Download Application of brass scrubber filter with copper hydroxide

Environ. Eng. Res. 2015; 20(2): 000-000
http://dx.doi.org/10.4491/eer.2014.062
pISSN 1226-1025
eISSN 2005-968X
Short Communication
Application of brass scrubber filter with copper hydroxide
nanocomposite structure for phosphate removal
Ki-Ho Hong1, In-Sang Yoo2,3, Sae-Hoon Kim3, Duk Chang4, Young Sunwoo4, Dae-Gun Kim2
†
1
Division of Interdisciplinary Studies, Konkuk University, Seoul 143-701, Korea
2
Green Energy and Environment Laboratory (GE ), Yeongwol-gun 230-884, Korea
3
Department of Ceramic Engineering, Gangneung-Wonju National University, Gangneung 210-702, Korea
4
Department of Environmental Engineering, Konkuk University, Seoul 143-701, Korea
2
ABSTRACT
In this study, a novel phosphorus removal filter made of brass scrubber with higher porosity of over 96% was fabricated and evaluated. The
brass scrubber was surface-modified to form copper hydroxide on the surface of the brass, which could be a phosphate removal filter for advanced
wastewater treatment because the phosphates could be removed by the ion exchange with hydroxyl ions of copper hydroxide. The evaluation
of phosphate removal was performed under the conditions of the batch type in wastewater and continuous type through filters. Filter recycling
was also evaluated with retreatment of the surface modification process. The phosphate was rapidly removed within a very shorter contact
time by the surface-modified brass scrubber filter, and the phosphate mass of 1.57 mg was removed per gram of the filter. The possibility
of this surface-modified brass scrubber filter for phosphorus removal was shown without undesirable sludge production of existing chemical
phosphorus removal techniques, and we feel that it would be very meaningful as a new wastewater treatment.
Keywords: Brass scrubber, Copper hydroxide, Nanocomposite, Phosphate removal, Surface modification
1. Introduction
The biological phosphorus removal process requires a highly efficient secondary clarifier and maintenance of sufficient organics
concentration. In addition, the main disadvantages in chemical
precipitation are higher maintenance cost, problems associated
with the handling of chemicals, and the disposal of large amounts
of produced sludge. The common and inherent limitation of these
two methods is that neither of them can produce an effluent containing less than 0.5 mg/L as P [11, 12].
Therefore, ion exchange and adsorption methods can be a good
candidate for phosphorus removal, which is defined as the displacement of one ion by another. To overcome the disadvantages of
biological nutrient removal and chemical precipitation methods,
an ion exchange and adsorption techniques which are cost effective,
easily performed, offers limited sludge production, and has the
potential for retained phosphate recycling are needed to remove
the phosphate effectively. Concerning phosphate removal through
an ion exchange and adsorption method, the use of a filter is
more desirable than is an adsorbent. If one is able to selectively
remove the phosphorus and to repeatedly use a recycle treatment,
it can be a very effective method for advanced wastewater treatment
because chemical sludges will not occur and the removed phospho-
Wastewater is relatively rich in phosphorus compounds, and the
phosphorus is a nutrient used by organisms for growth. Phosphates
come from a variety of sources including agricultural fertilizers,
domestic wastewater, detergents, industrial process wastes and
geological formations. Phosphates are classified as orthophosphates, polyphosphates and organic phosphates [1, 2]. The discharge of wastewater containing phosphorus may cause algae
growth in quantities sufficient to cause taste and odor problems
in drinking water supplies [3-5]. Phosphorus can also interfere
with coagulation and with lime soda softening [6]. Dead and decaying algae can cause oxygen depletion problems which in turn
can kill fish and other aquatic organisms in streams. For this
reason, phosphorus removal is an essential role of wastewater
treatment plants and testing for phosphorus in the plant effluent
is critical [7].
Biological nutrient removal and chemical precipitation are the
most commonly used methods for removal of phosphates in wastewater [8-10], whereas both methods have certain disadvantages.
Received September 13, 2014 Accepted May 19, 2015
This is an Open Access article distributed under the terms
of the Creative Commons Attribution Non-Commercial License
(http://creativecommons. org/ licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any
medium, provided the original work is properly cited.
† Corresponding author
Email: [email protected]
Tel: +82-10-9436-4292 Fax: +82-2-2201-6392
Copyright © 2015 Korean Society of Environmental Engineers
1
K. H. Hong et al.
rus can be a useful element as a resource. In addition, there will
be no requirement for a large area to set-up a wastewater treatment
system. There are other major advantages: low energy consumption,
easy upgrading of existing facilities, continuous separation, better
effluent quality, and avoidance of any chemical addition. Although
there are many kinds of adsorbents for phosphate removal such
as activated alumina treated with aluminium sulfate, boehmite,
goethite, akaganeite, yttrium carbonate, and polymeric ligand exchanger [13-18], an additional collection process after the phosphate adsorption should be considered. The recycling requirements
for these adsorbents should also be addressed.
In our previous research [19], a sintered porous aluminium
filter covered by Al(OH)3 through surface modification by alkali
treatment and stabilization process was designed for phosphorus
removal. Phosphorus in artificial wastewater was removed by ion
exchange mechanism from aluminium hydroxide to aluminium
phosphate (AlPO4). However, the filter had limitations such as
low porosity resulting in severely lower permeability and application of very small amount of artificial wastewater.
In this research, thus, a phosphorus removal filter was fabricated
by using a brass scrubber with higher porosity. The brass scrubber
was surface-modified to form copper hydroxide (Cu(OH)2) on the
surface of the brass, which acts as a phosphate removal filter
for advanced wastewater treatment because phosphate ions may
be removed by the ion exchange with hydroxyl ions of copper
hydroxide. The evaluation of phosphate removal was performed
under conditions of an immersion state of the filters in wastewater
and a flowing state through filters. Filter recycling was also evaluated with retreatment of the surface modification process.
Fig. 1. Brass scrubber filter with flexible porous structure.
2.2. Methods
2.2.1. Batch type experiments using synthetic wastewater
For the evaluation of phosphorus removal by batch type experiments under conditions of various concentrations, synthetic wastewaters with phosphate concentrations of 5 mg/L and 50 mg/L
were used. The surface-modified brass scrubber filters, with a
weight of 35 g, were immersed in each batch reactor filled with
synthetic wastewater of 2 L, and the phosphate concentration
in the wastewater was measured at an interval of 10 minutes
for 1 hour.
2.2.2. Continuous flow type experiments using synthetic wastewater
Samples with lower phosphate concentrations of 5 mg/L and 10
mg/L, similar to that of typical wastewater, were used in the continuous flow type experiments. The surface-modified brass scrubber filters were stacked in an acryl tube with a diameter of 30
mm, and the wastewater was consecutively sent through the filter
stack in the tube. After filtering the wastewater, the brass scrubbers
were re-treated by alkali solution using the same method and
then filtering was performed once again.
2. Materials and Methods
2.1. Material
The brass scrubber filter with an average weight of 35 g for each
has a flexible porous structure entangled by the coil with a thickness of 40 μm and width of 1 mm, as shown in Fig. 1. This
is chemically surface-modified to form a functional surface for
the preparation of a phosphorus removal filter. The surface modification process composed of three step, surface oxidation, alkali-treatment, and stabilization, was applied to form the micro-porous surface [20].
The oxidation of the copper surface was performed by boiling
in hydrogen peroxide solution of 34% for 30 minutes. The alkali-treatment was subsequently performed by boiling in sodium
hydroxide solution of 10 mM for 2 hours. The alkali-treated body
was then immersed in boiling distilled water for 30 minutes to
stabilize the surface layer after the alkali-treatment. For the recycle
of brass scrubber filter, it was re-treated by alkali solution by
the same method. The microstructure of the brass scrubber filter
was evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
Three types of experiments were performed for the evaluation
of phosphorus removal performance. The measurement of phosphate was conducted using the ascorbic acid method in the
American public health association (APHA) standard methods [21].
2.2.3. Batch type experiments with typical wastewater
For the performance evaluation of phosphorus removal in typical
wastewater, samples with phosphate concentration of 7.3 mg/L
were collected from the end of a grit chamber in a small sized
wastewater treatment plant in Korea. The biochemical oxygen
demand (BOD), total nitrogen (TN) and total phosphorus (TP)
of the raw municipal wastewater ranged 110-190 mg/L (average
155 mg/L), 28.0-39.5 mg/L (average 35.5 mg/L), and 2.7-8.2 mg/L
(average 7.3 mg/L), respectively. Experimental procedure was performed in the same manner with the batch type experiments using
synthetic wastewater as mentioned above.
3. Results and Discussion
Ion exchange, which is defined as the displacement of one ion
by another, can be a good candidate for phosphorus removal in
wastewater. The displaced ion is originally a part of the insoluble
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Environmental Engineering Research 20(2) 41-50
a
b
c
Fig. 2. Scanning electron micrographs (SEM) of the surfaces of brass (a), that treated by H2O2 (b), and the phosphate removal filter (c).
material and the displacing ion is originally in the soluble
material. The ion exchange reactions are governed by equilibrium, so that effluents from ion exchange processes never
yield pure water. In case of anions, the displacement preferential
-2
-2
order for ion exchange can be arranged as follows: SO4 , CrO4 ,
-3
-3
-2
NO3 , AsO4 , PO4 , MoO4 , I , Br , Cl , F , and OH [22]. That
is, former anions in this sequence can displace the ions coming
after them. Thus, the phosphate ion can replace the hydroxide
ion which can be formed on the surface of filter. As discussed
in a previous study [19], a phosphate removal filter was suggested
using porous aluminum, surface-modified to form aluminum
hydroxide on the surface. The chemical surface modification
treatment gave a unique structure on the surface inducing metal
hydroxide.
In this study, the brass scrubber with extremely higher porosity
of over 96% was employed for higher permeability. Generally,
a highly permeable filter does not guarantee higher filtration
efficiency. However, a nanoporous structure on the filter surface
revised in this study increases specific surface area which leads
to enhanced filtration efficiency.
Fig. 2 shows the surface morphologies of (a) brass, (b) oxidized
brass and (c) surface-modified brass. The surface of brass is very
smooth. Then, the brass surface was oxidized and became rough
by H2O2 treatment as depicted in Fig. 2(b), in which it looks like
irregular particulates of several nanometers covered the surface
with nanoporous morphology. When the brass was treated in boiling H2O2, oxidation of Cu (Cu+H2O2→CuO+H2O) took place, and
then alkali treatment resulted in the reaction of CuO with NaOH
as CuO+2NaOH→Na2[Cu(OH)2]. Soluble Na2[Cu(OH)2] salt on the
surface is transformed into Cu(OH)2 in the boiling water;
Na2[Cu(OH)2]+H2O→Cu(OH)2+2NaOH+H2O. At this point, Cu2+
prefers a square planar coordination with OH , and this leads
to an extended chain that can be connected with each other forming
a two-dimensional (2D) structure. Finally, the 2D layers are stacked
through the relatively weak hydrogen bond interactions, become
a three-dimensional (3D) crystal [23]. This self-assembly can give
Cu(OH)2 nanowhiskers. Fig. 2(c) presents the surface morphology
of completely treated brass. The copper hydroxide nanowhiskers
are grown with a very narrow width of around 20 nm to 100
nm. The nanowhiskers are shaped like corals. This surface structure
of the nanowhiskers distribution typically increases the specific
surface area by several times.
a
b
c
Fig. 3. Transmission electron micrographs (TEM) for the cross-sectioned
surface of the phosphate filter; high magnification (a), low magnification
(b) and (c).
Fig. 3(a) shows the cross-sectional TEM micrograph of the surface
of phosphate filter covered by copper hydroxide. The nanowhiskers
of copper hydroxide were grown on the flat surface of brass with
a porous structure of which thickness was over 1μm. Near the
surface, large nanowhiskers of 200 nm length were grown in a
vertical direction to the brass surface, while the small whisker
particles aggregated forming a network on the large nanowhiskers
which were observed from an overhead view of the filter surface
as presented in Fig. 2(c). Fig. 3(b) shows several large nanowhiskers
near the brass surface. Their shape looks like a single crystal
but several grains are observed in the large whiskers. However,
the small whiskers on the large ones were single crystal grains
and they were mutually coagulated. Fig. 3(c) presents a high magni-
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K. H. Hong et al.
fication micrograph of the end of a nanowhisker in which the
lattice fringe is observed in the vertical direction to the longitudinal
direction of the nanowhisker. Such a lattice fringe is revealed
to be with 0.2616 nm distance and the longitudinal direction of
the nanowhisker is the z direction of orthorhombic copper
hydroxide.
The copper hydroxide nanowhiskers formed on the brass surface
have many pores so that the surface area is extremely increased.
These nanoporous surfaces of Cu(OH)2 supplies a large number
of sites for ion exchange with phosphates. The brass coil macroporous structure has a higher permeability, and such nanoporous
surfaces of Cu(OH)2 should have advanced filtration efficiency.
Fig. 4 shows the phosphate removal characteristics of the filter
for when it was immersed in the synthetic wastewaters with phosphate concentrations of 50 mg/L and 5 mg/L, as mentioned regarding
the first batch type experimental procedure. The phosphate concentration of 50 mg/L dramatically decreased to around 23 mg/L during
the first 10 minutes, and then instantly saturated, as shown in
Fig. 4(a). The phosphate concentration decreased to around 2 mg/L
during the first 10 minutes when the filter was immersed in wastewater with the lower concentrations of 5 mg/L, and it decreased
very slowly to about 1 mg/L at 60 minutes as illustrated in Fig.
4(b). The ion exchange site of Cu(OH)2 on the filter surface can
easily meet the phosphate ions in wastewater with higher concentrations so that the surface of the filter can change almost completely
from Cu(OH)2 to Cu3(PO4)2. Whereas, the phosphate in wastewater
with lower concentrations is pressed to find ‘vacant’ Cu(OH)2 sites
between previously ion-exchanged Cu3(PO4)2 parts for absorption
onto the filter surface. This means that the filtration of wastewater
with lower phosphate concentration should require more sufficient
contact time for higher removal of phosphate in wastewater.
Fig. 5 and Fig. 6 show the results of the continuous flow type
experiments, as mentioned regarding the second experimental
procedure. The synthetic wastewaters with phosphate concentrations of 5 mg/L and 10 mg/L were passed through the acryl
tube stacked with surface-modified brass scrubber filters for only
several seconds. After the first flowing experiments, filters retreated
by alkali solution were used for the saturation evaluation of the
filter.
As shown in Fig. 5(a), the phosphate concentration rapidly
decreased during the first filtering of 1 L, whereas the concentration
gradually increased due to saturation of the filter later. When
the wastewater of 20 L with a concentration of 5 mg/L was filtered,
about 40 mg of phosphate mass was removed, and the removed
a
b
Fig. 4. Change of phosphate concentration and removed phosphate mass when the phosphate filter is immersed in the synthetic wastewaters
with concentrations of 50 mg/L (a) and 5 mg/L (b).
a
b
Fig. 5. Change of phosphate concentration (a) and removed phosphate mass (b) when the synthetic wastewater with concentrations of 5 mg/L
is passed through the phosphate removal filters.
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Environmental Engineering Research 20(2) 41-50
a
b
Fig. 6. Change of phosphate concentration (a) and removed phosphate (b) when the synthetic wastewater with concentrations of 10 mg/L is
passed through the phosphate removal filters.
amount of phosphate was about 40%. The removal also showed
similar tendency for the wastewater with a concentration of
10 mg/L. However, rapid saturation was observed and the removed amount of phosphate decreased to about 25% due to
the relatively higher phosphate concentration. For both cases,
the filtering characteristics were maintained after recycling of
used filters.
Fig. 7 shows the phosphate removal characteristics of the filter
on a typical wastewater of 10 L with a concentration of about
7 mg/L. For this experiment, wastewater was collected from the
end of a grit chamber in a small sized wastewater treatment plant.
At the initial filtering, the phosphate concentration decreased to
about 2.5 mg/L and gradually increased due to saturation of the
filter as with the case of the synthetic wastewater. After filtration,
the phosphate concentration was about 4 mg/L and the removal
amount of phosphate was over 50%.
Therefore, this filter was very effective in removing phosphate
ions from typical wastewater as well as from the synthetic ones,
which is a meaningful result, having done so without additional
phosphate treatments. The phosphate has various states in typical
wastewater, different from synthetic wastewater. The phosphate
filtering by ion exchange can be an applicable method for
phosphorus removal process because small wastewater treatment
facilities generally do not have counter measures for that. The
phosphate filtering system can be easily added to a small wastewater
treatment facility without change to the original set-up. Also,
recycling of used filters was very simple and the extracted
phosphate ions could be applied as an industrial resource for
synthesis of phosphate compounds.
4. Conclusions
In this study, the possibility of fabricating and recycling a brass
scrubber filter through surface modification for phosphate removal
was evaluated. The brass scrubber filter was surface-modified to
form copper hydroxide on the surface of the brass, which acted
as a phosphate removal filter for advanced wastewater treatment
because phosphate ions could be removed by the ion exchange
with hydroxyl ions of copper hydroxide. The phosphate was rapidly
removed within a very shorter contact time by the surface-modified
brass scrubber filter, and the phosphate mass of about 1.6 mg
was removed per gram of the filter.
The results showed the possibility of this phosphorus removal
without undesirable sludge production of existing chemical phosphorus removal techniques. This surface-modified silica filter
could be an alternative option for phosphorus removal in
small-scale wastewater treatments facilities suffering from unbalanced influent with relatively higher concentration of phosphorus than other components.
Acknowledgements
Fig. 7. Change of phosphate concentration and removed phosphate
when typical wastewater of about 7 mg/L concentration is passed through
the phosphate removal filters.
This subject is supported by the Korea Research Foundation Grant
funded by the Korean Government (MOEHRD)"(KRF-2006511-D00181).
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K. H. Hong et al.
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