Journal of Environmental Radioactivity 142 (2015) 29e35
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Biosorption of uranium by human black hair Amardeep Singh Saini, Jose Savio Melo* Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 October 2014 Received in revised form 5 January 2015 Accepted 6 January 2015 Available online
Naturally available low cost materials have gained importance as effective alternative to conventional sorbents for the removal of metal ions from water. The present study describes the use of black hair waste as a sorbent for the removal of uranium ions from an aqueous medium. Alkali treatment of the biomass resulted in a significant increase in its uptake capacity. The optimum pH and contact time for uranium removal were 4.5 and 2 h respectively. It was observed that the experimental data fits well in Ho's pseudo-second order kinetic model. Binding of uranium to the biomass was confirmed using FT-IR spectroscopy. Thus, the present study could demonstrate the utility of human black hair to remove uranium from aqueous medium. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Black hair Uranium Biosorption Kinetics
1. Introduction A surge in industrialization has led to an increase in metal contamination of aquatic bodies, causing a worldwide problem. Also, metal toxicity and non-biodegradability pose a challenge related to health hazards. Hence, there is a need for economical methods to treat such waste. Uranium is one such metal that is known to pollute the environment through activities associated with nuclear industry. It has both radiochemical and toxicological effects. Excessive amounts of uranium can cause nephritis in human beings and due to carcinogenicity, lead to bone cancer (Katsoyiannis, 2007). Maximum contaminant level (MCL) of uranium in potable drinking water has been established as 15 mg L1 by WHO (2004). A large amount of uranium gets added every year to the sea by the global fresh water streams (Sodaye et al., 2009). Thus, the removal of uranium from waste water is a subject of continual research. Conventional systems of treatment are best suited for solutions having high metal concentrations. With increasing stringency in regulations and the possibility of discharge limits decreasing even further, there arises a need to devise alternative or complementing systems for waste treatment. Biosorption is becoming one of the most attractive and efficient processes to remove metals and radionuclides. Biosorbents have shown potential for accumulating metal ions present in low
* Corresponding author. Tel.: þ91 22 25592760; fax: þ91 22 25505151. E-mail addresses: [email protected] (A.S. Saini), jsmelo@barc. gov.in (J.S. Melo). http://dx.doi.org/10.1016/j.jenvrad.2015.01.006 0265-931X/© 2015 Elsevier Ltd. All rights reserved.
concentrations in the medium. In view of this, natural materials have been attracting much interest as sorbents. To date, various natural materials such as Cladophora hutchinsiae (Tuzen and Sari, 2010), Aspergillus fumigatus (Wang et al., 2010), Catenella repens (Bhat et al., 2008) and rice straw (Ding et al., 2012) have been reported for metal removal. Melo and D'Souza (2004) reported on the use of a natural bioresource, Ocimum basilicum seeds, for chromium uptake. Chakraborty et al. (2007) further investigated this resource for cesium and strontium removal, whereas Gupte et al. (2012) applied it for biosorption of copper. Non-living biomasses of filamentous fungi and bacteria have been reported in our laboratory for the removal of uranium from aqueous medium (Bhainsa and D'Souza, 1999; Sar and D'Souza, 2001). Recently, Saini and Melo (2013) showed the use of biosynthesized melanin pigment for the removal of uranium from an aqueous system in a batch process. Also, Kar and Misra (2004) showed the use of keratin fiber extracted from bird feathers for the separation of metals from water. Suyama et al. (1996) used chicken feathers directly for the biosorption of precious metals such as gold and platinum. Black hair is a bioresource that contains keratin as well as melanin in a naturally immobilized form. The black hair fiber mainly consists of keratin proteins that comprise about 65e95% of the total hair fiber by weight. The remaining constituents are water, lipids, melanin and trace elements (Robbins and Crawford, 1991). The majority of the hair shaft mass comprises the cortex, which is responsible for mechanical properties of the hair fiber. Inside the cortex are the melanin granules that constitute about 3% by weight of hair (Carolina et al., 2007). In India, and other
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countries in the sub-continent, there is large availability of black hair which was the primary reason for choosing black hair for the present study. To the best of our knowledge, black hair has not been investigated for uranium bioremediation. The advantage of human black hair waste over other similar biosorbents is because hair is an abundant and cheap bioresource. Moreover the properties like high tensile strength, non-toxicity and water insolubility make it more attractive for biosorption. It is highly resistant to the action of acids, other harsh chemicals and also to environmental degradation, all of which might have adverse effects on other types of biomass. Many biomass materials require further processing in terms of pelletization or immobilization unlike hair which can be used directly. Therefore the application of this material for treating waste water is economical and involves the utilization of one waste to treat another waste. Thus, in the present study, removal of uranium was studied using human black hair waste which is widely available as a natural resource. The factors affecting the sorption process such as pH, equilibration time and initial uranium concentration were investigated. Kinetics of the adsorption process was studied and equilibrium sorption data was fitted into well known adsorption isotherms. The presence of uranium on the biomass was confirmed with the help of FT-IR spectroscopy.
biomass was kept as control in all the experiments. All studies were performed in triplicates and the data represented are mean of triplicates with standard deviation as the error bar. 2.5. Kinetic and equilibrium studies For kinetic studies, uranium solution (pH 4.5) at 200 mg L1 was kept in contact with treated hair and samples of liquid were taken at regular intervals for measurement of uranium. Kinetic modeling of uranium sorption onto treated hair was done by using Lagergren's pseudo-first and Ho's pseudo-second-order equations. Equilibrium studies were carried out by varying the initial uranium concentration from 100 to 500 mg L1 at a fixed sorbent concentration of 2 g L1. Samples were taken after 24 h of contact, as it was sufficient for the reaction to reach equilibrium. The relation between sorbed and aqueous concentration of uranium at equilibrium was examined using Langmuir and Freundlich adsorption isotherms. 2.6. Uranium estimation and metal uptake capacity
2. Materials and methods
Uranium concentration was estimated in the supernatant obtained after centrifuging, by using Arsenazo III reagent (Shumate et al., 1978). Uranium uptake per gram of hair was calculated using the following equation:
2.1. Biomass
qe ¼ ðC0 Ce ÞV=W
The black hair samples collected from a nearby salon were thoroughly washed with detergent and water to wash out any impurities and then with acetone, to remove oil/lipids. The biomass was then dried at 303 K for 24 h and stored at room temperature for further use. 2.2. Preparation of biomass Alkali treatment of hair was carried out by using varying concentrations of NaOH. For this, 100 mg of dried hair sample was added to 25 mL of different concentrations of NaOH (0.01, 0.1, 0.2 N, 0.3 N) respectively and left for treatment overnight at 298 K on an orbital shaker (MAXQ 4000, Thermo Scientific) at 150 rpm. After 24 h the alkali was decanted and hair samples were washed thoroughly with distilled water to get rid of traces of NaOH. After washing, the hair samples were further dried completely at 303 K for 24 h and stored at room temperature. The resulting biomass is referred to as treated biomass. 2.3. Solutions Uranium stock solution of 2000 mg L1 was prepared by dissolving the required amount of uranyl nitrate hexahydrate (Merck, Germany) in distilled water at room temperature and later diluted to the desired concentration as required. All the other chemicals used were of analytical grade. 2.4. Batch sorption studies Biomass (0.2 N NaOH treated hair) at 2 g L1 was kept in contact with 200 mg L1 of uranium solution unless otherwise indicated. The pH of the solution was adjusted to the required value by adding 0.1 N NaOH or HNO3 before contact with the biomass. The samples were agitated at 150 rpm on orbital shaker maintained at 298 K. Aliquots were collected at regular time intervals and centrifuged (Spinwin, Tarsons, 5585 g) for 5 min, to quantify the residual uranium concentration in the supernatant. A solution without the
(1)
where qe represents the metal uptake capacity, ‘C0’ and ‘Ce’ represent the concentration of uranium (mg L1) before and after sorption respectively. ‘V’ stands for the volume of uranium solution in L and ‘W’ is the amount of hair used in grams. 2.7. Desorption study For desorption studies, different eluents such as hydrochloric acid, nitric acid, sulfuric acid, sodium carbonate and sodium bicarbonate were added at a constant molar concentration of 1 M. The solutions were agitated at 150 rpm on an orbital shaker and the % desorption was calculated using the following equation:
%desorption ¼ ðUdesorbed =Uadsorbed Þ 100
(2)
where Udesorbed represents the concentration of uranium in the supernatant after desorption and Uadsorbed is the concentration of uranium bound to hair after the adsorption cycle. Before carrying out the desorption study, adsorption of uranium on treated hair was performed. For this, treated hair (2 g L1) was contacted with 50 mL of 100 mg L1 uranium solution at pH 4.5. After 24 h of contact, the solution was centrifuged in order to quantify uranium present in the supernatant and the hair pellet was dried at 310 K for 3 h. After drying, 5 mL of respective 1 M eluent was added to the uranium bound hair pellet for desorption. 2.8. FT-IR analysis of treated hair bound with uranium Treated hair (1 g L1) was kept in contact with uranium solution of 200 mg L1 (pH 4.5) at 298 K and agitated at 150 rpm. After 24 h of contact the solution was centrifuged and the pellet obtained was dried completely and used for FT-IR analysis. Treated hair (1 g L1) incubated in distilled water under the above mentioned conditions served as a control. For FT-IR, hair samples with and without uranium were cut into fine pieces with the help of a scissor and mixed with IR grade KBr powder (4% w/w). The mixture was then ground using a mortar and pestle and the FT-IR spectrum of this ground mixture was recorded using Jasco FT-IR 660 plus spectrometer. The
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spectra were recorded over 4000e400 cm1 range with a resolution of 4 cm1. 3. Results and discussion 3.1. Effect of treatment on uranium uptake by black hair Different concentrations of NaOH (0.01, 0.1, 0.2, 0.3 N) were used to study the effect of alkali on uranium uptake by the hair samples. As seen from Fig. 1, as the concentration of NaOH increased from 0.01 to 0.3 N, the metal uptake capacity also increased from 9.1 ± 0.1 mg g1 to 18.7 ± 0.2 mg g1. The uranium uptake by the control (without alkali treatment) was 3.9 ± 0.3 mg g1 whereas, hair treated with 0.2 N NaOH showed an uptake of 17.6 ± 0.4 mg g1, which was almost four times more than that of control. Such increase in the metal uptake after alkali treatment has also been reported by Tan et al. (1985) and attributed to the increase the porosity of the keratin structure. As there was no significant increase (P < 0.05) in the qe value on treatment with 0.3 N NaOH as compared to 0.2 N NaOH, hair treated with 0.2 N NaOH was used for further studies. 3.2. Effect of pH on sorption pH is one of the most important parameters affecting the adsorption process. The effect of pH on the uranium uptake capacity of alkali treated hair samples was studied in the pH range of 2.5e7. As seen from Fig. 2, when the pH of the system increased from 2.5 to 7, the uptake capacity of the treated biomass increased up to pH 4.5 and then decreased. Less uptake value at lower pH can be due to the competition of Hþ ions with uranyl ions for the binding sites present on the biomass. Also, at low pH value divalent UOþ2 2 are present as the dominant species. Being divalent in nature it replaces two protons from adjacent sides, however if these sites are far apart then they are not available for binding. In other words, at low pH some binding sites are not available to the divalent UOþ2 2 . However, at an acidic pH of 2.5, it was possible to achieve an uptake capacity of 6.2 ± 0.4 mg g1 which is nearly 52% of the value obtained at pH 4.5. Similar results were observed by Bhat et al. (2008) wherein they indicated the possible use of the biomass at acidic pH. Mechanisms such as ion exchange and complexation can play an important role in binding to uranium. Hair in general contains keratin which shows the presence of carboxylic group in its structure. These groups have a pKa value around 4.5. When the pH
Fig. 1. Effect of different concentrations of NaOH on uptake capacity (C0 ¼ 200 mg L1, W ¼ 2 g L1, V ¼ 50 mL, pH e 4.5).
Fig. 2. Effect of pH on uranium uptake capacity of treated and untreated biomass (C0 ¼ 50 mg L1, W ¼ 2 g L1, V ¼ 50 mL).
of the system reaches this value, these groups get ionized completely and are available for binding, resulting in high uptake. Also at pH of 4.5, monovalent and divalent hydrolyzed ions þ2 UO2OHþ, ðUO2 Þ3 ðOHÞþ exist in the solution. 5 , and ðUO2 Þ2 ðOHÞ2 According to Collins and Stotzky (1992), hydrolyzed species can be sorbed better than the free hydrated ions. Particularly, compared with the divalent hydrolyzed ions, the monovalent ions have even higher affinity to the biomass in ion exchange with the protons because they could replace single protons on separate binding sites in the biomass. At higher pH values, formation of solid schoepite takes place which decreases the dissolved uranium concentration in the solution, and consequently leads to the reduced sorption of uranium onto the biomass. Guibal et al. (1992) observed a decrease in uranium uptake on filamentous fungus biomass at pH 6.0. A maximum qe value of 12 ± 0.3 mg g1 was obtained at pH 4.5 and hence further experiments were carried out at this pH value. 3.3. Effect of contact time The effect of contact time on uranium uptake is shown in Fig. 3. It was observed that the equilibrium could be reached within 2 h of
Fig. 3. Effect of contact time on uranium uptake (C0 ¼ 200 mg L1, W ¼ 2 g L1, V ¼ 50 mL, pH e 4.5).
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contact. The entire uptake process comprised of two different stages. In the first stage which lasted for 45 min, there was a rapid uptake due to the availability of large number of binding sites. However, as the process continued the number of sites available reduced resulting in a slower uptake which represented the second stage. Such a rapid initial uptake is considered as a good characteristic of a biosorbent (Saini and Melo, 2013). For all the subsequent studies it was ensured that sufficient contact time was provided in order to reach equilibrium.
3.4. Kinetic modeling Lagergren's pseudo first-order and Ho's pseudo-second-order equations were used to model the experimental kinetic data for uranium sorption. The integrated form of Lagergren's pseudo-firstorder reaction can be expressed as follows:
logðqe qt Þ ¼ logðqe Þ ðk1 =2:303Þt
(3)
where qe, qt are the amount of metal sorbed (mg) per unit dry weight (g) of the biosorbent at equilibrium and at time t (min) respectively and k1 is the rate constant of pseudo-first-order sorption (min1). The value of k1 and qe can be calculated from the plot of log(qe qt) versus t. The linear form of Ho's equation for pseudo-second-order reaction can be expressed as (Ho and Wang, 2004):
. t=qt ¼ 1 k2 q2e þ ð1=qe Þt
(4)
where k2 (g mg1 min1) is the rate constant for the pseudosecond-order sorption. The pseudo-second-order rate constant (k2) and qe can be calculated from the intercept and slope of the linear plot of t/qt versus t. The initial uptake rate h [mg (g min)1] can be given as:
h ¼ k2 $q2e
(5)
Rate constant values for uranium uptake by treated hair are shown in Table 1. The value of R2 for pseudo-first-order reaction was found to be 0.91 and the rate constant k1 was 2.3 103 min1. For pseudo-second-order reaction these values were 0.99 and 2.99 103 g mg1 min1 respectively. The experimental qe value is close to the value obtained from pseudo-second-order equation by plotting the graph of t/qt versus t. This suggests that the kinetic data for uranium sorption by treated hair can be well modeled by Ho's pseudo-second-order equation.
Fig. 4. [A] Effect of initial uranium concentration on uptake (C0 ¼ 100e500 mg L1, W ¼ 2 g L1, V ¼ 50 mL, pH e 4.5). [B] Distribution coefficient (Kd) of uranium uptake by treated hair.
sorbent (when the metal ion concentration increases) which provides a driving force and decreases the mass transfer resistance. Distribution coefficient (Kd) is an important parameter describing the sorption process. It is described as the ratio of the equilibrium metal concentration in solid and aqueous phase; having units as mL g1 of biosorbent. The value of Kd decreased from 101 mL g1 to 52 mL g1 as the equilibrium metal ion concentration increased from 86.8 mg L1 to 479 mg L1 (Fig. 4B). The value of Kd in the present study is nearly ten times more than that of adsorbents having Kd values as low as 10 mL g1 which are used in various industrial processes (Chen et al., 1996). A higher Kd value was obtained at lower equilibrium metal concentration, which is an important feature of any sorbent.
3.5. Sorption isotherm 3.5.1. Effect of initial uranium concentration on uptake capacity The effect of initial uranium concentration was studied in the range of 100e500 mg L1 and the results are presented in Fig. 4A. As the initial concentration of the metal was increased, there was an increase in the uptake capacity of the biomass. This could be due to the high probability of collision between the metal ions and the
Table 1 Lagergren's pseudo-first-order, pseudo-second-order, and experimental values for uranium sorption (C0 ¼ 50 mg L1, pH e 4.5, W ¼ 2 g L1). Experimental qe (mg g1)
Pseudo-first-order 1
k1 (min 18.6
2.3
) 10
3
Initial rate, h [mg (g min)1]
Pseudo-second-order 1
qe (mg g 7.2
)
2
R
k2 (g mg
0.91
2.99
1
min
1
) 10
3
qe (mg g 18.8
1
)
2
R
0.99
1.1
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3.5.2. Equilibrium modeling The analysis of sorption equilibrium data is essential as it can be used to compare different biomaterials under different operational conditions. In order to examine the relationship between sorption and aqueous metal concentration at equilibrium, the equilibrium sorption data was modeled using Langmuir and Freundlich adsorption isotherm models. The linearized logarithmic form of Freundlich's equation can be given as follows (Mellah et al., 2006):
ln qe ¼ ln Kf þ 1=nðln Ce Þ
(6)
where ‘qe’ is the equilibrium metal uptake capacity (mg g1), and ‘Ce’ is the residual uranium concentration in the solution (mg L1). The constant ‘Kf’ represents Freundlich constant and it is a measure of adsorption capacity and ‘1/n’ the intensity of adsorption. The linearized form of Langmuir isotherm can be represented as (Bhat et al., 2008):
Ce =qe ¼ ½ð1=qmax Þð1=bÞ þ Ce =qmax
(7)
where ‘qmax’ is the maximum metal uptake (mg g1) and ‘b’ is the ratio of adsorption/desorption rates related to energy of adsorption. qmax and b were calculated from the slope and intercept of the linear plot of Ce/qe versus Ce respectively. The value of another sorption parameter called as separation factor (RL) helps us to understand whether the process is favorable. The value of RL > 1 suggests that the sorption process is unfavorable, RL ¼ 1 represents linear, 0 < RL < 1 relates to favorable and RL ¼ 0 indicates the process is irreversible. It can be observed from Fig. 5C that the separation factor value ranges between 0 and 1 which indicates that uptake of uranium by treated hair sample is favorable under the studied conditions. Also, as the initial concentration of metal ion increases the value of RL decreases. The sorption isotherm parameters were calculated from the slope and intercept values obtained from the Langmuir and Freundlich plot (Fig. 5A,B) and the values are represented in Table 2. Maximum uptake capacity calculated from Langmuir plot was found to be 62.5 mg g1 and compared with different sorbents (Table 3). The constant ‘b’ has a very low value of 0.002 which indicates that the biomass has an affinity towards the metal (Vijayaraghavan et al., 2006). Also, value of 1/n was between 0 and 1 which reflects that the sorption process was favorable under the studied conditions. An uptake in excess of 15% has been shown to have industrial potential (Macaskie and Dean, 1990; Melo and D'Souza, 2004). 3.6. Desorption studies Selection of a suitable eluent for desorption of uranium from the biomass will provide better utilization of the biomass for metal recovery purpose. Desorption studies were carried out in a batch mode using different eluents (1 M each, to recover uranium from hair in a minimum volume of desorbent) for 2 h and the results obtained are shown in Fig. 6. As seen from the graph, nitric acid was found to be the best eluent among the desorbents studied. The order in which the percent desorption decreased was nitric acid > sodium carbonate > hydrocholoric acid > sulfuric acid > sodium bicarbonate. It was possible to achieve a metal
Fig. 5. [A] Langmuir isotherm. [B] Freundlich isotherm for U uptake by treated hair (C0 ¼ 100e500 mg L1, W ¼ 2 g L1, V ¼ 50 mL, pH e 4.5). [C] Separation factor (RL) of uranium uptake by treated hair based on Langmuir isotherm at varying initial uranium concentration.
Table 2 Values of constants obtained from Langmuir and Freundlich isotherms. Langmuir isotherm constants
Freundlich isotherm constants
qmax (mg g1)
b
R2
Kf
n
R2
62.5
0.002
0.98
5
4
0.95
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Table 3 Comparison of maximum loading capacity for uranium by different sorbents (calculated from Langmuir adsorption isotherm). Sorbent material
Biomass (g L1)
U sorption capacity (mg g1)
pH
C0 (mg L1)
References
Impregnated cellulose beads Orange peel Shrimp shells Magnetic chitosan Biocomposite adsorbent Activated carbon NaOH treated hair Exopolysaccharide from Pseudomonas sp.
7 6 20 10 10 4 2 1
7.6 16.1 25.8 42 50.3 57.8 62.5 96
7 4 3.6 5 4 6 4.5 5.7
25e100 25e200 50e875 50e500 25e150 25e300 100e500 25e250
Rule et al., 2014 Li et al., 2013 Ahmed et al., 2014 Stopa and Yamaura, 2010 Aytas et al., 2011 Kütahyali and Eral, 2010 Present study s et al., 1990 Marque
recovery of about 62% under the studied conditions, using nitric acid as a desorbent. Hair is a complex matrix consisting of different moieties which can contribute in the uptake of uranium through co-ordination, complexation or ionic interactions. The recovery of 62% uranium, using 1 M HNO3 represents the metal that was bound through ionic interaction. In HNO3 solution, uranium(VI) generally forms uranyl nitrate which is soluble in water (Li et al., 2013). Also, the higher desorption in the case of using nitric acid lies more on the side that a highly acidic desorbent provides an abundance of Hþ ions and the sorbent's active sites tend to protonate, thus favoring desorption. Thus, nitric acid at a concentration of 1 M was used for desorption of uranium from the hair samples. Moreover, not being able to fully recover sorbed uranium limits the re-use of the material in repeated sorption-desorption cycles.
frequencies of various peaks were shifted. The shift in the peak position from 2848 cm1 to 2881 cm1, changes at around 1178 cm1 and the disappearance of peak at 1784 cm1 indicates the possible role of carboxyl group in the binding of uranium. The shift in peak positions at around 1663 cm1 and 1048 cm1 is due to the changes in the aromatic ring structures of the amino acids present in the hair protein. Peak shift from 1383 cm1 to 1397 cm1 is due to the eCN stretching of amines present in the protein structure of the biomass (after binding to uranium). A sharp and intense peak at 927 cm1 appeared after binding of uranium. This is characteristic of uranyl ion groups and it confirms the binding of uranium to the biomass (Saini and Melo, 2013). Changes in the peak position at around 550e1000 cm1 region can be assigned to the asymmetric stretching vibration of uranyl ion and the stretching vibrations of the weakly bonded oxygen ligand with uranium (Sufia et al., 2009).
3.7. FT-IR analysis
4. Conclusions
FT-IR is useful to identify the functional groups present in a molecule. FT-IR spectra of the biomass before and after uranium binding are shown in Fig. S1. The major peaks that can be assigned to the biomass (before contacting with uranium) are at 3461 cm1 due to the eNeH stretching of amines present in the protein structure of hair, at 2848 cm1 due to eOH stretching of carboxyl group, and around 1663 cm1 due to the eC]Ce stretching overtone of aromatic ring (Silverstein et al., 2005). Peaks at 1784, 1536, 1383 cm1 can be attributed to the eC]O stretching of carboxylic acid, eCeHe bending of alkane, and eCNe stretch of amides respectively. The ^CeHe out of plane bending vibration of aromatic ring is seen at around 1048 cm1 (Silverstein et al., 2005). Due to the interaction of uranium with the biomass the vibrational
Biosorption by natural materials has gained interest in the recent past due to their low cost and wide availability. The present study describes the use of black hair waste, which is commonly available, to remediate uranium in waste water. Alkali treatment significantly increased the uptake capacity of hair. Optimum pH and contact time for uptake was found to be 4.5 and 2 h respectively. qmax of 62.5 mg g1 and Kd value of 100.8 mL g1 were achieved. Thus, considering the advantages of hair in terms of nontoxicity, strength and the non requirement for pelletization, it is possible to use hair directly in a modified on-line water filter for the treatment of uranium contaminated aquatic systems. Appendix A. Supplementary material Supplementary data related to this article can be found online at http://dx.doi.org/10.1016/j.jenvrad.2015.01.006. References
Fig. 6. Effect of different eluent on % desorption of uranium.
Ahmed, S.H., Sheikh, E.M.E., Morsy, A.M.A., 2014. Potentiality of uranium biosorption from nitric acid solutions using shrimp shells. J. Environ. Radioactivity 134, 120e127. Aytas, S., Turkozu, D.A., Gok, C., 2011. Biosorption of uranium(VI) by bifunctionalized low cost biocomposite adsorbent. Desalination 280, 354e362. Bhainsa, K.C., D'Souza, S.F., 1999. Biosorption of uranium(VI) by Aspergillus fumigatus. Biotechnol. Tech. 13, 695e699. Bhat, S.V., Melo, J.S., Chaugule, B.B., D'Souza, S.F., 2008. Biosorption characteristics of uranium(VI) from aqueous medium onto Catenella repens, a red alga. J. Hazard. Mater. 158, 628e635. Carolina, A., Nogueira, S., Joekes, I., 2007. Hair melanin content and photodamage. J. Cosmet. Sci. 58, 385e391. Chakraborty, D., Maji, S., Bandyopadhyay, A., Basu, S., 2007. Biosorption of cesium137 and strontium-90 by mucilaginous seeds of Ocimum basilicum. Bioresour. Technol. 98, 2949e2952. Chen, J.P., Chen, W.R., Hsu, R.C., 1996. Biosorption of copper from aqueous solutions by plant root tissues. J. Ferment. Bioeng. 81, 458e463. Collins, Y.E., Stotzky, G., 1992. Heavy metals alter the electrokinetic properties of bacteria, yeasts and clay minerals. Appl. Environ. Microbiol. 58, 1592e1600.
A.S. Saini, J.S. Melo / Journal of Environmental Radioactivity 142 (2015) 29e35 Ding, Y., Jing, D., Gong, H., Zhou, L., Yang, X., 2012. Biosorption of aquatic cadmium(II) by unmodified rice straw. Bioresour. Technol. 114, 20e25. Guibal, E., Roulph, C., Le, C.P., 1992. Uranium biosorption by a filamentous fungus Mucor meihei: pH effect on the mechanisms and performances of uptake. Water Res. 26, 1139e1145. Gupte, A., Karjikar, M., Nairarar, J., 2012. Biosorption of copper using mucilaginous seeds of Ocimum basilicum. Acta Biol. Indica 1, 113e119. Ho, Y.S., Wang, C.C., 2004. Pseudo-isotherms for the sorption of cadmium ion onto tree fern. Process Biochem. 39, 759e763. Kar, P., Misra, M., 2004. Use of keratin fiber for separation of heavy metals from water. J. Chem. Technol. Biotechnol. 79, 1313e1319. Katsoyiannis, I.A., 2007. Carbonate effects and pH-dependence of uranium sorption onto bacteriogenic iron oxides: kinetic and equilibrium studies. J. Hazard. Mater. B 139, 31e37. Kütahyali, C., Eral, M., 2010. Sorption studies of uranium and thorium on activated carbon prepared from olive stones: kinetic and thermodynamic aspects. J. Nucl. Mater. 396, 251e256. Li, X., Wu, J., Liao, J., Zhang, D., Yang, J., Feng, Y., Zeng, J., Wen, W., Yang, Y., Tang, J., Liu, N., 2013. Adsorption and desorption of uranium(VI) in aerated zone soil. J. Environ. Radioactivity 115, 143e150. Macaskie, L.E., Dean, A.C.R., 1990. Metal-sequestering biochemicals. In: Volesky, B. (Ed.), Biosorption of Heavy Metals. CRC Press, Boca Raton, Florida, pp. 199e248. s, A.N., Bonet, R., Simon-Pujol, M.D., Fuste , M.C., Congregado, F., 1990. Marque Removal of uranium by an exopolysaccharide from Pseudomonas sp. Appl. Microbiol. Biotechnol. 34, 429e431. Mellah, A., Chegrouche, S., Barkat, M., 2006. The removal of uranium(VI) from aqueous solutions onto activated carbon: kinetic and thermodynamic investigations. J. Colloid Interf. Sci. 296, 434e441. Melo, J.S., D'Souza, S.F., 2004. Removal of chromium by mucilaginous seeds of Ocimum basilicum. Bioresour. Technol. 92, 151e155. Robbins, C.R., Crawford, R.J., 1991. Cuticle damages and the tensile properties of human hair. J. Cosmet. Sci. 42, 59e67. Rule, P., Balasubramanian, K., Gonte, R.R., 2014. Uranium(VI) remediation from aqueous environment using impregnated cellulose beads. J. Environ. Radioactivity 136, 22e29.
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Saini, A.S., Melo, J.S., 2013. Biosorption of uranium by melanin: kinetic, equilibrium and thermodynamic studies. Bioresour. Technol. 149, 155e162. Sar, P., D'Souza, S.F., 2001. Biosorptive uranium uptake by a Pseudomonas strain: characterization and equilibrium studies. J. Chem. Technol. Biotechnol. 76, 1286e1294. Shumate II, S.E., Strandberg, G.W., Parrott Jr., J.R., 1978. Biological removal of metal ions from aqueous process streams. Biotechnol. Bioeng. Symp. 8, 13e20. Silverstein, R.M., Webster, F.X., Kiemle, D.J., 2005. Spectrometric Identification of Organic Compounds, seventh ed. John Wiley & Sons Inc., New York. Sodaye, H., Nisan, S., Poletiko, C., Prabhakar, S., Tewari, P.K., 2009. Extraction of uranium from the concentrated brine rejected by integrated nuclear desalination plants. Desalination 235, 9e32. Stopa, B., Yamaura, M., 2010. Uranium removal by chitosan impregnated with magnetite nanoparticles: adsorption and desorption. Int. J. Nucl. Energy Sci. Technol. 5, 283e289. Sufia, K.K., D'Souza, S.F., Sar, P., 2009. Uranium and thorium sequestration by a Pseudomonas sp.: mechanism and chemical characterization. J. Hazard. Mater. 163, 65e72. Suyama, K., Fukazawa, Y., Suzumura, H., 1996. Biosorption of precious metal ions by chicken feather. Appl. Biochem. Biotechnol. 57e58, 67e74. Tan, T.C., Chia, C.K., Teo, C.K., 1985. Uptake of metal ions by chemically treated human hair. Water Res. 19, 157e162. Tuzen, M., Sari, A., 2010. Biosorption of selenium from aqueous solution by green algae (Cladophora hutchinsiae) biomass: equilibrium, thermodynamic and kinetic studies. Chem. Eng. J. 158, 200e206. Vijayaraghavan, K., Palanivelu, K., Velan, M., 2006. Biosorption of copper(II) and cobalt(II) from aqueous solutions by crab shell particles. Bioresour. Technol. 97, 1411e1419. Wang, J., Hu, X., Liu, Y., Xie, S., Bao, Z., 2010. Biosorption of uranium(VI) by immobilized Aspergillus fumigatus beads. J. Environ. Radioactivity 101, 504e508. World Health Organization, 2004. Uranium in Drinking Water (Background Document for the Development of WHO Guidelines for Drinking-water, Quality. WHO/SDE/WSH/03.04/118).
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Journal of Environmental Radioactivity journal homepage: www.elsevier.com/locate/jenvrad
Biosorption of uranium by human black hair Amardeep Singh Saini, Jose Savio Melo* Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 October 2014 Received in revised form 5 January 2015 Accepted 6 January 2015 Available online
Naturally available low cost materials have gained importance as effective alternative to conventional sorbents for the removal of metal ions from water. The present study describes the use of black hair waste as a sorbent for the removal of uranium ions from an aqueous medium. Alkali treatment of the biomass resulted in a significant increase in its uptake capacity. The optimum pH and contact time for uranium removal were 4.5 and 2 h respectively. It was observed that the experimental data fits well in Ho's pseudo-second order kinetic model. Binding of uranium to the biomass was confirmed using FT-IR spectroscopy. Thus, the present study could demonstrate the utility of human black hair to remove uranium from aqueous medium. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Black hair Uranium Biosorption Kinetics
1. Introduction A surge in industrialization has led to an increase in metal contamination of aquatic bodies, causing a worldwide problem. Also, metal toxicity and non-biodegradability pose a challenge related to health hazards. Hence, there is a need for economical methods to treat such waste. Uranium is one such metal that is known to pollute the environment through activities associated with nuclear industry. It has both radiochemical and toxicological effects. Excessive amounts of uranium can cause nephritis in human beings and due to carcinogenicity, lead to bone cancer (Katsoyiannis, 2007). Maximum contaminant level (MCL) of uranium in potable drinking water has been established as 15 mg L1 by WHO (2004). A large amount of uranium gets added every year to the sea by the global fresh water streams (Sodaye et al., 2009). Thus, the removal of uranium from waste water is a subject of continual research. Conventional systems of treatment are best suited for solutions having high metal concentrations. With increasing stringency in regulations and the possibility of discharge limits decreasing even further, there arises a need to devise alternative or complementing systems for waste treatment. Biosorption is becoming one of the most attractive and efficient processes to remove metals and radionuclides. Biosorbents have shown potential for accumulating metal ions present in low
* Corresponding author. Tel.: þ91 22 25592760; fax: þ91 22 25505151. E-mail addresses: [email protected] (A.S. Saini), jsmelo@barc. gov.in (J.S. Melo). http://dx.doi.org/10.1016/j.jenvrad.2015.01.006 0265-931X/© 2015 Elsevier Ltd. All rights reserved.
concentrations in the medium. In view of this, natural materials have been attracting much interest as sorbents. To date, various natural materials such as Cladophora hutchinsiae (Tuzen and Sari, 2010), Aspergillus fumigatus (Wang et al., 2010), Catenella repens (Bhat et al., 2008) and rice straw (Ding et al., 2012) have been reported for metal removal. Melo and D'Souza (2004) reported on the use of a natural bioresource, Ocimum basilicum seeds, for chromium uptake. Chakraborty et al. (2007) further investigated this resource for cesium and strontium removal, whereas Gupte et al. (2012) applied it for biosorption of copper. Non-living biomasses of filamentous fungi and bacteria have been reported in our laboratory for the removal of uranium from aqueous medium (Bhainsa and D'Souza, 1999; Sar and D'Souza, 2001). Recently, Saini and Melo (2013) showed the use of biosynthesized melanin pigment for the removal of uranium from an aqueous system in a batch process. Also, Kar and Misra (2004) showed the use of keratin fiber extracted from bird feathers for the separation of metals from water. Suyama et al. (1996) used chicken feathers directly for the biosorption of precious metals such as gold and platinum. Black hair is a bioresource that contains keratin as well as melanin in a naturally immobilized form. The black hair fiber mainly consists of keratin proteins that comprise about 65e95% of the total hair fiber by weight. The remaining constituents are water, lipids, melanin and trace elements (Robbins and Crawford, 1991). The majority of the hair shaft mass comprises the cortex, which is responsible for mechanical properties of the hair fiber. Inside the cortex are the melanin granules that constitute about 3% by weight of hair (Carolina et al., 2007). In India, and other
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countries in the sub-continent, there is large availability of black hair which was the primary reason for choosing black hair for the present study. To the best of our knowledge, black hair has not been investigated for uranium bioremediation. The advantage of human black hair waste over other similar biosorbents is because hair is an abundant and cheap bioresource. Moreover the properties like high tensile strength, non-toxicity and water insolubility make it more attractive for biosorption. It is highly resistant to the action of acids, other harsh chemicals and also to environmental degradation, all of which might have adverse effects on other types of biomass. Many biomass materials require further processing in terms of pelletization or immobilization unlike hair which can be used directly. Therefore the application of this material for treating waste water is economical and involves the utilization of one waste to treat another waste. Thus, in the present study, removal of uranium was studied using human black hair waste which is widely available as a natural resource. The factors affecting the sorption process such as pH, equilibration time and initial uranium concentration were investigated. Kinetics of the adsorption process was studied and equilibrium sorption data was fitted into well known adsorption isotherms. The presence of uranium on the biomass was confirmed with the help of FT-IR spectroscopy.
biomass was kept as control in all the experiments. All studies were performed in triplicates and the data represented are mean of triplicates with standard deviation as the error bar. 2.5. Kinetic and equilibrium studies For kinetic studies, uranium solution (pH 4.5) at 200 mg L1 was kept in contact with treated hair and samples of liquid were taken at regular intervals for measurement of uranium. Kinetic modeling of uranium sorption onto treated hair was done by using Lagergren's pseudo-first and Ho's pseudo-second-order equations. Equilibrium studies were carried out by varying the initial uranium concentration from 100 to 500 mg L1 at a fixed sorbent concentration of 2 g L1. Samples were taken after 24 h of contact, as it was sufficient for the reaction to reach equilibrium. The relation between sorbed and aqueous concentration of uranium at equilibrium was examined using Langmuir and Freundlich adsorption isotherms. 2.6. Uranium estimation and metal uptake capacity
2. Materials and methods
Uranium concentration was estimated in the supernatant obtained after centrifuging, by using Arsenazo III reagent (Shumate et al., 1978). Uranium uptake per gram of hair was calculated using the following equation:
2.1. Biomass
qe ¼ ðC0 Ce ÞV=W
The black hair samples collected from a nearby salon were thoroughly washed with detergent and water to wash out any impurities and then with acetone, to remove oil/lipids. The biomass was then dried at 303 K for 24 h and stored at room temperature for further use. 2.2. Preparation of biomass Alkali treatment of hair was carried out by using varying concentrations of NaOH. For this, 100 mg of dried hair sample was added to 25 mL of different concentrations of NaOH (0.01, 0.1, 0.2 N, 0.3 N) respectively and left for treatment overnight at 298 K on an orbital shaker (MAXQ 4000, Thermo Scientific) at 150 rpm. After 24 h the alkali was decanted and hair samples were washed thoroughly with distilled water to get rid of traces of NaOH. After washing, the hair samples were further dried completely at 303 K for 24 h and stored at room temperature. The resulting biomass is referred to as treated biomass. 2.3. Solutions Uranium stock solution of 2000 mg L1 was prepared by dissolving the required amount of uranyl nitrate hexahydrate (Merck, Germany) in distilled water at room temperature and later diluted to the desired concentration as required. All the other chemicals used were of analytical grade. 2.4. Batch sorption studies Biomass (0.2 N NaOH treated hair) at 2 g L1 was kept in contact with 200 mg L1 of uranium solution unless otherwise indicated. The pH of the solution was adjusted to the required value by adding 0.1 N NaOH or HNO3 before contact with the biomass. The samples were agitated at 150 rpm on orbital shaker maintained at 298 K. Aliquots were collected at regular time intervals and centrifuged (Spinwin, Tarsons, 5585 g) for 5 min, to quantify the residual uranium concentration in the supernatant. A solution without the
(1)
where qe represents the metal uptake capacity, ‘C0’ and ‘Ce’ represent the concentration of uranium (mg L1) before and after sorption respectively. ‘V’ stands for the volume of uranium solution in L and ‘W’ is the amount of hair used in grams. 2.7. Desorption study For desorption studies, different eluents such as hydrochloric acid, nitric acid, sulfuric acid, sodium carbonate and sodium bicarbonate were added at a constant molar concentration of 1 M. The solutions were agitated at 150 rpm on an orbital shaker and the % desorption was calculated using the following equation:
%desorption ¼ ðUdesorbed =Uadsorbed Þ 100
(2)
where Udesorbed represents the concentration of uranium in the supernatant after desorption and Uadsorbed is the concentration of uranium bound to hair after the adsorption cycle. Before carrying out the desorption study, adsorption of uranium on treated hair was performed. For this, treated hair (2 g L1) was contacted with 50 mL of 100 mg L1 uranium solution at pH 4.5. After 24 h of contact, the solution was centrifuged in order to quantify uranium present in the supernatant and the hair pellet was dried at 310 K for 3 h. After drying, 5 mL of respective 1 M eluent was added to the uranium bound hair pellet for desorption. 2.8. FT-IR analysis of treated hair bound with uranium Treated hair (1 g L1) was kept in contact with uranium solution of 200 mg L1 (pH 4.5) at 298 K and agitated at 150 rpm. After 24 h of contact the solution was centrifuged and the pellet obtained was dried completely and used for FT-IR analysis. Treated hair (1 g L1) incubated in distilled water under the above mentioned conditions served as a control. For FT-IR, hair samples with and without uranium were cut into fine pieces with the help of a scissor and mixed with IR grade KBr powder (4% w/w). The mixture was then ground using a mortar and pestle and the FT-IR spectrum of this ground mixture was recorded using Jasco FT-IR 660 plus spectrometer. The
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31
spectra were recorded over 4000e400 cm1 range with a resolution of 4 cm1. 3. Results and discussion 3.1. Effect of treatment on uranium uptake by black hair Different concentrations of NaOH (0.01, 0.1, 0.2, 0.3 N) were used to study the effect of alkali on uranium uptake by the hair samples. As seen from Fig. 1, as the concentration of NaOH increased from 0.01 to 0.3 N, the metal uptake capacity also increased from 9.1 ± 0.1 mg g1 to 18.7 ± 0.2 mg g1. The uranium uptake by the control (without alkali treatment) was 3.9 ± 0.3 mg g1 whereas, hair treated with 0.2 N NaOH showed an uptake of 17.6 ± 0.4 mg g1, which was almost four times more than that of control. Such increase in the metal uptake after alkali treatment has also been reported by Tan et al. (1985) and attributed to the increase the porosity of the keratin structure. As there was no significant increase (P < 0.05) in the qe value on treatment with 0.3 N NaOH as compared to 0.2 N NaOH, hair treated with 0.2 N NaOH was used for further studies. 3.2. Effect of pH on sorption pH is one of the most important parameters affecting the adsorption process. The effect of pH on the uranium uptake capacity of alkali treated hair samples was studied in the pH range of 2.5e7. As seen from Fig. 2, when the pH of the system increased from 2.5 to 7, the uptake capacity of the treated biomass increased up to pH 4.5 and then decreased. Less uptake value at lower pH can be due to the competition of Hþ ions with uranyl ions for the binding sites present on the biomass. Also, at low pH value divalent UOþ2 2 are present as the dominant species. Being divalent in nature it replaces two protons from adjacent sides, however if these sites are far apart then they are not available for binding. In other words, at low pH some binding sites are not available to the divalent UOþ2 2 . However, at an acidic pH of 2.5, it was possible to achieve an uptake capacity of 6.2 ± 0.4 mg g1 which is nearly 52% of the value obtained at pH 4.5. Similar results were observed by Bhat et al. (2008) wherein they indicated the possible use of the biomass at acidic pH. Mechanisms such as ion exchange and complexation can play an important role in binding to uranium. Hair in general contains keratin which shows the presence of carboxylic group in its structure. These groups have a pKa value around 4.5. When the pH
Fig. 1. Effect of different concentrations of NaOH on uptake capacity (C0 ¼ 200 mg L1, W ¼ 2 g L1, V ¼ 50 mL, pH e 4.5).
Fig. 2. Effect of pH on uranium uptake capacity of treated and untreated biomass (C0 ¼ 50 mg L1, W ¼ 2 g L1, V ¼ 50 mL).
of the system reaches this value, these groups get ionized completely and are available for binding, resulting in high uptake. Also at pH of 4.5, monovalent and divalent hydrolyzed ions þ2 UO2OHþ, ðUO2 Þ3 ðOHÞþ exist in the solution. 5 , and ðUO2 Þ2 ðOHÞ2 According to Collins and Stotzky (1992), hydrolyzed species can be sorbed better than the free hydrated ions. Particularly, compared with the divalent hydrolyzed ions, the monovalent ions have even higher affinity to the biomass in ion exchange with the protons because they could replace single protons on separate binding sites in the biomass. At higher pH values, formation of solid schoepite takes place which decreases the dissolved uranium concentration in the solution, and consequently leads to the reduced sorption of uranium onto the biomass. Guibal et al. (1992) observed a decrease in uranium uptake on filamentous fungus biomass at pH 6.0. A maximum qe value of 12 ± 0.3 mg g1 was obtained at pH 4.5 and hence further experiments were carried out at this pH value. 3.3. Effect of contact time The effect of contact time on uranium uptake is shown in Fig. 3. It was observed that the equilibrium could be reached within 2 h of
Fig. 3. Effect of contact time on uranium uptake (C0 ¼ 200 mg L1, W ¼ 2 g L1, V ¼ 50 mL, pH e 4.5).
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contact. The entire uptake process comprised of two different stages. In the first stage which lasted for 45 min, there was a rapid uptake due to the availability of large number of binding sites. However, as the process continued the number of sites available reduced resulting in a slower uptake which represented the second stage. Such a rapid initial uptake is considered as a good characteristic of a biosorbent (Saini and Melo, 2013). For all the subsequent studies it was ensured that sufficient contact time was provided in order to reach equilibrium.
3.4. Kinetic modeling Lagergren's pseudo first-order and Ho's pseudo-second-order equations were used to model the experimental kinetic data for uranium sorption. The integrated form of Lagergren's pseudo-firstorder reaction can be expressed as follows:
logðqe qt Þ ¼ logðqe Þ ðk1 =2:303Þt
(3)
where qe, qt are the amount of metal sorbed (mg) per unit dry weight (g) of the biosorbent at equilibrium and at time t (min) respectively and k1 is the rate constant of pseudo-first-order sorption (min1). The value of k1 and qe can be calculated from the plot of log(qe qt) versus t. The linear form of Ho's equation for pseudo-second-order reaction can be expressed as (Ho and Wang, 2004):
. t=qt ¼ 1 k2 q2e þ ð1=qe Þt
(4)
where k2 (g mg1 min1) is the rate constant for the pseudosecond-order sorption. The pseudo-second-order rate constant (k2) and qe can be calculated from the intercept and slope of the linear plot of t/qt versus t. The initial uptake rate h [mg (g min)1] can be given as:
h ¼ k2 $q2e
(5)
Rate constant values for uranium uptake by treated hair are shown in Table 1. The value of R2 for pseudo-first-order reaction was found to be 0.91 and the rate constant k1 was 2.3 103 min1. For pseudo-second-order reaction these values were 0.99 and 2.99 103 g mg1 min1 respectively. The experimental qe value is close to the value obtained from pseudo-second-order equation by plotting the graph of t/qt versus t. This suggests that the kinetic data for uranium sorption by treated hair can be well modeled by Ho's pseudo-second-order equation.
Fig. 4. [A] Effect of initial uranium concentration on uptake (C0 ¼ 100e500 mg L1, W ¼ 2 g L1, V ¼ 50 mL, pH e 4.5). [B] Distribution coefficient (Kd) of uranium uptake by treated hair.
sorbent (when the metal ion concentration increases) which provides a driving force and decreases the mass transfer resistance. Distribution coefficient (Kd) is an important parameter describing the sorption process. It is described as the ratio of the equilibrium metal concentration in solid and aqueous phase; having units as mL g1 of biosorbent. The value of Kd decreased from 101 mL g1 to 52 mL g1 as the equilibrium metal ion concentration increased from 86.8 mg L1 to 479 mg L1 (Fig. 4B). The value of Kd in the present study is nearly ten times more than that of adsorbents having Kd values as low as 10 mL g1 which are used in various industrial processes (Chen et al., 1996). A higher Kd value was obtained at lower equilibrium metal concentration, which is an important feature of any sorbent.
3.5. Sorption isotherm 3.5.1. Effect of initial uranium concentration on uptake capacity The effect of initial uranium concentration was studied in the range of 100e500 mg L1 and the results are presented in Fig. 4A. As the initial concentration of the metal was increased, there was an increase in the uptake capacity of the biomass. This could be due to the high probability of collision between the metal ions and the
Table 1 Lagergren's pseudo-first-order, pseudo-second-order, and experimental values for uranium sorption (C0 ¼ 50 mg L1, pH e 4.5, W ¼ 2 g L1). Experimental qe (mg g1)
Pseudo-first-order 1
k1 (min 18.6
2.3
) 10
3
Initial rate, h [mg (g min)1]
Pseudo-second-order 1
qe (mg g 7.2
)
2
R
k2 (g mg
0.91
2.99
1
min
1
) 10
3
qe (mg g 18.8
1
)
2
R
0.99
1.1
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33
3.5.2. Equilibrium modeling The analysis of sorption equilibrium data is essential as it can be used to compare different biomaterials under different operational conditions. In order to examine the relationship between sorption and aqueous metal concentration at equilibrium, the equilibrium sorption data was modeled using Langmuir and Freundlich adsorption isotherm models. The linearized logarithmic form of Freundlich's equation can be given as follows (Mellah et al., 2006):
ln qe ¼ ln Kf þ 1=nðln Ce Þ
(6)
where ‘qe’ is the equilibrium metal uptake capacity (mg g1), and ‘Ce’ is the residual uranium concentration in the solution (mg L1). The constant ‘Kf’ represents Freundlich constant and it is a measure of adsorption capacity and ‘1/n’ the intensity of adsorption. The linearized form of Langmuir isotherm can be represented as (Bhat et al., 2008):
Ce =qe ¼ ½ð1=qmax Þð1=bÞ þ Ce =qmax
(7)
where ‘qmax’ is the maximum metal uptake (mg g1) and ‘b’ is the ratio of adsorption/desorption rates related to energy of adsorption. qmax and b were calculated from the slope and intercept of the linear plot of Ce/qe versus Ce respectively. The value of another sorption parameter called as separation factor (RL) helps us to understand whether the process is favorable. The value of RL > 1 suggests that the sorption process is unfavorable, RL ¼ 1 represents linear, 0 < RL < 1 relates to favorable and RL ¼ 0 indicates the process is irreversible. It can be observed from Fig. 5C that the separation factor value ranges between 0 and 1 which indicates that uptake of uranium by treated hair sample is favorable under the studied conditions. Also, as the initial concentration of metal ion increases the value of RL decreases. The sorption isotherm parameters were calculated from the slope and intercept values obtained from the Langmuir and Freundlich plot (Fig. 5A,B) and the values are represented in Table 2. Maximum uptake capacity calculated from Langmuir plot was found to be 62.5 mg g1 and compared with different sorbents (Table 3). The constant ‘b’ has a very low value of 0.002 which indicates that the biomass has an affinity towards the metal (Vijayaraghavan et al., 2006). Also, value of 1/n was between 0 and 1 which reflects that the sorption process was favorable under the studied conditions. An uptake in excess of 15% has been shown to have industrial potential (Macaskie and Dean, 1990; Melo and D'Souza, 2004). 3.6. Desorption studies Selection of a suitable eluent for desorption of uranium from the biomass will provide better utilization of the biomass for metal recovery purpose. Desorption studies were carried out in a batch mode using different eluents (1 M each, to recover uranium from hair in a minimum volume of desorbent) for 2 h and the results obtained are shown in Fig. 6. As seen from the graph, nitric acid was found to be the best eluent among the desorbents studied. The order in which the percent desorption decreased was nitric acid > sodium carbonate > hydrocholoric acid > sulfuric acid > sodium bicarbonate. It was possible to achieve a metal
Fig. 5. [A] Langmuir isotherm. [B] Freundlich isotherm for U uptake by treated hair (C0 ¼ 100e500 mg L1, W ¼ 2 g L1, V ¼ 50 mL, pH e 4.5). [C] Separation factor (RL) of uranium uptake by treated hair based on Langmuir isotherm at varying initial uranium concentration.
Table 2 Values of constants obtained from Langmuir and Freundlich isotherms. Langmuir isotherm constants
Freundlich isotherm constants
qmax (mg g1)
b
R2
Kf
n
R2
62.5
0.002
0.98
5
4
0.95
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Table 3 Comparison of maximum loading capacity for uranium by different sorbents (calculated from Langmuir adsorption isotherm). Sorbent material
Biomass (g L1)
U sorption capacity (mg g1)
pH
C0 (mg L1)
References
Impregnated cellulose beads Orange peel Shrimp shells Magnetic chitosan Biocomposite adsorbent Activated carbon NaOH treated hair Exopolysaccharide from Pseudomonas sp.
7 6 20 10 10 4 2 1
7.6 16.1 25.8 42 50.3 57.8 62.5 96
7 4 3.6 5 4 6 4.5 5.7
25e100 25e200 50e875 50e500 25e150 25e300 100e500 25e250
Rule et al., 2014 Li et al., 2013 Ahmed et al., 2014 Stopa and Yamaura, 2010 Aytas et al., 2011 Kütahyali and Eral, 2010 Present study s et al., 1990 Marque
recovery of about 62% under the studied conditions, using nitric acid as a desorbent. Hair is a complex matrix consisting of different moieties which can contribute in the uptake of uranium through co-ordination, complexation or ionic interactions. The recovery of 62% uranium, using 1 M HNO3 represents the metal that was bound through ionic interaction. In HNO3 solution, uranium(VI) generally forms uranyl nitrate which is soluble in water (Li et al., 2013). Also, the higher desorption in the case of using nitric acid lies more on the side that a highly acidic desorbent provides an abundance of Hþ ions and the sorbent's active sites tend to protonate, thus favoring desorption. Thus, nitric acid at a concentration of 1 M was used for desorption of uranium from the hair samples. Moreover, not being able to fully recover sorbed uranium limits the re-use of the material in repeated sorption-desorption cycles.
frequencies of various peaks were shifted. The shift in the peak position from 2848 cm1 to 2881 cm1, changes at around 1178 cm1 and the disappearance of peak at 1784 cm1 indicates the possible role of carboxyl group in the binding of uranium. The shift in peak positions at around 1663 cm1 and 1048 cm1 is due to the changes in the aromatic ring structures of the amino acids present in the hair protein. Peak shift from 1383 cm1 to 1397 cm1 is due to the eCN stretching of amines present in the protein structure of the biomass (after binding to uranium). A sharp and intense peak at 927 cm1 appeared after binding of uranium. This is characteristic of uranyl ion groups and it confirms the binding of uranium to the biomass (Saini and Melo, 2013). Changes in the peak position at around 550e1000 cm1 region can be assigned to the asymmetric stretching vibration of uranyl ion and the stretching vibrations of the weakly bonded oxygen ligand with uranium (Sufia et al., 2009).
3.7. FT-IR analysis
4. Conclusions
FT-IR is useful to identify the functional groups present in a molecule. FT-IR spectra of the biomass before and after uranium binding are shown in Fig. S1. The major peaks that can be assigned to the biomass (before contacting with uranium) are at 3461 cm1 due to the eNeH stretching of amines present in the protein structure of hair, at 2848 cm1 due to eOH stretching of carboxyl group, and around 1663 cm1 due to the eC]Ce stretching overtone of aromatic ring (Silverstein et al., 2005). Peaks at 1784, 1536, 1383 cm1 can be attributed to the eC]O stretching of carboxylic acid, eCeHe bending of alkane, and eCNe stretch of amides respectively. The ^CeHe out of plane bending vibration of aromatic ring is seen at around 1048 cm1 (Silverstein et al., 2005). Due to the interaction of uranium with the biomass the vibrational
Biosorption by natural materials has gained interest in the recent past due to their low cost and wide availability. The present study describes the use of black hair waste, which is commonly available, to remediate uranium in waste water. Alkali treatment significantly increased the uptake capacity of hair. Optimum pH and contact time for uptake was found to be 4.5 and 2 h respectively. qmax of 62.5 mg g1 and Kd value of 100.8 mL g1 were achieved. Thus, considering the advantages of hair in terms of nontoxicity, strength and the non requirement for pelletization, it is possible to use hair directly in a modified on-line water filter for the treatment of uranium contaminated aquatic systems. Appendix A. Supplementary material Supplementary data related to this article can be found online at http://dx.doi.org/10.1016/j.jenvrad.2015.01.006. References
Fig. 6. Effect of different eluent on % desorption of uranium.
Ahmed, S.H., Sheikh, E.M.E., Morsy, A.M.A., 2014. Potentiality of uranium biosorption from nitric acid solutions using shrimp shells. J. Environ. Radioactivity 134, 120e127. Aytas, S., Turkozu, D.A., Gok, C., 2011. Biosorption of uranium(VI) by bifunctionalized low cost biocomposite adsorbent. Desalination 280, 354e362. Bhainsa, K.C., D'Souza, S.F., 1999. Biosorption of uranium(VI) by Aspergillus fumigatus. Biotechnol. Tech. 13, 695e699. Bhat, S.V., Melo, J.S., Chaugule, B.B., D'Souza, S.F., 2008. Biosorption characteristics of uranium(VI) from aqueous medium onto Catenella repens, a red alga. J. Hazard. Mater. 158, 628e635. Carolina, A., Nogueira, S., Joekes, I., 2007. Hair melanin content and photodamage. J. Cosmet. Sci. 58, 385e391. Chakraborty, D., Maji, S., Bandyopadhyay, A., Basu, S., 2007. Biosorption of cesium137 and strontium-90 by mucilaginous seeds of Ocimum basilicum. Bioresour. Technol. 98, 2949e2952. Chen, J.P., Chen, W.R., Hsu, R.C., 1996. Biosorption of copper from aqueous solutions by plant root tissues. J. Ferment. Bioeng. 81, 458e463. Collins, Y.E., Stotzky, G., 1992. Heavy metals alter the electrokinetic properties of bacteria, yeasts and clay minerals. Appl. Environ. Microbiol. 58, 1592e1600.
A.S. Saini, J.S. Melo / Journal of Environmental Radioactivity 142 (2015) 29e35 Ding, Y., Jing, D., Gong, H., Zhou, L., Yang, X., 2012. Biosorption of aquatic cadmium(II) by unmodified rice straw. Bioresour. Technol. 114, 20e25. Guibal, E., Roulph, C., Le, C.P., 1992. Uranium biosorption by a filamentous fungus Mucor meihei: pH effect on the mechanisms and performances of uptake. Water Res. 26, 1139e1145. Gupte, A., Karjikar, M., Nairarar, J., 2012. Biosorption of copper using mucilaginous seeds of Ocimum basilicum. Acta Biol. Indica 1, 113e119. Ho, Y.S., Wang, C.C., 2004. Pseudo-isotherms for the sorption of cadmium ion onto tree fern. Process Biochem. 39, 759e763. Kar, P., Misra, M., 2004. Use of keratin fiber for separation of heavy metals from water. J. Chem. Technol. Biotechnol. 79, 1313e1319. Katsoyiannis, I.A., 2007. Carbonate effects and pH-dependence of uranium sorption onto bacteriogenic iron oxides: kinetic and equilibrium studies. J. Hazard. Mater. B 139, 31e37. Kütahyali, C., Eral, M., 2010. Sorption studies of uranium and thorium on activated carbon prepared from olive stones: kinetic and thermodynamic aspects. J. Nucl. Mater. 396, 251e256. Li, X., Wu, J., Liao, J., Zhang, D., Yang, J., Feng, Y., Zeng, J., Wen, W., Yang, Y., Tang, J., Liu, N., 2013. Adsorption and desorption of uranium(VI) in aerated zone soil. J. Environ. Radioactivity 115, 143e150. Macaskie, L.E., Dean, A.C.R., 1990. Metal-sequestering biochemicals. In: Volesky, B. (Ed.), Biosorption of Heavy Metals. CRC Press, Boca Raton, Florida, pp. 199e248. s, A.N., Bonet, R., Simon-Pujol, M.D., Fuste , M.C., Congregado, F., 1990. Marque Removal of uranium by an exopolysaccharide from Pseudomonas sp. Appl. Microbiol. Biotechnol. 34, 429e431. Mellah, A., Chegrouche, S., Barkat, M., 2006. The removal of uranium(VI) from aqueous solutions onto activated carbon: kinetic and thermodynamic investigations. J. Colloid Interf. Sci. 296, 434e441. Melo, J.S., D'Souza, S.F., 2004. Removal of chromium by mucilaginous seeds of Ocimum basilicum. Bioresour. Technol. 92, 151e155. Robbins, C.R., Crawford, R.J., 1991. Cuticle damages and the tensile properties of human hair. J. Cosmet. Sci. 42, 59e67. Rule, P., Balasubramanian, K., Gonte, R.R., 2014. Uranium(VI) remediation from aqueous environment using impregnated cellulose beads. J. Environ. Radioactivity 136, 22e29.
35
Saini, A.S., Melo, J.S., 2013. Biosorption of uranium by melanin: kinetic, equilibrium and thermodynamic studies. Bioresour. Technol. 149, 155e162. Sar, P., D'Souza, S.F., 2001. Biosorptive uranium uptake by a Pseudomonas strain: characterization and equilibrium studies. J. Chem. Technol. Biotechnol. 76, 1286e1294. Shumate II, S.E., Strandberg, G.W., Parrott Jr., J.R., 1978. Biological removal of metal ions from aqueous process streams. Biotechnol. Bioeng. Symp. 8, 13e20. Silverstein, R.M., Webster, F.X., Kiemle, D.J., 2005. Spectrometric Identification of Organic Compounds, seventh ed. John Wiley & Sons Inc., New York. Sodaye, H., Nisan, S., Poletiko, C., Prabhakar, S., Tewari, P.K., 2009. Extraction of uranium from the concentrated brine rejected by integrated nuclear desalination plants. Desalination 235, 9e32. Stopa, B., Yamaura, M., 2010. Uranium removal by chitosan impregnated with magnetite nanoparticles: adsorption and desorption. Int. J. Nucl. Energy Sci. Technol. 5, 283e289. Sufia, K.K., D'Souza, S.F., Sar, P., 2009. Uranium and thorium sequestration by a Pseudomonas sp.: mechanism and chemical characterization. J. Hazard. Mater. 163, 65e72. Suyama, K., Fukazawa, Y., Suzumura, H., 1996. Biosorption of precious metal ions by chicken feather. Appl. Biochem. Biotechnol. 57e58, 67e74. Tan, T.C., Chia, C.K., Teo, C.K., 1985. Uptake of metal ions by chemically treated human hair. Water Res. 19, 157e162. Tuzen, M., Sari, A., 2010. Biosorption of selenium from aqueous solution by green algae (Cladophora hutchinsiae) biomass: equilibrium, thermodynamic and kinetic studies. Chem. Eng. J. 158, 200e206. Vijayaraghavan, K., Palanivelu, K., Velan, M., 2006. Biosorption of copper(II) and cobalt(II) from aqueous solutions by crab shell particles. Bioresour. Technol. 97, 1411e1419. Wang, J., Hu, X., Liu, Y., Xie, S., Bao, Z., 2010. Biosorption of uranium(VI) by immobilized Aspergillus fumigatus beads. J. Environ. Radioactivity 101, 504e508. World Health Organization, 2004. Uranium in Drinking Water (Background Document for the Development of WHO Guidelines for Drinking-water, Quality. WHO/SDE/WSH/03.04/118).
