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ISSN 2522-1841 (Online) AZ9RBAYCAN KIMYA JURNALI № 3 2018 ISSN 0005-2531 (Print)
UDC 541.64:547.458.81 SYNTHESIS AND APPLICATION OF ZEOLITE SUPPORTED ZERO VALENT IRON NANOPARTICLES AS MEMBRANE COMPONENT FOR REMOVAL OF NITRATE
G.R.Allahverdiyeva, A.M.Maharramov, U.A.Hasanova
Baku State University gunel. allahverdiyeva. 89@gmail. com Received 26.09.2017
Synthesis and characterization of zeolite supported zero valent iron nanoparticles (ZVI NPs) are reported. ZE-ZVI NPs size, composition, morphology were characterized by Scanning Electron Microscopy, Atomic Force Micrsocopy, Energy Dispersive Spectroscopy. Synthesized nanostructures were used as reducing agents of nitrate. Nitrate removal effiency (at initial concentration 50 mg/ml) was rapidly increased from 34 to 90% for ZE-ZVI NPs at 60-240 min time interval. Also was studied the efficacy of prepared ZE-ZVI NPs as membrane component with 5 % ZVI NPs mass content for nitrate for solution that made 85% for ZE-ZVI NPs respectively. The results of this study indicate that the application of ZE-ZVI NPs as membrane component is advantageous because it allows to prevent the additional pollution of treated solution caused by unreacted ZVI NPs.
Keywords: ZVI NPs, ZE-ZVI NPs, nitrate removal, adsorption, reduction.
Introduction
The interest in nanoscale particles applicable for the solving of environmental problems has been growing day by day. The different routes of a synthesis of nanostructures have been developed and they reveal the high application potential in various fields. Particularly in recent years zero valent iron nanoparticles ZVI NPs attract the significant interest as a soft reducing agent, and due to its biocompatibility it can be used in green environmental technologies. There are developed different synthetic procedures for obtaining ZVI NPs [1-3]. Among them practically importante are the methods of engineering of nanopartciles surface in order to avoid their oxidation, agglomeration and as consequence the increase the efficiency in situ reactions [4-6]. Many field tests have demonstrated the promising results for in situ remediation [7, 8].
The excess amount of nitrate has become a serious problem affecting water quality. Nitrates are potential harmful contaminants towards living organisms, and due to high solubility, they can easily contaminate soil and groundwater. Nitrates can be introduced into environment mainly as a result of excessive use of fertilizers and through industrial wastes. It has been found that nitrate in living organisms is enzymatically reduced to nitrite, thus causing cancer [9]. The maximum allowed level of nitrate in drinking water in accordance to the World Health Organization should not exceed 10 mg/L NO3-N. There are some studies
reporting of successful application of ZVI NPs for removal of nitrates from the ground and water [10]. But at the same time the authors underlined the drawbacks of use of ZVI NPs, that is they can also act, in turn, as contaminant of the environment. In order to apply ZVI NPs as reducer for the purification of soil and water, the development of new nano formulation containing ZVI NPs is a matter of practical interest. Recently, the use of some supportive materials has been suggested in order to prevent their agglomeration and their release into the environment.
Experimental part
Materials and equipment
The natural zeolite and glass fiber were purchased from St.Cloud Mine in Winston, NM. After washing with hot distillite water, dried raw zeolite was sieved with 200 mesh screen prior to use.
Ferrous sulphate heptahydrate (FeS04'7H20) and sodium borohydride (NaBH4) were purchased from Tianjin Fuchen Agent Manufactory, China. The Ethanol (95%), NaOH (99%), HC1 (98%), KNO3 (98%), PAA (polyacrylic acid), CTAB (cetyltrimethylammonium bromide) were purchased from Merck (Darmstadt, Germany).
Synthesis and characterization of ZE-ZVI NPs and GF-ZVI NPs
The synthesis of ZE-ZVI NPs and GF-ZVI NPs (GF - glass fiber) was based on the reduction of ferrous sulphate heptahydrate
(0.822 g) with potassium borohydride (0.244 g), at room temperature [11], where zeolite and glass fiber acted as a porous support material. The prepared ZVI NPs were stabilized by PAA and CTAB. The reaction was carried out under vigorous stirring in a nitrogen atmosphere. The reduction of Fe + to Fe° occurred according to the following reaction [12]:
Fe2++2BH4+ 6H2O^Fe°+2B(OH)3+7H2t (1)
The formed NPs were separated by centrifu-gation and repeatedly washed with ethanol, in order to remove the interfering ions prior to use [13].
SEM and EDS analysis of prepared samples of ZE-ZVI NPs and GF-ZVI NPs were taken on Field Emission Scanning Electron Microscope JEOL JSM-7600F at an accelerating voltage of 15.0 kV, SEI regime.
Ultrasonic processing of materials made in the instrument Sonics Vibramobil VCX 500.
The morphology of samples was studied by means of AFM Integra-Prima (NT-MDT, Russia). Special silica cantilevers, covered by ferromagnetic with curvature radii of 20 nm and a resonance frequency of 40-97 Hz were used for the scanning. The scanning area was 750x750 nm. The measurements were implemented in semi-contact regime on air, and the determination of changes of cantilever amplitude oscillation allowed definition of the surface topography. Scanning rate was 1.969 Hz and the number of scanned lines was 256.
The concentration of ions in solution was analyzed based on the guidelines given in the 20th edition of the standard methods by means UV/Vis spectrophotometer (UV-1800 Series WL=340 nm).
Adsorption-reduction experiments
Batch experiments were first carried out in order to evaluate the removing efficiency of ZVI NPs. The aqueous solutions of nitrate were prepared by dissolving of appropriate amount of KNO3 in 100 ml of distilled water. The batch experiments were carried out in 100 ml glass flasks containing 0.05 g of ZE-ZVI NPS. The prepared solutions were stirred at room temperature and sampled at certain time points (30, 90, 120, 180, 240 min) then each sample was filtered and remaining concentrations of pollutants in the solu-
tion were analyzed and compared. The removal efficiency (R, %) and the adsorption capacity (qs, mg/g) of sorbents (ZE-ZVI NPs and GF-ZVI NPs) were calculated as follows:
R = C° ~Ce 100%, C
(C0-Ce)F
</e ,
m
where: Co, Ce = concentrations of ions at initial and equilibrium (mg/L), m = mass of sorbent (g), V= volume of solution (L).
Membrane experiments were then carried out, using ZE-ZVI NPs and GF-ZVI NPs as membranes components for filtration of nitrate and dichromate containing solutions. Membrane experiments were performed in a glass funnel with bottom in which there were holes with diameters of 0.5 mm, as shown in Figure 1.
Results and discussions
The morphology and structure of ZVI NPs, ZE-ZVI NPs and GF-ZVI NPs were analyzed by SEM, EDS and the results are given in Figure 2. As it seen from Figure 2 the produced ZVI NPs were evenly distributed and the size of ZVI NPs ranged 35-50 nm. The peaks indicated in the EDS spectra depict the presence of Fe, C, Zn, Na (Figure 2 c) as the main elements of the ZE-ZVI sample. The samples before EDS study were coated by thin layer of Pt in order to avoid their charging and this explains the presence of peak that is characteristic to platinum. The samples also were analyzed by AFM (Figure 3) and the results of AFM scanning showed a very good correlation with the results of SEM analysis. According to the AFM analysis the size of ZVI NPs changes was in the range of 40-50 nm. As it can seen from the Figures 2 and 3, the ZVI NPs resulted evenly distributed in the matrix of supported material without significant agglomeration.
In order to investigate nanomaterials (ZE-ZVI NPs and GF-ZVI NPs) effectiveness, batch experiments were then carried out. Nitrate removal efficiency (at initial concentration 50 mg/mL) was rapidly increased from 34 to 90% for ZE-ZVI NPs at 60-240 min time interval Figure 4, a.
The reduction of nitrate ions occurs in accordance to the reaction: 4Fe°+N03"+10H+=4Fe2++NH4++3H20. (2)
GF-ZVI OR ZE -ZVI NPs
Fig. 1. The schema of filtering of contaminated water by means of GF-ZVI NPs and ZE-ZVI NPs as membrane components.
a b c
Fig. 2. SEM images of PAA stabilised ZVI NPs (a)., ZE-ZVI NPs (/>). EDS of ZE-ZVI NPs (c).
a b
Fig. 3. AFM 2D images of ZE-ZVI NPs (a). 3D image of ZE-ZVI NPs (b).
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Fig. 4. Removal efficiency of nitrate ZE-ZVI NPs (a): Adsorption capacity of ZE-ZVI (b).
Total decrease of nitrate concentration in the solution was 90% for ZE-ZVI NPs. As it can be seen from Figure 4 (b) the adsorption capacity also increased from 3.4 to 9 mg/g for ZE-ZVI NPs.
In order to test the efficiency of ZE-ZVI NPs as membrane component we filtered the contaminated water through prepared materials with 5% of ZVI NPS weight content. The rate of water passage through filter was 0.5 mL/min. The calculated removal efficiency of nitrate was 85% for ZE-ZVI NPs.
Conclusion
In this study ZVI NPs supported by zeolite was synthesized and characterized, and applied to the removal of nitrate from water. The ZVI nano-particles were evenly dispersed in the supported material without any significant aggregation, and they were characterized by high specific surface area and an average size of 45 nm.
Zeolite and Glass are inexpensive materials so it can be promisingly used as supporting material for the preparation of membrane component for removal of contaminated ions from water. Furthermore, the application of ZE-ZVI NPs as membrane component allow to prevent the additional pollution of treated solution caused by contamination by unreacted ZVI NPs.
Batch experiments showed that the nitrate removal was 90% by application of ZE-ZVI NPs.
References
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SEOLiTLO DOSTOKLONMiS SIFIR VALENTLi DOMiR NANOHiSSOCibCLORlNiN SiNTEZi УЭ MEMBRAN KOMPONENTi KIMI NiTRATIN TOMiZLONMOSiNDO TOTBiQi
G.RAllahverdiyeva, A.M.Maharramov, Ü.O.Hasanova
Scolitlo dostoklonmis sifir valentli domir nanohissociklorinin (Se-SVD NH) sintezi vo xarakteriza olunmasi toqdim edilir. Scolitlo dostoklonmis sifir valentli domir nanohissociklori nin ölciisii. torkibi vo morfologiyasi Skanedici Elektron Mikroskopu (SEM), Atom Qüvvot Mikroskopu (AQM), Eneiji Dispcrslosdirici Spekstroskopi (EDS) ib xaraktcrizo cdilmisdir. Sintez cdilmis nanoquruluslar nitratin reduksiyaedici agenti kimi istifado cdilmisdir. Nitratin tomi/lonmo ef-fektivliyi seolitb dostoklonmis sifir valentli domir nanohissociklori iiciin 60-240 doq vaxt intervalinda 34% dan 90%-э qalxmisdir. Homcinin ha/irlanmis seolit sifir valentli domir nanohissociklorinin nitratin tomi/lonmosindo membran kimi effektivliyi övronilmisdir. Noticolor gösbrdi ki, seolitb dostoklonmis sifir valentli domir nanohissociklori nin membran komponenti kimi istifadosi üstünliivo malikdir, cünki о tomi/lonon mohlulun ola\o reaskiyaya daxil olmamis sifir valentli domir nanohissociklori ib cirklonmosinin qarsisini alir.
Agar söz.for: sifir valentli d3mir nanohissacikbro, seolit-sifir valentli d3mir nanohissacikbri, adsrobsiya, reduksiya.
СИНТЕЗ И ПРИМЕНЕНИЕ НАНОСЧАСТИЦ С НУЛЕВЫМ ВАЛЕНТНЫМ ЖЕЛЕЗОМ НА ОСНОВЕ ЦЕОЛИТА В КАЧЕСТВЕ МЕМБРАННОГО КОМПОНЕНТА ДЛЯ УДАЛЕНИЯ НИТРАТА
Г.Р.Аллахвердиева, А.М. Магеррамов, У.А.Гасанова
Сообщается о синтезе и характеристиках иаиочастиц с нуль-валентным железом на цеолите (Це-НВЖ НЧ). Размер, состав, морфология Ze-ZVI NPs, охарактеризованы сканирующей электронной микроскопией (СЭМ), атомно-силовой микроскопией (АСМ), энергодисперсионной спектроскопией (ЭДС). Эффективность удаления нитратов (при начальной концентрации 50 мг/мл) быстро увеличивалась с 34 до 90% для Це-НВЖ НПЗ за 60-240 мин. Также была изучена эффективность приготовленных Це-НВЖ ZeZVI НЧ в качестве мембранного компонента с весовым содержанием 5% ZVI NPs для раствора нитрата. Результаты этого исследования показывали, что применение Це-НВЖ НЧ в качестве мембранного компонента является выгодным, поскольку оно позволяет предотвратить дополнительное загрязнение раствора, вызванное непрореагировавшими НВЖ НЧ.
Ключевые слова: НВЖ НПЗ, Це-НВЖ НПЗ, очистка нитратов, адсорбция, восстановление.
