Abstract: (SEM), before and after biosorption to determine

Abstract:

Aquatic
system poses a serious threat from industrial effluents having heavy metals,
and chromium due to its wide use in industry, it becomes prime responsibility
for removal chromium ions from effluents before discharged into the aquatic
body. Biosorption comes as an effective technology in removal of heavy metals
from industrial effluents. Biosorption of chromium was studied using microalgae
Chaetomorpha antennina sp., as an adsorbent, which was charcterised
using Fourier Transform Infrared
analysis (FTIR) and Scanning Electron Microscope (SEM), before and after biosorption to determine the functional groups and the structural
characteristics respectively.
Equilibrium and optimization studies for various process parameters like pH
(1-11), adsorbent dosage (0.2 – 1 g/L), initial chromium concentration (10 µg –
100 µg/mL) and agitation time (0 – 50 mins) were examined using batch process. The maximum percent removal of
chromium ions was found to be 83% at pH 1 at adsorbent dosage of 1g at contact
time of 30 min, which showed maximum adsorption. The experimental data of
biosorption of chromium ions onto Chaetomorpha Antennina sp. surface, showed
that the biosorption of metal ions onto Chaetomorpha Antennina sp. was
dependent on the equilibrium pH of the solution, biosorbent and contact time.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

Keywords: Biosorption, Chromium, Chaetomorpha antennina sp.,
Optimization, Industrial effluent.

Introduction:

Presence
of heavy metal in aquatic system has become the most pervasive threat towards
the environment. In the age of unplanned industrialization and urbanization,
discharge of non-treated industrial effluent into the water bodies is impending
dangerous towards human health and aquatic environment due to presence of toxic
heavy metals (1). The concern regarding heavy metals is toxicity and their
persistency in bio accumulating in living organisms. Chromium is widely used
metal, and finds its application in stainless steel production, chromate
preparation and textile industries. Chromium is serious water pollutant, which
exits in two forms: hexavalent and trivalent (3). Trivalent form of chromium
(Cr III ion) is an essential trace element found in insulin and lipid
metabolism (9), but still it is debated issue owing to its toxicity effects (13).
Another form is hexavalent, which is most serious pollutant than its former Cr
III and creates concern due to its toxicity causing cancer, severe diarrhea,
hemorrhage (8) and it is considered as one of the hazardous substance according
to The Agency for Toxic Substance and Disease Registry (ATSDR).

There
are various methods reported for removal of metal ions exchange, chemical
precipitation, activated carbon, reverse osmosis and adsorption. Among the
reported methods bio-adsorption comes as a versatile and efficient method in
removal of metal ions which overcomes the costly methods as chemical
precipitation where there is huge amount of chemical required to effectively remove
the metal ions and activated carbon which comes as a costly adsorbent.

Biosorption
of heavy metals has gained interest as an alternative method for activated
carbon. There is a wide range of studies done on biosorption: using spirulina
(3), Cr III biosorption using brown seeds algae (4), Rhizopus nigricans (10), chitosan based bio-sorbents (12), Bacillus thurigiensis (15), Chaetomorpha antennina sp. (6). Process
of biosorption depends upon various parameters like pH, temperature, type of
bio sorbent material used, contact time, material dosage (16).

There
are very less reports on biosorption properties of microalgae Chaetomorpha antennina and this is the first
time reporting on biosorption of chromium VI using Chaetomorpha antennina sp. Purpose of this study was to evaluate
properties of Chaetomorpha antennina
as a potential adsorbent and optimization of various parameters in removal of
chromium VI from aqueous solution of industry effluents using cost-effective
and simple methods as an application in small scale industries.

Material and Methods:

Stock
solution:

About
100 mg of potassium dichromate (Bio Rad) was dissolved in 100 mL of deionized
water for preparation of stock solution, which was further diluted for
experiments as per required concentrations. Different pH values for experiment
were obtained by using 1 N HCl/ 1 N NaOH.

Chaetomorpha antennina sp. – Biosorbent:

Chaetomorpha antennina sp. is a green algae species of the
family Cladophoraceace. Phytochemical analysis of Chaetomorpha antennina sp. showed
presence of carbohydrates, alkaloids, quinones, triterpenoids, caumarins and
flavonoids (2 citation). Due to presence of these functional groups, the
biosorption/removal of anions and cations present in aqueous solution
increases. The seaweeds were collected from the Ennore beach, Chennai. Species
identification of the collected sample, was done at Madras University. Sample
was thoroughly washed with water for removal of dirt. Then the sample was sun
dried for 3 days, which was thoroughly grinded into powder using mixer and size
was found to be around 300 µm. Obtained powder was stored in air-tight
container and no extra chemical treatment was required.

Batch
process and optimization:

Dilution
of stock solution was done to obtain the different concentrations (10 -100 µg/ml)
of standard test solution (Cr VI). Batch process was carried out using 250 ml
of flask containing 50 ml of standard test solution at agitation speed of 150
rpm (6) in orbital shaker and biosorbent was added with desired quantity (0.2-1
g). To obtain the optimum parameters for biosorption process, experimental
study was done by varying the one parameter at a time while keeping other
parameter constant and this method was followed to obtain each optimum
parameter.

Test
solution was measured at different time interval to find the residual
concentration of chromium ions, until the reaction reached equilibrium point.
Using Whatmann filter paper, biosorbent was filtered after which it was
centrifuged at 7000 rpm for 10 min and filtrate was measured using atomic
absorption spectroscopy to analyze the chromium concentration. Under similar
conditions blank studies were carried out.

Results and discussions:

Optimization
of pH:

Bio-sorption
is a surface phenomenon where pH acts an important parameter in binding of
ionic form heavy metals onto the surface of adsorbent (2). The experimental
study was carried out to find the optimal pH for removal of chromium IV (Cr (VI))
ions from aqueous solution. As per the earlier studies (17) suggest that
precipitation of Cr (VI) ions occurs at higher pH values due to negative charge
on the overall surface of biosorbent decreases the biosorption of Cr ions.

The
results depicted in the fig 1 gives the clear information about Cr (VI) ions
were adsorbed at lower pH 1-3 and adsorption decreased as the pH range
increased. Optimum pH was found to be at 1 and was used as optimum value for
further experimental studies. Chemistry behind positively charged surface of
biosorbent is due to protonation occurring at lower pH values, which makes easy
binding of Cr (VI) anions to surface functional groups of biosorbent, and
biosorption increases at lower pH due to higher protonation on surface of
biosorbent.

Biosorption
of Cr (VI) decreases as the pH values goes higher, this can be explained by
decrease in the hydrogen ion concentration as pH increases. As a result,
chromium ions with negative charge are prevented from binding to biosorbent
having negatively charged surface, with that biosorption decreases (18).

Optimization
of Contact time at different initial concentration:

The
effect of contact time at different metal ions concentration was conducted at
varying concentration from 20-100 µg/ml and contact time was between 10-50 min
at biosorbent 1g. Experimental studies shown in fig 2 reveals that adsorption
of chromium ions was better till 30 min after that there was decrease in
biosorption. As shown in fig 2 the biosorption increased at higher
concentration like 60 µg/ml ,80 µg/ml and 100 µg/ml till 30 min. Due to higher
concentration of chromium ions available for biosorption can be related to increased
adsorption in aqueous solution. Metal ions at increased concentration have
greater chances to collide with functional sites present on biosorbent giving
the Cr (VI) required thrust to overcome the resistant between aqueous phase and
solid phase during the mass transfer (19).   

 

Optimization
of Bio sorbent dosage:

Effect
of biosorbent dosage experiment was carried out at varying dosages (0.2-1 g/l)
at optimum values which were already carried out with chromium concentration of
60 µg/ml. Results shown in fig 3 indicates that biosorption of Cr (VI)
increased at higher concentration and it was found out that .8 and 1 g/l values
showed better biosorption rate upto 82 %(citation).

 

Effect
of optimized parameters:

After
biosorbent dosage, pH and initial concentration was were optimized, a study was
conducted to correlate the results observed in aforementioned parameters. In
this experimental study varying concentrations of Cr (VI) ions from 60 µg/ml to
500 µg/ml were taken as part of study to see any effect was observed. The
contact time was about 30 min at pH 1 with dosage level of 1g/L. Results in fig
4 showed about 83 % removal of Cr ions at concentration of 60 µg/ml, after
which removal of Cr ions decreased and biosorption became constant (data not
shown).

Characterization
studies of bio sorbent before and after treatment with Chromium VI:

FTIR
studies of Biosorbent:

Fourier
Transform Infrared spectroscopy revealed functional sites like hydroxyl,
carbonyl, carboxyl, amine, amide and ether groups present on biosorbent.
Presence of Carboxylic group was confirmed by OH and carbonyl groups present at
around 3400 cm-1 and 1600 cm-1. Biosorption was assumed
to take place due to smaller shift in range of peak indicating involment of NH,
OH, C=O groups towards the binding of metal ions in aqueous solution. Table 1
shows the range of peaks observed before and after adsorption.

Scanning
Electron Microscopy of Biosorbent:

SEM
images taken at higher resolutions shown in fig 5a,b and 6a,b clearly depicts accumulation
of Cr ions onto the surface of biosorbent.

Conclusion:

Biosorption
process was found to be dependent of certain parameters like pH, adsorbent
dosage, initial concentration and contact time. Maximum removal of chromium
ions occurred at the pH 1 due to protonation of anionic Cr (VI) ions onto the
surface functional sites of biosorbent resulted in better adsorption by Chaetomorpha antennina sp. Initial
concentration was the factor for the time taken by biosorbent for adsorption of
Cr (VI) ions, similarly the adsorption rate decreased as initial concentration
was increased. After optimal parameters were found, 83% of chromium ions were
removed at pH 1 with contact time of 30 min having 60 µg/ml as the initial
concentration. Characterization studies like FTIR revealed certain functional
groups like hydroxyl, amine, amide, carboxyl and carbonyl groups present on
biosorbent which were assumed to be responsible for biosorption. SEM images
before and after biosorption showed the clear image of metal uptake by the Chaetomorpha antennina sp. The
experimental results obtained from the batch process studies of green algae Chaetomorpha antennina sp. provided fundamental information about
the biosorption properties of Chaetomorpha
antennina sp., and can be used as efficient and ecofriendly biosorbent.         

 

 

 

 

 

 

 

Absorption cm-1

Assignment

Before treatment

After treatment

3416.086
 

3436.629

O-H
stretch
N-H
symmetric & asym. Stretch

 

3426.950

O-H
stretch
N-H
symmetric & asym. Stretch

2923.032

2922.988

C-H
stretch
O-H
stretch

1632.424

1642.317

C=O
stretch

1252.485

1056.617

O=C-O-C
stretch

1062.769

1056.617

C-F,
C-O stretch

710.386

 

C-H
bend

698.507

629.188

C- Br,I,Cl
stretch

 

BACK TO TOP
x

Hi!
I'm Nicholas!

Would you like to get a custom essay? How about receiving a customized one?

Check it out