- Email: [email protected]
Silica Stabilized Magnetic-Chitosan Beads for Removal of Arsenic from Water
Colloid and Interface Science Communications 19 (2017) 14–19
Contents lists available at ScienceDirect
Colloid and Interface Science Communications journal homepage: www.elsevier.com/locate/colcom
Rapid Communication
Silica Stabilized Magnetic-Chitosan Beads for Removal of Arsenic from Water
MARK
Deepika Malwala, P. Gopinatha,b,⁎ a b
Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand -247667, India Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand -247667, India
A R T I C L E I N F O
A B S T R A C T
Keywords: Chitosan Magnetic nanoparticles Silica Arsenic Adsorption
Over the years, the heavy metal contamination of the water systems has remained a matter of global concern. In view of this, silica stabilized magnetic-chitosan beads were developed using simple precipitation method assisted with post silica deposition. The as prepared beads were characterized for their structural and morphological analysis using several techniques such as Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric analysis (TGA). The magnetic properties of the magnetic chitosan beads were determined using Vibrating Sample Magnetometer (VSM) analysis. The arsenic removal efficiency of the hybrid chitosan beads was further evaluated and compared with alone chitosan beads. Finally, the kinetic studies were performed to determine the adsorption capacity and rate of uptake of arsenic (As (V)) from water by the adsorbents. Thus, such organic-inorganic hybrid materials will find huge potential in future water remediation applications.
Heavy metal contamination in the water bodies is one of the major threats to the public health and the environment [1,2]. Among these, arsenic is the most toxic one which has serious health effects even upon the intake of very small concentration for long time [3]. There are several sources of release of arsenic in water systems such as utilization of arsenic containing pesticides, extensive extraction of groundwater and various industries [4]. Due to severe negative impacts of arsenic, its permissible concentration in water has been limited to 10 μg/L by World Health Organization (WHO) [5]. Thus, it is very important to eliminate and reduce the level of arsenic in drinking water. Till date several techniques such as adsorption, ion-exchange, membrane filtration, coagulation and flocculation have been employed [6–9]. Among these, adsorption is the simplest and cost effective methodology which is extensively utilized in water remediation applications because of its favorability and feasibility [10]. As adsorbent, biopolymer chitosan possess huge potential for the efficient removal of heavy metals from water because of its easy availability, biodegradability, biocompatibility, non-toxicity [11]. Moreover, chitosan is ideal for water remediation applications as it can be transformed into beads and films. But generally, alone chitosan beads are nonporous, show high swelling behavior and hence exhibit lower adsorption capacity. These shortcomings can be overcome by incorporating silica and magnetic nanoparticles with the chitosan beads in order to build organic-inorganic hybrid materials with improved
⁎
properties [12–15]. For long time, magnetic chitosan hybrid beads have been efficiently used for the arsenic removal [16–19]. The major advantage of beads like structure is that they can be easily used in columns for large scale applications and they are easy to store as compared to the powders. Here, in the present study we have prepared silica stabilized magnetic chitosan hybrid beads. Silica is just utilized to stabilize the chitosan beads as in the pristine form they are highly unstable under extreme conditions. In addition, the incorporation of Fe3O4 nanoparticles to the chitosan network helps to improve the adsorption efficiency of the sample [20,21]. Therefore, such hybrid beads are employed as adsorbents for the efficient removal of arsenic from water. Biopolymers such as chitosan and alginate have been utilized for the preparation of efficient adsorbents for long time. Chitosan is a well known polymer for the microencapsulation of different nanomaterials because of its gel forming behavior [22,23]. In chitosan, gel is formed upon pH inversion when an acidic suspension is dropped into a basic coagulation solution [24]. Further, the cross-linking was done with glutaraldehyde which improves the stability of the beads in extreme pH conditions. After that, silica was layered onto the beads making organic-inorganic (chitosan-silica) hybrid structures. The major advantage of this procedure is that chemical interactions and linkages are formed between both materials (chitosan and silica).The whole procedure for the synthesis of silica stabilized hybrid chitosan beads is
Corresponding author at: Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand-247667, India. E-mail addresses: [email protected], [email protected] (P. Gopinath).
http://dx.doi.org/10.1016/j.colcom.2017.06.003 Received 22 April 2017; Received in revised form 14 June 2017; Accepted 19 June 2017 2215-0382/ © 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Colloid and Interface Science Communications 19 (2017) 14–19
D. Malwal, P. Gopinath
Fig. 1. Schematic representation of synthesis of silica stabilized hybrid beads.
magnetization (Ms) value. The hysteresis loop for silica@ magnetic hybrid beads shown in fig. 4(b) depicts the superparamagnetic behavior of Fe3O4 nanoparticles embedded in chitosan beads. However, these hybrid spheres exhibit a very low value of Ms. of 9.1 emug− 1 that is due to the fact that Fe3O4 nanoparticles are embedded in the chitosan molecules. Further, the functional groups of the as-prepared samples were identified using FTIR spectra as shown in fig. 4(c). In the spectra for chitosan beads, there are characteristic bands of CeO, CeN, –CH2, NeH, OeH, and CeH at wavenumber 1015.75, 1161.01, 1365.99, 1562.90, 1650.80, 2962.75 and 3438.39 cm− 1, respectively. In case of silica stabilized magnetic chitosan beads, additions bands at 468.59, 531.54, 1033.50 and 1329.67 cm− 1 can be observed which are attributed to O-Si-O, FeeO, Si-O-Si, FeeO stretches, respectively. So, the FTIR spectrum indicates the presence of silica as well as magnetic nanoparticles along with the chitosan molecules. Further, TGA was performed to investigate the stability of the microspheres at high temperatures (Fig. 4(d)). It was observed that silica stabilized magnetic hybrid beads were more stable as compared to pristine chitosan beads upto 200 °C. In case of alone chitosan beads, there is a stepwise degradation and complete degradation occurred upto 800 °C. On the other hand, about 20% of the weight left after continuous heating of silica stabilized hybrid beads upto 800 °C due to the presence of silica and magnetite nanoparticles. Afterwards, the adsorptive behavior of the beads was investigated for the removal of As(V) from water. It can be observed from the Fig. 5(a) that about 80% of the arsenic was removed within 4 h while hardly 5% of As(V) was removed using alone chitosan beads. The kinetics of adsorption was studied to explain the rate of solute uptake by the microspheres, defining the efficiency of the adsorbent [26]. Fig. 5(b) represents the time dependent adsorption of arsenic onto the chitosan and silica@ magnetic hybrid beads. It was observed that the adsorption capacity of hybrid beads was greater than 1.7 mg/g which is much higher than the alone chitosan beads. It was observed that the adsorption was fast initially and then slowed down reaching the equilibrium. Based on the data obtained, the mechanism of adsorption could be concluded that the metal ions first adhere to the
schematically represented in Fig. 1. The as-prepared black spongy beads as shown in Fig. 2(a) were initially characterized by FE-SEM to investigate their morphology. Fig. 2 (b) represents the cross-sectioned view of a silica stabilized magnetic chitosan bead which depicts its porous structure as they are highly fibrous in nature as clearly shown in fig. 2(c) and 2(d). In addition, the Fe3O4 nanoparticles can also be observed embedded in the chitosan beads in the fig. 2(d). It is very important to note that the drying has significant impact on the morphology of the chitosan microspheres. To investigate the effect of drying, the as-prepared wet beads were dried using two different techniques: (i) simple air drying and (ii) freeze-drying in which the beads were rapidly frozen at −80 °C and then dried in the presence of vacuum. Fig. 3(a) and 3 (b) represents the air dried beads which indicates their rigid and non-porous structure. On the other hand, freeze dried chitosan beads were found with aerogel kind of structure with high porosity as can be observed in Fig. 3 (c), (d), (e) and (f). It is reported in the literature that freeze drying increases the porosity of the gel by producing a weaker shrinking force [25]. Such porous and fibrillar morphology of the beads is highly beneficial in the adsorptive removal of heavy metal ions from the water. Fig. 4(a) represents the typical XRD pattern for chitosan beads and the silica stabilized hybrid beads. The broad characteristic peaks for chitosan can be observed at 2Ө value of 19.9° and 29.8°. The same peaks were also observed in silica stabilized hybrid beads along with the characteristic peaks of silica at 2Ө value of 20.8° and 26.1° (as per JCPDS ref. and magnetic nanoparticles which confirms the presence of all these components. The peaks at 2Ө value of 20.8° and 26.1° are attributed to the (100) and (101) planes of hexagonal silica, respectively as per JCPDS reference no 00–033-1161. The rest of the sharp peaks at 2Ө value of 35.5°, 43.0°, 57.1° and 62.8° are attributed to the (311), (400), (511) and (440) planes, respectively depicting the crystalline cubic magnetite structure (JCPDS reference no 00–001-1111). The peaks of magnetite nanoparticles are little bit suppressed due to their entrapment into chitosan beads. The magnetization behavior of silica stabilized magnetic chitosan beads was investigated using VSM by measuring the saturation 15
Colloid and Interface Science Communications 19 (2017) 14–19
D. Malwal, P. Gopinath
Fig. 2. (a) Digital photograph of SiO2@chitosan beads; FESEM images of (b) chitosan hybrid spheres, (c) and (d) Fe3O4 nanoparticles embedded in chitosan beads.
Fig. 3. FE-SEM images of (a) Air dried chitosan bead, (b) inner view of air dried chitosan bead, (c), (d), (e) and (f) Cross sectional views of freeze-dried chitosan bead at different magnifications.
16
Colloid and Interface Science Communications 19 (2017) 14–19
D. Malwal, P. Gopinath
Fig. 4. (a) XRD pattern for chitosan beads and the silica stabilized chitosan hybrid beads (* represents the peaks for silica); (b) VSM graph for the magnetic hybrid beads; (c) FTIR spectra and (b) TGA graph for chitosan beads and silica coated hybrid beads.
beads for As(V) removal from water. Besides this, the correlation coefficient (R2) values for Chitosan and hybrid beads are 0.982 and 0.999, respectively which supports pseudo-second order kinetics as best fit model for our adsorption system.
external surface of CZ nanofibers and after that, they try to move inside the pores of the adsorbent. As the molecules diffuse inside the pores, diffusion resistance increases due to which the rate of adsorption decreases [27]. In addition, magnetite (Fe3O4) nanoparticles play important role in arsenate ion removal with more specific interactions i.e. via formation of inner-sphere complexes between arsenate's donor atom (oxygen) and the acceptors (Fe) of the magnetite [28,29]. In addition to this, pseudo-second order kinetics can be best fitted to as obtained experimental data [30,31]. The pseudo-second order kinetics obeys the following equation:
Table1: Pseudo-second order kinetic model parameters for pristine chitosan and silica@ chitosan hybrid beads.
t qt = 1 k2q e2 + t q e where k2 (g/mg/h) is the rate constant of adsorption, qe (mg/g) is the equilibrium adsorption capacity and qt is the amount of As(V) adsorbed onto the adsorbent at a particular time t. The linear plot between t vs. t/ qt as shown in Fig. 5(c) facilitates the calculation of the value of k2 and qe using slope and intercept of the graph which have been tabulated in the Table 1. It was observed that the adsorption capacity of silica stabilized hybrid beads is about 20 times higher than that of pure chitosan beads. Moreover, the rate of adsorption for hybrid beads was calculated as 15.552 g/mg/h which is much greater than that of pure chitosan beads with the value 2.183 g/mg/h. So, these results affirm the enhanced adsorption efficiency of hybrid beads as compared to chitosan
S·No. Sample Name
qe (mg/ g)
K2 (g/mg/ h)
R2
1. 2.
0.082 1.699
2.183 15.552
0.982 0.999
Chitosan beads SiO2@hybrid chitosan beads
After utilization, it is very important to remove the adsorbent from water properly without making them release into the water. Since we added magnetic nanoparticles in the chitosan beads, it is easy to retrieve the beads using external magnet as shown in Fig. 5(d). Thus, such materials prevent the chance of secondary pollutant due to adsorbent itself. In summary, we have successfully prepared the silica stabilized hybrid chitosan microspheres using very simple precipitation method with post-deposition of silica. Deposition of silica greatly enhanced the stability of the chitosan beads so that can be used in varying 17
Colloid and Interface Science Communications 19 (2017) 14–19
D. Malwal, P. Gopinath
Fig. 5. (a) Comparative plot showing the effective adsorptive behavior of silica stabilized hybrid chitosan beads over alone chitosan beads; (b) Time dependent removal of arsenic using chitosan and silica stabilized hybrid beads; (c) Pseudo-second order kinetic plot for the adsorption of arsenic onto the as-prepared adsorbents and (d) magnetic separation of hybrid beads after use using external magnet.
Appendix A. Supplementary data
environments of water. The morphological analysis depicted the highly porous structure of these beads because they possess aerogel kind of structure. Moreover, the addition of magnetite (Fe3O4) nanoparticles also enhances the surface area of the beads which results in the improved As(V) adsorption efficiency of hybrid beads as compared to alone chitosan beads. Further, the adsorption efficiency of the chitosan beads and the hybrid beads were calculated as 0.082 and 1.699 mg/g, respectively. Thus, such organic-inorganic materials are highly promising candidates to be used in columns for fast and efficient removal of toxic metal ions from water. Fig. 5(a) Comparative plot showing the effective adsorptive behavior of silica stabilized hybrid chitosan beads over alone chitosan beads; (b) Time dependent removal of arsenic using chitosan and silica stabilized hybrid beads; (b) Pseudo-second order kinetic plot for the adsorption of arsenic onto the as-prepared adsorbents and (c) magnetic separation of hybrid beads after use using external magnet.
Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.colcom.2017.06.003. References [1] J. Liu, Z. Zhao, G. Jiang, Coating Fe3O4 magnetic nanoparticles with humic acid for high efficient removal of heavy metals in water, Environ. Sci. Technol. 42 (2008) 6949–6954. [2] Y. Wei, R. Yang, Y.X. Zhang, L. Wang, J.H. Liu, X.J. Huang, High adsorptive γAlOOH(boehmite)@SiO2/Fe3O4 porous magnetic microspheres for detection of toxic metal ions in drinking water, Chem. Commun. 47 (2011) 11062–11064. [3] S.W. Al Rmalli, C.F. Harrington, M. Ayub, P.I. Haris, A biomaterial based approach for arsenic removal from water, J. Environ. Monit. 7 (2005) 279–282. [4] C. Fan, K. Li, Y. Wang, X. Qiana, J. Jia, The stability of magnetic chitosan beads in the adsorption of Cu2 +, RSC Adv. 6 (2016) 2678–2686. [5] V. Chandra, J. Park, Y. Chun, J.W. Lee, I. Hwang, K.S. Kim, Water-dispersible magnetite-reduced graphene oxide composites for arsenic removal, ACS Nano 4 (2010) 3979–3986. [6] D. Malwal, P. Gopinath, Rapid and efficient removal of arsenic from water using electrospun CuO–ZnO composite nanofibers, RSC Adv. 6 (2016) 115021–115028. [7] V. Pallier, G.F. Cathalifaud, B. Serpaud, J.C. Bollinger, Effect of organic matter on arsenic removal during coagulation/flocculation treatment, J. Colloid Interface Sci. 342 (2010) 26–32. [8] J. Kim, M.M. Benjamin, Modeling a novel ion exchange process for arsenic and nitrate removal, Water Res. 38 (2004) 2053–2062. [9] J. He, T. Matsuura, J.P. Chen, A novel Zr-based nanoparticle-embedded PSF blend hollow fiber membrane for treatment of arsenate contaminated water: material development, adsorption and filtration studies, and characterization, J. Membr. Sci. 452 (2014) 433–445. [10] S. Kumar, R.R. Nair, P.B. Pillai, S.N. Gupta, M.A.R. Iyengar, A.K. Sood, Graphene
Acknowledgements We give sincere thanks to the Department of Science and Technology (Water Technology Initiative- Project No. DST/TM/WTI/ 2K13/94 (G)), Government of India, for the financial support. DM is thankful to the Ministry of Human Resource Development, Government of India, for the fellowship. Department of Chemistry and Institute Instrumentation Centre and Indian Institute of Technology Roorkee are sincerely acknowledged for providing various analytical facilities. 18
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[11]
[12] [13] [14] [15]
[16]
[17]
[18] [19]
[20]
[21]
nanoparticles, J. Hazard. Mater. 166 (2009) 1415–1420. [22] J. Roosen, K. Binnemans, Adsorption and chromatographic separation of rare earths with EDTA- and DTPA-functionalized chitosan biopolymers, J. Mater. Chem. A 2 (2014) 1530–1540. [23] J. Roosen, J. Spooren, K. Binnemans, Adsorption performance of functionalized chitosan-silica hybrid materials toward rare earths, J. Mater. Chem. A 2 (2014) 19415–19426. [24] B.N. Estevinho, F. Rocha, L. Santos, A. Alves, Microencapsulation with chitosan by spray drying for industry applications − a review, Trends Food Sci. Technol. 31 (2013) 138–155. [25] W. Cai, R.B. Gupta, Fast responding bulk hydrogels with microstructure, J. Appl. Polym. Sci. 83 (2002) 169–178. [26] J.S. Yamani, S.M. Miller, M.L. Spaulding, J.B. Zimmerman, Enhanced arsenic removal using mixed metal oxide impregnated chitosan beads, Water Res. 46 (2012) 4427–4434. [27] V.M. Boddu, K. Abburi, J.L. Talbott, E.D. Smith, R. Haasch, Removal of arsenic (III) and arsenic (V) from aqueous medium using chitosan-coated biosorbent, Water Res. 42 (2008) 633–642. [28] B. An, Q. Liang, D. Zhao, Removal of arsenic (V) from spent ion exchange brine using a new class of starch-bridged magnetite nanoparticles, Water Res. 45 (2011) 1961–1972. [29] C.H. Liu, Y.H. Chuang, T.Y. Chen, Y. Tian, H. Li, M.K. Wang, W. Zhang, Mechanism of arsenic adsorption on magnetite nanoparticles from water: thermodynamic and spectroscopic studies, Environ. Sci. Technol. 49 (2015) 7726–7734. [30] D. Malwal, P. Gopinath, Efficient adsorption and antibacterial properties of electrospun CuO-ZnO composite nanofibers for water remediation, J. Hazard. Mater. 321 (2017) 611–621. [31] M. Yazdani, T. Tuutijärvi, A. Bhatnagar, R. Vahala, Adsorptive removal of arsenic (V) from aqueous phase by feldspars: kinetics, mechanism, and thermodynamic aspects of adsorption, J. Mol. Liq. 214 (2016) 149–156.
oxide–MnFe2O4 magnetic Nanohybrids for efficient removal of lead and arsenic from water, ACS Appl. Mater. Interfaces 6 (2014) 17426–17436. D.W. Cho, B.H. Jeon, C.M. Chon, Y. Kim, F.W. Schwartz, E.S. Lee, H. Song, A novel chitosan/clay/magnetite composite for adsorption of cu(II) and as(V), Chem. Eng. J. 200 (2012) 654–662. T. Coradin, N. Nassif, J. Livage, Silica-alginate composites for microencapsulation, Appl. Microbiol. Biotechnol. 61 (2003) 429–434. F. Hoffmann, M. Cornelius, J. Morell, M. Froba, Silica-based mesoporous organicinorganic hybrid materials, Angew. Chem., Int. Ed. 45 (2006) 3216–3251. W. Lan, S. Li, J. Xu, G. Luo, One-step synthesis of chitosan silica hybrid microspheres in a microfluidic device, Biomed. Microdevices 12 (2010) 1087–1095. K. Molvinger, F. Quignard, D. Brunel, M. Boissiere, J.M. Devoisselle, Porous chitosan-silica hybrid microspheres as a potential catalyst, Chem. Mater. 16 (2004) 3367–3372. J. Wang, W. Xu, L. Chen, X. Huang, J. Liu, Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water, Chem. Eng. J. 251 (2014) 25–34. Y. J. Jiang, X. Y. Yu, T. Luo, Y. Jia, J. H. Liu, X. J. Huang, γ-Fe2O3 Nanoparticles Encapsulated Millimeter-Sized Magnetic Chitosan Beads for Removal of Cr(VI) from Water: Thermodynamics, Kinetics, Regeneration, and Uptake Mechanisms, J. Chem. Eng. Data 58 (2013) 3142–3149. J. He, F. Bardelli, A. Gehin, E. Silvester, L. Charlet, Novel chitosan goethite bionanocomposite beads for arsenic remediation, Water Res. 101 (2016) 1–9. M. Hasanzadeh, F. Farajbakhsh, N. Shadjou, A. Jouyban, Mesoporous (organo) silica decorated with magnetic nanoparticles as a reusable nanoadsorbent for arsenic removal from water samples, Environ. Technol. 36 (2015) 36–44. W. Tang, Q. Li, S. Gao, J.K. Shang, Arsenic (III, V) removal from aqueous solution by ultrafine α-Fe 2 O 3 nanoparticles synthesized from solvent thermal method, J. Hazard. Mater. 192 (2011) 131–138. T. Tuutijärvi, J. Lu, M. Sillanpää, G. Chen, As (V) adsorption on maghemite
19
Contents lists available at ScienceDirect
Colloid and Interface Science Communications journal homepage: www.elsevier.com/locate/colcom
Rapid Communication
Silica Stabilized Magnetic-Chitosan Beads for Removal of Arsenic from Water
MARK
Deepika Malwala, P. Gopinatha,b,⁎ a b
Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand -247667, India Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand -247667, India
A R T I C L E I N F O
A B S T R A C T
Keywords: Chitosan Magnetic nanoparticles Silica Arsenic Adsorption
Over the years, the heavy metal contamination of the water systems has remained a matter of global concern. In view of this, silica stabilized magnetic-chitosan beads were developed using simple precipitation method assisted with post silica deposition. The as prepared beads were characterized for their structural and morphological analysis using several techniques such as Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric analysis (TGA). The magnetic properties of the magnetic chitosan beads were determined using Vibrating Sample Magnetometer (VSM) analysis. The arsenic removal efficiency of the hybrid chitosan beads was further evaluated and compared with alone chitosan beads. Finally, the kinetic studies were performed to determine the adsorption capacity and rate of uptake of arsenic (As (V)) from water by the adsorbents. Thus, such organic-inorganic hybrid materials will find huge potential in future water remediation applications.
Heavy metal contamination in the water bodies is one of the major threats to the public health and the environment [1,2]. Among these, arsenic is the most toxic one which has serious health effects even upon the intake of very small concentration for long time [3]. There are several sources of release of arsenic in water systems such as utilization of arsenic containing pesticides, extensive extraction of groundwater and various industries [4]. Due to severe negative impacts of arsenic, its permissible concentration in water has been limited to 10 μg/L by World Health Organization (WHO) [5]. Thus, it is very important to eliminate and reduce the level of arsenic in drinking water. Till date several techniques such as adsorption, ion-exchange, membrane filtration, coagulation and flocculation have been employed [6–9]. Among these, adsorption is the simplest and cost effective methodology which is extensively utilized in water remediation applications because of its favorability and feasibility [10]. As adsorbent, biopolymer chitosan possess huge potential for the efficient removal of heavy metals from water because of its easy availability, biodegradability, biocompatibility, non-toxicity [11]. Moreover, chitosan is ideal for water remediation applications as it can be transformed into beads and films. But generally, alone chitosan beads are nonporous, show high swelling behavior and hence exhibit lower adsorption capacity. These shortcomings can be overcome by incorporating silica and magnetic nanoparticles with the chitosan beads in order to build organic-inorganic hybrid materials with improved
⁎
properties [12–15]. For long time, magnetic chitosan hybrid beads have been efficiently used for the arsenic removal [16–19]. The major advantage of beads like structure is that they can be easily used in columns for large scale applications and they are easy to store as compared to the powders. Here, in the present study we have prepared silica stabilized magnetic chitosan hybrid beads. Silica is just utilized to stabilize the chitosan beads as in the pristine form they are highly unstable under extreme conditions. In addition, the incorporation of Fe3O4 nanoparticles to the chitosan network helps to improve the adsorption efficiency of the sample [20,21]. Therefore, such hybrid beads are employed as adsorbents for the efficient removal of arsenic from water. Biopolymers such as chitosan and alginate have been utilized for the preparation of efficient adsorbents for long time. Chitosan is a well known polymer for the microencapsulation of different nanomaterials because of its gel forming behavior [22,23]. In chitosan, gel is formed upon pH inversion when an acidic suspension is dropped into a basic coagulation solution [24]. Further, the cross-linking was done with glutaraldehyde which improves the stability of the beads in extreme pH conditions. After that, silica was layered onto the beads making organic-inorganic (chitosan-silica) hybrid structures. The major advantage of this procedure is that chemical interactions and linkages are formed between both materials (chitosan and silica).The whole procedure for the synthesis of silica stabilized hybrid chitosan beads is
Corresponding author at: Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand-247667, India. E-mail addresses: [email protected], [email protected] (P. Gopinath).
http://dx.doi.org/10.1016/j.colcom.2017.06.003 Received 22 April 2017; Received in revised form 14 June 2017; Accepted 19 June 2017 2215-0382/ © 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Colloid and Interface Science Communications 19 (2017) 14–19
D. Malwal, P. Gopinath
Fig. 1. Schematic representation of synthesis of silica stabilized hybrid beads.
magnetization (Ms) value. The hysteresis loop for silica@ magnetic hybrid beads shown in fig. 4(b) depicts the superparamagnetic behavior of Fe3O4 nanoparticles embedded in chitosan beads. However, these hybrid spheres exhibit a very low value of Ms. of 9.1 emug− 1 that is due to the fact that Fe3O4 nanoparticles are embedded in the chitosan molecules. Further, the functional groups of the as-prepared samples were identified using FTIR spectra as shown in fig. 4(c). In the spectra for chitosan beads, there are characteristic bands of CeO, CeN, –CH2, NeH, OeH, and CeH at wavenumber 1015.75, 1161.01, 1365.99, 1562.90, 1650.80, 2962.75 and 3438.39 cm− 1, respectively. In case of silica stabilized magnetic chitosan beads, additions bands at 468.59, 531.54, 1033.50 and 1329.67 cm− 1 can be observed which are attributed to O-Si-O, FeeO, Si-O-Si, FeeO stretches, respectively. So, the FTIR spectrum indicates the presence of silica as well as magnetic nanoparticles along with the chitosan molecules. Further, TGA was performed to investigate the stability of the microspheres at high temperatures (Fig. 4(d)). It was observed that silica stabilized magnetic hybrid beads were more stable as compared to pristine chitosan beads upto 200 °C. In case of alone chitosan beads, there is a stepwise degradation and complete degradation occurred upto 800 °C. On the other hand, about 20% of the weight left after continuous heating of silica stabilized hybrid beads upto 800 °C due to the presence of silica and magnetite nanoparticles. Afterwards, the adsorptive behavior of the beads was investigated for the removal of As(V) from water. It can be observed from the Fig. 5(a) that about 80% of the arsenic was removed within 4 h while hardly 5% of As(V) was removed using alone chitosan beads. The kinetics of adsorption was studied to explain the rate of solute uptake by the microspheres, defining the efficiency of the adsorbent [26]. Fig. 5(b) represents the time dependent adsorption of arsenic onto the chitosan and silica@ magnetic hybrid beads. It was observed that the adsorption capacity of hybrid beads was greater than 1.7 mg/g which is much higher than the alone chitosan beads. It was observed that the adsorption was fast initially and then slowed down reaching the equilibrium. Based on the data obtained, the mechanism of adsorption could be concluded that the metal ions first adhere to the
schematically represented in Fig. 1. The as-prepared black spongy beads as shown in Fig. 2(a) were initially characterized by FE-SEM to investigate their morphology. Fig. 2 (b) represents the cross-sectioned view of a silica stabilized magnetic chitosan bead which depicts its porous structure as they are highly fibrous in nature as clearly shown in fig. 2(c) and 2(d). In addition, the Fe3O4 nanoparticles can also be observed embedded in the chitosan beads in the fig. 2(d). It is very important to note that the drying has significant impact on the morphology of the chitosan microspheres. To investigate the effect of drying, the as-prepared wet beads were dried using two different techniques: (i) simple air drying and (ii) freeze-drying in which the beads were rapidly frozen at −80 °C and then dried in the presence of vacuum. Fig. 3(a) and 3 (b) represents the air dried beads which indicates their rigid and non-porous structure. On the other hand, freeze dried chitosan beads were found with aerogel kind of structure with high porosity as can be observed in Fig. 3 (c), (d), (e) and (f). It is reported in the literature that freeze drying increases the porosity of the gel by producing a weaker shrinking force [25]. Such porous and fibrillar morphology of the beads is highly beneficial in the adsorptive removal of heavy metal ions from the water. Fig. 4(a) represents the typical XRD pattern for chitosan beads and the silica stabilized hybrid beads. The broad characteristic peaks for chitosan can be observed at 2Ө value of 19.9° and 29.8°. The same peaks were also observed in silica stabilized hybrid beads along with the characteristic peaks of silica at 2Ө value of 20.8° and 26.1° (as per JCPDS ref. and magnetic nanoparticles which confirms the presence of all these components. The peaks at 2Ө value of 20.8° and 26.1° are attributed to the (100) and (101) planes of hexagonal silica, respectively as per JCPDS reference no 00–033-1161. The rest of the sharp peaks at 2Ө value of 35.5°, 43.0°, 57.1° and 62.8° are attributed to the (311), (400), (511) and (440) planes, respectively depicting the crystalline cubic magnetite structure (JCPDS reference no 00–001-1111). The peaks of magnetite nanoparticles are little bit suppressed due to their entrapment into chitosan beads. The magnetization behavior of silica stabilized magnetic chitosan beads was investigated using VSM by measuring the saturation 15
Colloid and Interface Science Communications 19 (2017) 14–19
D. Malwal, P. Gopinath
Fig. 2. (a) Digital photograph of SiO2@chitosan beads; FESEM images of (b) chitosan hybrid spheres, (c) and (d) Fe3O4 nanoparticles embedded in chitosan beads.
Fig. 3. FE-SEM images of (a) Air dried chitosan bead, (b) inner view of air dried chitosan bead, (c), (d), (e) and (f) Cross sectional views of freeze-dried chitosan bead at different magnifications.
16
Colloid and Interface Science Communications 19 (2017) 14–19
D. Malwal, P. Gopinath
Fig. 4. (a) XRD pattern for chitosan beads and the silica stabilized chitosan hybrid beads (* represents the peaks for silica); (b) VSM graph for the magnetic hybrid beads; (c) FTIR spectra and (b) TGA graph for chitosan beads and silica coated hybrid beads.
beads for As(V) removal from water. Besides this, the correlation coefficient (R2) values for Chitosan and hybrid beads are 0.982 and 0.999, respectively which supports pseudo-second order kinetics as best fit model for our adsorption system.
external surface of CZ nanofibers and after that, they try to move inside the pores of the adsorbent. As the molecules diffuse inside the pores, diffusion resistance increases due to which the rate of adsorption decreases [27]. In addition, magnetite (Fe3O4) nanoparticles play important role in arsenate ion removal with more specific interactions i.e. via formation of inner-sphere complexes between arsenate's donor atom (oxygen) and the acceptors (Fe) of the magnetite [28,29]. In addition to this, pseudo-second order kinetics can be best fitted to as obtained experimental data [30,31]. The pseudo-second order kinetics obeys the following equation:
Table1: Pseudo-second order kinetic model parameters for pristine chitosan and silica@ chitosan hybrid beads.
t qt = 1 k2q e2 + t q e where k2 (g/mg/h) is the rate constant of adsorption, qe (mg/g) is the equilibrium adsorption capacity and qt is the amount of As(V) adsorbed onto the adsorbent at a particular time t. The linear plot between t vs. t/ qt as shown in Fig. 5(c) facilitates the calculation of the value of k2 and qe using slope and intercept of the graph which have been tabulated in the Table 1. It was observed that the adsorption capacity of silica stabilized hybrid beads is about 20 times higher than that of pure chitosan beads. Moreover, the rate of adsorption for hybrid beads was calculated as 15.552 g/mg/h which is much greater than that of pure chitosan beads with the value 2.183 g/mg/h. So, these results affirm the enhanced adsorption efficiency of hybrid beads as compared to chitosan
S·No. Sample Name
qe (mg/ g)
K2 (g/mg/ h)
R2
1. 2.
0.082 1.699
2.183 15.552
0.982 0.999
Chitosan beads SiO2@hybrid chitosan beads
After utilization, it is very important to remove the adsorbent from water properly without making them release into the water. Since we added magnetic nanoparticles in the chitosan beads, it is easy to retrieve the beads using external magnet as shown in Fig. 5(d). Thus, such materials prevent the chance of secondary pollutant due to adsorbent itself. In summary, we have successfully prepared the silica stabilized hybrid chitosan microspheres using very simple precipitation method with post-deposition of silica. Deposition of silica greatly enhanced the stability of the chitosan beads so that can be used in varying 17
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Fig. 5. (a) Comparative plot showing the effective adsorptive behavior of silica stabilized hybrid chitosan beads over alone chitosan beads; (b) Time dependent removal of arsenic using chitosan and silica stabilized hybrid beads; (c) Pseudo-second order kinetic plot for the adsorption of arsenic onto the as-prepared adsorbents and (d) magnetic separation of hybrid beads after use using external magnet.
Appendix A. Supplementary data
environments of water. The morphological analysis depicted the highly porous structure of these beads because they possess aerogel kind of structure. Moreover, the addition of magnetite (Fe3O4) nanoparticles also enhances the surface area of the beads which results in the improved As(V) adsorption efficiency of hybrid beads as compared to alone chitosan beads. Further, the adsorption efficiency of the chitosan beads and the hybrid beads were calculated as 0.082 and 1.699 mg/g, respectively. Thus, such organic-inorganic materials are highly promising candidates to be used in columns for fast and efficient removal of toxic metal ions from water. Fig. 5(a) Comparative plot showing the effective adsorptive behavior of silica stabilized hybrid chitosan beads over alone chitosan beads; (b) Time dependent removal of arsenic using chitosan and silica stabilized hybrid beads; (b) Pseudo-second order kinetic plot for the adsorption of arsenic onto the as-prepared adsorbents and (c) magnetic separation of hybrid beads after use using external magnet.
Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.colcom.2017.06.003. References [1] J. Liu, Z. Zhao, G. Jiang, Coating Fe3O4 magnetic nanoparticles with humic acid for high efficient removal of heavy metals in water, Environ. Sci. Technol. 42 (2008) 6949–6954. [2] Y. Wei, R. Yang, Y.X. Zhang, L. Wang, J.H. Liu, X.J. Huang, High adsorptive γAlOOH(boehmite)@SiO2/Fe3O4 porous magnetic microspheres for detection of toxic metal ions in drinking water, Chem. Commun. 47 (2011) 11062–11064. [3] S.W. Al Rmalli, C.F. Harrington, M. Ayub, P.I. Haris, A biomaterial based approach for arsenic removal from water, J. Environ. Monit. 7 (2005) 279–282. [4] C. Fan, K. Li, Y. Wang, X. Qiana, J. Jia, The stability of magnetic chitosan beads in the adsorption of Cu2 +, RSC Adv. 6 (2016) 2678–2686. [5] V. Chandra, J. Park, Y. Chun, J.W. Lee, I. Hwang, K.S. Kim, Water-dispersible magnetite-reduced graphene oxide composites for arsenic removal, ACS Nano 4 (2010) 3979–3986. [6] D. Malwal, P. Gopinath, Rapid and efficient removal of arsenic from water using electrospun CuO–ZnO composite nanofibers, RSC Adv. 6 (2016) 115021–115028. [7] V. Pallier, G.F. Cathalifaud, B. Serpaud, J.C. Bollinger, Effect of organic matter on arsenic removal during coagulation/flocculation treatment, J. Colloid Interface Sci. 342 (2010) 26–32. [8] J. Kim, M.M. Benjamin, Modeling a novel ion exchange process for arsenic and nitrate removal, Water Res. 38 (2004) 2053–2062. [9] J. He, T. Matsuura, J.P. Chen, A novel Zr-based nanoparticle-embedded PSF blend hollow fiber membrane for treatment of arsenate contaminated water: material development, adsorption and filtration studies, and characterization, J. Membr. Sci. 452 (2014) 433–445. [10] S. Kumar, R.R. Nair, P.B. Pillai, S.N. Gupta, M.A.R. Iyengar, A.K. Sood, Graphene
Acknowledgements We give sincere thanks to the Department of Science and Technology (Water Technology Initiative- Project No. DST/TM/WTI/ 2K13/94 (G)), Government of India, for the financial support. DM is thankful to the Ministry of Human Resource Development, Government of India, for the fellowship. Department of Chemistry and Institute Instrumentation Centre and Indian Institute of Technology Roorkee are sincerely acknowledged for providing various analytical facilities. 18
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D. Malwal, P. Gopinath
[11]
[12] [13] [14] [15]
[16]
[17]
[18] [19]
[20]
[21]
nanoparticles, J. Hazard. Mater. 166 (2009) 1415–1420. [22] J. Roosen, K. Binnemans, Adsorption and chromatographic separation of rare earths with EDTA- and DTPA-functionalized chitosan biopolymers, J. Mater. Chem. A 2 (2014) 1530–1540. [23] J. Roosen, J. Spooren, K. Binnemans, Adsorption performance of functionalized chitosan-silica hybrid materials toward rare earths, J. Mater. Chem. A 2 (2014) 19415–19426. [24] B.N. Estevinho, F. Rocha, L. Santos, A. Alves, Microencapsulation with chitosan by spray drying for industry applications − a review, Trends Food Sci. Technol. 31 (2013) 138–155. [25] W. Cai, R.B. Gupta, Fast responding bulk hydrogels with microstructure, J. Appl. Polym. Sci. 83 (2002) 169–178. [26] J.S. Yamani, S.M. Miller, M.L. Spaulding, J.B. Zimmerman, Enhanced arsenic removal using mixed metal oxide impregnated chitosan beads, Water Res. 46 (2012) 4427–4434. [27] V.M. Boddu, K. Abburi, J.L. Talbott, E.D. Smith, R. Haasch, Removal of arsenic (III) and arsenic (V) from aqueous medium using chitosan-coated biosorbent, Water Res. 42 (2008) 633–642. [28] B. An, Q. Liang, D. Zhao, Removal of arsenic (V) from spent ion exchange brine using a new class of starch-bridged magnetite nanoparticles, Water Res. 45 (2011) 1961–1972. [29] C.H. Liu, Y.H. Chuang, T.Y. Chen, Y. Tian, H. Li, M.K. Wang, W. Zhang, Mechanism of arsenic adsorption on magnetite nanoparticles from water: thermodynamic and spectroscopic studies, Environ. Sci. Technol. 49 (2015) 7726–7734. [30] D. Malwal, P. Gopinath, Efficient adsorption and antibacterial properties of electrospun CuO-ZnO composite nanofibers for water remediation, J. Hazard. Mater. 321 (2017) 611–621. [31] M. Yazdani, T. Tuutijärvi, A. Bhatnagar, R. Vahala, Adsorptive removal of arsenic (V) from aqueous phase by feldspars: kinetics, mechanism, and thermodynamic aspects of adsorption, J. Mol. Liq. 214 (2016) 149–156.
oxide–MnFe2O4 magnetic Nanohybrids for efficient removal of lead and arsenic from water, ACS Appl. Mater. Interfaces 6 (2014) 17426–17436. D.W. Cho, B.H. Jeon, C.M. Chon, Y. Kim, F.W. Schwartz, E.S. Lee, H. Song, A novel chitosan/clay/magnetite composite for adsorption of cu(II) and as(V), Chem. Eng. J. 200 (2012) 654–662. T. Coradin, N. Nassif, J. Livage, Silica-alginate composites for microencapsulation, Appl. Microbiol. Biotechnol. 61 (2003) 429–434. F. Hoffmann, M. Cornelius, J. Morell, M. Froba, Silica-based mesoporous organicinorganic hybrid materials, Angew. Chem., Int. Ed. 45 (2006) 3216–3251. W. Lan, S. Li, J. Xu, G. Luo, One-step synthesis of chitosan silica hybrid microspheres in a microfluidic device, Biomed. Microdevices 12 (2010) 1087–1095. K. Molvinger, F. Quignard, D. Brunel, M. Boissiere, J.M. Devoisselle, Porous chitosan-silica hybrid microspheres as a potential catalyst, Chem. Mater. 16 (2004) 3367–3372. J. Wang, W. Xu, L. Chen, X. Huang, J. Liu, Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water, Chem. Eng. J. 251 (2014) 25–34. Y. J. Jiang, X. Y. Yu, T. Luo, Y. Jia, J. H. Liu, X. J. Huang, γ-Fe2O3 Nanoparticles Encapsulated Millimeter-Sized Magnetic Chitosan Beads for Removal of Cr(VI) from Water: Thermodynamics, Kinetics, Regeneration, and Uptake Mechanisms, J. Chem. Eng. Data 58 (2013) 3142–3149. J. He, F. Bardelli, A. Gehin, E. Silvester, L. Charlet, Novel chitosan goethite bionanocomposite beads for arsenic remediation, Water Res. 101 (2016) 1–9. M. Hasanzadeh, F. Farajbakhsh, N. Shadjou, A. Jouyban, Mesoporous (organo) silica decorated with magnetic nanoparticles as a reusable nanoadsorbent for arsenic removal from water samples, Environ. Technol. 36 (2015) 36–44. W. Tang, Q. Li, S. Gao, J.K. Shang, Arsenic (III, V) removal from aqueous solution by ultrafine α-Fe 2 O 3 nanoparticles synthesized from solvent thermal method, J. Hazard. Mater. 192 (2011) 131–138. T. Tuutijärvi, J. Lu, M. Sillanpää, G. Chen, As (V) adsorption on maghemite
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