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BADMUS et al 2007 Removal of Heavy Metal from Industrial Wastewater using Hydrogen Peroxide

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BADMUS et al 2007 Removal of Heavy Metal from Industrial Wastewater using Hydrogen Peroxide
African Journal of Biotechnology Vol. 6 (3), pp. 238-242, 5 February, 2007
Available online at http://www.academicjournals.org/AJB
ISSN 1684–5315 © 2007 Academic Journals
Full Length Research Paper
Removal of heavy metal from industrial wastewater
using hydrogen peroxide
M.A.O. Badmus*, T.O.K. Audu and B.U. Anyata
Department of Chemical Engineering, University of Benin, Benin-City, Nigeria.
Accepted 17 November, 2006
The batch removal of heavy metals lead (Pb), zinc (Zn) and copper (Cu) from industrial wastewater
effluent under different experimental conditions using hydrogen peroxide was investigated.
Experimental results indicated that at pH 6.5, pre-treatment analysis gave the following values: Pb
57.63 mg/l, Zn 18.9 mg/l and Cu 13.9 mg/l. Removal of heavy metals was optimum at pH 7.6, a
o
temperature of 30 C, 1.5% hydrogen peroxide concentration and 60 min holding time, reducing the
amounts of Pb, Zn and Cu by 83.5, 85.5 and 82.23%, respectively.
Keywords: Alum, effluent, hydrogen peroxide.
INTRODUCTION
One of the main causes of industrial pollution is the
discharge of effluents containing heavy metals. Heavy
metals can have serious effects on human and animal
health. Beside the health effects, heavy metals are nonrenewable resources. Therefore, effective recovery of
heavy metals is as important as their removal from waste
streams.
Disposal of industrial wastewater has always been a
major environmental issue. Pollutants in industrial
wastewater are almost invariably so toxic that wastewater
has to be treated before its reuse or disposal in water
bodies. Industrial processes generate wastewater
containing heavy metal contaminants. Since most of
heavy metals are non-degradable into non-toxic end
products, their concentrations must be reduced to
acceptable levels before discharging them into
environment. Otherwise these could pose threats to
public health and/or affect the aesthetic quality of potable
water. According to World Health Organization (WHO)
the metals of most immediate concern are chromium,
zinc, iron, mercury and lead (WHO, 1984). Maximum
allowed limits for contaminants in “treated” wastewater
are enforced in developed and many developing
countries.
*Corresponding author. E-mail: [email protected]
The treatment of contaminated waters is as diverse
and complicated as the operation from which it comes. A
number of conventional treatment technologies have
been considered for treatment of wastewater contaminated with heavy metals. Previous investigations on the
removal of heavy metals from wastewater (Howari and
Garmoon, 2003; Shwarts and Ploethner, 1999; El-Awady
and Sami, 1997) suggest that systems containing calcium
in the form CaO or CaCO3 and carbonates in general, are
particularly effective in the removal of heavy metals from
wastewater. Some of the conventional techniques for
removal of metals from industrial wastewater include
chemical precipitation, adsorption, solvent extraction,
membrane separation, ion exchange, electrolytic
techniques, coagulation/flotation, sedimentation, filtration,
membrane process, biological process and chemical
reaction (Blanco et al., 1999; Blanchard et al., 1984;
Gloaguen and Morvan, 1997; Jeon et al., 2001; Kim et
al., 1998; Lee et al., 1998; Mofa, 1995; Lujan et al., 1994;
Gardea-Torresdey et al., 1996). Each method has its
merits and limitations in application. Similarly, hydrogen
peroxide (H2O2) has been used in different experiments
to improve supply and oxidation rate of suspended and
dissolved particles that cause pollution in such water
effluent (Bami, 1989; Muganlinskii and Adeyinka, 1987;
Adeyinka, 1996; Adeyinka and Rim-Rukeh, 1999; Chen
et al., 1996).
Badmus et al.
Great importance has been attached to the treatment
of industrial wastewater effluent since local and
international authorities require that wastewaters from
industries be treated and made to meet a set standard
before it is discharged into the water bodies. Chemical
treatment of industrial wastewater is preferable since
industrial wastewaters are frequently complex, high in
pollutant load and often containing materials toxic or
resistant to the organisms on which biological processes
depend. Also, chemical treatment systems are more
predictable and inherently more subject to control by
simple technique and chemicals are usually relatively
tolerant to temperature changes.
In the chemical treatment of wastewater, the use of
hydrogen peroxide has gained much popularity. H2O2 is a
powerful oxidizer that looks like water in its appearance,
chemical formula and reaction products. Despite its
power, it is a versatile oxidant which is both safe and
effective. It is one of the most powerful oxidizers known,
stronger than chlorine, chlorine dioxide, and potassium
permanganate, and through catalysis, H2O2 can be
converted into hydroxyl radical (OH ) with reactivity
second only to fluorine. However, a review of the
literature showed that very little investigation has been
conducted to find out the effects of certain factors that
contribute to H2O2 decomposition in the treatment of
wastewater. Such factors include temperature, pH, H2O2
dose, etc. Hence, the objective of this work is to
2+
investigate the effect of H2O2 activated with Cu on the
removal of heavy metal ions in industrial wastewater
effluent.
EXPERIMENTAL
Materials
Industrial effluent from a brewing industry in Nigeria was collected
at the point of discharge into the stream. Materials used for sample
collection were pretreated by washing the container with dilute
hydrochloric acid and rinsed with distilled water. The containers
were later dried in an oven for 1h at 110 ± 5oC and allowed to cool
to ambient temperature. At the collection point, containers were
rinsed with samples thrice and then filled with the sample, corked
tightly and taken to the laboratory for treatment and analysis. All
reagents used were of good analytical grade.
Wastewater sample preparation and analysis
10 ml of the wastewater sample was digested with 50 ml of conc.
HNO3 for 1 h. Thereafter, 40 ml of HCl was added at ratio 1:1 and
digested for about 2 h on a hot plate magnetic stirrer. 1 ml of dilute
HCl was further added to the sample and boiled for 1 h, filtered
while hot with Whatman No 4 filter paper, washed with HCl and the
volume made up to 100 ml with distilled water. The metals (Pb, Zn,
and Cu) were determined using Atomic Absorption Spectrophotometer (AAS) Model: Phillip PU 9100 × with a hollow cathode lamp
and a fuel rich flame (air acetylene). Sample was aspirated and the
mean signal response recorded at each of the elements waveleng-
239
th.
Wastewater treatment
Precipitation of metal ions: A sample of the wastewater was
divided into six portions of equal volumes (500 ml), labeled A1, A2,
A3, A4, A5, and A6. The first portion was further divided into five
equal volumes (100 ml), labeled A11, A12, A13, A14, and A15 and each
of the volume was treated with 50 ml of standard alum solution of
varying concentrations (10, 20, 30, 40 and 50 ml/l). This was done
to assess clarification and sedimentation by precipitation of
complex metal ions that can be formed as a result of cation
exchange reactions, especially Cu and Zn. Each of the five volumes
(chemical and samples) was mixed slowly using a mechanical
device for 30 min to create good sample-chemical contact. After
this, they were filtered individually through a bed of activated clay
and sodium ion exchange. The clarified effluents were collected
and pH, Cu2+, Pb2+ and Zn2+ were measured.
Study of the effect of H2O2 dose: The second experiment on the
sample was done by dividing the sample, A2 into five equal volumes
labeled A21, A22, A23, A24 and A25 and treating each of the samples
with alum concentration with maximum percentage removal in A1
with the addition of 50 ml of standard volume of H2O2 solution of
30% concentration. Each of the five portions of the sample was
then treated with the H2O2 (0.5, 1.0, 1.5, 2.0 and 2.5%) volume of
the effluent. The liquid content of sample-H2O2 mixture was agitated
for 30 min with a mechanical device for effective sample-chemical
contact after which it was filtered through a bed of activated clay
followed by sodium ion exchange. Clarified effluents were collected
and analysed for parameters as in above.
Study of contact time effect: The third portion of the effluent, A3
was divided into five equal volumes, A31, A32, A33, A34 and A35.
Using H2O2 concentration with maximum percentage removal in
treatment two above, the effect of contact time was determined by
keeping the concentration of H2O2 constant and agitating each of
the samples for 20, 40, 60, 80 and 100 min in order to ensure
effective sample-chemical contact. After this, the content was
filtered as in treatment one and the resulting clarified effluent was
analysed.
Study of temperature effect: The fourth portion of the effluent, A4
was also divided into five equal volumes A41, A42, A43, A44 and A45.
Using the H2O2 concentration in treatment two, time with maximum
percentage removal in treatment three, the samples were agitated
at various temperatures; 10, 20, 30, 40, and 50°C, respectively.
After this, the content was filtered as in treatment one and the
resulting clarified effluent was analysed.
Study of pH effect: A similar procedure was carried out for the fifth
portion of the sample, A51, A52, A53, A54, and A55 and using H2O2
concentration with maximum percentage removal in treatment two
and pH of 4, 6, 8, 10 and 12 , respectively, for each of the portions.
For effective effluent-chemical contact, the mixture was agitated
using the best contact time in treatment three. The content was
filtered as in treatment one and the resulting clarified effluent was
analysed.
Study of the effect H2O2 activated with CuSO4: The last portion
of the effluent, A6 was divided into five equal volumes, A61, A62, A63,
A64 and A65 respectively. Using H2O2 concentration with maximum
percentage removal in treatment two, the effect of H2O2 activated
with CuSO4 (15, 25, 35, 45 and 55 ml) on treatment method was
determined by using contact time with maximum percentage
removal in treatment three; temperature with maximum percentage
removal and pH in treatments four and five, respectively, and agitat-
240
Afr. J. Biotechnol.
ing each of the samples in order to ensure effective samplechemical contact. After this, the content was filtered and the
resulting clarified effluent was analysed.
35
30
Lead ion
25
Sample treatment was carried out using alum for
clarification while hydrogen peroxide and copper (II)
sulphate were used as treatment reagent. Interesting
results were obtained using H2O2 activated with CuSO4.
The physico-chemical analysis of the wastewater is
presented in Table 1.
Zinc ion
% R e d u c tio n
RESULTS AND DISCUSSION
Copper ion
20
15
10
5
0
0
Table 1. Characterization of the effluent wastewater.
pH
6.5
Pb
2+
Zn
2+
57.63
18.90
2+
13.90
Cu
1
1.5
2
2.5
3
Hydrogen peroxide (% v/v)
Concentration (mg/l)
Figure 2. Quality of effluents obtained from hydrogen peroxide and
treatment in a bed of activated clay.
35
25
Lead ion
20
% R e d u c tio n
Zinc ion
15
% R e d u ctio n
Parameter
0.5
Lead ion
30
Zinc ion
Copper ion
25
Copper ion
20
10
15
5
0
0
0
10
20
30
40
50
60
Alum conc. (mg/l)
Figure 1. Quality of effluents obtained from alum clarification and
treatment in bed of activated clay.
Analysis after precipitation of metal ions
Figure 1 depicts the result obtained from treatment one in
which the alum-clarified sample was passed through a
bed of activated clay and sodium-ion exchange. The
results are expressed in term of the percentages of metal
ion removal from the water sample. The sodium-ion
exchange was used in all the experiments to remove
alum traces that may be dissolved in the effluent during
clarification, as well as to remove other ions that may
cause impurities in the water (Adeyinka and Rim-Rukeh,
1999). Analyses of the effluent showed a reasonable red2+
uction of Pb from 57.63 to 46.58 mg/l (19.17% removal)
20
40
60
80
100
120
Figure 3. Effect of contact time on quality of effluents obtained.
2+
while Zn was reduced from 18.9 to 16.44 mg/l giving a
2+
13.02% removal. Cu was reduced from 13.90 mg/l to
11.81mg/l (15.04% removal).
Influence of hydrogen peroxide
Figure 2 shows the results of the influence of H2O2 dose
on wastewater effluents. Analysis of the treatment and
2+
the results showed a considerable reduction of Pb
(1.5% H2O2 conc.) from 57.63 to 41.05 mg/l (28.77%
2+
removal), while Zn was reduced from18.9 to 14.79 mg/l
2+
(21.75% removal). Cu was reduced from 13.9 to 10
mg/l (28.06% removal).
Influence of contact time
2+
2+
Figure 3 represents the percent removal of Pb , Zn and
2+
Cu at different contact times. The results showed that
Badmus et al.
241
2+
80
Pb removal was more than 31.51% at a contact time of
2+
2+
60 min, while Zn and Cu removal are 36.93 and
36.04% respectively.
70
% R ed u ctio n
Lead ion
60
Zinc ion
Influence of temperature
Copper ion
Figure 4 indicates the influence of temperature on the
2+
2+
2+
percent removal of Pb , Zn and Cu . It was observed
o
2+
that maximum removal occurred at the 30 C with Pb
2+
reduced from 57.63 to 15.79 mg/l (72.60%); Zn from
2+
18.9mg/l to 6.58 mg/l (65.19%) and Cu from 13.9 mg/l
to 5.14 mg/l (63.02%). This is due to the fact that
decomposition of H2O2 is favoured by increasing
temperature (Bishop, 1968). The reduction in percent
removal after this temperature may be possible due to
the abundance of OH ions causing increased hindrance
to diffusion of metal ions.
50
40
30
0
10
20
30
40
50
60
Temperure (oC)
Figure 4. Effect of temperature on quality of effluents obtained.
90
% Reduction
80
Lead ion
Zinc ion
70
Copper ion
60
50
40
2
4
6
8
10
12
14
pH
Fig 5. Effect of pH on quality of effluent obtained
Figure 5. Effect of pH on quality of effluent obtained.
90
% Reduction
80
Influence of pH
Figure 5 depicts the effect of pH on percent removal of
determined physico-chemical properties. The result
shows that maximum removal occurs at pH of 7.6, with
2+
Pb reduced from 57.63 to 12.69 mg/l (77.98% removal);
2+
Zn was reduced from 18.9 to 3.54 mg/l (81.27%) and
2+
Cu from 13.9 to 3.24 mg/l (76.70%). The result shows
that with the increase in the pH of the wastewater
sample, the extent of removal increases. But after pH 8,
there is a decrease in the removal of metal ions. This
decrease may be due to the formation of soluble hydroxyl
complexes. According to Baes and Mesmer (1973), as
the sample pH increases, the onset of the metal
hydrolysis and the precipitation began at pH > 6. The
hydrolysis of cations occurs by the replacement of metal
ligands in the inner co-ordination sphere with the hydroxyl
groups (Gau et al., 1985). This replacement occurs after
the removal of the outer hydration of metal cat ions. This
tremendous increase in percent reduction of metal ions
with increase in pH up to 8 is due to the fact that
decomposition of H2O2 is favoured by increasing pH
especially at pH 6 – 8 (Bishop, 1968).
Influence of Cu
70
Lead ion
Zinc ion
60
Copper ion
50
40
10
20
30
40
50
60
Copper sulphate (ml)
Figure 6. Effect of hydrogen peroxide activated with copper
sulphate on quality of effluent obtained.
2+
2+
Figure 6 represents the effect of Cu on treatment
method. It was observed that the extent of percent
2+
removal decreased with increasing concentration of Cu .
2+
Analysis of the result, showed that Cu (45 ml) activated
2+
H2O2 synergetically leading to Pb reduction from 57.63
to 9.47 mg/l (83.57%) with a correlation coefficient of
2+
0.8928, Zn from 18.9 to 2.74 mg/l (85.5%) with a corre2+
lation coefficient of 0.9323, whilst Cu was reduced from
13.9 to 2.47 mg/l (82.23%) with a correlation coefficient of
0.8774. This treatment showed improved effluents quality
242
Afr. J. Biotechnol.
and higher oxidative ability. Decomposition of H2O2 to
give H2O and O2 is highly favoured. Increasing
contamination especially with transition metals activates
(catalytic activity) the breaking down of H2O2 molecule to
H2O and O2. The results showed higher effectiveness
relative to other treatments formulated for the effluents
treatment.
Conclusion
In the present study, the removal of heavy metals, Pb, Zn
and Cu using H2O2 was found to be effective. The
process efficiency was enhanced by activating the H2O2
2+
with Cu , increasing the breaking down of H2O2 molecule
to H2O and O2. The results obtained show that hydrogen
peroxide can be used effectively in the removal of heavy
metal ions from industrial wastewaters.
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