scholarly journals Conductivity at Low Humidity of Materials Derived from Ferroxane Particles

2012 ◽  
Vol 2012 ◽  
pp. 1-7
Author(s):  
Alberto Lapina ◽  
Peter Holtappels ◽  
Mogens Mogensen
Keyword(s):  
Aqueous Solution ◽  
Acetic Acid ◽  
Carboxylic Acid ◽  
Room Temperature ◽  
Sintered Material ◽  
Nitrogen Adsorption ◽  
Proton Conductors ◽  
Low Humidity ◽  
Adsorption Desorption ◽  
Sintered Materials

Carboxylic-acid-stabilisedγ-FeOOH particles (ferroxanes) are synthesized using a precipitation from aqueous solution, and a following reaction with acetic acid. The materials produced with these powders are investigated by XRD, SEM, nitrogen adsorption-desorption, and impedance spectroscopy. Conductivity of both sintered and unsintered materials decreases strongly with a decrease in water partial pressure in the atmosphere during the test. The highest conductivity (7·10−3 S cm−1) is measured in air (pH2O = 0.037 atm) at room temperature on sintered material. The conductivity values are compared with other works in the literature and the dependence of conductivity on surface area and pore size is discussed. It is suggested that both unsintered and sintered materials act as proton conductors at room temperature under moderate humidity conditions.

scholarly journals Phenol Red Adsorption from Aqueous Solution on the Modified Bentonite

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Nguyen Le My Linh ◽  
Tran Duong ◽  
Hoang Van Duc ◽  
Nguyen Thi Anh Thu ◽  
Pham Khac Lieu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Cetyltrimethylammonium Bromide ◽  
Nitrogen Adsorption ◽  
Isotherm Models ◽  
Phenol Red ◽  
Order Kinetic ◽  
Equilibrium Data ◽  
Order Kinetic Model ◽  
Red Dye ◽  
Adsorption Desorption

In the present work, the modified bentonites were prepared by the modification of bentonite with cetyltrimethylammonium bromide (CTAB), both cetyltrimethylammonium bromide and hydroxy-Fe cations and both cetyltrimethylammonium bromide and hydroxy-Al cations. X-ray diffraction (XRD), thermal analysis (TG-DTA), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption/desorption isotherms were utilized to characterize the resultant modified bentonites. The modified bentonites were employed for the removal of phenol red dye from aqueous solution. Phenol red adsorption agreed well with the pseudo-second-order kinetic model. The equilibrium data were analyzed on the basis of various adsorption isotherm models, namely, Langmuir, Freundlich, and Dubinin‒Radushkevich models. The highest monolayer adsorption capacity of phenol red at 30°C derived from the Langmuir equation was 166.7 mg·g−1, 125.0 mg·g−1, and 100.0 mg·g−1 for CTAB‒bentonite, Al‒CTAB‒bentonite, and Fe‒CTAB‒bentonite, respectively. Different thermodynamic parameters were calculated, and it was concluded that the adsorption was spontaneous (∆G° < 0) and endothermic (∆H° > 0), with increased entropy (∆S° > 0) in all the investigated temperature ranges.

Catalytic Activity of Argentum-loaded MCM-41 for Ozonation of p- Chlorobenzoic Acid (p-CBA) in Aqueous Solution

2015 ◽  
Vol 18 (1) ◽  
Author(s):  
Zhaoqi Pan ◽  
Junyu Zeng ◽  
Bingyan Lan ◽  
Laisheng Li
Keyword(s):  
Aqueous Solution ◽  
Nitrogen Adsorption ◽  
Hexagonal Structure ◽  
Bet Surface Area ◽  
X Ray Diffraction ◽  
Chlorobenzoic Acid ◽  
Transmission Electron ◽  
Initial Ph ◽  
Adsorption Desorption ◽  
Mcm 41

AbstractArgentum-loaded MCM-41 (Ag/MCM-41) was synthesized successfully by a hydrothermal method and used as a catalyst for the ozonation of p-chlorobenzoic acid (p-CBA) in aqueous solution. Ag/MCM-41 was characterized by low angle X-ray diffraction (XRD), nitrogen adsorption-desorption and transmission electron microscopy (TEM). Characterizations suggest that the prepared samples retained a highly regulated mesopores of hexagonal structure and a high BET surface area. The influences of argentum content, initial pH, reaction temperature on the catalytic ozonation were also evaluated. Ag/MCM-41/O

scholarly journals Ultrasound-Assisted Rapid ZIF-8 Synthesis, Porous ZnO Preparation by Heating ZIF-8, and Their Photocatalytic Activity

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Pham Dinh Du ◽  
Nguyen Trung Hieu ◽  
Tran Vinh Thien
Keyword(s):  
Photocatalytic Activity ◽  
Room Temperature ◽  
Diffuse Reflectance ◽  
Nitrogen Adsorption ◽  
X Ray Diffraction ◽  
Zeolitic Imidazolate Framework ◽  
X Ray ◽  
Photocatalytic Activities ◽  
Ft Ir ◽  
Adsorption Desorption

Zeolitic imidazolate framework-8 (ZIF-8) is synthesized quickly at room temperature in methanol with the support of ultrasound. Porous ZnO is also prepared via the thermal treatment of ZIF-8. The photocatalytic activities of the obtained materials are demonstrated via methylene blue (MB) decomposition under UV radiation. The obtained materials are characterized by means of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, UV-Vis diffuse reflectance spectra (DR-UV-Vis), and photoluminescence spectra. The results indicate that ZIF-8 and the materials obtained from ZIF-8 by heating in the air have photocatalytic activity under UV irradiation. The ZnO sample obtained by ZIF-8 calcination at 660°C for 5 h has the highest photocatalytic activity. However, the MB degradation photocatalytic efficiency of the ZnO samples is even lower than that of the ZIF-8 samples, indicating that ZIF-8 is an effective photocatalyst in the treatment of environmental pollution.

New oxidation products of tryptophan

1975 ◽  
Vol 28 (10) ◽  
pp. 2275 ◽  
Author(s):  
WE Savige
Keyword(s):  
Acetic Acid ◽  
Carboxylic Acid ◽  
Propionic Acid ◽  
Alkaline Solution ◽  
Sodium Borohydride ◽  
Room Temperature ◽  
Oxidation Products ◽  
Acid Oxidation ◽  
Peroxyacetic Acid ◽  
Molar Equivalent

Oxidation of L- or DL-tryptophan by one molar equivalent of peroxyacetic acid in water at 0-5� gives principally a mixture of 3a- hydroxy-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid (A) diastereoisomers, while oxidation by two or three equivalents of oxidant gives mainly N?-formylkynurenine (C11H12N2O4) and a diastereoisomeric product (B), C11H12N2O5, tentatively assigned the structure 2-amino-3-(4-hydroxy-2-oxo-1,4-dihydro-2H-3,1-benzoxazin-4- yl)propionic acid. ��� Oxidation of (A) by peroxyacetic acid also gives formylkynurenine and (B). Rearrangement of (A) to oxindolylalanine occurs in 12N HCl at 20� or 2N HCl at 80�. (A) is also obtained by reduction of dioxindolylalanine with sodium borohydride. Compound (B) readily undergoes decarboxylation to kynurenine in 0.1N acetic acid at 80�, while in neutral or alkaline solution rapid autoxidation can occur even at room temperature.

scholarly journals Adsorptive removal of methylene blue from aqueous solution using coal fly ash-derived mesoporous silica material

2019 ◽  
Vol 37 (3-4) ◽  
pp. 333-348 ◽  
Author(s):  
Ning Yuan ◽  
Hui Cai ◽  
Tian Liu ◽  
Qi Huang ◽  
Xinling Zhang
Keyword(s):  
Aqueous Solution ◽  
Methylene Blue ◽  
Fly Ash ◽  
Mesoporous Silica ◽  
Coal Fly Ash ◽  
Nitrogen Adsorption ◽  
Mesoporous Silica Material ◽  
Adsorptive Removal ◽  
Silica Material ◽  
Adsorption Desorption

In the present work, coal fly ash-derived mesoporous silica material (CFA-MS) has been successfully fabricated without employing any extra silica source. The obtained CFA-MS was characterized by Fourier transform infrared spectroscopy, nitrogen adsorption–desorption measurement, powder X-ray diffraction and transmission electron microscopy. Nitrogen adsorption–desorption measurement disclosed that CFA-MS possesses Brunauer–Emmett–Teller-specific surface area of 497 m2·g−1 and pore volume of 0.49 cm3·g−1, respectively. Furthermore, CFA-MS was evaluated for the adsorptive removal of methylene blue from aqueous solution. Several influence parameters on the removal of methylene blue including contact time, pH, initial concentration and temperature were studied in detail. Moreover, Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were employed for interpretation of the adsorption process, while the pseudo-first-order and pseudo-second-order kinetics equations were applied to investigate the adsorption kinetics. Results in the current work demonstrate that CFA-MS can be used as an efficient adsorbent for methylene blue removal.

Synthesis of Ni(II)-imprinted Mesoporous Silica Adsorbents by Surface Imprinting Technology for Removal of Ni(II) from Aqueous Solution

2014 ◽  
Vol 997 ◽  
pp. 146-149
Author(s):  
Xiang Guo Meng ◽  
Wen Lu Guo ◽  
Min Luo ◽  
Ping Sun
Keyword(s):  
Aqueous Solution ◽  
Mesoporous Silica ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Surface Imprinting ◽  
Surface Imprinting Technique ◽  
Silica Adsorbents ◽  
Ft Ir ◽  
Surface Imprinting Technology ◽  
Adsorption Desorption

Ni(II)-imprinted polymer has been prepared by surface imprinting technique based on support matrix of mesoporous silica SBA-15. The obtained adsorbent was characterized by FT-IR, SEM, and nitrogen adsorption-desorption. The compound retained mesoporous structure and the polymer coated inside channels and outside surface hole wall. The adsorption behavior was carried out with Ni(II)-IIP in batch experiments. The results suggested that Ni(II)-IIP could be used as an excellent adsorbent for efficient removal of Ni(II) from aqueous solution.

The adsorption of Sb(III) in aqueous solution by Fe2O3-modified carbon nanotubes

2013 ◽  
Vol 68 (3) ◽  
pp. 658-664 ◽  
Author(s):  
Tingchao Yu ◽  
Chao Zeng ◽  
Miaomiao Ye ◽  
Yu Shao
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Aqueous Solution ◽  
Ph Value ◽  
Removal Rate ◽  
Nitrogen Adsorption ◽  
Solution Ph ◽  
Freundlich Adsorption Isotherm ◽  
Modified Carbon Nanotubes ◽  
Adsorption Desorption

A novel kind of iron oxide supported on carbon nanotubes (CNTs) was prepared for adsorption of antimony (Sb)(III) in aqueous solution. The iron (III) oxide (Fe2O3)-modified CNTs were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption and Fourier transform infrared spectrometer. Parameters affecting the adsorption efficiencies, including solution pH value, initial Sb(III) concentration, adsorbent dosage, adsorption time and temperature, were investigated. The results indicate that the removal rate of Sb(III) by Fe2O3-modified CNTs is 99.97% under the initial Sb(III) concentration of 1.5 mg/L, adsorbents dosage of 0.5 g/L, temperature of 25 oC and pH value of 7.00, which is 29.81% higher than that of the raw CNTs. The adsorption capacity increased correspondingly from 3.01 to 6.23 mg/g. The equilibrium adsorption data can be fitted to the Freundlich adsorption isotherm. In addition, it has been found that the solution pH values and adsorption temperatures have no significant influence on Sb(III) removal.

scholarly journals Adsorption of Arsenate from Aqueous Solution onto Modified Vietnamese Bentonite

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Nguyen Le My Linh ◽  
Duc Hoang Van ◽  
Tran Duong ◽  
Mai Xuan Tinh ◽  
Dinh Quang Khieu
Keyword(s):  
Aqueous Solution ◽  
Nitrogen Adsorption ◽  
X Ray Diffraction ◽  
Solution Ph ◽  
X Ray ◽  
Surface Areas ◽  
Layered Clays ◽  
Monolayer Adsorption ◽  
Langmuir Isotherm Model ◽  
Adsorption Desorption

In this study, pillared layered clays were prepared by modifying Vietnamese bentonite with polymeric Al and Fe. The obtained materials were characteristic of X-ray diffraction analysis, thermal analysis, and nitrogen adsorption/desorption isotherms. The results indicated that hydroxy-aluminum ([Al13O4(OH)24(H2O)12]7+) and poly-hydroxyl-Fe or polyoxo-Fe cations were intercalated into layers of clay, resulting in an increase of d001 values and of the specific surface areas compared with those of initial bentonite. Modified bentonites were employed to adsorb As(V) from aqueous solution. The adsorption of As(V) was strongly dependent on solution pH, and the maximum adsorption of modified bentonites was obtained in the pH 3.0 for Fe-bentonite and the pH 4.0 for Al-bentonite. The equilibrium adsorption study showed that the data were well fit by the Langmuir isotherm model. The maximum monolayer adsorption capacity of As(V) at 30°C derived from the Langmuir equation was 35.71 mg/g for Al-bentonite and 18.98 mg/g for Fe-bentonite. Adsorption kinetics, thermodynamics, and reusability of modified bentonites have been addressed.

Adsorption Behavior of Phenol in Aqueous Solution on MCM-41 Grafted by Different Functional Groups

2014 ◽  
Vol 955-959 ◽  
pp. 74-79
Author(s):  
Xiao Jun Sun ◽  
Xiao Chun Yan ◽  
Yu Jie Feng ◽  
Xian Bin Liu
Keyword(s):  
Aqueous Solution ◽  
Adsorption Capacity ◽  
Functional Groups ◽  
Ph Value ◽  
Nitrogen Adsorption ◽  
Adsorption Behaviors ◽  
Prepared Material ◽  
Adsorption Amount ◽  
Adsorption Desorption ◽  
Mcm 41

Four types of organo-functionalized mesoporous silicas were synthesized by post-grafting method, and characterized by powder X-ray diffraction, nitrogen adsorption/desorption and fourier transform infrared spectroscopy. In addition, adsorption behaviors of the prepared material modified with different functional groups were studied by adsorption of phenol in aqueous solution. When the concentration of phenol was 800 mg/L, the equilibrium adsorption capacity of N-aminoethyl-γ-aminopropyl-MCM-41, aminopropyl-MCM-41, mercaptopropyl-MCM-41 and propyl-MCM-41 was respectively as 2.5 times, 2.2 times, 1.9 times, and 1.7 times as that of MCM-41. It was due to the introduction of organo-functional groups, changing the polarity of the channel surface, and increasing the hydrophobic properties. N-aminoethyl-γ-aminopropyl and aminopropyl groups could generate acid-base interactions with phenol, therefore, their adsorption capacity increased much more. Besides, the pH value of the solution could significantly affect the adsorption amount of phenol on samples. The result showed that with the increase of pH, the adsorption amount of phenol increased at first, and then decreased. The maximum adsorption amount of all the prepared materials occurred at about pH value of 6.

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