Vietnam Academy of Science and Technology: Journals Online
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MODIFYING WASTE POLYSTYRENE TO ION EXCHANGE MATERIAL: OPTIMIZING THE SULFONATION PROCESS AND COLUMN STUDY FOR THE REMOVAL OF Cr3+
No full textThe incredible growth of plastic waste is a major concern for the whole society in recent years. The accumulation of plastic waste has badly effects on wildlife, habitat, and humans. Plastics that act as pollutants are categorized into different sizes, from micro to macro. Disposable plastic waste was collected at the bakery shop and removed the residue food by tap water and NaOH 1M to remove residual food. This study focuses on modify waste plastic by sulfuric acid to bind the sulfonated function group on the structure of the polystyrene chain at room temperature. The sulfonated product was used for removing heavy metal ion in water with the mechanism of the ion exchange process. The prepared ion exchange material was characterized by FTIR and SEM to ensure that the sulfonation process has happened. The chromium (III) ion removal by modified ion exchange product in continuous mode was affected by an operational parameter such as the bed height of sulfonated material. The Yoon-Nelson and Thomas model were used to analyze the experimental result and the model parameters were evaluated. From this result, it can be concluded that with the increasing amount of sulfonated waste polystyrene, exchange capacity, and the time required for a 50% adsorbate breakthrough was higher
Assessment of pollution load from industrial activities of Nghi Son Economic Zone (Thanh Hoa province)
No full textThanh Hoa coastal waters have received a large amount of waste from industrial activities of Nghi Son Economic Zone such as thermal power, vegetable oil production, wood processing, steel rolling and petroleum refinery. Employing environmental rapid assessment method, the discharged industrial wastewater from Nghi Son Economic Zone was calculated. The pollution load includes organic matter (13 thousand tons), total nitrogen - TN (27.4 thousand tons), total phosphorous - TP (967.8 tons), total suspended solid - TSS (12.3 thousand tons). In addition, wastewater also contained phenol, oil and grease, cyanide, sulfites, heavy metals (Fe, Zn, Cr). If this wastewater is not treated, the amount of pollutant discharged to Thanh Hoa coastal area will be much greater and impact on sensitive ecosystems.
Finite element modeling of fluid flow in fractured porous media using unified approach
No full textUnderstanding fluid flow in fractured porous media is of great importance in the fields of civil engineering in general or in soil science particular. This study is devoted to the development and validation of a numerical tool based on the use of the finite element method. To this aim, the problem of fluid flow in fractured porous media is considered as a problem of coupling free fluid and fluid flow in porous media or coupling of the Stokes and Darcy equations. The strong formulation of the problem is constructed, highlighting the condition at the free surface between the Stokes and Darcy regions, following by the variational formulation and numerical integration using the finite element method. Besides, the analytical solutions of the problem are constructed and compared with the numerical solutions given by the finite element approach. Both local properties and macroscopic responses of the two solutions are in excellent agreement, on condition that the porous media are sufficiently discretized by a certain level of finesse. The developed finite element tool of this study could pave the way to investigate many interesting flow problems in the field of soil science
Sponge’s biodiversity in the limestone islands in Vietnam sea
No full textIn 2017, 2018 and 2020, sponge samples were collected at 41 points in the waters surrounding Vietnam’s coastal limestone islands (Bai Tu Long, Ha Long bay, Cat Ba and Ba Lua archipelago). Research results have identified 54 species belonging to 33 genera, 24 families of Demosponge class distributed in this area. Ha Long bay area has the highest number of species (53 species), followed by Cat Ba (46 species), Bai Tu Long 19 species; Ba Lua archipelago (Kien Giang) has the least number of species (3 species). Sponges are concentrated in coral reefs with the highest number of species (48 species) and the lowest in the mud and sand bottom (4 species). Biomass of sponges varies from 0.2–1.5 kg/m2. There are 11 sites with high biomass, which have the potential to become Vietnam’s medicinal drug area.
Detection of Luminescence Centers in Colloidal CdZnS Nanocrystals by Synchronous Luminescence Spectroscopy
Get PDFWith the advantages of selectivity, spectral resolution and reduction of interference on account of light scattering, synchronous luminescence spectroscopy (SLS) is successfully applied to analyze complex mixtures with overlapped emission and/or excitation spectra. In fact, it is difficult to clearly distinguish the contributions of various luminescence centers to low-energy band of semiconductor nanocrystals (NCs). Herein, we report the application of SLS method to detect luminescence centers in colloidal Cdsub0.3/subZnsub0.7/subS NCs. Their conventional luminescence and synchronous luminescence spectra were comparatively investigated. Differently from conventional luminescence spectrum, the emission peaks at 460 and 515 nm were found using SLS method. They are attributed to the emission transitions related to sulfur and zinc/cadmium vacancies. The obtained results are useful to clarify the nature of luminescence centers as well as relaxation mechanism in Cdsubx/subZnsub1-x/subS NCs
Size dependent of the effective conductivity of composite with imperfect interfaces
Get PDFBased on the circle assemblage model, the effective properties of the inclusion with imperfect interface are derived. The equivalent inclusion is incorporated in the Fourier Transform algorithm to determine the effective conductivity of the composite with lowly conducting or highly conducting interface. The size effect is considered for both cases. Numerical results are provided to illustrate the dependence of the effective conductivity on the size of inhomogeneities
Heterologous phytase expression in the food filamentous fungus Aspergillus oryzae using the added rice husk cultivation model
Get PDFAspergillus oryzae, a safe filamentous fungus, is widely used in food and enzyme production. In this study, we examined a cultivation model using rice husks as carrier to assess the capacity of recombinant protein production in A. oryzae. The model was first tested with the A. oryzae strain expressing the DsRed reporter gene. Expression of DsRed was easily detected by the pink color of the fungal mycelium on culture media and under a fluorescence microscope. The model was then evaluated with the phyA gene encoding a phytase from the fungus Aspergillus fumigatus. The phyA expression cassette regulated by the amyB promoter was permanently integrated into the genome of A. oryzae via Agrobacterium tumefaciens-mediated transformation with the pyrG nutritional marker. Results showed that A. oryzae transgenic strains carrying 2−3 copies of the phyA gene in their genomes exhibited a significant increase in phytase activity on agar medium supplemented with phytate. With rice husks added, these transgenic strains could secrete the recombinant phytase into the culture and phytase activity of the crude enzyme solution increased by 4.3 times compared to the unstransgenic A. oryzae. The established cultivation model and the transgenic approach in this study represent a potential for being used in production of secreted recombinant enzymes for animal feeds.
Construction of complete chloroplast genome of the endemic species Paphiopedilum delenatii Guillaumin (1924) of Vietnam
No full textChloroplasts and mitochondria are organelles that have their own genome in a cell. The chloroplast genome provides information on the evolutionary relationship and species identification, valuable markers for transgenic plants, and cloning plants, etc. The application of Next Generation Sequencing has improved the chloroplast genome sequencing. However, the assembly process of chloroplast genome is quite complicated due to the need of different complex bioinformatics tools, high configuration computer and laborous. Here we configured the process of assembling the chloroplast genome of Paphiopedilum delenatii. The assembled chloroplast genome was 160,955 bp in length, including a large and a small single copy region (LSC, SSC) separated by a pair of inverted repeats (IR). Total genes were 130 genes, GC content is 35.6%. Genome data was mapped and registered in GenBank under accession number MK463585. The optimal parameters for genome assembling were recommended. This study not only provided information for conservation of the Vietnam endemic Paphiopedilum delenatii species but also supported the genome assemble researches which could be applied on other subjects
Isolation, screening antimicrobial activity and identification of fungi from marine sediments of the area Thanh Lan, Co To, Vietnam
Get PDFMarine environment is rich in natural product resources, including marine microorganisms, especially fungi which are not only seen as a potential source of highly applicable bioactive substances but also can provide for science new chemical structures. The objective of this study is to isolate and screen fungal strains with antibacterial activity from the marine environment. Twenty five strains of fungi were isolated from marine sediments of Thanh Lan, Co To island and assessed on antibiotic activity against 7 tested microbial strains, including three Gram-negative bacteria (Escherichia coli ATCC25922, Pseudomonas aeruginosa ATCC27853, Salmonella enterica ATCC13076), three Gram-positive bacteria (Enterococcus faecalis ATCC29212, Stapphylococus aureus ATCC25923, Bacillus cereus ATCC 13245), and the yeast Candida albicans ATCC10231. The minimum inhibitory concentration (MIC) against the tested microorganisms was determined for the crude extracts obtained from the culture broths after ethyl acetate extraction and vacuum rotary evaporation. Three strains with the highest antimicrobial activity M26, M30 and M45 were capable of inhibiting 4 - 5 of the 7 tested microorganisms with MIC values from 64 to 256 μg/ml, depending on each tested strain. Morphological and phylogenetic investigations based on 18S rRNA gene sequences of the three selected strains showed that strains M26 and M30 belonged to the genus Penicillium, whereas strain M45 belonged to the genus Neurospora. The sequences of 18S rRNA gene of three strains M26, M30 and M45 were registered on GenBank database with accession numbers: MH673730, MH673731, MH673732, respectively. Research results showed that marine environment has a great potential in isolation of fungal strains for the search for antibacterial substances as well as other biologically active compounds
Đa dạng sinh học hệ thực vật nổi ở vùng Duyên Hải, tỉnh Trà Vinh
No full textThis study was conducted to enhance the understanding of phytoplankton diversity of Duyen Hai town, Tra Vinh province. We selected 12 representative sampling sites and investigated phytoplankton diversity in both dry and rainy seasons. The phytoplankton of this area were comprised of 134 species, belonging to 64 genera, 45 families, 31 orders, 8 classes and 5 divisions. Among those divisions, Bacillariophyta was the most dominant in species, accounting for 70% of the total number of species and Cyanobacteria commonly had high density at 12 surveyed sites. The average density of phytoplankton was 1,195 cells/l in the rainy season and 2,020 cells/l in the dry season, respectively. For water bodies with the exchange of freshwater and marine water, the diversity is typically higher than in water bodies with purely freshwater or marine conditions.Nghiên cứu được thực hiện trong năm 2017 với dữ liệu đa dạng của 2 mùa ở 12 vị trí đại diện cho các hệ thống thủy vực vùng Duyên Hải – Trà Vinh. Hệ thực vật nổi của Duyên Hải – Trà Vinh gồm có 134 loài thuộc 64 chi, 45 họ, 30 bộ, 8 lớp, 5 ngành tảo. Trong số các ngành tảo ghi nhận được, ngành tảo Silic chiếm ưu thế về thành phần loài với trên 70% tổng số loài và ngành tảo Lam chiếm ưu thế về sinh lượng ở hầu hết vị trí khảo sát. Mật độ tế bào thực vật nổi trung bình là 1.195 tế bào/lít trong mùa mưa và 2.020 tế bào/lít ở mùa khô. Các thủy vực nơi có sự giao thoa giữa nước mặn và ngọt có độ đa dạng cao hơn các thủy vực chỉ nước mặn hoặc nước ngọt