Đề tài nêu lên một phương pháp đơn giản cho sự tổng hợp chất hấp phụ hỗn hợp nano oxid mangan-sắt để hấp phụ ion kim loại As(V) từ dung dịch nước. Phương pháp kính hiển vi điện tử truyền qua (TEM), nhiễu xạ tia X (XRD), kính hiển vi điện tử quét (SEM), phổ hồng ngoại (FTIR), phân tích BET được sử dụng để xác định kích thước hạt và đặc trưng của hỗn hợp nano oxid mangan-sắt. Mời các bạn cùng tham khảo!
Trang 1SYNTHESIS AND APPLICATION OF MIXED MANGANESE-IRON OXIDE NANOPARTICLES FOR ADSORPTION OF As(V)
FROM AQUEOUS SOLUTIONS Synthesis of adsorbent and its adsorption
a The Faculty of Chemistry, Dalat University, Lamdong, Vietnam Correspoding author: Email: chungln@dlu.edu.vn
Abstract
A simple method has been used to synthesize nanoparticles of mixed manganese-iron oxide for the adsorption of As(V) metal ions from aqueous solutions Transmission Electron Microscopy (TEM), X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), BET analysis were used to determine particle size and characterization of produced nanoparticles The x-ray diffraction pattern indicated that the as-synthesized adsorbent is amorphous with 288.268 m 2 /g surface area; the amorphous synthesized products were aggregated with many nanosized particles The crystallinity of the
Mn 2 O 3 /Fe 2 O 3 were obtained at 400°C and 600°C calcination temperature The FTIR spectra confirmed the presence of -OH group and H-O-H group localized at 3200 - 3400 cm –1 and 1618-1653 cm −1 ; theses intense bands is weak (fade) at the high calcination temperature of the mixed manganese-iron oxide nanoparticles In addition, when the calcination temperature of the mixed manganese-iron oxide nanoparticles was 400 O C, the weak absorption bands at 630 cm −1 due to the vibrations of (Fe-O) The results showed that the mixed manganese-iron oxide nanoparticles has high selectivity for As(V)
Keywords: Mixed manganese-iron oxide nanoparticles; Amorphous; As(V)
Trang 254
TỔNG HỢP VÀ ỨNG DỤNG HỖN HỢP NANO OXID
MANGAN-SẮT ĐỂ HẤP PHỤ As(V) TỪ DUNG DỊCH NƯỚC
Tổng hợp chất hấp phụ và tính chất hấp phụ
a Khoa Hóa học, Trường Đại học Đà Lạt, Lâm Đồng, Việt Nam
*Tác giả liên hệ: Email: chungln@dlu.edu.vn
Tóm tắt
Một phương pháp đơn giản cho sự tổng hợp chất hấp phụ hỗn hợp nano oxid mangan-sắt để hấp phụ ion kim loại As(V) từ dung dịch nước Phương pháp kính hiển vi điện tử truyền qua (TEM), nhiễu xạ tia X (XRD), kính hiển vi điện tử quét (SEM), phổ hồng ngoại (FTIR), phân tích BET được sử dụng để xác định kích thước hạt và đặc trưng của hỗn hợp nano oxid sắt Nhiễu xạ tia X cho thấy chất hấp phụ tổng hợp là hỗn hợp nano oxid mangan-sắt có cấu trúc vô định định hình có diện tích bề mặt 288.268 m 2 /g và bị hiện tượng aggregation Khi nung hỗn hợp nano oxid mangan-sắt ở nhiệt độ 400 O C và 600 O C sẽ xuất hiện cấu trúc của tinh thể Mn 2 O 3 /Fe 2 O 3 Phổ hồng ngoại FTIR cũng xác nhận hỗn hợp nano oxid mangan-sắt được tổng hợp có sự hiện diện của nhóm –OH và nhóm H-O-H tại dải hấp thụ 3200 - 3400 cm –1 và 1618-1653 cm −1 ; cường độ của dải hấp thụ này sẽ yếu đi khi hỗn hợp nano oxid sắt nung ở nhiệt độ cao Hơn nữa, khi hỗn hợp nano oxid mangan-sắt nung đến nhiệt độ 400 O C thì xuất hiện peak hấp thụ yếu tại 630 cm −1 gây nên do nhóm Fe-O Kết quả cũng chỉ rằng hỗn hợp nano oxid mangan-sắt có tính chọn lọc cao đối với As(V)
Keywords: Mixed manganese-iron oxide nanoparticles, Amorphous , As(V)
Trang 31 INTRODUCTION
Water plays important roles in the natural environment, human activities, and social development However, the presence of arsenic in natural waters has become a
in USA, China, Chile, Bangladesh, Taiwan, Mexico, Romania, United Kingdom, Argentina, Poland, Canada, Hungary, New Zealand, Vietnam, Cambodia, Japan and India
[1-7]
general, As(V) is stable in aerobic environment and As(III) often exists in anaerobic environment The toxicity of arsenic species is different, generally the toxicity of inorganic arsenic compounds is about 100 times higher than organic arsenic compounds, and the toxicity of inorganic As(III) compounds are approximately 60–80 times higher to
as well as pigmentation changes, skin thickening (hyperkeratosis), neurological disorders,
remove arsenic from water to make sure that our environment is safe
Adsorption has been recognized as a promising technique for removing arsenic from drinking water due to its high removal capacity and ease of operation However, As(III) is less efficiently removed than As(V) from aqueous solutions by almost all of the
Recently, increasing attention has been focused on metal oxide sorbents such as iron, aluminum, titanium, manganese, and zirconium Among these iron oxides were the mostly studied because of their high affinity to arsenic species, low cost and
or more metals) as adsorbents to remove As from contaminated water The results showed
also show a synergistic effect of higher adsorption capacity than that of individual metal oxides (Lata and Samadder 2016) For instances, Zhang et al (2005) developed an Fe-Ce bimetal oxide sorbent, which has a much higher As(V) adsorption capacity than the individual Ce and Fe oxide Zhang et al (2007) prepared an Fe-Mn binary oxide sorbent,
report a simple method to synthesize the mixed manganese-iron oxide nanoparticles and used it as selective adsorbent for adsorption of As(V) from aqueous solutions
Trang 456
2.1 Chemicals and Instruments
2.1.1 Chemicals
of analytical grade and purchased without any further purification
2.1.2 Preparation of Adsorbate Solutions
The solutions of As(V), Cd(II), Co(II), Cu(II), Zn(II) were used as adsorbates, the As(V), Cd(II), Co(II), Cu(II), Zn(II) solutions were prepared by the standard solutions (1000 ppm) of Merck production for AAS Studied solutions have been diluted to concentration about 20, 50, 100, 150, 200, 250, 300,…ppm (~mg/L), and used for a short period of time that not exceeding three days
2.1.3 Instruments
Atomic Absorption Spectrophotometer (Spectrometer Atomic Absorption AA –
7000 made in Japan by Shimadzu.) The pH measurements were done with a pH-meter (MARTINI Instruments Mi-150 Romania); the pH-meter was standardized using HANNA instruments buffer solutions with pH values of 4.01±0.01, 7.01±0.01, and 10.01±0.01 Temperature-controlled shaker (Model IKA R5) was used for equilibrium studies
work, the mixed manganese-iron oxide nanoparticles was prepared by adding gradually
the room temperature Stirring continued for four hours
the product The synthesized products are amorphous nanoparticles The amorphous nanoparticles were crystallized using an annealing process at different temperatures (fig.1-2)
2.3 Batch adsorption study of metal ions
in a 100 mL conical flask Effect of pH (26), contact time (20240 minutes) and initial
Trang 5metal ion concentration (Co) (20500 mg/L) were examined The obtained mixture was centrifugal at 5000 rpm within 10 minutes, then was purified by PTFE Syring Filters with
(Spectrometer Atomic Absorption AA – 7000) was used to analyze the concentrations of the different metal ions in the filtrate before and after adsorption process
Adsorption capacity was calculated by using the mass balance equation for the
Co C Ve
q
m
concentration and the equilibrium concentration (mg/L), respectively V is the volume (L) of solution and m is the mass (g) of adsorbent used
3.1 Characterization of the mixed manganese-iron oxide nanoparticles
The crystal structure of mixed manganese-iron oxide nanoparticles was identified with X-ray powder diffraction analysis, as shown in Figure 1-2 The diffraction patterns
Figure 1 X-ray powder diffraction of the Mn-Fe mixed sorbent
Figure 1 reveal that the mixed manganese-iron oxide nanoparticle is amorphous Absence of sharp peaks confirms the absence of ordered crystalline structure in the prepared sorbent nanoparticles
Figure 2(a,b,c) shows the XRD pattern of the mixed manganese-iron oxide
on the XRD pattern, whereas the synthesized products calcined at 200°C proved to be amorphous (Fig 2a)
VatLieuNano_Mn_Fe_1_2
VatLieuNano_Mn_Fe_1_2 - File: VatLieuNano_Mn_Fe_1_2.raw - Type: 2Th/Th locked - Start: 15.000 ° - End: 84.990 ° - Step: 0.030 ° - Step time: 1 s - Temp.: 25 °C (Room) - Time Started: 8 s - 2-Theta: 15.000 ° - T
0 10 20 30 40 50 60 70 80 90 100
2-Theta - Scale
Trang 658
Figure 2a X-ray powder diffraction of the Mn-Fe mixed sorbent after calcination
at 200°C
Figure 2c X-ray powder diffraction of the Mn-Fe mixed sorbent after calcination
at 600°C Figures 2b, the synthesized products calcined at 400°C, clearly revealed that the
the reported data of hematite However, the XRD data did not show any presence of Mn
Nano_Mn_Fe_1_2_L2_200C
Nano_Mn_Fe_1_2_L2_200C - File: Nano_Mn_Fe_1_2_L2_200C.raw - Type: 2Th/Th locked - Start: 15.000 ° - End: 84.990 ° - Step: 0.030 ° - Step time: 1 s - Temp.: 25 °C (Room) - Time Started: 15 s - 2-Theta: 15.0
0 10 30 50 60 80 100 110 130 150 160 180 200
2-Theta - Scale
15 20 30 40 50 60 70 80
Nano_Mn_Fe_1_2_L2_400C
00-033-0664 (*) - Hematite, syn - Fe2O3 - WL: 1.5406 - Rhombo.H.axes - a 5.03560 - b 5.03560 - c 13.74890 - alpha 90.000 - beta 90.000 - gamma 120.000 - Primitive - R-3c (167) - 6 - 301.926 - I/Ic PDF 2.4 - F30=
Nano_Mn_Fe_1_2_L2_400C - File: Nano_Mn_Fe_1_2_L2_400C.raw - Type: 2Th/Th locked - Start: 15.000 ° - End: 84.990 ° - Step: 0.030 ° - Step time: 1 s - Temp.: 25 °C (Room) - Time Started: 14 s - 2-Theta: 15.0
0 10 30 50 70 90 100 120 140 160 180 200
2-Theta - Scale
Nano_Mn_Fe_1_2_L2_600C
00-041-1442 (*) - Bixbyite-C, syn - Mn2O3 - WL: 1.5406 - Cubic - a 9.40910 - b 9.40910 - c 9.40910 - alpha 90.000 - beta 90.000 - gamma 90.000 - Body-centered - Ia-3 (206) - 16 - 832.998 - I/Ic PDF 4.5 - S-Q 24.3 00-033-0664 (*) - Hematite, syn - Fe2O3 - WL: 1.5406 - Rhombo.H.axes - a 5.03560 - b 5.03560 - c 13.74890 - alpha 90.000 - beta 90.000 - gamma 120.000 - Primitive - R-3c (167) - 6 - 301.926 - I/Ic PDF 2.4 - S-Q 7 Nano_Mn_Fe_1_2_L2_600C - File: Nano_Mn_Fe_1_2_L2_600C.raw - Type: 2Th/Th locked - Start: 15.000 ° - End: 84.990 ° - Step: 0.030 ° - Step time: 1 s - Temp.: 25 °C (Room) - Time Started: 14 s - 2-Theta: 15.0
0 10 30 50 70 90 100 120 140 160 180 200
2-Theta - Scale
Trang 7oxide particles in the Mn-Fe mixed oxide system which confirmed that Mn (III) enter into
Nevertheless, when the calcination temperature of the synthesized products was
Formation of the mixed manganese-iron oxide nanoparticle was further supported
by FTIR analysis
Fig 3 FTIR spectrum of the manganese-iron oxide nanocomposite particles Fig 3 shows the FTIR spectrum of the mixed manganese-iron oxide nanoparticles
bands is weak (fade) at the high calcination temperature of the mixed manganese-iron oxide nanoparticles In addition, when the calcination temperature of the mixed
may be the vibrations of (Fe-O), which are indicative of formation of mixed metal oxides
SEM and TEM Analysis
The SEM images of the mixed manganese-iron oxide nanoparticles (the synthesized products) were obtained to observe the particle size and morphology (fig.4)
Trang 860
Fig 4 The SEM images of the manganese-iron oxide nanocomposite particles (the
synthesized products) with different magnification From the SEM photographs, it was understood that the grains are connected with each other (It was found that the grains present jointly with each other) In few places, bigger grains are also seen It is seen that the synthesized products consists of nanoparticles aggregated together to form large clusters It is a common phenomenon
Fig 5 The TEM image of the manganese-iron oxide nanocomposite
The TEM analysis shows the particles size of the mixed manganese-iron oxide nanoparticles are in the range of 20-30nm (fig.5) The surface area of the mixed manganese-iron oxide nanoparticles were measured by a BET analyzer, and the surface area of the samples was calculated to be 288.268 m²/g
Trang 93.2 Adsorption of As (V) onto mixed manganese-iron oxide nanoparticles
3.2.1 Affecting Factors
Effect of pH
Determination of optimum pH is very important since the pH value affects not only the surface charge of adsorbent, but also the degree of ionization and speciation of adsorbate during reaction Adsorption experiments were carried out in the pH range of
2-6 for the synthesized products by keeping all other parameters constant (As(V) concentration = mg/l; stirring speed = 240 rpm; contact time = 120 min, adsorbent dose
= 0.1g, room temperature = 25°C)
The result showed that more adsorption at acidic pH indicates that the lower pH
electrostatic attraction between positively charged adsorbent surface and As(V) arsenate
Figure 6 Effect of pH on the As(V) adsorption
Effect of contact time
The effect of contact time was studied at optimum condition of dose, pH, and agitation speed From Fig 7, it is observed that the adsorption of As(V) increased as contact time increased The adsorption percentage of metal ions approached equilibrium within 120 min After this equilibrium period, the amount of adsorbed metal ions did not
50 60 70 80 90 100
pH
250 ppm
300 ppm
Trang 1062
Figure 7 Effect of contact time on the As(V) adsorption
Effect of initial As(V) concentration
The adsorption of As(V) with synthesized products was studied by varying As(V) concentration (100ppm - 1000ppm) keeping other parameters (adsorbent dose, stirring speed, solution pH, temperature and contact time) constant As illustrated in Fig 8, As(V) uptake reduced from 99.89% to ~ 30%, as the As(V) concentration increased from 100ppm to 1000ppm
Figure 8 Effect of initial As(V) concentrations on the As(V) adsorption 3.2.2 Comparation of Bivalent Cationic Metals Adsorption Cd(II), Co(II), Cu(II), Zn(II) and As(V) on mixed manganese-iron oxide nanoparticles
The results of Table 1 showed that the mixed manganese-iron oxide nanoparticles
aqueous solution on concentration of 20ppm for each (or more), inversely strongly adsorption of As(V) on mixed manganese-iron oxide nanoparticles This remarkable
0 10 20 30 40 50 60 70 80 90
0 20 40 60 80 100 120 140 160 180 200
The contact time (min)
262,97ppm 304,41ppm
0 20 40 60 80 100
0 200 400 600 8001000
0.1 g…
Trang 11difference is probably due to the difference ionic radius (table 2) and the greater the valence Danny et al (2004) and Lee and Moon (2001) explained that the smaller the ionic radius
Therefore, the mixed manganese-iron oxide nanoparticles have successfully used for the adsorption of As(V) from aqueous solution
Table 1 Adsorption percentage of metal ions on to mixed manganese-iron oxide
nanoparticles
pH Adsorption of metal ions on to mixed manganese-iron oxide nanoparticles, (%)
As(V)
(150ppm)
Cd(II) (20ppm)
Co(II) (20ppm)
Cu(II) (20ppm)
Zn(II) (20ppm) Adsorption
percentage, % SD*
2 99.89 0.01 non-ads non-ads - -
3 98.45 0.09 non-ads non-ads - -
4 95.28 0.05 non-ads non-ads non-ads non-ads
5 96.46 0.06 non-ads non-ads - -
6 96.51 0.01 non-ads non-ads - -
Note: (*) Standard deviation (SD)
Table 2 Effective ionic radii in pm of elements
Ion As(V) Cd(II) Co(II) Cu(II) Zn(II) Effective ionic radii (pm) 46 95 65 73 74
A simple method has been used to synthesize nanoparticles of mixed manganese-iron oxide for the adsorption of As(V) metal ions from aqueous solutions under batch conditions Transmission Electron Microscopy (TEM), X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), BET analysis were used to determine particle size and characterization of produced nanoparticles Moreover, the effects of pH, contact time and adsorbent weight on adsorption process were investigated The high uptake of As(V) by the mixed manganese-iron oxide nanoparticles may be due to its relatively high surface area
REFERENCES
water through adsorption-A Review Recent Research in Science and Technology 6(1), pp 219-226