427
XXII ENTMME I VIl MSHMT- Ouro Preto-MG, novembro 2007.
A PERSPECTIVE OF BONE CHAR USE lN THE TREATMENT OF
INDUSTRIAL LIQUID EFFLUENTS CONTAlNING HEAVY METALS
1
2
T.S. Gucdes , M.B.Mansur and S.D.F. Rocha 3
3
contacting author, sdrocha(â1demin.uting .br
Universidade Federal de Minas Gerais, 1Chcmical Enginccring undcrgraduatc studcnt, 2Metallurgical and Materiais
Engineering Dcpartment and 3 Mining Engincering Dcpartment
3
Rua Espírito Santo 35 , 7" andar, Centro, 30160-030 - Belo Horizonte, MG, Brazil.
RESUMO
O carvão de ossos bovinos já é utilizado tradicionalmente na remoção de cor na indústria do açúcar. Esta excelente
característica adsorvcnte tem impulsionado sua utilização cm diversas outras áreas, tais como na indústria minerometalúrgica, para a remoção de metais presentes cm efluentes líquidos. Esse trabalho apresenta uma comparação entre
as características do carvão de ossos produzido no Brasil c aqueles disponíveis no mercado internacional, c também
apresenta o desempenho do carvão nacional na remoção de Zn, Cu, Cd, Co, Pb e Ni , metais comumente present~s em
efluentes da indústria minero-metalúrgica. Os resultados apontam numa perspectiva de utilização do carvão de osso no
tratamento de efluentes líquidos industriais contendo metais já que se observou uma remoção satisfatória dos metais
estudados. Foram avaliados os tratamentos de um efluente proveniente da indústria do zinco e efluentes sintéticos. O
carvão de ossos bovinos de granulomctria fina apresentou resultados mais satistàtórios do que o de granulometria
grosseira; esse é um dado importante, tendo em vista que o carvão fino é um produto de baixo valor agregado. As
vantagens e limitações da aplicação do carvão são discutidas, bem como as possibilidades de destinação final do
adsorventc carregado com metais. Quando a operação se dá em coluna, observou-se uma competição entre os metais
cádmio e o zinco, para o efluente industrial, o que merece estudo adicional.
Palavras chaves: adsorção, remoção de metais, carvão de ossos bovinos
ABSTRACT
Bonc char is traditionally uscd for color and turbidity remova! in sugar processes. Due to its exccllent adsorptive
character its utilization has bccn studicd and expandcd to other applications, such as the metais remova! from mining
anel metallurgical eftluents containing metais, and also for the remova! of residual color and organic matter from textile
cftlucnts. A comparison bctwcen thc charactcristics of imported and national Bonc char is reported in this work. The
perfonnance and also thc kinetic of Bonc char for the remova! of Zn, Cu, Cd, Co, Pb and Ni present in acidic solutions
are presentcd. Thc results dcpict a good perspective of processes with bone char. The use of bonc char for the remova!
of metais form ctllucnts generated by the zinc industry has shown promising rcsults. Best results were obtained using
the fine fraction of bonc char in comparison with thc com·sc fraction; this is an important rcsult sincc the fine fraction of
bone char h as a low commercial value. Thc advantages and limitations of the application of bone char are discussed, as
well as the possible attractivc for the final dcstination of metal loaded charcoal. A competitive separation betwecn
metais zinc and cadmium has bcen vcrifíed in column operations, so further studies are necessary.
Key-words: adsorption, metais remova!, bone char
Thematic arca: effluent treatment
428
Thiago Santos Guedes , Marcelo Borges Mansur and Sônia Denise Ferreira Rocha
1. INTRODUCTION
Due to its high toxicity to human healthy and also to cnvironment, heavy metais must be removed from wastcwatcrs
generated by many types of industries such as metal processing, metal rccycling as well as surfacc treatmcnt companies
(galvanization) and many others. The wastewaters are mainly contaminatcd with hcavy metais such as Zn, Cu, Cd , Co,
Pb and Ni. The effluents are usually trcatcd by a prccipitation processes, using an alkali as prccipitant agcnt for metais
hydroxides. Precipitation of metais is largely used duc to the low cost of alkalis usually availablc, and its rclativcly casy
operation. However, duc to the strcngthening of cnvironmental standards and also to thc necding of rccycling watcr in
the processes, altemative processes have been investigated (Sonumc & Ghate, 2004), mainly in cases when metais are
complexed, associated with organic compounds and also for trace conccntrations.
Adsorption is an intcresting alternative to be used whcn it is dcsircd to gel such lowcr residual concentrations of
contaminants in water. ln opposition to precipitation, therc is no limit for the residual concentration of metais in the
solution. ln the case of precipitation, the residual conccntration of metal is dctcrmincd by thc solubility of thc metal
hydroxide, also a function of the system tempcraturc. The residual conccntration of the contaminant in the solution after
a treatmcnt using adsorption depends on various factors , mainly thc aftinity bctween adsorbcnt and lhe adsorbate and
the operational conditions of the process. Adsorption can be used for immobilization of species "in situ". Many
investigations have been carried out with a variety of organics adsorbents such as activated carbon, biomass and also
inorganic, zeolites, clays, solids wastes (Kadirvelu et ai, 200 I; Hanzlik ct ai., 2002; Aklil et ai., 2004). The present work
depicts the use of bone char in thc remova! of metais Zn, Cu, Cd, Co, Pb and Ni present in acidic solution and also Zn,
Cd and Pb from an industrial effluent from zinc mining industry. The bone char used is produccd by a Braz ilian
company from bonc wastes. Thc kinetic of adsorption and also the adsorptive capacity for ali metais was determined.
The bone charcoal is produced by the pyrolisis of crushed ox bones at 800°C in atmosphere of limited concentration of
oxygen. Bone charcoal contains about I 0% of carbon on the opposite of normal activatcd carbon, which is majoritary
carbon. Bones charcoals present mainly hidroxiapatite and minor amounts of calcium carbonatc. Thc presence of
carbonates gives to bone char a buffer capacity. Despitc thc bone char is used in sugar proccss for more than a century,
its use as adsorbent for diverse compounds has been the objcct ofmany studics (Cheung et a/., 2000; Dahbi et a/., 2002;
Wilson et ai., 2003 ; Cheung et a!., 2004; Ko et ai., 2003; Choy and McKay, 2005; Guedes and Rocha , 2005). Wilson et
a/. (2003) invcstigated the adsorption of copper and zinc by bonc char Brimac 216 20/60 (250-850 11m). The
experiments were carried out with 20 mg/L of charcoal in solutions containing O mg/ L to 4000 mg/L of Cu and O mg/L
to 2000 mg/L of Zn prepared from their nitrates, without adjust of pH. A good agrecmcnt of results with thc Langmuir
adsorption model was observed, cquation I, being the maximum adsorption capacity (Omox) dctennined as cqual to
27±1 mg/g and 24±3 mg/g for Cu and Zn, respectivcly .
.c,_
Qc
= KL
X
Qmax
+
--.C..c.._
Qmax
(I)
where:
Ce: equilibrium concentration (mgmera1/L);
Qe: ratio of amount adsorbed and adsorbcnt mass (mgmctallgadsorbcnt);
Omax: maximum adsorptive capacity (mgmctallgadsorbcnt);
KL: Langmuir constant (LI mgmctaJ).
Guedes & Rocha (2005) obscrved that thc Brazilian bone charcoal prescnts similar adsorptive capacity to thc imported
(Brimac) for lhe remova! of zinc and copper. Adsorption cxpcrimcnts with I O mg/L of bone charcoal of two sizes (6+ 16) mesh Tyler and ( -20+40) mcsh Tylcr, in contact with solutions containing 50-300 mg/L of Cu and 50-300 mg/L
of Zn, preparcd from thcir sulfates, initial pl-1 equal to 4,0 wcre carricd out at ambient tcmpcraturc (28"C). The
maximum adsorptive capacity was detcrmincd for coppcr and zincas 25.7 mg/g and 25.3 mg/g, rcspcctively.
2.MATERIALS AND METHODS
2.1 Batch adsorption experiments
Samples of Brazilian bone charcoal were supplied by Boncchar Carvão Ativado do Brasil located at Maringá-PR, in
two distinct size ranges: coarse ( -6+ 16) mesh Tyler and fine (-20+40) mcsh Tyler. Charcoal was charactcrized with
respect to its real density (picnometry with Hc, Stcrcopycnomctcr Quantachrome SPY -3), morphology (Scanning
electron microscopy, JEOL, modcl 6360L V), presence of crystalline phases by X-ray diffraction (X-ray PhilipsPAnalytical PW 171 O Diffratometer) and specific surface arca (multiple point BET- Quantachrome- Nova 1200).
429
XXII ENTMME I VIl MSHMT - Ouro Prcto-MG, novembro 2007 .
Initially lhe bone charcoal was dried ai 120"C, for a period of time of 2 hours and slored in a dissecalor. Samples
withoul pre-lrealmenl of 1.0 g were weighted and placed inlo an erlenmeyer containing lhe synlhelic metal solution
with 50, I 00, 150, 200, 250 e 300 mg/L of metal, prepared using ZnS0 4 . 7H 2 0, CdS0 4 .8/3H 20, CoS0 4 . 7H 2 0
CuS0 4 .5H 20, NiS0 4 .6H 20 and Pb(N0 3) 2 salts. The pH was adjusted to the desired value (4,0) with sulphuric acid
solution and in the case of lead, nitric acid was used. The initial solid-liquid ratio was equal to lO mg/L. Erlenmeyers
containing lhe solulion and bone char were stirred ai 200 rpm in a shaker Dubnoff under conlrolled temperature of
28"C. i\fter 140 minutes, time enough to gel the equilibrium as verified in a preliminary study, experimenls ended and
lhe pulp was vacuum filtercd . Metais concentralions in solution were determined by atomic absorption speclrometry
(GBC 932 plus).
2.2 Column adsorption experiments
Semi-conlinuous adsorption experiments were carried out in an acrylic column 53 cm high and 2,2 cm diameter. Bone
charcoal of (-20+40) mesh Tyler was previously washed wilh distilled water for a period of time of 2 minutes in a
becker, al a solid-liquid ratio of 0.15 g/ml. Further, pulp was fillered and solids were dried at 60°C for 12 hours. The
column was filled with 30g of lhe adsorbent. The industrial effluent containing mainly Zn, Cd, Pb and ions sulfate was
continuously fed lo the column ai a flow rate of 0,014 L/min by a peristaltic pump (Cole-Parmer, Masterflex). Samples
were collecled in the column outlet and metais concentrations were detennined by atomic absorption spectrometry
(GBC 932 plus).
2.3 Desorption experiments
Desorption experiments were carricd out for two distinct sizes of charcoal: coarse (-6 + 16 mesh Tyler) and fine (-20
+40 mesh Tyler). i\ 506.8 mg/1 zinc solution of pH 4.0 (adjusted with sulphuric acid) was prepared in order to load the
fresh bone charcoal. F our samples of 5 g of bone eh ar of each size were weight and each one was contacted with 100 ml
of the zinc solution previously prepared for 180 min at 28°C and under stirring rate of 240 rpm. The initial and final pH
and lhe initial and final zinc concentrations were obtained. After lhe loading step lhe pulp was vacuum filtered and
further dried ai 60"C for 12 hours. The solids were homogenized and smaller samples of about 2.4 g were taken. The
adsorbed mass on charcoal was determined by a mass balance. The first desorption test was carried out with 10 g/L of
bone eh ar in distilled water of pH 5.4 for both sizes of bone char, coarse and fine. The pulp was stirred for 200 minutes
at 28°C. i\t lhe end of the experiment, the pH was measured and the pulp was vacuum filtered . The second desorption
experiment was carried out with sulphuric acid solution of pH 2.0 ai the same conditions as the Desorption carried out
with distilled water. The Desorplion time was extended for 240 minutes.
3. RESULTS AND DISCUSSION
3.1 Bone Charcoal Characterization
The Brazilian bone charcoal of coarse and fine sizes presented low humidity content, 2,9% e I ,3%, respectively. These
values are in a good agrecmcnt with lhe specification given by lhe producer (<5%). The main physical and chemical
properties of both charcoals are depicted in Table I.
T a bl e 1 - M am properl!es o fB raztTtan an tmporte db one char
Brazilian Bone
Imported
Property
eh ar
Carbon content
9-11%
9-11%
Soluble ash in acid
<3%
<3%
Tricalcium phosphate
70 - 76%
70-76
Calcium carbonate
7-9%
7-9%
Calcium sulphate
0,1-0,2%
0.1-0.2
2,81
Real density (g/cm 3 )
2,86
129,4 m-!g
123,2
Total specific surface área (B ET)
Iron
< 0,3%
<0.3
Medium Porous diameter
94,8
98,6
Porous volume (cmj/g)
0,3189{d<974,9Â)
0,2919(d<978,5 À)
Humidity
<5%
<5%
The values presented are in accordance with those reported by Wilson et al. (2002), except for the surface area. Figures
I and 2 illustrate the high porosily and irregularities on the charcoal surface. Fine particles of carbon, attached to the
430
Thiago Santos Guedes, Marcelo Borges Mansur and Sônia Denise Ferreira Rocha
surface can be observed, since the material was not washed previously. The identification of chemical specics on the
surface by SEM, according to Figure 3, cvideoced high contents of calcium and phosphorous, as expected. This is
coherent with the raw material ofthe bonc char, and also with the literature (Wilson et a/., 2003). The bearing phasc of
phosphorus identified by the X-ray diffraction analysis is the hydroxiapatite. Minor amOtmts of calcite were also
identified.
(a)
(b)
Figure I - Micrographs ofbone char coarse. Secondary electron image. (a) 30x (b)
IOOOx
~'"'
(a)
.....
.....
(b)
Figure 2 - Micrographs ofbone eh ar fine. Secondary electrons i moges. (a} 30x (b)
!OOOx
..
•
..
p
"
"
"~ca
Figure 3 - Scanning electron microscopy of fine bone char at region C.
3.2 Batch Adsorption Experiments
The adsorption isotherms (28°C) for the whole metais studied are preseoted in Figure 4 with the points adjusted for lhe
Langmuir equation. The relationship between the amount of metal adsorbed per mass of adsorbent (Qe) and the metal
equilibrium concentration (Ce) is useful to predict the character of adsorption. Two adsorption models werc tested in
order to verify their applicability to the system. The Frcundlich equation derives from an empirical model of adsorption
tbat considers that Qc increases linearly witb Ce (equatioo 2)
431
XXII ENTMME I VIl MSHMT- Ouro Preto-MG, novembro 2007.
log Oc = log Kr- + 1/n log Cc
(2)
where:
Qe: ratio of amount adsorbed and adsorbent mass (mgmctallgadso
Ce: equilibrium concentration (mg/ L);,bcnt);
KF and n: Constants.
jofinecharcoal
i
l
O fine charco ai
I
()coars e chan.: oal
Ocoarse charc_oaj
I·----
o
100
200
o
300
I
Ce (mg/L)
100
200
Ce (mg/L}
I
_j
Co
êi
Õl
.§.
Q)
CJ
Cd
-------- -------- - 1
25
20
15
10
5
l
1
jD ,,;;-;;charco ai
'<>co a rs c charconl_
I
100
200
~--
30
I
I
I
õi
300
Ce (mg/L)
_
_
_
j
O finc-ch-a~c ~~ ~-- ~
i
<)c o a rs c c h arco a j
Õl 20
E
- "
o
o
300
Q)
I
I
1
I
!
I
IL _
10
CJ
I
0 -
o
50
100
150
200
Ce (mg/L)
_ _ _ ___ ___ _ ________
Zn
__J
Cu
------ - - - -- - 10
:k;:=:=
o
100
200
O fn1e c ha rcoal
Ocoarse charco a!
300
Ce (mg/L)
Ni
Figure 4 - Adsorption isotherms for metais studied at 28°C.
On the other hand, the Langmuir equation (equation I) derives from a model were the main considerations are
adsorption occurring in monolayers, without interactions between solutes. The parameters obtained adjusting both
equations to the results are presented in Table 2 anda good agreement with those reported by Wilson et a/., (2003) has
been obtained. 8oth models showed a good adjust to experimental results, being the Freundlich model slight superior in
some cases. H can be clearly noticed that the bone char of small size presents higher remova! of metais such result is
probably related to lhe higher surface area for metais adsorption. The results of isotherm for lead are not presented,
since lhe remova! was complete for this metal in a short period of time. So, lhe bone char has a high affinity for lead.
432
Thiago Santos Guedes, Marcelo Borges Mansur and Sônia Denise Ferreira Rocha
Table II- Freundlich and Langmuir equations parameters obtained by di verse metais adsorption in bone char
Freundlich equation parametcrs
R1/n
KF
0.755
0.9799
1.31
0.9871
16.47
2.83
0.9632
1.455
3.04
1.047
3.60
0.9359
0.9225
1.569
1.92
0.668
1.72
0.9778
6.637
3.31
0.9807
2.114
2.65
0 .9974
0 .9735
32.24
3.78
0.922
2.59
0.9950
Bone char size
Metal
Fine
Coarse
Fine
Coarse
Fine
Coarse
Fine
Coarse
Fine
Coarse
Copper
Nickel
Zinc
Cadmium
Cobalt
Langmuir cquation paramctcrs
RKt
Q rnax
25,7
0,839
0,9567
0,601
10,9
0,9830
9,3
0,9861
0,287
5,4
0,148
0,9851
25,3
0,9837
0,552
22,8
0,102
0,8989
0,9962
2.567
27.0
16,9
0,498
0,98 78
12,9
0,904
0,9963
0,177
9,2
0.9785
lt was verificd a mass reduction of the adsorbent during lhe experiments of about 4%. This occurred due to thc
dissolution of calcite present in the bone char. The other phases present, calei um phosphate (apatite) and calcium sulfate
(anhydrite) are rather insoluble. This was also responsible for the increase in the pH of lhe solution obscrved (Figure 5).
The pH was higher for lower initial metal concentration and close lo valucs of about 8.5. For higher metal
concentrations, pH values between 7 and 8 were reached, dcpending on lhe metal ion . Exception is for coppcr
(adsorplion on fine charcoal) and for copper and lead (adsorplion for coarsc charcoal) when lowcr values for hi gher
concentrations were reached . Taking into consideration a 4% of calcium carbonale dissolution , a total carbonale
concenlralion in solution was 4x 10·4 Molar (solid-liquid concenlration was I Omg/L) . According to Stumm and Morgan
(1981 ), in the Me-H 20-C0 2 system, in lhe presence of earth atmosphere, carbonales are frcqucntly more stable than
oxides or hydroxides as solid phases. Thus, in naturally syslems, the concenlralion of some metal ions is conlrolled by
lhe solubility of metal carbonates.
For a divalenl cation, the following reactions represenl lhe system:
MeC0 3<sl
= Me 2+ + COt
(3)
Me C 0 3<sl + H += Me-'+ + H c 0 3-,_
McCOJ<sl + H2C03 = Me
9
8.5
8
7.5
:I:
7
c..
6.5
6
5.5
5 I
o
§
D
2
(4)
+ 2HCO/"
'
(5)
9
l!.
~
é
:.:
o
tl
o
~
D
o
I ~Ni i
liC
I
o.
! o Cu :
!!.
D
D
-- --, -100
.
,- -
..
200
D
-- -,
300
metal concentration (mg/L)
(a)
Pb
1
xCo
D
:.:Zn
400
-
i
o Cd i
- --
~
8.5
8
7.5
:I:
7
c..
D
l!.
~
é
:.:
o
tl
o
o
~
liC
D
·~ 1
D
D
5.5 5
o
o.
100
200
D
D
300
i <> Ni
i
. o Cu
I
: !!. Pb
i xCo ·
i :.:Zn i
400 i o Cd
metal concentration (mg/L)
(b)
Figure 5 - Variation ofpH during the adsorption expcriments (a) fine bone char and (b) com·se bonc char
This reactions show that, depending on the total carbonate concenlralion and also ofpH, solid carbonales can be formed
in solution. As the bone char contains calcite that dissolves and release in solution carbonate ions, ii is expected that the
metal remova! mechanism from solution by bone char may bc thc association between adsorption and also precipit ation .
The carbonate concentration present in the solution was not enough to respond by the remova( of the metal only by
precipitation. Precipitation and adsorplion are complementary processes (Madeira et ai. , 2005). However the extension
of each phenomena is not known which thus suggest that the remova( mechanism still deserves additional investigation.
433
XXII ENTMME I VII MSHMT- Ouro Preto-MG, novembro 2007.
3.3 Column Experiments
The industrial effluent under investigation, pH 6,8, eontains 347 mg/L of Zn, 12,3 mg/L of eadmium and 0,7 mg!L of
lcad. The sulphate eonccntration is 7,9 g/L. Thc cnvironmental standard for dischargc of cftluents in watcr is 5 mg/L for
Zn, 0,1 mg/L for both Cd and Pb (DN I 0/86 COPAM-MG). Figure 7 prcscnts the mpturc curve for cadmium and zinc.
Alllcad was removcd (Final concentration was lower than the detection Iimit ofthc spectrometer, equal to 0,001 mg/L).
lt is obscrvcd that zinc is prcfcrcntially rcrnovcd, sincc thc rupturc for cadmium occutTed first, despitc zinc continued to
be rcmoved.
0.8
o 0.6
u
0.4
0.2
•
o o
u
o
IIJ
------T•
o.
o
••
•o •o •o •o o o
o
~
l
-------,
10
20
40
30
Residence time (min)
Figure 6 - Rupture curve for cadmium and zinc in column experiments.
3.4 Desorption
Fine and coarsc bonc char werc loaded with zinc in ordcr to verify thc desorption step, needed to regenerate the carbon
in an industrial process. lt was obtained a fine charcoal with 9,9 mg Zn!g charcoal and a coarse eharcoal loaded with
8. 9 rng/g charcoal. Figure 7 prcscnts thc desoqJtion curves obtained with distilled water of pH 5.4 and sulphuric acid
solution of pH 2.0. Thc final pH with distilled watcr was 7.5 for both charcoal and for sulphuric acid solution, pH was
cqual to 5.5 for fine charcoal and 3.5 for coarsc charcoal. lt is obscrved that dcscrtion with distilled water was not
effcctive and a solution containing l mg/L of zinc was obtained for both charcoal, representing only 1% of desorption.
1.2
1.2
-...J
• • •
1
ê>
.§. 0.8
•
•
0::
,g o.6
-
0.4
0::
o
u 02
••
•
•
0.6
'E
1!
•
0.4
•
0::
8
0.2
50
100
150
200
••
o+----~-­
o.-·-·------~--------,------------~----~----~
o
•
0::
fo
~
~
o
250
---~~--~
50
100
250
50.0
35.0
45.0
30.0
::;-
25.0
•
40.0
Ch 35.0
.s 30.0
~ 200
~
..., 25
]!:
.o
15.0
:ii
20.0
~ 100
u
u
"E
200
(b) eom·sc charcoaL distillcd water ofpH=5.4
(a) fine charcoal, distillcd watcr ofpH=5.4
.s
150
Time (min)
Time (min)
~
• • •
•
1
...J
ê>
.§. 0.8
~
8 150
5.0
10.0
5.0
0.0 +---~---~---------~-
00
50
100
150
200
250
300
Time (mln)
50
100
150
200
250
300
Time (min)
L __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
(c) fine charcoal, sulphuric acid solution of pH = 2,0
(d) coarsc charcoal, sulphuric acid solution ofpH = 2,0
Figure 7- Dcsorption curves for bone char loaded with zmc as a function oftirne
434
Thiago Santos Guedes, Marcelo Borges Mansur and Sônia Denise FctTcira Rocha
Probably, thc zinc rcleased to water was not adsorbcd but only adhcrcd to thc surface ofthc bone char. Whcn desorption
was catTicd out with the sulphuric acid solution, the metal conccntration initially incrcascs, thus reaching high valucs,
and then decreases, being this phenomena most pronounced for thc fine bone char. This can be attributcd to the
precipitation of part of the metal dcsorbcd, dueto thc dissolution of residual carbonate prcscnt in thc bonc char. This is
coherent with the final pH values measured in solution, cqual to 5.5 for fine bonc char and 3.5 for coarsc charcoal. Thc
levei of dcsorption was 30% for fine charcoal and 40% for coarse charcoal.
4. CONCLUSIONS
lt was observcd that the Brazilian bonc char is similar to the importcd bonc char with similar bchavior in thc remova! of
metais from solutions. The adsorption of zinc, cadmium, nickel, cobalt and coppcr was studicd and the Langmuir and
Frcundlich models were similar in rcpresenting the systcms. Fine bone char prescntcd highcr loading capacity, but
desorption from coarse bone char was better. The mechanism of metal remova! seems to involve an association of
carbonatcs precipitation and adsorption, but still descrves investigation. An industrial application requires additional
studies in order to determine the cost of the process. It was observed a competition between metais whcn the process
was catTied out in column.
5. REFERENCES
Aklil, A.; Mouflih, M.; Sebti, S. Remova! of metal ions from watcr by using calcincd as a new adsorbent. Journa/ of
Hazardous Materiais, 2004.
Cheung, C. W.; Choy, K.K.H .; Ko, D.C.K. ; McKay, G.; P011er, J. F. S01vtion equilibria of metal ions on bone char.
Chemosphere 54, p.273-281, 2004.
Cheung, C. \V.; McKay, G.; Porter, J. F. Sorption kinetics for the remova! of copper and zinc from cftluents using bone
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ACKNOWLEDGEMENTS
Authors are grateful to Bonechar- Carvão Ativado do Brasil and also to FAPEMIG- Fundação do Amparo à Pesquisa do
Estado de Minas Gerais for the financial suppot1.