Preparation and characterization of nanosilica from rice husk ash by chemical treatment combined with calcination
- 2017
Le Nghiem Anh Tuan, Lai Thi Kim Dung, Le Doan Thanh Ha, Nguyen Quoc Hien, Dang Van Phu, Bui Duy Du
This work presented the results of the study on synthesis and characterization of nanosilica from rice husk ash (RHA). Nanosilica was obtained by calcination of HCl treated RHA at 700 oC for 2 h. X-ray diffraction (XRD) pattern showed only one peak at 2q ~22o confirming the amorphous structure of nanosilica. The chemical composition assessed by energy dispersive X-ray spectroscopy (EDX) showed that the obtained nanosilica was of high purity. TEM image measured by transmission electron microscopy (TEM) revealed that the obtained nanosilica was in spherical morphology with the average diameter of about 45.5±7.2 nm. The particle size distribution of nanosilica determined by dynamic laser scattering (DLS) was of Gaussian mode. The FTIR spectrum indicated the presence of silanol and siloxane groups in nanosilica. Thus, the synthesized nanosilica can be used for application in different fields. Keywords. Rice husk ash, nanosilica, amorphous.
#Rice husk ash #nanosilica #amorphous
Flavonoid glycosides from Antidesma ghaesembilla
Tập 53 Số 2e - 2015
Four flavone glycosides were isolated from the leaves of Antidesma ghaesembilla. They were elucidated to be vitexin, orientin, isovitexin, and homoorientin by 1D- and 2D-NMR and in comparison with literature data. These compounds have been reported from the genus Antidesma for the first time.
#Antidesma ghaesembilla #vitexin #orientin #isovitexin #homoorientin
Study of the formation of porous hydroxyapatite ceramics from corals via hydrothermal process.
Tập 48 Số 5 - 2012
The hydrothermal method was used for preparation porous hydroxyapatite (HA) ceramic from coral scaffold, in two ways: synthesized directly from coral skeleton and synthesized from CaO, which was product of coral thermal decomposition. The obtained samples were characterized by techniques including X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The analytical results confirmed that HA ceramic was formed by the indirect synthesis from fresh obtained CaO from coral aragonite. Determined reaction conditions were at 180oC and 14 atm pressure for 36 hours.
Visible light photocatalytic degradation of organic dyes using W‐modified TiO2/SiO2 catalyst
Tập 59 Số 5 - Trang 620-638 - 2021
Nguyễn Xuân Cường, Bùi Thị Minh Nguyệt, Nguyen Huu Nghi, Vo Thang Nguyen, Thai Vu Binh, Nguyen Thi Thanh Tu, Nguyen Nho Dung, Đinh Quang Khiếu
AbstractIn the present study, the synthesis of W‐modified TiO2/SiO2 composite and its catalytic activity in the visible light region is demonstrated. The W‐modified TiO2/SiO2 composite was obtained from the hydrolysis of a mixture containing titanium (IV) oxysulfate, ammonium metatungstate, and SiO2 powder in an alkaline medium. The obtained materials were characterized by using X‐ray diffraction (XRD), Fourier transformation‐infrared spectroscopy (FT‐IR), high‐resolution transmission electron microscopy (HRTEM), energy dispersive X‐ray elemental mapping observation, nitrogen adsorption/desorption isotherms, photoluminescence spectra (PL), and ultraviolet visible diffusive reflectance spectroscopy (UV‐Vis DRS). In this material, W‐modified TiO2 nanoparticles of about 3‐5 nm were highly dispersed on the silica network. Both W‐modified TiO2 and W‐modified TiO2 decorated on the SiO2 substrate significantly promoted the visible light absorption of the material. The photocatalytic activity of the prepared catalyst was assessed through the photodegradation of Methylene blue, Rhodamine‐B, Methyl orange, and Congo red dyes under visible light illumination. It was found that the kinetic and equilibrium data of the photocatalytic process fitted the modified Langmuir‐Hinshelwood model well. Recyclable studies have shown that the catalyst still retained its original activity after the third cycle.
Futher study on chemical constituents and biological activities of Alpinia conchigera Griff. (Zingiberaceae)
Tập 45 Số 2 - 2012
β-Sitosterol, stigmasterol, cardamomin (1), chalconaringenin 2′-O-methyl ether (2), alpinetin (3), and naringenin 5-O-methyl ether (4) were isolated from the MeOH extract of Alpinia conchigera Griff. (Zingiberaceae). Their structures were determined on the basis of spectroscopic analyses. The antimicrobial and free radical scavenging activities of the isolates 1-4 were evaluated in correlation with those of the soluble fractions.Key words: Alpinia conchigera; Zingiberaceae; chalcone; flavanone; antimicrobial activity; free radical scavenging activity.
Kinetics and mechanism of graft polymerization of acrylic acid onto starch initiated with ceric ammonium nitrate.
Tập 48 Số 5 - 2012
Graft polymerization of acrylic acid (AA) onto tapioca starch was carried out using ceric ammonium nitrate (CAN) as initiator in aqueous nitric acid medium. The kinetics of the graft polymerization of AA onto starch was studied by gravimetric method. The following rate expression (rate of graft polymerization) Rg = k. [AA]1.02 [CAN]0.478 [Starch]0.543 was obtained and a suitable mechanism was suggested. The overall activation energy was found to be 41.33kJ/mol within the temperature range of 30 - 40oC.
Study on the Chemistry and Antimicrobial Activity of Psychotria reevesii Wall. (Rubiaceae)
Tập 45 Số 5 - 2012
The first chemical investigation on Vietnamese medicinal plant Psychotria reevesii Wall. (Rubiaceae) led to the isolation and structural determination of β-sitosterol and stigmasterol as a mixture, 1-octacosene, and asperglaucide from n-hexane- and CHCl3-soluble fractions of MeOH extract from the aerial parts of P. reevesii. Phytochemical screening based on color reactions, HPLC analysis, and NMR spectroscopy revealed the concentration of condensed tannins in EtOAc- and n-BuOH soluble fractions. The high accumulation of tannins may be responsible for the antibacterial activities of the polar fractions against Staphylococcus aureus, Pseudomonas aeruginosa, Shigella sonnei, and Shigella flexneri. However, they did not exhibit any inhibitory effect against Escherichia coli, Candida albicans, and Candida stellatoides.Keywords: Psychotria reevesii; Rubiaceae; asperglaucide; antibacterial activity; antifungal activity.
Triterpene from the roots of Codonopsis pilosula.
Tập 46 Số 4 - 2012
From the roots of Codonopsis pilosula (Franch) Nannf (Campanulaceae) five triterpenoids: taraxerol, taraxeryl acetate, 14-a-taraxeran-3-one and D:B-friedoolean-5-ene-3-b-ol as well as a-spinasterone were isolated. Their structures have been identified by MS, 1H-, 13C-NMR spectroscopy and comparison with reported data.
Phân lập và xác định cấu trúc của các hợp chất tritecpen từ cây xạ đen
Tập 46 Số 4 - 2012
Chemical investigation of Celastrus hindsii Benth. growing in Quang Binh province, Vietnam led to the isolation and structural elucidation of clionasterol, D:A-friedo-oleanane-3,21-dione, lup-20(29)-ene-3b-ol and lup-12-ene-3b-ol. Their structures were determined on the basis of MS, NMR spectra and comparison with reported data.
Corrosion protection of carbon steel by polyurethane coatings containing graphene oxide
Tập 58 Số 1 - Trang 108-112 - 2020
Nguyễn Thùy Dương, Tran Boi An, Phan Thanh Thao, Vũ Kế Oanh, Trịnh Anh Trúc, Phạm Gia Vũ, Tô Thị Xuân Hằng
AbstractIn this work, graphene oxide (GO) was prepared by modified Hummer's method. Polyurethane coatings with different GO concentrations (0.1‐0.5 %) were prepared for corrosion protection of carbon steel. Synthesized GO was characterized by FTIR and XRD. Corrosion resistance of polyurethane coatings containing GO was investigated by electrochemical impedance spectroscopy and salt fog test. The effects of GO on protection performance of polyurethane coatings depended on its dispersion ability. GO at a concentration of 0.1 % significantly improved corrosion resistance of polyurethane coatings.
