close

Вход

Забыли?

вход по аккаунту

?

Removal of Ferriccyanide using Micellar Enhanced Ultrafiltration (MEUF).

код для вставкиСкачать
Dev. Chem. Eng. Mineral Process. 13(1/2), pp. 137-146, 2005.
Removal of Ferriccyanide using Micellar
Enhanced Ultrafiltration (MEUF)
K. Baek' and J.-W. Yang2*
'Department of Environmental Engineering, Kumoh National Institute
of Technology, 188, Shinppng-dong, Gumi, Gyeongbuk 730-701,
Republic of Korea
Environmental Remediation Engineering Laboratory, Department of
Chemical and Biomolecular Engineering, Korea Advanced Institute of
Science and Technology, 3 73-1 Gusong-dong, Yuseong-gu,
Daejeon 305-701, Republic of Korea
Cyanides are used in a number of chemical synthesis and metallurgical processes (as
simple salts or cyanide complexes). As a class, cyanides are highly toxic and must be
destroyed or removed fiom wastewaters prior to being discharged. Micellarenhanced ultrafiltration (MEUF) involves the addition of a surfactant above the
critical micellar concentration in order to entrap small solutes in solution. The
increased hydrodynamic size of the solutes enables their rejection by polymeric
ultrajiltration membranes. Solute rejection and permeate flux depend on solute and
membrane characteristics. MEUF-based separation of Fe(CN);- using regenerated
cellular acetate membranes was studied in order to assess the potential of MEUF for
the remediation of wastewater polluted with ferriccyanide. The solute rejection
coeflcient of ferriccyanide increasedfiom 59 % to 81% and to 99.9% as the molar
ratio of cetylpyridinium chloride to ferriccyanide increased from 1 to 2, and 2 to 3,
respectively, at a ferriccyanide concentration of 1 mM. The rejection coefficient of
ferriccyanide increasedfiom 78 % to 99.9 % as the molar ratio increasedfrom I to 3
at a ferriccyanide concentration of 5 mM. The permeation flux and permeation of
surfactant molecules across the membrane were evaluated in relation to the
experimental conditions.
* Authorfor correspondence fjhyang@kaist.ac.kr).
137
K. Baek and J. W Yang
Introduction
Various pollutants such as heavy metals, Cl., and surfactants are containel in the
wastewater generated from an electroplating process. Currently hydroxide
precipitation is one of the most widely used techniques to treat heavy metals [l].
However, the chemical precipitation method becomes ineffective for treatment of the
wastewater containing CN due to the formation of complexes between metals and
CN. A well-known method to treat CN is the alkaline chlorination technique which
oxidizes CN under alkaline conditions. Recently, electrooxidation of copper-cyanides
with a T f l t electrode was reported as a new method to treat wastewaters containing
cyanides [2].
I
CPC
I
B
Figure 1. Schematic diagram of MEUF for removal of ferriccyanide;
(A) the experimental apparatus; (B) the ultrafdtration cell.
138
Removal of Ferriccyanide using Micellar Enhanced Ultrafiltration (MEUF)
Micellar-Enhanced Ultrafiltration (MEUF) is a recently proposed method to treat
wastewaters containing heavy metals and toxic organic compounds [2-181. It
combines the high selectivity of reverse osmosis with the higher flow rate of
ultrafiltration. The underlying principle is to increase the size of the pollutant
molecules, so they can be removed as concentrated retentate when passed over a
membrane with an appropriate pore size. For removal of heavy metals, anionic
surfactants such as sodium dodecyl sulphate (SDS) were used. Cationic surfactants
such as cetylpyridinium chloride (CPC) and hexadecyltrimethylammonium bromide
were used for removal of anionic pollutants including nitrate and chromate [4- 181.
Cationic surfactant micelles can form complexes with micelle-femccyanide as
cationic micelle-nitrate or cationic micelle-chromate. The schematic diagram of
MEUF for removal of femccyanide with cationic surfactant is shown in Figure 1.
In this study, the characteristics of M E W were evaluated for CN-femc
complexes, a form of cyanide-metal complex. Removal efficiency and permeate flux
of ferriccyanide were investigated as a function of membrane materials, molar ratio of
ferriccyanide to surfactant, and concentration of pollutants in the feed solution.
Materials Used and Experimental Methods
The cetylpyridium chloride (CPC) obtained from Sigma chemicals was of 98% purity,
the ferriccyanide was also purchased from Sigma chemicals. Deionized water was
used in preparing all solutions. The ultrafiltration experiments were operated in a
batch stirred cell (Amicon 8400, Millipore, USA). The ultrafiltration membranes were
regenerated cellulose membrane and polysulfone with diameter 76 mm and effective
area 0.00454 m2 (Millipore, USA). The pore size of the membrane was 10,000
molecular weight cut-off (MWCO). The pressure was maintained at 4 bar gauge and
the temperature was held constant at 25°C.
The feed solution was prepared by mixing stoichiometric amounts of CPC and
ferriccyanide. The cell was initially filled with 100 ml of feed solution and
ultrafiltration proceeded until 50 ml had passed through the membrane. The
139
K.Baek and J.W Yang
concentrations of ferriccyanide and CPC of the permeate samples were analysed by
UV spectrophotometer (HP 8452, USA) at wavelengths of 418 nm and 258 nm,
respectively. The rejection (removal) efficiencies of ferriccyanide and CPC were
calculated from the following equation:
C
% R = (l-+xlOo
Cf
where C, is the feed concentration of ferriccyanide or CPC; and C, is the
concentration of ferriccyanide in the permeate.
Results and Discussion
It is known that the adsorption of ions into the ionic micelle is dependent upon the
surface properties of the micelle, the ionic size and the valence of the ion. It is
interesting that the content of femccyanide ion adsorbed can be influenced by the
micelle concentration and femccyanide concentration. The effect of varying
CPC/femccyanide molar concentration ratios on the CPC and ferriccyanide rejections
was investigated using a regenerated cellulose acetate membrane and a polysulfone
membrane. Different CPC/ferriccyanide molar concentration ratios in the feed
solutions were prepared by maintaining constant feed femccyanide concentration
(i.e. 1 mM) while changing the CPC concentration. The rejection of ferriccyanide as a
function of filtration time is shown in Figure 2, where the rejection of ferriccyanide
increased with increasing CPC/ferriccyanide molar ratio. It has been observed that at
all concentration ratios of CPUferriccyanide, the ferriccyanide rejection curves show
similar trends. It can be seen from Figure 2 that as the CPC concentration in the feed
solution increases, the steady-state rejection increases. Regardless of the ratio of
CPC/ferriccyanide, the rejection at all concentration ratios reached steady-state within
2 minutes.
Figures 3 and 4 illustrate the variation of the steady-state ferriccyanide rejection as
a function of ferriccyanide concentration and CPC/ferriccyanide molar concentration
I40
Removal of Ferriccyanide using Micellar Enhanced Ultrafiltration (MEUF)
ratio in the feed solutions, using a regenerated cellulose acetate membrane and a
polysulfone membrane, respectively. As shown in Figures 3 and 4, the rejection of
femccyanide sharply increased with a constant concentration of femccyanide in the
feed as the CPC/femccyanide concentration ratio increased, regardless of the
membrane material.
From Figure 3 using a regenerated cellulose acetate membrane, as the
ferriccyanide concentration in the feed increased from 1 mM to 5 mM, the rejection of
femccyanide gradually decreased until it was saturated at 3 mM of ferriccyanide, for
molar ratio of CPC/femccyanide at 1:1. At the molar ratio of 2: 1, the rejection was
saturated at 2 mh4 of femccyanide concentration. With the ratio of 3:1, there are no
significant changes in the rejection of femccyanide.
-5
cu
80-5
m m
m
m
@
0
C
0
8
.-
P
6 0 - m o a Q o o
Q
L
P
c
0
0
.e
0
cu
'3
fx
0
40
.
0
0
20 -
A
0
5
10
molar ratio of CPC lo cyanide 1
molar ratio of CPC lo cyanide ' 2
molar rauo of CPC lo cyanide 3
15
20
25
30
Duration of filtration (min)
Figure 2. Eme offrriccyanide rejection as a function
of CPCflerriccyanide molar concentration ratio;
initial concentration of ferriccyanide was I mM;
regenerated cellulose acetate membrane was used for
filtration with 4 bar pressure.
141
K.Baek and J. H! Yang
100
h
5
80-
Q,
eC
m
x
60 -
0
.&!E"
Y-
O
c
40
0
.c
.
'F
a
-
20 -
-e-a--P-
0
0
1
2
CPC : ferriccyanide = 1:l
CPC : ferriccyanide = 2 : l
CPC : ferriccyanide = 3:l
I
I
1
3
4
5
Conc. of ferriccyanide in the feed (mM)
Figure 3. Efects of CPCflerriccyanide molar concentration
ratio as a function of ferriccyanide concentration in the feed
for the regenerated cellulose acetate membrane.
For the polysulfone membrane results in Figure 4,significant differences were not
observed for different the ferriccyanide concentrations in the feed. However, the
rejection of ferriccyanide for the polysulfone membrane with a molar ratio of 1: I and
2: 1 were lower than those for the regenerated cellulose acetate membrane. Therefore,
the performance of MEUF for femccyanide depends on the membrane material when
a low concentration of CPC is used. With a CPC/ferriccyanide concentration ratio of
3:1, the rejection of ferriccyanide exceeded 99.9% regardless of the ferriccyanide
concentration in the feed or the membrane material.
Figures 5 and 6 show the variation of the steady-state CPC rejection as a function
of ferriccyanide concentration and CPC/ferriccyanide molar concentration ratio in the
feed solutions, using the regenerated cellulose acetate membrane and the polysulfone
membrane, respectively. As shown, the trends for the rejection of CPC were similar to
I42
Removal of Ferriccyanide using Micellar Enhanced Ultrafiltration (MEUF)
t
-
0
h
loo
I
2o
0 '
0
-e-e--a-
I
2
3
C P C : ferriccyanide
C P C : ferriccyanide
C P C : ferriccyanide
= 1:l
= 2:l
=3 1
4
5
C o n c . of ferriccyanide in the f e e d (m M )
Figure 4. Effects of CPCflerriccyanide molar concentration
ratio as a function of ferriccyanide concentration in the feed
for the polysulfone membrane.
those for femccyanide. In general, the rejection of surfactants in the MEUF process
depends on the surfactant concentration in the feed [5-12, 17-18]. However, the
rejection of CPC in t h s MEUF process was a function of CPC/femccyanide molar
concentration ratio rather than CPC concentration in the feed. With a
CPC/ferriccyanide concentration ratio of 3: 1, the rejection of CPC was greater than
99.9 % regardless of the ferriccyanide and CPC concentrations in the feed.
Conclusions
MEUF for removal of femccyanide from wastewater is an effective method. Rejection
of femccyanide reached steady-state within 2 minutes. With a CPUferriccyanide
concentration ratio of 3:1, the rejection of femccyanide increased above 99.9%
irrespective of concentration of femccyanide in the feed. Rejection of CPC was a
fbnction of CPC/ferriccyanide concentration ratio, and exceeded 99.9% at similar
conditions.
143
K.Baek and J.W Yang
-
100
8
60 -
60-
.c
0
s
-
40
'F
-
K
2o
t
%-
CPC
CPC
ferriccyanlde
ferriccyanide
=2 1
=31
0
3
0
6
9
12
15
Conc. o f CPC in the feed ( m M )
Figure
5.
Efects
of
CPCflerriccyanide
molar
concentration ratio as a function of CPC concentration
in the feed for the regenerated cellulose acetate
membrane.
loo
2o
i
.
-
t
-6-
A
0
Figure
3
6.
8
C P C : lerrlccyanide =
C P C : lerriccyanide =
9
C o n c . of
C P C in
Efects
of
12
2 1
3:l
15
the f e e d ( m M )
CPCJerriccyanide
molar
concentration ratio as a function of CPC concentration in
the feed for the polysulfone membrane.
144
Removal of Ferriccyanide using Micellar Enhanced Ultraflltration (MEUF)
Acknowledgments
This work was supported financially by a grant (Ml-0203-00-0001) from the Korean
Ministry of Science and Technoiogy through the National Research Laboratory
program.
References
1. Szpyrkowicz, L., Zillio-Grandi, F., Kaul, S.N.,and Polcaro, A.M. 2000. Copper electro-deposition and
oxidation of complex cyanide from wastewater in an electrochemical reactor with a Ti/& anode. Ind.
Eng. Chem. Res., 39,2132-2139.
2.
Lee, K.-W., Cho, S.-H.,and Park, S.-W. 1995. Studies on the treatment of wastewater bearing cyanide
and heavy metals by micelle enhanced ultrafiltration technique. J. Envirun. Sci. Health, A 30(3), 467484.
3. Ahmadi, S., Tseng, L.K., Batchelor, B., and Koseoglu, S.S. 1994. Micellar-enhanced ultrafiltration of
heavy-metals using lecithin. Sep. Sci. Technol., 29,2435-2450.
4. Morel, G, Graciaa, A., and Lachaise, J. 1991. Enhanced nitrate ultrafiltration by cationic surfactant. J.
Membrane. Sci., 56, 1-12.
and Yang, J.-W. 2003a. Removal characteristics of anionic metals by
5 . Baek, K., Kim, B.-K., Cho, H.-J.,
micellar-enhanced ultrafiltration. J. Hazard. Muter., 99,303-3 11.
6. Baek, K., Kim, B.-K., and Yang, J.-W. 2003b. Application of micellar-enhanced ultrafiltration for
nutrients removal. Desalinalion, 156, 137-144.
7. Baek, K., Kim, B.-K., and Yang, J.-W. 2004. Removal of phosphorous using micellar-enhanced
ultrafiltration with cationic surfactant: Effects of surrounding pH. Fresen. Environ. Bull., 13, 105-1 11.
8. Baek, K., Lee, H . 4 , and Yang, J.-W. 2003c. Micellar-enhanced ultrafiltration for simultaneous
removal of femccyanide and nitrate. Desalination, 158, 157-166.
9. Baek, K., and Yang, J.-W. 2004a. Cross-flow micellar-enhanced ultrafiltration for removal of chromate
and nitrate. J. Hazard. Muter, 108,119-123.
10. Baek, K., and Yang, J.-W. 2004b. Effect of valences on removal of anionic pollutants using micellarenhanced ultrafiltration. Desalination, 167, 119-125.
11. Baek, K., and Yang, J.-W. 2004c. Micellar-enhanced ultrafiltration of chromate and nitrate: binding
competition between chromate and nitrate. Desalination, 167, 111-1 18.
12. Baek, K., and Yang, J.-W. 2004d. Competitive bind of anionic metals with cetylpyridinium chloride
micelle in micellar-enhanced ultrafiltration. Desalination, 167, 101-1 10.
13. Baek, K., and Yang, J.-W. 2004e. Removal of iron-cyanide complexes using micellarenhanced
ultrafiltration. European J. Mineral Process. Environ. frol.. in press.
145
K.Baek and J. W Yang
14. Keskinler, B., Danis, U., Cakici, A,, and Akay, G 1997. Chromate removal from water using
surfactant-enhancedcrossflow filtration.Sep. Sci. Techno/.,32(1 l), 1899-1920.
15. Danis, U., and Keskinler, B. 2002. Use of Micellar-enhanced ultrafiltration to remove chromate from
aqueous streams, Fresen. Envimn. Bull., 11( 6), 300-305.
16. Scamehom, J.F., Christian, S.D., El-Sayed, D.A., Uchiyama, H., and Younis, S.S. 1994. Removal of
divalent metal cations and their mixtures from aqueous streams using micellar-enhanced ultrafiltration,
Sep. Sci. Techno/.,29,809-830.
17. Akay, G, and Wakeman, R.J. 1994. Crossflow microfiltration behaviour of a double-chain cationic
surfactant dispersion in water. I. The effect of process and membrane characteristics on permeate flux
and surfactant rejection, Chem. Eng. Sci..49,271-283.
18. Yildiz. E., Pekdemir, T., Keskinler, B., Cakici, A., and Akay, G 1996. Surfactant-mediated separation
processes: Surfactant-enhanced crossflow filtration in nitrate removal from water, Trans. IChemE, 74,
Part A, 546-553.
I46
Документ
Категория
Без категории
Просмотров
1
Размер файла
351 Кб
Теги
ultrafiltration, using, removal, meuf, ferriccyanide, enhance, micellar
1/--страниц
Пожаловаться на содержимое документа