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The present investigation entails the biosorption studies of radiotoxic Strontium (90Sr), from aqueous medium employing dry cow dung powder (DCP) as an indigenous, inexpensive and, eco-friendly material without any pre or post treatments. The Batch experiments were conducted employing 90Sr(II) as a tracer and the effect of various process parameters such as optimum pH, temperature, amount of resin, time of equilibration, agitation speed and concentration of metal ions have been studied. The kinetic studies were carried out employing various models but the best fitting model was Lagergren pseudo-second order model with high correlation coefficient R 2 value of 0.999 and cation exchange capacity of DCP was found to be 9.00 mg/g. The thermodynamic parameters for biosorption were evaluated as ΔG° = −5.560 kJ/mol, ΔH° = −6.396 kJ/mol and ΔS° = 22.889 J/mol K, which indicated spontaneous and exothermic process with high affinity of Sr(II) for DCP.
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Biosorption of radiotoxic
Sr by green adsorbent: dry cow
dung powder
Nisha Suresh Barot Hemlata Kapil Bagla
Received: 29 October 2011 / Published online: 20 November 2011
´miai Kiado
´, Budapest, Hungary 2011
Abstract The present investigation entails the biosorp-
tion studies of radiotoxic Strontium (
Sr), from aqueous
medium employing dry cow dung powder (DCP) as an
indigenous, inexpensive and, eco-friendly material without
any pre or post treatments. The Batch experiments were
conducted employing
Sr(II) as a tracer and the effect of
various process parameters such as optimum pH, temper-
ature, amount of resin, time of equilibration, agitation
speed and concentration of metal ions have been studied.
The kinetic studies were carried out employing various
models but the best fitting model was Lagergren pseudo-
second order model with high correlation coefficient R
value of 0.999 and cation exchange capacity of DCP was
found to be 9.00 mg/g. The thermodynamic parameters for
biosorption were evaluated as DG"=-5.560 kJ/mol,
DH"=-6.396 kJ/mol and DS"=22.889 J/mol K, which
indicated spontaneous and exothermic process with high
affinity of Sr(II) for DCP.
Keywords Biosorption !Radiotoxic strontium !
Dry cow dung powder !Green adsorbent
In the domain of toxic radionuclide persisting in our envi-
Sr is considered as one of the most hazardous
fission product due to its long physical half-life of 29 years
[1] and its inevitable presence in the water, soil and food
chain. The anthropogenic activities such as nuclear weapon
testing, reprocessing of liquid spent fuel, etc. are major
source of
Sr in our environment. Strontium is referred as a
bone seeker as it imitates the calcium in the human body
and increases the risk of bone cancer, leukemia, etc. [2]. On
the contrary, if managed scientifically, it has also been
proved to be aiding to mankind.
Sr has been used as a
power source for radioisotope thermoelectric generators
(RTGs), as well as used in cancer therapy and in forensic
sciences [3]. Hence, there is a great necessity to adapt a
methodology which can be employed for the eco-friendly
removal of
Sr from the aqueous system with a view of
reprocessing the same and to reap out its aforementioned
In the field of radionuclide research, some of the well
established processes such as chemical precipitation, mem-
brane process, liquid extraction, and ion exchange [4,5] have
been applied as a tool for the removal of this metal ion. These
all methods are not considered to be greener due to some of
their shortcomings such as incomplete metal ion removal,
high requirement of energy and reagents, generation of toxic
sludge or other waste materials which in turn require treat-
ments for their cautious disposal. Eventually, it adds on to the
cost, time and feasibility of the entire procedure.
The greener and cleaner approach of biosorption is a
sure solution to this situation. Biosorption phenomenon is
acquiring strong footage due to its mechanism based on
non-directed physico-chemical interactions that occur
between metal species and dead biomass. Biosorption deals
with both living biomass as well as non-living aggregates
of biomaterial. But biosorption by dead biomass is often
faster [6], since only passive cell wall based binding
transport, into the cell takes place.
N. S. Barot !H. K. Bagla (&)
Department of Nuclear & Radiochemistry, Kishinchand
Chellaram College, 124 D. W. Road, Churchgate, Mumbai,
Maharashtra, India
N. S. Barot
J Radioanal Nucl Chem (2012) 294:81–86
DOI 10.1007/s10967-011-1539-3
Author's personal copy
Literature survey reveals that in the domain of natural
adsorbent, materials such as Rhytidiadelphus squarrous
[7], magnetically modified yeast cells [8], Azolla filiculo-
ides [9], brucite [10], clay minerals [11], Oscillatoria
homogenea cynobacterium [12], Cystoseira indica brown
alga [13], seeds of Ocimum basilicum [14], Pakistani coal
[15], etc. have been utilized for Sr(II) removal. These
naturally available materials require some degree of
physical and chemical enhancement so as to optimize,
which add on to the economy of entire adsorption process.
The HA has been successfully extracted by authors from
DCP and this piece of work has been published in the
International Journal [16]. Also, biosorption with living
media leads to biological and chemical sludge due to
growing biomass and nutrients. Hence, for the efficient
biosorption method, economy of environmental remedia-
tion dictates that the biomass must come from nature or
even has to be a waste material.
Materials and methods
DCP (100 mesh) was provided by Keshav Shrushti,
Research Centre on Cow product (Thane, India) and due
precautions were taken to avoid the contaminations. DCP is
naturally available bio-organic, complex, polymorphic
fecal matter. It is enriched with minerals, carbohydrates,
fats, proteins, bile pigments, aliphatic–aromatic species
such as ‘humic acid’ and many functional groups such as
carboxyl, phenols, quinols, amide, etc. which enhances its
adsorption properties.
Characterization of DCP
Cow dung powder was dried properly before its utilization,
so as to prevent its oxidation by acid due to presence of
mixture of alcohols if any. The absence of alcohol is also
supported by FTIR analysis of DCP, which is devoid of any
characteristic band of alcohol. The integrity of DCP before
and after the adsorption was studied by measuring the mesh
size and was found to be same; indicating during adsorp-
tion process there was no physical attrition of resin. All the
characterization techniques have been carried out at Indian
Institute of Technology, IIT, Powai, Mumbai. The DCP has
been characterized using XRF technique for its quantitative
as well as qualitative elemental composition and for the
complete elemental assay, complimentary to XRF tech-
nique, C, H, N, S, O technique, has also been obtained as
detailed in Table 1.
The SEM pattern of DCP clearly reveals the surface
texture and porosity of the DCP. The porous morphology
of DCP is responsible for the easier diffusion during
adsorption process. For the confirmation of biosorption
process EDAX (Energy dispersive X-ray analysis) spec-
trum of DCP, after and before the adsorption of Sr(II) have
been studied. The EDAX spectrum of DCP before and after
biosorption of Sr(II) (Fig. 1a, b), indicated that Si, K, Ca,
Ti, Mn, Fe, Zn are naive metal ion of the matrix and after
biosorption of Sr(II) on DCP, Sr(II) was present along with
all other natural elements indicating that ion exchange is
not the mechanism for Sr(II) adsorption on DCP.
All the chemicals used were of analytical grade. The stock
solution of Sr(II) 1 mg/mL was prepared using SrCl
distilled water. All the solutions were standardized by
standard analytical methods [17].
Tracer technique
It is the radio analytical technique in which micro amount
of radioactive isotope is added to a system in order to trace
or monitor [18] the chemical reaction of a certain element
in the system. In comparison to classical approach, tracer
technique offers some unique advantage such as, high
sensitivity, non-destructive pattern, freedom from reagent
blank, etc. The Radiotracer
Sr(II) (beta-emitter) was
procured from BRIT (Board of Radiation and Isotope
Technology, Mumbai, India).
Table 1 XRF data of DCP
S.No. Elements % Occurrence
1 Na 0.946
2 Mg 2.853
3 Al 1.684
4 Si 22.691
5 P 3.883
6 K 3.343
7 Ca 2.360
8 Ti 0.329
9 Mn 0.115
10 Fe 2.419
11 Cl 1.560
12 Cr 0.014
13 N 1.086
14 H 1.800
15 S 1.202
16 C 13.087
17 O 13.018
82 N. S. Barot, H. K. Bagla
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Batch equilibration mode
A known amount of DCP was mixed with 10 mL of solution
containing radiotracer and 1 mg/mL solution of carrier. The
pH was adjusted using dil. HCl and NaHCO
as per the
requirement. The resultant aliquot was equilibrated for
10 min with mechanical stirrer and was then centrifuged.
After separating supernatant, adsorbent was washed with
5 mL of distilled water and activity present in supernatant
was measured using end window type Geiger–Muller
Counter (PEA GCS 101P) in conjugation with a decade
scalar, timer and a high voltage unit, for the beta-emitter.
The effect of different experimental parameters such as
pH (from 1 to 10), metal ion concentration (0.5–20 mg/mL),
contact time (0–30 min), agitation speed (0–5,000 rpm),
amount ofadsorbent (50–650 mg), temperature (283–363 K),
have been studied so as to optimize the parameters for
developing efficient adsorption process. The kinetic and
thermodynamic studies have also been carried out so as to
optimize the system under study for the removal of
Sr(II) ions from aqueous medium. All experimental data
were measured in triplicate and percentage sorption was
calculated using formula given below:
%Adsorption ¼AiðÞ%AðfÞ
AiðÞ &100
where A(i) =activity taken, A(f) =total activity in
Results and discussion
All the aforementioned parameters were comprehensively
studied for the optimization of the system. The results
revealed that having 10 min of contact time, at 4,000 rpm
of agitation speed, at the optimum pH of 6, 350 mg of DCP
can effectively remove Sr(II) up to 85–90%.
Effect of pH
DCP being heterogeneous adsorbent possess positively
charged site owing to some proteins, enzymes and negatively
charged sites due to presence of some acidic groups. Hence,
on varying the pH of a solution, the overall surface charge of
DCP could be modified so as to get maximum adsorption.
The adsorptive behavior of Sr(II) ions on DCP might be
explained on the basis of electrostatic force of attraction
between the oppositely charged adsorbate and adsorbent. On
varying the pH from 1 to 10 as shown in Fig. 2, it was
observed that, the optimum pH for maximum adsorption of
Sr(II) on DCP was at pH 6. At low pH, adsorption became
unfavorable due to electrostatic repulsion between the posi-
tive charged surface, in excess of H
ions, and Sr(II) ions,
resulting in the decrease in the adsorption. The neutral range
of pH favored the adsorption of Sr(II) ions on the DCP which
was indicative from the figure.
On further increase in pH, the adsorption was found to
decrease, which may be due to preference of Sr(II) ions to
form a stable complex of SrCO
then to get adsorbed on
DCP surface. It was observed that the maximum sorption
of Sr(II)on DCP was obtained at pH 6.
Effect of amount of adsorbent
Adsorption being surface phenomenon, the extent of
adsorption is directly proportional to the surface area
Ti Zn
Ti Mn
Ca ZnSi
0 2 4 6 8 10 12 14 16 18 20 22
Full Scal e 21521 cts Curs o r : 8.081 (5970 cts)
PA - 2
0 2 4 6 8 10 12 14 16 18 20 22
Full Scal e 21693 cts Curs o r : 2.768 (11808 cts)
DCP-6_ PA - 1
Fig. 1 EDAX spectrum before (a) and after biosorption (b)
Fig. 2 Effect of pH on adsorption (contact time =10 min; amount
of resin =350 mg; metal ion concentration =1 mg/mL; agitation
speed =4,000 rpm at room temperature)
Biosorption of radiotoxic
Sr by green adsorbent 83
Author's personal copy
available. Increasing the adsorbent amount, increase in
adsorption percentage was observed. After certain dose of
adsorbent, maximum adsorption sets in after which the
percentage adsorption was almost constant. This suggests
that after optimum dose, number of ions bound to adsorbent
and the number of free ions remained constant even with
further addition of the adsorbent. It may be due to partial
aggregation of active adsorbent sites [19]. Our results sug-
gest that optimum amount of DCP for Sr(II) was 350 mg.
Effect of contact time
To optimize contact time for the experiment, keeping all
other parameters constant, contact time was varied from 0
to 30 min. The results reveals that as contact time
increased, percentage adsorption also increased, but after
some time, it gradually approached a constant value,
denoting attainment of equilibrium. Further increase in
contact time, did not increase adsorption due to desorption
of ions on the available adsorption sites of adsorbent.
Effect of metal ion concentration
Metal ion concentration was varied from 0.5 to 20 mg. As
shown in Fig. 3, percentage adsorption decreased with
increase in metal ion concentration. In case of low metal ion
concentration, the ratio of number of moles of metal ions to
the available surface area of adsorbent was lower and sub-
sequently the fractional adsorption becomes independent of
metal ion concentration [20]. On increasing the concentra-
tion of Sr(II) ions, the metal ion concentration becomes
higher than that of the sorbent binding sites, resulting in
decreased sorption percentage. This study reveals that
350 mg of DCP can absorb 20 mg/mL of Sr(II) up to 50%.
Also, on increasing the amount of DCP, the removal of Sr(II)
can be increased even at higher metal ion concentration.
Effect of temperature
In the process of biosorption, temperature plays a vital role
and these processes are normally exothermic. Hence, the
extent of adsorption generally increases with decrease in
temperature. For this purpose the temperature was varied
between 283 and 363 K. Our results reveal that the
adsorption of metal ions increases at lower temperature and
were found to be maximum at the room temperature range.
On further increasing the temperature, percentage adsorp-
tion was decreased and it may be due to desorption caused
by an increase in the available thermal energy. Also, higher
temperature induces mobility of adsorbate, eventually
causing desorption, due to weakening of adsorptive forces
between the active sites of adsorbent and adsorbate species
and also between the adjacent molecules of the adsorbed
phase [21]. Hence, the temperature ranges, i.e. 293–303 K
favors the adsorption rate of the system under study.
Effect of agitation speed
This experiment proved that speed of agitation has
important role in the process of biosorption. All agitation
speeds were found to have a positive impact on the system.
Increasing the speed at rate of 500 rpm, percentage
adsorption showed markedly high values. This is because
agitation facilitates proper contact between the metal ions
in solution [22] and the binding sites and thereby promotes
effective transfer of adsorbate ions to the adsorbent sites.
The agitation speed of 4,000 rpm was standardized.
Thermodynamic parameters
Thermodynamic considerations are necessary to conclude
whether the process is spontaneous or not. The Gibb’s free
energy change, DG"is an indication of spontaneity of
chemical reactions. The free energy of biosorption reaction
can also be evaluated by considering the biosorption
equilibrium constant K
which is given by the following
DG'¼%RT ln Kað1Þ
Where, DG"is the standard free energy change (J), Ris
the universal gas constant =8.314 J/mol K, and Tis
absolute temperature (K). The free energy change for the
temperature range of 293–308 K using Eq. 1has been
evaluated and has obtained the negative values of DG"for
the entire range as shown in Table 2. Any reaction if
occurs spontaneously at a given temperature, its DG"is
always a negative quantity. The negative value also
confirms the feasibility and the spontaneous nature of
biosorption process of Sr(II) on DCP with DG
-5.560 kJ/mol.
A plot of ln K
, versus temperature 1/T 910
, was
found to be linear, Fig. 4. The values of DH"and DS"were
determined from the slope and intercept of the plot. The
enthalpy change DH", and the entropy change DS", for the
Fig. 3 Effect of metal ion concentration on adsorption (pH =6;
contact time =10 min; amount of resin =350 mg; agitation speed =
4,000 rpm at room temperature)
84 N. S. Barot, H. K. Bagla
Author's personal copy
biosorption process were deduced from the graph to be
-6.396 kJ/mol and 22.889 J/mol K, respectively. The
negative value of enthalpy suggests the exothermic reac-
tion. The positive value of entropy change suggest the
increase in the randomness at the solid/liquid interface
reflecting affinity of DCP for the Sr(II) ions.
Kinetic parameter
The kinetic adsorption data could be processed to under-
stand the dynamics of the biosorption reaction in terms of
the order of the rate constant. The different kinetic models
such as first order, second order, pseudo-first order, pseudo-
second order and the intraparticle diffusion have been
studied. But among these models, best fitting model was
Lagergren pseudo-second order model. The correlation
coefficients have R
values close to one as shown in
Table 3, indicating the applicability of pseudo-second
order model to the present system. The kinetic data was
treated with the Lagergren pseudo-second order kinetic
model [23]. It is generally expressed as follows:
dt ¼k2qe%qt
where q
and q
is adsorption capacity at equilibrium and at
time t, respectively (mg/g) and k
is the second order rate
constant of adsorption (g/mg min). Integrating Eq. (1) for
the boundary conditions q=0 to q=q
at t=0 to t=tis
to obtain the following equation:
The plot of t/q
versus tshould show a linear relationship
if the second order kinetics is applicable and same is
evident from the graph. The equilibrium rate constant, k
and equilibrium capacity or adsorption capacity or cation
exchanged capacity, q
were determined from the slope and
intercept of the line in Fig. 5. The applicability of this
model suggested that biosorption of elements under study,
on DCP was based on chemical reaction, between metals
and active sites of the biosorbent.
A simple and eco-friendly method for the utilization of DCP
as an effective green adsorbent material for the removal of
Sr from aqueous medium has been developed.
Being naturally and easily available, DCP can be employed
without any pre or post treatment. Hence, it has an edge over
other processed natural and synthetic adsorbent considering
their production cost, time, and energy efficiency.
Acknowledgments We thank Gemmological Institute of India,
Mumbai, for providing EDAX facility. We are also thankful to Dr.
Raju Apte, Head of Gaushala, Keshav Shrushti, Thane, for providing
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Fig. 4 A plot of ln K
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Biosorption of radiotoxic
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... These activities and more lead to the pollution of the environment by various pollutants. Examples of some of these pollutants are heavy metals (such as Chromium [4], Cobalt [5], Strontium [6], Cadmium [7], and Lead [8]) and dyes. Some of these pollutants are non-biodegradable and further accumulate in the food chain [6,9]. ...
... Examples of some of these pollutants are heavy metals (such as Chromium [4], Cobalt [5], Strontium [6], Cadmium [7], and Lead [8]) and dyes. Some of these pollutants are non-biodegradable and further accumulate in the food chain [6,9]. The pollutants churned out by some industries, such as textiles, rubber, plastic, pulp, and paint industries, are mostly dyes [10]. ...
... Activated carbon (AC) is one of the most popular adsorbents commonly used for the adsorption of pollutants from water, but due to its high cost, poor removal, and recyclability properties, the need to obtain better alternatives has been widely considered and studied [23]. An ideal adsorbent must be relatively cheap, abundant, easily undergo modification, and exhibit better removal efficiency [6]. In developing countries, dumping animal waste products as solid trash in the environment without processing or composting, or simply washing them into water canals, has dangerous health consequences for humans and other living species. ...
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An ideal adsorbent must be relatively cheap, abundant, easily undergo modification, and exhibit better removal efficiency. Animal wastes are much better adsorbents in comparison with activated carbon adsorbents with respect to being cost-effective and their zero regeneration process factor. The review aims to report the efficiency of utilized cow-dung based adsorbents for the sequestration of a wide spectrum of pollutants from aqueous media. It discusses the potential of utilizing cow dung as a cheap and effective adsorbent. It was observed that cow dung-based adsorbents were efficient for the removal of dyes, heavy metals, and other pollutants from aqueous solutions. The maximum reported uptake capacity of dyes and heavy metals was 501 mg/g and 625.26 mg/g for Methylene blue and lead, respectively, which were both for cow dung activated carbon. The Langmuir and Freundlich isotherm models emerged as the best-fit models for almost all studies. Based on the review outcome, a pseudo-second-order model was reported as the kinetic model of best fit in all cases. Other adsorption studies such as adsorption mechanism, thermodynamic modelling, desorption, column adsorption, and competitive adsorption were also included in this study. Finally, the study identified some knowledge gaps that could aid future investigation in this research field. Summarily, it can be deduced that cow dung-based adsorbent has exhibited good potential as an adsorbent for the mitigation of pollutants from water.
... Testing of Nuclear weapon testing and liquid spent reprocessing fuel like human activities are major source of its pollution. Its toxicity increases the risk of fatal diseases like blood cancer (Barot and Bagla 2012). Cowdung powder have diverse characteristics that act as site with positive charge to enzymes that result in biosorption of 90Sr from any aqueous medium (Barot and Bagla 2012). ...
... Its toxicity increases the risk of fatal diseases like blood cancer (Barot and Bagla 2012). Cowdung powder have diverse characteristics that act as site with positive charge to enzymes that result in biosorption of 90Sr from any aqueous medium (Barot and Bagla 2012). ...
In the present review, farmyard manure is explained as a perfect source of nutrients for plant growth as well as for soil microbiota. It is one of the efficient and effective organic manures. It can provide organic matter to soil microbes as a source of carbon. An increase in microbial population leads to the degradation of pesticides and heavy metals to less harmful compounds. In addition to it, ions of harmful elements get adsorb on organic colloids and become immobile in soil. Application of farmyard manure not only increases the availability of nutrients in the soil but also improves the soil properties like soil structure, water holding capacity, bulk density, cation exchange capacity, etc. Studies revealed that farmyard manure is an excellent organic manure for sustaining good soil health along with achieving desired food production.
... Literature survey reveals that Sr(II) and its radioactive counterparts like 90 Sr and 85 Sr have been separated from aqueous solutions by employing water imbibed seeds of Ocimum basilicum [8], chemically modified biosorbents derived from Azolla filiculoides [9], immobilized moss [10], lichen like Hypogymnia physodes [11], modified eggshell waste [12], saponified orange juice residue [6], roots of Taraxacum officinale [13] and dry cowdung powder [14]. A diverse range of microbial cultures including Scenedesmus spinosus [15], Aspergillus terreus [16], Saccharomyces cerevisiae [17], Oscillatoria homogenea cyanobacterium [18], among several others [19][20][21] have also been employed for the biosorption of Sr(II). ...
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... Fig. 9. Sr 2+ outlet concentrations of (a) crab carapace, (b) Kurion-TS-G™ and (c) and SrTREAT® in biosorption columns (initial concentration: 1.4 mg/L; no pH adjustment; dose of sorbent: 10 g; flow rate: 2.8 mL/min; temperature: 20 ± 2°C). Aqueous solutions with a radioactive tracer Dry cow dung powder 9.0 mg/g pH: 6; biosorbent dose: 350 mg; time: 10 min; C 0 : 20 mg/L; rpm: 4000; T: 22°C (Barot and Bagla, 2012) Aqueous solutions from high level natural radiation area γ-Ray irradiated baker's yeast 33.0 mg/g pH: 4.5; biosorbent dose: 4 g/L; time: 1440 min; C 0 : 400 mg/L; rpm: 120; T: 30°C (Dai et al., 2014) Aqueous solutions Orange juice residues 833.4 mmol/kg. pH: 5.6; biosorbent dose: 10 mg; time: 24 h; C 0 : 5 mmol/L; rpm: n.a.; T: 30°C (Paudyal et al., 2014) Single solutions and synthetic wastes Spent coffee grinds 69.0 mg/g pH: 7; biosorbent dose: 0.1 g; time: 1 h; C 0 : 100 mg/L; rpm: 250.; T: 20°C (Imessaoudene et al., 2013) ...
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Removal of Sr2+ from aqueous media presents particular challenges, especially in complex wastes such as nuclear industry liquors. Commercial sorbents while effective, can be highly expensive and subject to negative effects from competing ions. Here we evaluate two potential biosorbents (crab carapace and spent distillery grain) as potential alternatives and compare their performance to two commercial sorbents for Sr2+ removal at industrially relevant concentrations (low mg/L). Physical and structural characterization of the materials was undertaken, and batch and dynamic studies were performed on Sr2+ solutions and simulated nuclear wastewater. Sorption performance was quantified with respect to contact time, initial concentration and ion-competition. Removal efficiencies were 20–70% for the biosorbents compared to 55–95% for the commercial materials. Results indicated sorption was predominantly through monolayer coverage on homogenous sites and could be described using a pseudo-second-order kinetic model. Studies with the simulant liquor showed Sr2+ sorption was reduced by 10–40% due to ion-competition for sites. Characterization of biosorbents before and after Sr2+ sorption suggested that outer-sphere complexation and ion-exchange were the primary Sr2+ removal mechanisms. The efficiency of crab carapace for Sr2+ removal from aqueous media (with adsorption capacity 3.92 mg/g.) at industrially relevant concentrations, together with its mechanical stability, implementation and disposal cost, makes it a competitive option compared to other biosorbents and commercial materials reported in the literature.
... Literature review reveals the characterization studies of DCP carried out by previous researchers 12,13 . It sheds light on the acidic and basic moieties present on the surface of the biosorbent which act as active sites for bonding. ...
... Over the past few years, DCP has been extensively studied as a green biosorbent for the remediation of several heavy metals and radionuclides from waste-waters [29,30]. Characterization of DCP was carried out by N. Barot and H. Bagla [31,32] using SEM and FTIR techniques, which confirmed the existence of phenol, quinol, amide, and carboxyl groups in the binding of metal ions. ...
Heavy metal pollution is caused due to anthropogenic activities and is considered as a serious environmental problem which endangers human health and environment. The present study deals with biosorption, an eco-friendly technique for the removal of heavy metal Zn(II) from aqueous medium. Various natural materials have been explored for the uptake of metal ions, where most of them are physically or chemically enhanced. Dry cowdung powder (DCP) has been utilized as a low-cost, environmentally friendly humiresin without any pre-treatment, thus demonstrating the concept of Green Chemistry. Batch biosorption studies using ⁶⁵Zn(II) tracer were performed and the impact of different experimental parameters was studied. Results revealed that at pH 6, 94 ± 2% of Zn(II) was effectively biosorbed in 5 min, at 303 K. The process was spontaneous and exothermic, following pseudo-second-order reaction. The mechanism of heavy metal biosorption employing green adsorbent was therefore elucidated in order to determine the optimal method for removing Zn(II) ions. DCP has a lot of potential in the wastewater treatment industry, as seen by its ability to meet 3A's affordability, adaptability, and acceptability criteria. As a result, DCP emerges as one of the most promising challengers for green chemistry and the zero-waste idea.
The real-time textile dyes wastewater contains hazardous and recalcitrant chemicals that are difficult to degrade by conventional methods. Such pollutants, when released without proper treatment into the environment, impact water quality and usage. Hence, the textile dye effluent is considered a severe environmental pollutant. It contains mixed contaminants like dyes, sodium bicarbonate, acetic acid. The physico-chemical treatment of these wastewaters produces a large amount of sludge and costly. Acceptance of technology by the industry mandates that it should be efficient, cost-effective and the treated water is safe for reuse. A sequential anaerobic-aerobic plant-microbe system with acclimatized microorganisms and vetiver plants, was evaluated at a pilot-scale on-site. At the end of the sequential process, decolorization and total aromatic amine (TAA) removal were 78.8% and 69.2% respectively. Analysis of the treated water at various stages using Fourier Transform Infrared (FTIR), High Performance Liquid Chromatography (HPLC)) Gas Chromatography-Mass Spectrometry (GC-MS) Liquid Chromatography-Mass Spectrometry (LC-MS) indicated that the dyes were decolourized and the aromatic amine intermediates formed were degraded to give aliphatic compounds. Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM) analysis showed interaction of microbe with the roots of vetiver plants. Toxicity analysis with zebrafish indicated the removal of toxins and teratogens.
Bacillus pumilus SWU7-1 was isolated from strontium ion (Sr(II))-uncontaminated soil, its biosorption potential was evaluated, and the effect of γ-ray radiation treatment on its biosorption was discussed. Domesticated under Sr(II) stress promoted the biosorption ability of B. pumilus to Sr(II), and the biosorption efficiency increased from 46.09% to 94.69%. At a lower initial concentration, the living bacteria had the ability to resist the biosorption of Sr(II). The optimal initial concentration range was 54-130 mg/L. The biosorption profile was better matched by Langmuir than Freundlich model, showing that the biosorption process of Sr(II) by the experimental strain was closer to the surface adsorption. According to Langmuir model, the maximum biosorption capacity of B. pumilus on Sr (II) was 299.4 mg/g. During the bacterial growth in the biosorption process, the changes in biosorption capacity and efficiency can be divided into two phases, and a pseudo-second-order model is followed in each phase. There was no significant difference in the biosorption efficiency of bacteria with different culture time after γ-ray radiation, and all of them were above 90%, which showed that B. pumilus had significant radiation resistance under experimental conditions. This study emphasized the potential application of B. pumilus in the treatment of radioactive Sr(II) pollution by biosorption.
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The effect of nitric acid concentration on the selectivity of a novel extraction chromatographic resin consisting of an octanol solution of 4,4′(5′)-bis(t-butyl-cyclohexano)-18-crown-6 sorbed on an inert polymeric support for strontium over a number of alkali, alkaline earth, and other metal cations was evaluated. The effect of macro quantities of selected elements on strontium retention by the resin was also examined. The resin is shown to exhibit excellent selectivity for strontium over nearly all of the test elements; only lead and tetravalent neptunium, polonium, and plutonium show significant affinity for the material. In addition, concentrations of calcium or sodium ion up to ∼ 0.1 M. are shown not to diminish the sorption of strontium appreciably. Several useful radiochemical separation schemes devised on the basis of the results obtained are described.
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The increased local and global concern, for alarming environmental pollution, offers incentives to explore new green and clean materials and methods for safeguarding the environment. The generation of benign alternate routes for any step in chemical processes, is the need for today and tomorrow. In the present work, humic acid (HA) has been extracted from a green source, “dry cow dung powder”, using simple, cost effective, and eco-friendly methods. HA has been extracted, isolated, and characterized by employing different spectroscopic methods. The process investigated herein imparts a boost to “Green Chemistry”, a promising solution to many global environmental problems.
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The sorption properties toward strontium of bentonitic clays modified with Fe(II) and Cu(II) ferrocyanides and Ti(IV), Sn(IV), and Sb(V) hydroxides were studied. The sorption properties of modified bentonites significantly surpass those of the natural mineral. The sorption equilibrium is attained in 2 h. The most efficient sorbent is the bentonitic clay modified with titanium hydroxide, with which K d reaches 3.2 × 104.
The adsorption characteristics of hexavalent chromium was studied with an adsorbent developed from waste tamarind hull. Experiments were conducted in batch mode to observe the influence of different parameters such as initial concentration of metal ions, adsorbent dosage, adsorbent particle size, stirrer speed, temperature and pH of the solution. Acidic pH strongly favored the adsorption. With decreasing the pH of the solution from 5.0 to 1.0, the removal of chromium was enhanced from 33% to 99%. The adsorption process was found to follow a pseudo-first-order rate mechanism and the rate constant was evaluated at 30°C. The Freundlich, Redlich–Peterson and the Fritz–Schlunder isotherm fit the equilibrium data satisfactorily. Adsorption of chromium was found to increase with increase in the process temperature. Using an adsorbent dosage of 1.0g/L and an acidic pH (2.0), the equilibrium adsorption capacity of the prepared adsorbent was found to be about 70mg/g at 30°C, which increased to about 81mg/g at 50°C. The entropy change, free energy change and heats of adsorption were determined for the process.
The ability of living filamentous cells of the cyanobacterium Oscillatoria homogenea to separate stable strontium and 90Sr from aqueous solution is demonstrated in this study. On a basis of filamentous cell biovolume, the removal were 43.78 nM·ml·(mm3)−1 and 3129.48 mBq·ml·(mm3)−1 after 240 hour incubation. The optimum pH for strontium uptake is 9±0.3. The increasing biovolume of the blue-green alga elevates sorption. In the liquid culture containing 21.2 mm3·ml−1 filamentous cells and 1000 nM·ml−1 initial strontium concentration, the maximum strontium removal was 455.34 nM·ml·(mm3)−1. At 1200 Lux illumination, the maximum removal value was 58.62 nM·ml·(mm3)−1, and at the initial strontium concentration of 6590 nM·ml−1, 235.40 nM·ml·(mm3)−1 removal was observed. The experimental data fitted to Langmuir isotherm and the model parameters and correlation coefficient (R 2) were q max = 7.143 μg·(mm3)−1, b = 0.003 and 0.99, respectively.