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Elsevier Editorial System(tm) for Bioresource TechnologyManuscript Draft
Manuscript Number:
Title: Influence of Pyrolysis Temperature on Cadmium and Zinc Sorption Capacity of Sugarcane Straw-Derived Biochar
Article Type: Original research paper
Keywords: Heavy metals; Biomass; Tropical soils; Adsorption
Corresponding Author: Dr. Leonidas Carrijo Azevedo Melo,
Corresponding Author's Institution: Universidade Federal de Viosa
First Author: Leonidas Carrijo Azevedo Melo
Order of Authors: Leonidas Carrijo Azevedo Melo; Aline R Coscione; Cleide A Abreu; Aline P Puga;Otvio A Camargo
Abstract: The effect of pyrolysis temperature (400, 500, 600 and 700 oC) on the characteristics andmetal sorption capacity of sugarcane straw derived-biochar (BC) was investigated. By increasing thepyrolysis temperature there was a reduction in the O/C and H/C molar ratios. Sorption capacity ofbiochar pyrolyzed at 700 C was nearly four-times greater than that produced at 400 C. In the Entisolmixture there was an increase up to seven-fold in the sorption of both Cd and Zn, while in the Oxisolmixture there was a maximum 20% increase in sorption, compared to the control. For remediationpurposes of Cd and Zn contaminated substrates the use of higher pyrolysis temperature biochars arerecommended due to their higher metal sorption capacity.
S gg t d R i L M
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Suggested Reviewers: Lena Ma
All authors are in agreement with the submission of the manuscript. Also, themanuscript is original work and has not been submitted earlier to BITE or to any other
journal. In this work it is described a detailed characterization and the utilization, asmetal sorbent, of biochar produced from sugar cane residues. It was found that byincreasing the pyrolytic temperature the sorption of zinc and cadmium was enhancedgreatly both in aqueous solution and in soils. The sugarcane industry produces a hugeamount of biomass that can be used to generate electricity as well as biochar. Therefore,such results may help to encourage the use of this type of biomass for a different use,i.e. as metal sorbent with potential to reclaim areas contaminated by heavy metals.Subject Classification number 40: BIOMASS & FEEDSTOCK UTILIZATION
Cover Letter
http://popupclassificationdetail%28185%29/http://popupclassificationdetail%28185%29/ -
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HIGHLIGHTS
Pyrolysis temperature affected the physicochemical properties of biochar.
Higher pyrolysis temperature increased the capacity of biochar to sorb Cd and Zn.
The effect of biochar in the sorption of Cd and Zn is pronounced in sandy soils.
*Highlights (for review)
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Influence of Pyrolysis Temperature on Cadmium and Zinc Sorption1
Capacity of Sugarcane Straw-Derived Biochar2
3Lenidas C. A. Melo, a,* Aline R. Coscione, b Cleide A. Abreu, b Aline P. Puga b and Otvio4A. Camargo b 5a Departamento de Solos, Universidade Federal de Viosa, CEP 36570-000, Viosa, MG, Brazil. 6*Corresponding author: Tel.: +55 31 3899 1048; Fax.: +55 31 3899 2648. E-mail adress:[email protected] 8
b Centro de Solos e Recursos Ambientais, Instituto Agronmico de Campinas, CEP 13020 902, Campinas, SP,9 Brazil.10
11
ABSTRACT12
The effect of pyrolysis temperature (400, 500, 600 and 700 oC) on the characteristics and13
metal sorption capacity of sugarcane straw derived-biochar (BC) was investigated. By14
increasing the pyrolysis temperature there was a reduction in the O/C and H/C molar ratios.15
Sorption capacity of biochar pyrolyzed at 700 C was nearly four-times greater than that16
produced at 400 C. In the Entisol mixture there was an increase up to seven-fold in the17
sorption of both Cd and Zn, while in the Oxisol mixture there was a maximum 20%18
*ManuscriptClick here to view linked References
mailto:[email protected]:[email protected]://ees.elsevier.com/bite/viewRCResults.aspx?pdf=1&docID=41629&rev=0&fileID=1034748&msid={7255CC8D-5649-42D3-8955-49CDB686BBC5}http://ees.elsevier.com/bite/viewRCResults.aspx?pdf=1&docID=41629&rev=0&fileID=1034748&msid={7255CC8D-5649-42D3-8955-49CDB686BBC5}mailto:[email protected] -
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chemical quality (Maia et al. 2011) and/or enhance carbon sequestration (Lehmann et al.28
2006). Most recently biochar has been considered as an option for remediation of heavy29
metals and organic pollutants contaminated soils, as reviewed by Beesley et al. (2011).30
Chemically, biochar is difficult to define due to the wide variety of biomass and31
charring conditions used in its production, which results in materials with a wide range of32
final characteristics (Lehmann and Joseph 2009). By increasing the pyrolysis temperature,33
there is a gradual increase in the aromaticity of the plant biomass, forming a continuum 34
from partially charred plant materials, to charcoal, soot and ultimately graphite (Preston and35
Schmidt 2006). In the range of temperature that biochar is produced (usually < 700 C),36
after an extensive characterization of grass and wood based biochar, Keiluweit et al. (2010)37
proposed a categorization based on its chemical and physical states during pyrolysis: (i)38
transition chars the crystalline character of the feedstock is preserved; (ii) amorphous39
chars - heat-altered molecules and incipient aromatic polycondensates are randomly mixed;40
(iii) composite chars - poorly ordered graphene stacks embedded in amorphous phases; and41
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in the environment that could an advantage to avoid field re-applications. Another51
mechanism of stability is the formation of mineral-biochar complexes related to increasing52
surface oxidation of the biochars during the aging, as observed by Lin et al. (2012) after53
incubation of an Fe rich soil (ferrosol) with biochars produced at 550 C.54
Chen et al. (2011) verified that corn straw-derived biochar pyrolyzed at 600 C55
adsorbed about twice as much of Cu(II) and Zn(II) from aqueous solution, as compared to a56
hardwood-derived biochar pyrolyzed at 450 C. On the other hand, Cao et al. (2009)57
observed that manure-derived biochar produced at 200 C (BC200) showed higher Pb58
sorption than the biochar formed at 350 C (BC350). This was mainly attributed to the59
precipitation of lead with soluble P, which was higher in BC200 than in BC350. Such60
research findings show that the use of biochar as metal sorbent depends strongly on the61
feedstock and pyrolysis conditions, and should be evaluated case-by-case.62
In Brazil, the sugarcane processing facilities convert the feedstock (sugarcane) into63
a variety of products such as sugar, bioethanol, electricity, and other by-products (Cavalett64
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sorption capacity is sought for future application of biochar to reclaim Zn contaminated73
mine soils.74
75
2. Material and Methods76
77
Sugarcane straw was collected in a field experiment, just after the harvest of78
sugarcane. The material was oven-dried at 60 C for 24h and placed in a pyrolyzer, sealed79
and heated to 400, 500, 600 and 700 C at the rate of 10 C/min. The desired temperature80
was held for about one hour (slow pyrolysis), after which the pyrolysed material was left to81
slowly cool down to room temperature. The weights of the starting biomass and of the82
resulting material (biochar - BC) were recorded to determine the BC yield. Biochar was83
ground to pass a stainless steel sieve (< 0.5 mm) and used for characterization and84
subsequent experimentation. A clay-rich Oxisol and an Entisol were used in the batch85
sorption experiments.86
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and two portions of 20 mL of the acetate solution. The excess solution (non-adsorbed96
NH 4+) was washed out with three portions of 30 mL of isopropyl alcohol. The biochar was97
rinsed with four portions of 50 mL of 1M KCl solution and the rinsate was collected and98
brought to the final volume of 250 mL and the NH 4+ was determined by the Kjeldahl99
method.100
Prior to the analysis of the point of zero charge (pH pzc ), the ash of biochar samples101
was removed by washing with 0.1 M HCl (27 g L -1) by constant stirring for 1 h, then the102
material was rinsed three times with distilled deionized water (DDW) and dried overnight103
at 80 C (Uchimiya et al. 2011b). The pH pzc was determined as described by Yang et al.104
(2004). In 60 mg of BC were added 20 mL of 0.01M CaCl 2 solution previously adjusted105
with diluted HCl or NaOH solutions to pH 4, 6, 8 and 10. After shaking for 24 h the pH106
was measured and when the final pH was equal to the initial pH (line 1:1) it was considered107
as pH pzc . The CHN elemental composition was determined in an elemental analyzer (Perkin108
Elmer series II 2400). The oxygen contents were estimated by mass difference, i.e. 100% -109
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119
2.2 FT-IR and thermal analysis120
121
Surface functional groups of BC were analyzed by Fourier transform-infrared122
spectroscopy (FT-IR, Spectrum One, Perkin Elmer), in the range of 4000 to 450 cm -1, by123
using 20 scans/min at 4 cm -1 resolution. Measurements were performed in pellets of BC124
blended with KBr.125
Thermogravimetric analysis of BC was performed in a TGA 2050 TA Instrument.126
The measurements were obtained under N 2 atmosphere from room temperature up to 950127
C at a heating rate of 20 C/min. Samples mass varying from 5.1 to 5.7 mg were used.128
129
2.3 Scanning Electron Microscopy130
131
Analysis of Scanning Electron Microscope (SEM) was carried out using a LEO Evo132
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extracted with a 1 M KCl solution and measured by titration with a 0.025 M NaOH142
solution. Phosphorus, Ca, Mg and K were extracted by ionic exchange resin and determined143
by ICP OES. The cation exchange capacity (CEC) was calculated as the sum of cations (Ca144
+ Mg + K + H + Al). Total acidity (H+Al) was estimated at pH 7.0 with buffer SMP145
solution. Available sulfur was extracted by Ca(H 2PO 4)2 0.01 M and determined146
turbidmetrically, after reaction with BaCl 2.2H 2O. Soil available concentrations of Cu, Fe,147
Mn and Zn were extracted with DTPA pH 7.3 (Lindsay and Norvell, 1978). Boron was148
extracted by hot water and determined colorimetrically. For a more detailed149
characterization of these soils see Melo et al. (2011).150
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2.5 Batch sorption experiments151
152
Sorption experiments were carried out following the procedures described by153
Uchimiya et al. (2011c), with modifications. Briefly, 0.2 g of BC or 2.0 g of soil + BC154
mixture (1.8 g of Oxisol or Entisol + 0.2 g of BC) were weighted into 50 mL centrifuge155
tubes, in duplicate. Then, 20 mL of synthetic rainwater (SR - obtained by addition of 10156
mM H 2SO 4 in deionized water until pH 4.5 was reached) were added to the sample and157
shaken horizontally for 24 h at 100 oscillations/min. After, 200 L of a 0.2 M stock158
solution of Cd or Zn were added in order to reach a final concentration of 2 mM and the159
tubes were shaken for another 24 h, and subsequently filtered. In the equilibrium solution160
Cd or Zn were measured by ICP-OES. Control treatments were achieved by using blank161
reagents in all batch procedures. Tests of sorption using longer times (i.e. 48 h and 96 h)162
were performed and showed no significant difference (data not shown), confirming the163
duration (24 h) was adequate for equilibration.164
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pH and electrical conductivities was observed, probably reflecting the greater ash content174
of biochar obtained at higher pyrolysis temperatures.175
The cation exchange capacity (CEC) reduced, while the increase of the carbon176
content corresponded to a decrease of O and H was observed at higher pyrolysis177
temperatures. Consequently there was a reduction in the O/C and H/C molar ratios. The178
reduction in CEC is probably related to loss of O containing functional groups. Such179
findings are in agreement with other authors (Singh et al., 2010; Mukherjee et al. 2011;180
Uchimiya et al. 2011a; Song and Guo 2012) that also observed similar results for the effect181
of temperature on these biochar parameters, produced from various biomasses suggesting182
that variations in these parameters with temperature occurs regardless of the parent biomass183
and seems to be a general rule. 184
The molar ratios obtained from the elemental analysis are commonly used to185
determine the degree of aromaticity (H/C) and polarity (O/C) of coal and have been used186
for biochar characterization (Uchimiya et al. 2011a) since by increasing the pyrolysis187
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expected to be more available. The relatively high levels of Ca, Mg and K in all BCs tested197
are due to the sugarcane straw s initial composition, which is rich in such elements, mainly198
K (Oliveira et al., 2002). It should be noted that since this BC presents alkaline reaction199
(pH ranging from 8.6 to 10.1) and is rich in nutrients, such factors indicate its good200
potential for reclaiming contaminated land, since it could act as a metal immobilizer and a201
nutrient supplier, allowing the growth of plants in bare soils. Such characteristics make this202
particular biochar an attractive option for this purpose. Al-Wabel et al. (2013) verified203
enrichment of 232%, 199% and 304% for Ca, Mg, K, respectively, for biochar produced204
from conocarpus wastes at 800 C. They concluded that such an increase in alkaline205
elements could be responsible for liming effects induced by biochar pyrolyzed at high206
temperatures.207
The FTIR spectra revealed in all cases bands at the region of 3500 to 3400 cm -1,208
which relates to stretches of hydroxyl groups and indicates hydrogen bonds (Figure 1). The209
bands between 2900 and 2800 cm -1 are related to the elongation of CH aliphatic chains.210
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decrease in the intensity of the peaks of different groups, which is consistent with the lower219
O contents of biochars at higher temperatures.220
The mass loss at different TGA stages analysis of the biochar samples are presented221
in Table 2. For all samples considered the stage 1, around 100 C, was observed and it is222
consistent with the loss of water (moisture) from samples. With the increase of furnace223
temperatures occurred a plateau until around 380 C (400 BC) and 450 C (700 BC), in224
which no effective loss of mass was observed. After, at stage 3 there was a sudden drop, of225
approximately 50% sample weight loss, up to 640 C. An exception here is the BC700, in226
which the mass loss is relatively low (23.7%) at stage 3, as compared to biochar samples227
obtained at lower temperatures. The mass loss at this range of temperature is related to the228
decomposition of organic remaining content of the BC samples, including cellulose and229
hemicellulose. The latter starts to decompose from 220 C up to 315 C, and it is followed230
by cellulose decomposition (Yang et al. 2007).231Finally, a loss of approximately 20% of samples mass that has occurred between232
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Furthermore, the surface properties of materials are also important to explain its240
reactivity. In general, the surface morphology of the sugarcane straw biochar samples,241
despite the temperature it is produced at, showed an irregular amorphous surface with a242
porous structure (Figure 2). This effect could be the result of melting and fusion process of243
the lignin and other small molecules compounds, such as pectin and inorganic compounds,244
as was described by Liu et al. (2010) in pinewood biochar produced at 300 C and 700 C.245
246
3.2 Adsorption of Cd and Zn in soils247
248
The Oxisol and the Entisol used for experimentation were slightly acidic and had249
contrasting characteristics, mainly governed by the clay content/fraction (63% for the250
Oxisol x 6% for the Entisol), CEC and organic matter content (Table 3). The lower251
available P and micronutrient (i.e. Cu, Fe, Mn and Zn) contents in the Oxisol as compared252
to the Entisol, indicate a naturally higher sorption capacity of the Oxisol.253
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removal from aqueous solution with biochar produced from a giant Miscanthus at higher263
pyrolysis temperature. Jiang et al. (2012) observed that the application of rice straw derived264
biochar in an Ultisol increased soil pH, making the surface charge more negative, and265
significantly reduced the acid soluble Cu(II) and Pb(II). They also found that the functional266
groups (i.e. -COOH e -OH) of the biochar formed stable complexes mainly with Cu(II),267
enhancing greatly its adsorption.268
Interesting results were found when biochar was mixed into the soils, as related to269
Cadmium (Cd) or Zinc (Zn) sorption (Figures 3B and 3C). The addition of 10% BC to the270
Oxisol increased the adsorption of either Cd or Zn up to 20%, as compared to the control.271
As discussed above the Oxisol is clay-rich and naturally exhibits a relatively high sorption272
capacity. Even so, BC played a role to increase metal sorption capacity in this soil. When273
BC was applied to the Entisol there was an increase up to seven-fold the sorption of both274
cations, as compared to the control (without BC). Uchimiya et al. (2011c) also found275
similar results for Cu retention in two soils (Norfolk and San Joaquin), with distinct276
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functional groups that are able to retain cationic metals. On the other hand, results from286
Uchimiya et al. (2011a) show that biochar formed at lower temperature (350 C) was more287
effective to retain heavy metals in an acidic and eroded soil than biochar formed at higher288
temperatures. They concluded that surface functional groups of biochars (which govern289
pH pzc and VM and oxygen contents) control their ability to retain heavy metals in the soil 290
Therefore; they stated that biochar selection for soil amendment must be made case-by-291
case based on the biochar characteristics, soil property, and the target function . In this292
particular case, the pH pzc of the BC at 350 C was the only one unit below the equilibrium293
pH. The higher is the difference between pH pzc and equilibrium pH the higher are expected294
to be the electrostatic interactions between cationic metal species and negatively charged295
surfaces (Uchimiya et al. 2011a), which in our case is for BC at 700 C, helping to explain296
its higher metal sorption.297
Uchimiya et al. (2012), however, found that BC poultry litter pyrolyzed at 350 C298
was better to retain and stabilize Pb in a contaminated soil than the BC produced at 650 C.299
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increased the capacity of sugarcane straw-derived biochar to sorb Cd and Zn. The effect of309
biochar in the sorption of Cd and Zn is much more pronounced in sandy soils with low310
natural ability to retain metal pollutants than in clayey soils. The specific intention being311
the application of sugarcane straw-derived biochars to Zn contaminated mine soils higher312
pyrolytic temperatures are recommended.313
314
Acknowledgments315
316
The authors are grateful for the financial support of the So Paulo Research317Foundation FAPESP (Grant. No. 2011/12346-3) and for the postdoctoral fellowship318
(Grant. No. 2011/02844-6) for the first author. We also are grateful to Prof. J.O. Brito319
(Esalq/USP) for kindly provide the biochar for the study and Dr. Luke Beesley (The James320
Hutton Institute) for the helpful comments on the article.321
322
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Cavalett, O., Junqueira, T.L., Dias, M.O.S., Jesus, C.D.F., Mantelatto, P.E., Cunha, M.P.,333
Franco, H.C.J., Cardoso, T.F., Maciel Filho, R., Rossell, C.E. V., Bonomi, A., 2011.334 Environmental and economic assessment of sugarcane first generation biorefineries in335Brazil. Clean Technol. Environ. Policy 14, 399 410.336
Chen, X., Chen, G., Chen, L., Chen, Y., Lehmann, J., McBride, M.B., Hay, A.G., 2011.337Adsorption of copper and zinc by biochars produced from pyrolysis of hardwood and338corn straw in aqueous solution. Bioresour. Technol. 102, 8877 8884.339
Ferreira-Leito, V., Gottschalk, L.M.F., Ferrara, M.A., Nepomuceno, A.L., Molinari,340H.B.C., Bon, E.P.S., 2010. Biomass residues in Brazil: availability and potential uses.341Waste Biomass Valorization 1, 65 76.342
Fuertes, A.B., Arbestain, M.C., Sevilla, M., Maci-Agull, J.A., Fiol, S., Lpez, R.,343Smernik, R.J., Aitkenhead, W.P., Arce, F., Macias, F., 2010. Chemical and structural344
properties of carbonaceous products obtained by pyrolysis and hydrothermal345carbonisation of corn stover. Aust. J. Soil Res. 48, 618 626.346
Jiang, J., Xu, R., Jiang, T., Li, Z., 2012. Immobilization of Cu(II), Pb(II) and Cd(II) by the347addition of rice straw derived biochar to a simulated polluted Ultisol. J. Hazard. Mater.348229-230, 145 150.349
Keiluweit, M., Nico, P.S., Johnson, M.G., Kleber, M., 2010. Dynamic molecular structure350of plant biomass-derived black carbon (biochar). Environ. Sci. Technol. 44, 1247 3511253.352
Kim, W.-K., Shim, T., Kim, Y.-S., Hyun, S., Ryu, C., Park, Y.-K., Jung, J., 2013.353
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Liu, Z., Zhang, F.-S., Wu, J., 2010. Characterization and application of chars produced366
from pinewood pyrolysis and hydrothermal treatment. Fuel 89, 510 514.367
Maia, C.M.B.F., Madari, B.E., Novotny, E.H., 2011. Advances in biochar research in368Brazil. Dynamic Soil, Dynamic Plant 5 (Special Issue 1), 53-58.369
Melo, L.C.A., Alleoni, L.R.F., Carvalho, G., Azevedo, R.A., 2011. Cadmium- and barium-370toxicity effects on growth and antioxidant capacity of soybean (Glycine max L.)371
plants, grown in two soil types with different physicochemical properties. J. Plant372
Nutr. Soil Sci. 174, 847 859.373
Mukherjee, a., Zimmerman, a. R., Harris, W., 2011. Surface chemistry variations among a374series of laboratory-produced biochars. Geoderma 163, 247 255.375
Oliveira, M.W., Trivelin, P.C.O., Boareto, A.E., Muraoka, T., Mortatti, J., 2002. Leaching376of nitrogen , potassium , calcium and magnesium in a sandy soil cultivated with377sugarcane. Pesqui. Agropecu. Bras. 37, 861 868.378
Preston, C.M., Schmidt, M.W.I., 2006. Black (pyrogenic) carbon: a synthesis of current379knowledge and uncertainties with special consideration of boreal regions.380Biogeosciences 3, 397 420.381
Quirk, R.G., Zwieten, L., Kimber, S., Downie, A., Morris, S., Rust, J., 2012. Utilization of382 biochar in sugarcane and sugar-industry management. Sugar Tech 14, 321 326.383
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Uchimiya, M., Klasson, K.T., Wartelle, L.H., Lima, I.M., 2011c. Influence of soil398
properties on heavy metal sequestration by biochar amendment: 1. Copper sorption399 isotherms and the release of cations. Chemosphere 82, 1431 1437.400
Uchimiya, M., Wartelle, L.H., Klasson, K.T., Fortier, C. a, Lima, I.M., 2011a. Influence of401 pyrolysis temperature on biochar property and function as a heavy metal sorbent in402soil. J. Agric. Food Chem. 59, 2501 2510.403
Wu, W., Yang, M., Feng, Q., McGrouther, K., Wang, H., Lu, H., Chen, Y., 2012. Chemical404
characterization of rice straw-derived biochar for soil amendment. Biomass Bioenergy40547, 268 276.406
Yang, H., Yan, R., Chen, H., Lee, D.H., Zheng, C., 2007. Characteristics of hemicellulose,407cellulose and lignin pyrolysis. Fuel 86, 1781 1788.408
Yang, Y., Chun, Y., Sheng, G., Huang, M., 2004. pH-dependence of pesticide adsorption409 by wheat-residue-derived black carbon. Langmuir 20, 6736 41.410
411
412
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Figure 1. FTIR spectra of sugarcane straw derived biochar pyrolyzed at four temperatures.424
425
Figure 2. Scanning Electron Microscope (SEM) images of biochar. The images show426
biochars produced at 400C (a; c) and 700C (b; d), at 200x (a; b) and 1000x magnification427
(c; d).428
429
Figure 3. Adsorption of Cadmium and Zinc in biochars prepared at different temperatures430
(A); and adsorption of Cadmium (B) or Zinc (C) in an Oxisol and an Entisol alone or mixed431
with 10 % (w/w) biochar pyrolyzed at different temperatures. *Fig. B has the same legend432
as Fig. C433
434Table 1435Characterization of the Biochar436Parameter Pyrolysis Temperature (C)
400 500 600 700
Yield (%, w/w) 45 38 35 31EC (mS cm -1) 3.3 3.8 3.4 5.1
pH H2O 8.6 9.8 9.7 10.1
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Table 2440
Temperature range and mass loss for TGA in biochar samples441 Samples Stage 1 Stage 2 Stage 3 Stage 4 Totalmassloss(%)
Temp.range(C)
Massloss(%)
Temp.range(C)
Massloss(%)
Temp.range(C)
Massloss (%)
Temp.range(C)
Massloss(%)
BC400 < 96 2.4 96-378 6.1 378-641 45.5 641-950 24.1 78.1BC500 < 99 2.2 99-410 5.7 410-677 50.1 677-950 23.4 81.3BC600 < 96 2.0 96-439 4.3 439-683 44.8 683-950 24.5 75.6BC700 < 114 3.2 114-451 3.5 451-648 23.7 648-950 29.8 60.2
442443
Table 3444Characterization of the soils used in the sorption experiment445Soil pH SOM CEC Al Ca Mg K
CaCl 2 (g kg- ) ----------------------------mmol c kg
- ----------------------------Oxisol 5.7 0.0 37 2 94 7 - 39 2 26 2 1.4 0.1Entisol 5.2 0.2 23 2 69 4 1.4 0.1 28 1 1.9 0.8 0.6 0.1
P S Cu Fe Mn Zn B----------------------------------------------------mg kg - -------------------------------------------------------
Oxisol 3.9 0 60 3 0.7 0.1 39 1 14 2 0.5 0.1 0.3 0Entisol 173 6 15 1 3.0 0.1 130 13 28 1 11 0.1 1.0 0Values are mean (n = 3) standard deviation. SOM = Soil Organic Matter; CEC = Cation Exchange Capacity; - not446detected 447
448449450451
Figure
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Wavenumber (cm -1)
5001000150020002500300035004000
BC 400
BC 500
BC 600
BC 700
O-H3430
C=C
C-H aliphatic
Absorbance
C-H 2C-O-C
C-Haromatic
29182850
16181438
1112
874-810
g
Figure
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200 m
b
100 m
a
20 m
dc
20 m
Figure
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T t t
Adsorbed metal (mg g
-1)
O x i s o lE n t i s o l
S 4 0 0 5 0 0 6 0 0 7 0 0
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0Z i n c
b
a a a a
c
b b b
a
T r e a t m e n t s
Adsorbed metal (mg g
-1)
S 4 0 0 5 0 0 6 0 0 7 0 00 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0C a d m i u m
b
a a a a
c
b a b a b
a
P y r o l y s i s te m p e r a t u r e ( C )
4 0 0 5 0 0 6 0 0 7 0 0
Adsorbed metal (mg g
-1)
0
4
8
1 2
1 6
2 0
C d
Z n
b
b
b
b
b
b
a
a