observation of thestructures (Fig. 4) and linear shrinkage (Fig. 5).

Fig. 7 shows the results of water absorption of tile pieces.Measurements of water absorption, which is related to the level ofopen porosity, confirm that the formulations containing solid pe-troleum waste densify more slowly than those with no added

0 1 2 3 4 5 6

3

4

5

6

7

8

9

Lin

ea

r s

hrin

ka

ge

(%

)

Petroleum waste (%)

Fig. 5. Linear shrinkage of the tile pieces versus waste content.

0 1 2 3 4 5 6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

Ap

pa

re

nt d

en

sity

(g

/c

m3

)

Petroleum waste (%)

Fig. 6. Apparent density of the tile pieces versus waste content.

0 1 2 3 4 5 6

20

25

30

35

40

45

50

55

Fle

xu

ra

l s

tre

ng

th

(M

Pa

)

Petroleum waste (%)

porcelain stoneware tile - FS > 35 MPa

Fig. 8. Flexural strength of the tile pieces versus waste content.

B.C.A. Pinheiro, J.N.F. Holanda / Journal of Environmental Management 118 (2013) 205e210 209

waste. This can be explained by the combined inverse effects ofweight loss and sintering.

The flexural strength of fired tile pieces is shown in Fig. 8. Themechanical behavior is quite correlated with all the other studiedproperties. Such data indicate a tendency toward lower mechanicalstrength with a higher solid petroleum waste amount. This findingwas expected, given that solid petroleum waste addition leads toa decrease of the densification level. Furthermore, for additionsabove 2.5 wt.%, the deleterious effect on the flexural strength ismore pronounced. This behavior may be related to an induction offlaws in the sintered tile matrix, due to the volatization of oil andthe presence of high concentration of quartz particles in the solidpetroleum waste.

Water absorption and flexural strength are properties which,according to ISO standard 13006 (ISO, 1998), define ceramic tileproduct class. The specified values of water absorption (WA) andflexural strength (FS) for porcelain stoneware tile (group BIa) arethe following: WA � 0.5% and FS � 35 MPa. In this study, porcelainstoneware tile was obtained for the following formulations: B0W,B1W, and B2W. Thus, the addition of a suitable amount of solidpetroleum wastes could result in porcelain stoneware tile (ISOstandard 13006 e group BIa) with excellent technical properties. Inaddition to the industrial utility of the solid petroleumwaste, there

0 1 2 3 4 5 6

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Wa

te

r a

bs

orp

tio

n (%

)

Petroleum waste (%)

porcelain stoneware tile - wa < 0.5 %

Fig. 7. Water absorption of the tile pieces versus waste content.

aremany environmental and economical benefits to be gained fromits management.

4. Conclusions

The following conclusions may be drawn from the experimentalresults and their discussion.

� The solid petroleum waste used in this study is a low-costmaterial, which can replace natural kaolin in porcelain stone-ware tile formulations.

� The replacement of natural kaolin with solid petroleum waste,in the range up to 2.5 wt.%, allows the production of porcelainstoneware tile (ISO standard 13006 e Group BIa) with goodtechnical properties.

� Leaching tests of porcelain stoneware tile pieces incorporatedwith solid petroleum waste showed that they do not causeserious environmental impacts.

� The management of solid petroleumwaste in the manufactureof porcelain stoneware tiles is an excellent way to reuse ofa solid waste material, whose production increases every year.

Acknowledgements

The authors acknowledge the CNPq and FAPERJ for the financialsupport, and the PETROBRAS by the supply of solid petroleumwaste.

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