Available online at www.sciencedirect.com
ScienceDirect IERI Procedia 9 (2014) 77 – 81
2014 International Conference on Environment Systems Science and Engineering
Regeneration Characteristics of Hybrid Nanobiosorbent Maxim Chubika, Alexey Tretyakova, Marianna Chubikb, Nina Osipovaa, Anna Moskalenkoa,*, Darya Galushkinaa a
b
Institute of Natural Resources, National Research Tomsk Polytechnic University, Tomsk 634050, Russia Institute of High Technology Physics, National Research Tomsk Polytechnic University, Tomsk 634050, Russia
Abstract
Given high importance of solving the problem of environmental pollution by radioactive elements, the goal of research is to develop the hybrid sorbent with application of various nanoforms (nanotubes, nanopowders) of metal oxides and modified by these nanoforms mycelium of nonpathogenic mold fungi of various kinds as components In this article we evaluated the possibility of regeneration of the developed hybrid sorbent after the sorption process. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/3.0/). review under responsibility of Engineering Information Engineering Selection Selection andand peerpeer review under responsibility of Information Research Institute Research Institute Keywords: Sorbent, nanobiotechnology, regeneration, radionuclides, environmental safety
1. Introduction Environmental condition is the one of the most urgent problems of modern society. Humanity has ingeniously solved the problem of energy crisis because of using of radioactive fuel. But it did not think about very serious consequences of this action. Apart from global environmental disturbances and shear climatic
* Corresponding author. Tel.: +7-913-829-0921 E-mail address:
[email protected].
2212-6678 © 2014 The Authors. 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/3.0/). Selection and peer review under responsibility of Information Engineering Research Institute doi:10.1016/j.ieri.2014.09.044
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conditions, there also exists the problem of accumulation of radioactive waste. Radioactive waste is the substance which is not further utilizable and the material in which the radionuclide content exceeds regulatory levels. As a result of nuclear power production about 200 000 m3 of low-level and intermediate radioactive wastes and 10.000 m3 of highly radioactive ones are formed every year all over the world [6]. The problem of environmental contamination by radionuclides is extremely relevant because the long-lived radionuclides do not degrade, but rather tend to accumulate easily transported over long distances and are often included in the biological cycle of substances [7]. About 80% of anthropogenic radioactive pollution enter on the aquatic environment of the Earth, turning it into the most powerful depot of radionuclides, getting into the groundwater and polluting drinking water supplies in areas of high population density. Effective technologies are needed for the radioactive wastes disposal from the environment. One of the important problems is development of materials that can efficiently sorb radionuclides, primarily from water bodies [2]. Specially synthesized, high-value polymers with specific functional groups are used usually for the selective retention of specified radionuclides [5]. However the question of new sorbent materials using is open now because a multipurpose and cheap sorbent that can extract radionuclides from wastewater selectively, efficiently and in large numbers has not been established yet [9]. In the last years in many countries research on new class sorbent development is actively progressing, these sorbents should constitute of biogenic substances and include them as the main element – biosorbent. For example, they are produced from microbe mass or fungi which are microbilogical industry wastes [8]. Apart from that, application of different nanoforms of metal oxides as a sorbent is viewed as promising [10]. The goal of research is to develop a hybrid sorbent with application of various nanoforms (nanotubes, nanopowders) of metal oxides and modified by these nanoforms mycelium of nonpathogenic mold fungi of various kinds as components. One of tasks of research is to evaluate the possibility of regeneration of the developed hybrid sorbent after the sorption process. 2. The prerequisites for modified by nanoforms of metal oxide mycelium of nonpathogenic mold fungi as component of sorbent The prerequisites for metal nanoparticles using as component of composite sorbent are hypotheses that state - the metal nanoparticles can be used as matrices for immobilization of plutonium, technetium, uranium and transuranic elements due to the ability to absorb radioactive ions while the deformation process of the nanomaterial takes place [4]. As a result, the absorbed radionuclides are permanently enclosed in the structure of the sorbent [2]. The prerequisites for mycelium of nonpathogenic mold fungi using as component of composite sorbent are hypotheses that state - the main characteristics of metal nanoparticles deposited on the growing mycelium of fungi are not differed from the nanoparticles properties suspended in the solution. At the same time there was no any preliminary modification of the particles or mold for the adsorption of nanoparticles on the surface of the growing mycelium [1]. For the research , the nanopowders of cupric and iron oxides, obtained by electrical explosion of cupric wire in air, the nanopowder of oxide – hydroxide aluminum phases and the titanium dioxide nanotubes, obtained by low-temperature sintering of electroexplosive nanopowders were used as components of composite sorbent. During the research as a biological component of composite sorbent mycelium of nonpathogenic mold fungi Aspergillus niger was used. Uranyl ions were sorbed from model uranyl nitrate solution with various initial concentration of (UO2)2+. ɋontaining of uranyl ions in solution was estimated by luminescent method on spectrofluorimeter «Fluorat02 Panorama» routinely.
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3. Regeneration of nanobiosorbent Prerequisites for possible regeneration of developed composite sorbent were noted in the foreign reference fact [3]. In this reference is considered the fact the regeneration of the sorbent based on mold fungi and metal ions. Uranium adsorbed in a precultured mycelial biomass was 94 to 99% extracted by alkali carbonates, up to 61% by EDTA, but only 0 to 3% by aqueous ammonia or organic acids. In this case the chemical regeneration method which occurs due to desorption is used. Desorption is the reduction of the component concentration in the surface layer of the material as compared with its value in volume of each phase. 3.1. Regeneration of sorbent using sodium carbonate solution For recovering of sorbents sorption properties that contain pollution, desorption produced in a neutral or alkaline medium. Due to research as a strippant solution of sodium carbonate (0.45g for 150 ml of water) was used. For the experiments five composite solutions Aspergilius niger with metal oxide nanoparticles was selected. The initial concentration of urinals ions in solutions was 1.2 mg/l. Containing of uranyl ions in model solutions after sorption process before desorption using sodium carbonate solution detailed in Table 1. ɋontaining of uranyl ions in model solutions after desorption using sodium carbonate solution detailed in Table 2. Table 1. Concentration of uranyl ions in model solutions after sorption process before desorption using sodium carbonate solution
1
Concentration of uranyl ions, mcg/l 2 3 4
5
Sorbent Fe3O4 + Aspergilius niger
113.7
115.1
114.6
109.4
109.0
Sorbent AlOOH + Aspergilius niger
69.8
69.2
68.4
67.2
66.7
Sorbent TiO2 + Aspergilius niger
103.5
103.0
102.0
101.9
103.0
Sorbent CuO + Aspergilius niger
110.8
113.5
113.8
112.4
111.5
Composite solution
Table 2. Concentration of uranyl ions in model solutions after desorption using sodium carbonate solution
Composite solution
1
Concentration of uranyl ions, mcg/l 2 3 4
5
Sorbent Fe3O4 + Aspergilius niger
1028.00
1017.00
1011.00
1012.00
1003.00
Sorbent AlOOH + Aspergilius niger
481.60
485.40
478.80
478.40
482.80
Sorbent TiO2 + Aspergilius niger
277.50
277.00
278.30
274.10
276.30
Sorbent CuO + Aspergilius niger
802.20
796.80
797.80
796.60
798.90
3.2. Regeneration of sorbent using ethylenediaminotetraacetic acid solution Often for desorption of heavy and radioactive metals organic complexing compounds are used. The most popular are the solutions of ethylenediaminetetraacetic acid (EDTA). We had been lead testing of EDTA desorption activity for regeneration of composite sorbents. Holding desorption EDTA showed that the regeneration of sorbents for uranium expedient to use a more concentrated EDTA solution. For the experiments 1-% (1g/99ml) and 5-% (5g/95ml) EDTA solutions were used for composite sorbents nanoparticles of cupric oxide and titanium dioxide based on Aspergilius niger. For studying the behavior of
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desorbate in different acid-base conditions the following solutions were selected: CuO + Aspergilius niger (pH 6-7), CuO + Aspergilius niger (pH 2-3), TiO2 + Aspergilius niger (pH 2-3). Research has identified that the process of desorption of the most actively proceeded in solution with cuprous oxide nanoparticles at a value pH 2-3, that is in a more acidic conditions. The rest sorbents firmly enough hold uranium which prevents the desorption process. Containing of uranyl ions in model solutions after sorption process before desorption using EDTA solution detailed in Table 3. ɋontaining of uranyl ions in model solutions after desorption using EDTA solution detailed in Table 4. Table 3. Concentration of uranyl ions in model solutions after sorption process before desorption using solution of EDTA
Composite solution
Concentration of uranyl ions, mcg/l 3 4 5
1
2
Sorbent CuO + Aspergilius niger (pH 6-7)
98.6
95.64
98.17
96.62
94.88
Sorbent CuO + Aspergilius niger (pH 2-3)
37.75
36.5
37.73
34.12
34.5
Sorbent TiO2 + Aspergilius niger (pH 2-3)
159.1
159.9
157.3
157.3
158.7
Table 4. Concentration of uranyl ions in model solutions after desorption using solution of EDTA
Composite solution
Concentration of uranyl ions, mcg/l 3 4 5
1
2
Sorbent CuO + Aspergilius niger (pH 6-7)
52.13
51.68
51.26
51.05
53.76
Sorbent CuO + Aspergilius niger (pH 2-3)
111.0
113.3
111.2
112.4
113.3
Sorbent TiO2 + Aspergilius niger (pH 2-3)
101.8
99.52
103.0
96.74
94.12
It can be seen on diagram on Fig.1 that the desorption capacity of sodium carbonate solution is in many times greater the desorption capacity of EDTA solution. 90
Desorption capacity, %
80 70 60 50
Sodium carbonate
40
EDTA
30 20 10 0
Fe3O4 + Aspergilius niger
CuO + Aspergilius niger
CuO + Aspergilius niger
Fig.1 Desorption capacity of sodium carbonate and EDTA solutions
4. Conclusion Due to the urgency of the waste utilization issue currently, using materials that capable of regeneration as
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sorbent is very attractive. In relation to developed composite sorbent desorption capacity of sodium carbonate solution is in many times greater than the desorption capacity of EDTA solution. It should also be noted that the most effective desorbate (sodium carbonate solution) manifests itself in solution with iron oxide nanoparticles where its desorption capacity reached about 85%. In addition, iron oxide nanoparticles have a magnetic properties that gives a significant advantage when the particles need to be removed from the aqueous medium and also it has the possibility of secondary use. Thus we can state the fact that the developed composite sorbent can be easily regenerated by carbonate solution.
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