BIOSORPTION OF Zn2+ WITH Nannochloropsis salina
Yusafir Halaa), M. Syahrula), Emma Suryatib), Paulina Tabaa)
a)Faculty
of Mathematic and Natural Sciences Hasanuddin University, Makassar, Indonesia
Email: yusafirhala@yahoo.co.in
b)Research Institute for Coastal Aquaculture, Maros, Indonesia
Email: emmasuryati@yahoo.com
ABSTRACT
The research was conducted to solve the problem of Zn 2+ ion pollution in the waters. Zn2+
ion is one of pollutants mostly caused by erosion and mining activities. The research used marine
microalgae, Nannochloropsis salina to adsorb Zn2+ ions in the aqueous solution. Many ways have
been done to remove heavy metal ions from water. However, the reason for using N. salina is as
follows: the cost for the method is low, the existence of N. Salina in the environment is abundance,
and the living cycle of N. salina is relatively short. Addition of various concentration of Zn2+ ion in the
Conwy medium with the salinity of 25 %o was conducted at the 8th day, i.e. at the time when the
optimum growth was achieved. Observation of N. salina growth after addition of Zn2+ ion was done
every day and the concentration of Zn2+ ion after adsorption was determined everyday by Atomic
Absorption Spectrophotometer. Results showed that N. salina can be used as biosorbent to decrease
the concentration of Zn2+ ion in water with the adsorption efficiency of 94,10% for the initial
concentration of 10 ppm.
Keywords : Nannochloropsis salina, zinc, Conwy, biosorption
1. INTRODUCTION
Pollution of heavy metals in the sea waters of Indonesia increased in the last decade. The
pollution of mercury in Dadap, Cilincing, Demak, and Pasuruan Waters was reported in 2001 and the
pollution in Pasuruan Waters was also recognized in 2002 [1]. In 2003, the concentration of Pb, Cd,
Cu, Cr, Ni, Zn, Mn, and Fe in the sea waters of Makassar Strit was still low but the concentration in
the sediment was relatively high [2]. The metals precipitated in the sediment can be redissolved by
the movement of water mass and the dissolved metal can enter the bulk water. Lestari and Edward
[3] also reported that the concentration of Hg, Pb, Cd, Cu, Zn, and Ni in Jakarta teluk has exceed the
limit value, and in 2005, the estuary of both Kahayan and Barito rivers has been contaminated by Cd
and Cu; that of Saguling Reservoir by Pb, Cd, and Cu; Cirata Reservoir by Hg; and Jatiluhur
Reservoir by Cu along with Cd [1]. In 2008, the average concentration of Fe, Mn, and Co in the
waters of Kuripan river (Lampung) was relatively high and there was indication that bioaccumulation
of metal in the sediment and Eremopyrgus eganensis occurred [4], [5].
Recovery of heavy metals from industrial waste plays an important role for the community as
recycling effort and conservation of essential metals [6], but remediation of metals by physicochemical
methods is expensive and environmental unfriendly. Results based on the biotechnological approach
recently can be accepted as the interested alternative method [7]. Microalgae are one of aquatic
microorganisms which have an ability to adsorb and accumulate heavy metals in its body. A previous
research showed that there was an interaction between Zn 2+ ion and microalgae, and the significantly
toxic effect was shown by Zn, followed by Ni and Pb [8]. Chaetoceros calcitrans can adsorb ion Cu2+
ion until the concentration of 40 mg L-1 under neutral pH [9]. In addition, Nannochloropsis salina was
significantly adsorbed Pb, Cd, and Zn ions [10]. In multi-metal system, the synergic and antagonism
interactions can occur in relation to the increase of the microalgae growth in the sea waters [11].
Based on the above description, a research on biosorption of Zn 2+ ion by N. Salina has been
conducted by observation of its growth and determination of the metal concentration adsorbed. The
research is expected to be one alternative solution for heavy metal contamination in the sea waters.
2. MATERIALS AND METHOD
2.1. Materials
Sterile sea water, pure culture of N. Salina, and Conwy Medium [12] with the composition
given in Table 1, were obtained from the Research Institute for Coastal Aquaculture (Balitbang BAP
Maros); HNO3 solution, aquabidest, alumunium foil. The stock solution of Zn2+ with a concentration of
The 2nd International Seminar on New Paradigm and Innovation on Natural Sciences and its Application
(INSPINSA-2), Semarang 4 October, 2012
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1000 ppm was prepared by weighing 2.8969 g of Zn(NO3)2 crystals, dissolving them in HNO3 p.a.,
and diluting the solution with aquabidest in a 1000 mL volumetric flask.
Table 1. Composition of Conwy Medium
Materials
Amount, g
Stock A
FeCl2. 6 H2O
MnCl2. 4 H2O
H3BO3
EDTA (Na-salt)
NaH2PO4. 2 H2O
NaNO3
Aquadest
1.3
0.36
33.6
45
20
100
1L
Stock B
ZnCl2
CoCl2. 6 H2O
(NH4)6MoO24. 4 H2O
CuSO4. 5 H2O
2.1
2
0.9
2
100 mL
Aquadest
Stock C
Vitamin B12
Vitamin B1
Aquadest
10
200
100 L
Stcok D
Na2SiO3. 5 H2O
Aquadest
Source [12]
4,00 g
100 mL
2.2. Apparatus
Haemocytometer Marienfeld LOT-No 4551, hand counter, Nikon SE microscope, Amara
aerator, magnetic strirrer, autoclave (All American No. 1925X), cellulose nitrate membrane filter
Millipore (0,45 µm), atomic absorption spectrophotometer (AAS) Buck Scientific model 205 VGP, the
apparatus from the laboratory of Inorganic Chemistry in the Faculty of Maths and Natural Sciences,
Hasanuddin University.
2.3. Procedure
2.3.1. Optimum growth of N. salina
Marine sea water with a salinity of 25%o was put into a 500 mL Erlenmeyer, and 1 mL of
Conwy medium and pure culture of N. salina were added into the Erlenmeyer with the initial
population around 25 x 104 cell mL-1. Marine sea water was then added into the Erlenmeyer until the
volume of the mixture achieved 500 mL. The solution was mixed, connected to the aerator, and
covered with aluminum foil. The growth of N. salina was observed with haemositometer every 24
hours until the optimum growth was obtained.
2.3.2. Addition of Zn2+ ion onto the N. Salina culture
After the achievement of the optimum growth of N. Salina, Zn2+ ion with various concentrations
of 10, 30, and 50 ppm was added into each Erlenmeyer containing N. salina. The growth was then
observed and the concentration of Zn2+ ion was determined every day.
2.3.3. Determination of adsorption efficiency of Zn2+ ion
The concentration of Zn2+ ion adsorbed (Cs) was calculated with an equation (1). Cs is the
difference between the initial concentration, Co, and the concentration of Zn2+ ion in the filtrate, Cf.
Adsorption efficiency (Ep) can be calculated using equation(2).
Cs = Co – Cf
𝐂
𝑬𝒑 = 𝐬 × 𝟏𝟎𝟎%
𝐂𝐨
(1)
(2)
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3. RESULTS AND DISCUSION
3.1. The optimum growth of N. salina
The optimum growth of N. salina was achieved in the 8th day with the population of 123 x 104
-1
cell mL . Figure 1 shows the relation between the number of population of N. salina and the growth
time. Naturally, the growth of N. salina decreases after the achievement of the optimum growth. This
is caused by the decrease in the amount of nutrition in the medium with increasing the population
number of N. salina. The decrease in the population number was also supported by the accumulation
of organic compounds from the dead biomass settled down to the bottom of the medium.
Population,(x 104 cell/mL)
140
123
120
104
91
100
80
85
73
67
67
56
52
60
40
90
82
38 41
48
35 32
25
26
20
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18
day
Figure 1. The growth of N. salina
The biomass acts as the new competitor for N. salina which still alive in finding the dissolved oxygen
and nutrition in the growth media environment [13].
140
Population (x 104 cell/mL)
120
control
100
10 ppm
30 ppm
80
50 ppm
60
40
20
0
1
2
3
4
5
6
7
8
9
10
11
day after Zn2+ addition
Figure 2. The growth of N. salina after addition of Zn2+ ions [a] 10 ppm, [b] 30 ppm, and [c] 50 ppm
Addition of Zn2+ ion with various concentrations causes the drastic decrease on the growth of
N. salina compared to the control (Figure 2). This occurs because the metal ion is interacted with the
fat layer on the surface of microalgae cells [14]. The body surface of microalgae is covered by the cell
membrane, therefore, the potential interaction between the membrane and the metal ion in the waters
is high [15]. The surface of cells contains various functional groups, such as N-terminal of –NH2, Cterminal of -COO-, S-terminal of –SH and functional groups of side chains which are potential as metal
binding sites [16].
The 2nd International Seminar on New Paradigm and Innovation on Natural Sciences and its Application
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47.05
46.89
47.02
45.93
46.19
46.18
47.33
47.10
47.10
47.02
27.91
28.17
27.61
27.90
27.90
28.00
27.90
28.00
28.02
50
28.13
The decrease of the N. Salina growth is affected by the metal ion concentration; the inhibition
effect on the growth caused by the Zn2+ ion with a concentration of 50 ppm is higher than that given
by the one with lower concentration. The Zn2+ concentration adsorbed at the first day to the 10th day
after addition of Zn2+ ion occurs dominantly at the beginning of the contact process between Zn2+ ions
and N. salina, whereas at the next day, the adsorption curve tends to be steady (Figure 3). Adsorption
of the metal ion by the active groups proceeds on the cell surface followed by the slow transport step
into the membrane and then to the cytoplasm [16]. In addition, metal ions in solution undergo
equilibrium with ligands produced and excreted by algae at all steps [17].
45
40
30
10 ppm
30 ppm
25
50 ppm
9.39
9.39
9.31
9.42
9.43
9.43
9.45
9.43
9.44
15
9.43
20
2
3
4
5
6
7
8
9
10
11
10
5
0
Conc. of Zn2+ absorbed, ppm
35
0
1
day after addition of Zn2+
Figure 3.
Concentration of Zn2+ adsorbed as a function of the time used after addition of Zn2+ ion.
Accumulation of several metals (such as Co, Mo, Ca, and Mg) on algae occurs through the
intracellular active biological transport. Toxic heavy metal ions will be isolated from the cytoplasm cell
through three possible ways, i.e. intracellular chelating by biological polymers; precipitation of heavy
metals on the surface of cell wall; or surface adsorption through metal ion binding by chemical
functional groups on the cell wall [18].
3.2. Adsorption Efficiency of Zn2+
Based on equation (1), the Zn2+ concentration adsorbed for each concentration added can be
seen in Table 2.
Table 2. The concentration of Zn2+ adsorbed by N. salina and the adsorption efficiency
Initial concentration
of Zn2+ (ppm)
10
30
Concentration of Zn2+
adsorbed (ppm)
9.41
27.95
50
46.78
Efficiency (%)
94.10
93.17
93.56
Table 2 shows that the highest adsorption (94.10%) occurs at the Zn2+ concentration of
10 ppm, because the population number of N. salina in the concentration is higher compared to that
in other concentrations. The adsorption efficiency at the Zn2+ concentration of 50 ppm is only 93.56%.
Based on the efficiency data, it can be said that N. salina has good ability in adsorbing Zn2+ until the
Zn2+ concentration added of 50 ppm.
The 2nd International Seminar on New Paradigm and Innovation on Natural Sciences and its Application
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4. CONCLUSION
The optimum growth of N. salina with the population number of 123 x 104 cell mL-1 was
achieved at the 8th day. The Zn2+ adsorbed inhibited the N. salina growth which was affected by the
metal ion concentration and the dominant adsorption occurred at the beginning of the contact
process. N. salina can be used as biosorbent for Zn2+ ions with the maximum adsorption efficiency of
94.10%.
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