Interpretation of 1H-NMR spectrum of alginate by 1H-1H TOCSY and COSY spectrum

The sodium alginate was prepared from brown seaweeds in Thua-Thien-Hue coastal area. The obtained alginate was characterized by 1H-NMR, 1H-1H TOCSY and COSY spectra. The  assignment of alginate peaks in 1H-NMR spectrum is 5.09, 4.446, 4.152, 4.318, 4.135 ppm in correspondence to H1, H2, H3, H4, H5 of D-mannuronic acid and 5.473, 4.318, 4.446, 4.571, 4.883 ppm in correspondence to H1, H2, H3, H4, H5 of L-guluronic acid, respectively. The present results are essential for the investigating guidance of alginate and its derivatives

Enhanced Adsorption of Methylene Blue by Chemically Modified Materials Derived from Phragmites australis Stems

In this study, the biomass of Phragmites australis was chemically modified using NaOH and subsequently citric acid to produce an effective adsorbent named SA-RPB. The absorbent was characterized using XRD, SEM, BET, and FT-IR methods. The study's findings indicated that the adsorbent existed mainly as cellulose crystals, contained micropores with an average diameter of 15.97 nm, and had a large number of hydroxyl and carboxyl groups on the surface. The adsorption process of SA-RPB was evaluated through the adsorption of methylene blue (MB) dye in aqueous solution. Adsorption kinetics showed that the pseudo-second-order model well described the adsorption process. The adsorption isotherm process satisfactorily fitted with the Langmuir model with the maximum adsorption capacity of 191.49 mg/g at 303 K. These findings show that MB may be efficiently removed from aqueous solutions using the adsorbent made from the raw biomass of Phragmites australis treated with NaOH and then citric acid

VẬT LIỆU TIO2/THAN HOẠT TÍNH TỪ TRO TRẤU VÀ KHẢ NĂNG HẤP PHỤ XANH METHYLENE

In the present work, TiO2/activated-carbon composite (TiO2/RHAC) was synthesized with an assembly method. Activated carbon was fabircated from rice husks. The water-soluble titanium complex was synthesized from anatase via the peroxide complex. The mixture of activated carbon and water-soluble TiO2 was calcined at 600 °C. The obtained samples were characterized by using XRD, SEM, EDX, and UV-Vis-DR. The results show that the obtained composites exhibit excellent adsorption toward methylene blue (MB). The equilibrium data fit the Langmuir isotherm model well. The maximum monolayer capacity calculated from the Langmuir model is 144.7 mg·g–1. The TiO2/RHAC could be self-cleaned after use by photocatalytic degradation. The adsorption capacity insignificantly decreases after three recycles of adsorption, and TiO2/RHAC is a promising adsorbent for removing dyes from the aqueous environment.Trong nghiên cứu này, TiO2/than hoạt tính từ tro trấu (TiO2/RHAC) đã được tổng hợp bằng phương pháp trộn lẫn than hoạt tính và phức titanium. Than hoạt tính được tổng hợp từ tro trấu và phức titanium hòa tan trong nước tổng hợp từ anatase bằng cách tạo phức peroxide. Hỗn hợp được nung trong môi trường thiếu oxy ở 600 °C. Vật liệu tổng hợp được phân tích bằng nhiễu xạ tia X, kính hiển vi điện tử quét và đẳng nhiệt hấp phụ/giải hấp phụ ni tơ. TiO2/RHAC có khả năng hấp phụ cao đối với xanh methylene. Số liệu đẳng nhiệt cân bằng tuân theo mô hình Langmuir và dung lượng hấp phụ cực đại tính theo mô hình này là 144,7 mg·g–1. Chất bị hấp phụ có thể được loại bỏ bằng cách chiếu sáng bằng đèn chiếu nhờ khả năng xúc tác quang hóa của nó. Sau ba lần tái sinh, dung lượng hấp phụ thay đổi không đáng kể. TiO2/RHAC có tiềm năng làm chất hấp phụ xử lý phẩm màu nói chung

SYNTHESIS OF Fe-MCM-41 WITH HIGHLY ORDERED MESOPOROUS STRUCTURE AND HIGH IRON CONTENT AND ITS ADSORPTION ISOTHERMS OF ARSENATE AND ARSENITE

Abstract. In this paper, the synthesis of iron containing MCM-41 material and its adsorption isotherms were investigated. Fe-MCM-41 materials were synthesized by direct process using K 2 [Fe(CN) 6 ] or iron oxalate as iron source. The materials obtained were characterized by XRD, adsorption/desorption isotherms of nitrogen. The results showed that using K 2 [Fe(CN) 6 ] as an iron source can provide Fe-MCM-41 with highly ordered mesoporous structure and high iron content with molar ratio of Si/Fe around 10. The isotherm study showed that the prepared Fe-MCM-41 sample exhibited high adsorption activity towards As(III) as well as As(V). The experimental data of adsorption of As(III) and As(V) onto Fe-MCM-41 followed the Langmuir models. The maximum monolayer adsorption capacities based on this model were 25.4 and 37.2 mg/g for As (III) and As(V), respectively

CHARACTERIZATION OF ALGINATE PREPARED FROM BROWN SEAWEEDS IN THUA THIEN-HUE PROVINCE, VIETNAM

The characterization of alginate prepared from brown seaweeds in TT-Hue province of Vietnam was investigated. Composition and the sequential structure of alginate were determined by 1HNMR, 13C-NMR, TOCSY, 1H-1H COSY, and 1H-13C-HSQC spectrum. It is found that alginate with molecular weight around 101 KDa is composed of homopolymeric regions of M and G blocks, interspersed with very small amount of regions of alternating structure of MG block.  This information is essential for application guideline of alginate in TT-Hue province

CHARACTERIZATION OF ALGINATE PREPARED FROM BROWN SEAWEEDS IN THUA THIEN-HUE PROVINCE, VIETNAM

The characterization of alginate prepared from brown seaweeds in TT-Hue province of Vietnam was investigated. Composition and the sequential structure of alginate were determined by 1HNMR, 13C-NMR, TOCSY, 1H-1H COSY, and 1H-13C-HSQC spectrum. It is found that alginate with molecular weight around 101 KDa is composed of homopolymeric regions of M and G blocks, interspersed with very small amount of regions of alternating structure of MG block.  This information is essential for application guideline of alginate in TT-Hue province

Removal of Pb(II) from Aqueous Solutions with Manganese Oxide-Modified Diatomite

In the present work, natural diatomite modified with manganese oxide (MnO2) was prepared via direct redox reaction with KMnO4 and HCl. The product was characterized by using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, and nitrogen adsorption-desorption isotherms. It was found that the nanorod manganese oxide was highly dispersed onto the diatomite porous matrix. The specific surface area of the obtained manganese oxide/diatomite (SBET=68.5 m2 g−1) is larger than that of natural diatomite (SBET=55.4 m2 g−1). It was utilized to remove Pb(II) in aqueous solutions. It exhibits an excellent Pb(II) adsorption capacity. The adsorption data fits well with the pseudo-second-order kinetics model, and the adsorption process is endothermic and spontaneous with an activation energy of 41.56 kJ mol−1 and follows the Freundlich isotherm model. The Mn/diatomite adsorption capacity for Pb(II) is 81.42 mg g−1, calculated with the Langmuir model. In addition, the adsorption mechanism of Pb(II) onto Mn/diatomite is also addressed

FABRICATION OF CARBON NANOTUBES FROM LIQUEFIED PETROLEUM GAS BY CHEMICAL VAPOUR DEPOSITION

This paper presents the fabrication of carbon nanotubes from liquefied petroleum gas (LPG) by chemical vapour deposition with Fe/SiO2 as a catalyst. The morphology and tube diameter of the carbon nanotubes are dependent on the flow rates of H2 and LPG, and the crystal growth temperature. The obtained CNTs were characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), scanning transmission electron microscope (STEM), and Brunauer-Emmett-Teller surface area analyses. The results indicate that the suitable conditions for forming the nano-sized tubes are 700 °C for 2 hours with the H2 and LPG flow rate of 140 mL·min–1 and 80  mL·min–1, respectively. The multi-walled structures with long, less defective tubes and identical external diameter of 52 nm and BET surface area of 93 m2·g–1 are obtained

A Study on Astrazon Black AFDL Dye Adsorption onto Vietnamese Diatomite

In the present paper, the adsorption of Astrazon Black AFDL dye onto Vietnamese diatomite has been demonstrated. The diatomite was characterized by XRD, SEM, TEM, EDS, and nitrogen adsorption/desorption isotherms. The results show that diatomite mainly constituted centric type frustules characterized by pores as discs or as cylindrical shapes. The adsorption kinetics and isotherms of dye onto Vietnam diatomite were investigated. The experimental data were fitted well to both Freundlich and Langmuir in the initial concentration range of 400–1400 mg L−1. The average value of maximum adsorption capacity, qm, calculated from Freundlich equation is statistically similar to the average value of maximum monolayer adsorption capacity calculated from Langmuir equation. The thermodynamic parameters evaluated from the temperature dependent on adsorption isotherms in the range of 303–343 K show that the adsorption process was spontaneous and endothermic. The Webber and pseudo-first/second-order kinetic models were used to analyze the mechanism of adsorption. The piecewise linear regression and Akaike’s Information Criterion were used to analyze experimental data. The results show that the dye adsorption onto diatomite was film diffusion controlled and the goodness of fit of experimental data for kinetics modes was dependent on the initial concentration