Fabrication of tubular ceramic-supported malic acid cross-linked poly(vinyl alcohol)/ rice husk ash-silica nanocomposite membranes for ethanol dehydration by pervaporation

Tran Minh Ngoc,Tran Minh Man,Mai Thanh Phong,Mai Thanh Phong,Nguyen Huu Hieu 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.4

Silica nanoparticles were prepared from rice husk ash (RHA-silica) by precipitation method. The characterization of RHA-silica was studied by X-ray fluorescence, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy, and Brunauer-Emmett-Teller specific surface area. Results showed that RHA-silica was successfully synthesized with a particle size of 5-15 nm and purity of 98.08%. The obtained RHA-silica was applied with different content for fabrication of tubular ceramic-supported poly(vinyl alcohol) membranes using malic acid as a cross-linking agent (RHA-silica/MA-PVA) by dip-coating and solvent evaporation methods. The tubular ceramic-supported RHA-silica/MA-PVA membranes were used for dehydration of 95 wt% ethanol solution by pervaporation (PV) technology. Results indicated membrane with 15 wt% RHA-silica (15RHA-silica/MA-PVA) was suitable for the dehydration with permeate flux of 0.0856 kg/m2·h, separation factor of 46.6, and pervaporation separation index of 3.9 kg/m2h. The tubular ceramic-supported 15RHA-silica/MA-PVA membrane was characterized using XRD, FTIR, scanning electron microscope, differential scanning calorimetry, and contact angle measurement. Results showed that this membrane was 30 m thick, mechanical stable (swelling rate, 133.9%), hydrophobic (contact angle, 81o), and thermal stable (glass transition temperature, 138.7 oC). Therefore, the tubular ceramic-supported nanocomposite membrane could be considered as a potential alternative for PV dehydration of ethanol.

Criteria for Supplier Selection in Textile and Apparel Industry : A Case Study in Vietnam

Nhu-Mai Thi NONG,Phong Thanh HO 한국유통과학회 2019 The Journal of Asian Finance, Economics and Busine Vol.6 No.2

The study aims to investigate some criteria of supplier selection in the textile and apparel (T&A) sector in Vietnam. Most research on supplier selection criteria for T&A sector was mainly conducted based on the review of literature. Therefore, the purpose of this study is to explore these criteria based on a framework in which an integrated approach of qualitative and quantitative was employed. First, an in-depth interview was used to explore what supplier selection criteria T&A companies were utilized after the literature on supplier selection criteria had been reviewed. Next, a prequestionnaire was built and sent to some practitioners and experts for their revision. Then, a pilot survey of 31 T&A companies with numerous statistical tests was conducted to validate the questionnaire. Finally, an official study of 282 respondents was conducted to determine supplier selection criteria which are best suited for T&A companies through exploratory factor analysis. The findings of the study suggest that there are eight supplier selection criteria including Quality, Cost, Delivery, Service, Capability, Company’s image, Relationship, and Sourcing country. Each criterion comprises certain sub-criteria to make the supplier selection criteria set more comprehensive. The findings will be a contribution to the selection process of T&A companies as they can utilize these criteria to select capable suppliers.

An online Indigenous Knowledge Database on Climate Change Adaptation of Farmers in the Vietnam Mekong Delta

Van Hoa Nguyen,Thi Mai Phung Bui,Thanh Phong Le,Hoang Tung Nguyen,Minh Tuyen Truong,Minh Nhut Do,Van Nha Duong 인간식물환경학회 2022 인간식물환경학회지 Vol.25 No.6

Background and objective: For countries vulnerable to climate change as Vietnam, indigenous knowledge (IK) might assist in revealing the values of local people's adaptations to environmental stresses and potentially support decision-making. Despite IK can provide the adaptive capacity of local people's activities within environmental contexts, but it is rapidly vanishing. This study aimed to describe the documentation of IK associated with climate change adaptation of farmers in the Vietnam Mekong Delta (VMD). Methods: We focused on collecting and establishing online access to IK documents through collaboration between IK holders, public sector, collecting institutions, and researchers in the five agro-ecological zones of the VMD. An online IK database for storing IK documents has been designed and implemented based on the web application schema. Results: Through interviews, we gathered IK from farming practices that are well-adapted to climate risks such as floods, droughts, and saltwater intrusions as well as traditional knowledge being used to forecast weather, flood, and saltwater intrusion. The database for storing IK documents has been successfully deployed using free and open-source software. The database currently contains more than 260 IK documents, with their location on agro-ecological zones displayed on a web-based map. Conclusion: We have captured and provided an online access to IK on climate change adaptation of the farmers in the VMD. This research is expected as an initial strategy for long-term sustainable development of the agriculture system in this region.

Optimization of the eco-friendly synthesis of graphene oxide from graphite using Plackett–Burman and Box–Behnken models for industrial production orientation

Phuc Nguyen Thien,Giang Nguyen Thi Huong,An Vu Nguyen Thien Truong,Nam Nguyen Thanh Hoai,Anh Ly Duc,Nguyen Huynh Cam,An Hoang,Phong Mai Thanh,Hieu Nguyen Huu 한국탄소학회 2023 Carbon Letters Vol.33 No.2

In this study, graphene oxide (GO) was synthesized by the improved Hummers’ method. The degree of oxidation from graphite (Gi) to GO was determined through interlayer spacing calculated from X–ray diffraction. Besides, the effect of KMnO4:Gi ratios (X1), H2SO4 volume (X2), oxidation temperature (X3), oxidation time of stage 1 (X4), and oxidation time of stage 2 (X5) was screened by the Plackett–Burman model. The simultaneous impact of three factors that influenced the degree of oxidation (X1, X2, and X3) was studied by the Box–Behnken experimental model of response surface methodology to achieve suitable conditions for the GO synthesis process. The characterization of GO product was investigated via the modern analytical methods: X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. In addition, the study was also carried out on a pilot scale for orientation in industrial application with the yield of 14 g/batch.

High-Resolution Simulations for Vietnam - Methodology and Evaluation of Current Climate

Jack Katzfey,Kim Nguyen,John McGregor,Peter Hoffmann,Suppiah Ramasamy,Hiep Van Nguyen,Mai Van Khiem,Thang Van Nguyen,Kien Ba Truong,Thang Van Vu,Hien Thuan Nguyen,Tran Thuc,Doan Ha Phong,Bang Thanh Ng 한국기상학회 2016 Asia-Pacific Journal of Atmospheric Sciences Vol.52 No.2

To assist the government of Vietnam in its efforts to better understand the impacts of climate change and prioritise its adaptation measures, dynamically downscaled climate change projections were produced across Vietnam. Two Regional Climate Models (RCMs) were used: CSIRO’s variable-resolution Conformal-Cubic Atmospheric Model (CCAM) and the limited-area model Regional Climate Model system version 4.2 (RegCM4.2). First, global CCAM simulations were completed using bias- and variance-corrected sea surface temperatures as well as sea ice concentrations from six Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models. This approach is different from other downscaling approaches as it does not use any atmospheric fields from the GCMs. The global CCAM simulations were then further downscaled to 10 km using CCAM and to 20 km using RegCM4.2. Evaluations of temperature and precipitation for the current climate (1980-2000) were completed using station data as well as various gridded observational datasets. The RCMs were able to reproduce reasonably well most of the important characteristics of observed spatial patterns and annual cycles of temperature. Average and minimum temperatures were well simulated (biases generally less than 1oC), while maximum temperatures had biases of around 1oC. For precipitation, although the RCMs captured the annual cycle, RegCM4.2 was too dry in Oct.-Nov. (−60% bias), while CCAM was too wet in Dec.- Mar. (130% bias). Both models were too dry in summer and too wet in winter (especially in northern Vietnam). The ability of the ensemble simulations to capture current climate increases confidence in the simulations of future climate.

Facile synthesis of MoS2 nanosheets-carbon nanofibers composite as catalysts for hydrogen evolution reaction

Nguyen Thi Minh Nguyet,Le Van Thang,Nguyen Huu HuyPhuc,Vinh-Dat Vuong,Tran Van Khai,Mai Thanh Phong 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.2

MoS2 nanosheets (NS) were directly grown on carbon nanofiber (CF) and employed as electrocatalyst for hydrogen evolutionreaction (HER). The structural, surface morphology and chemical composition of the nanocomposites were characterized byfield emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), energydispersiveX-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy. XRD and TEM-EDS measurementsshowed that the molybdenum oxide precursor was successfully transferred into MoS2 nanosheets. It was confirmed from FESEMand TEM images that NS was uniformly distribution on surface of the CF. The HR-TEM images disclosed that the NSwas formed perpendicular to surface of CF fibers via the MoS2 layers growth parallel to CF surface which act as interface. The HER current density was about 12 mA cm−2 at catalyst loading of only 60 μg cm−2 at -0.384 V (vs. RHE).

Effect of hydrothermal time on the structure and property of graphene oxide membrane

Tran Van Khai,Pham Thuy Trang,Le Ngoc Long,Le Van Thang,Tran Duc Chau,Vuong Vinh Dat,Mai Thanh Phong 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.4

Two dimensional graphene oxide (GO) has potential application in membrane separation owing to its unique structure andphysicochemical properties. In this study, the reduced graphene oxide (rGO) was synthesized from GO via hydrothermaltreatment at 160 oC for 1, 2, 3 and 4 h, and the rGO membranes were prepared on cellulose nitrate supporting membranesby vacuum filtration. The structural change and chemical composition of GO were investigated using X-ray diffraction (XRD),Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM),atomic force microscopy (AFM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) andcontact angle measurements. The result shows that uniformly intact rGO membranes with good hydrophobicity could beachieved by adjusting the reduction degree of GO through changing the hydrothermal reaction time. The huge improvementof the hydrophobic property of rGO could be attributed to the removal of the most the hydrophilic oxygen-containingfunctional groups on the surface of GO. Additionally, the structure, chemical composition, and d-spacing of the GO can alsobe controlled by adjusting the reduction time. This method holds great potential because it can be prepared in large quantitiesat low cost, and suitable for applications in membrane technologies.

Phenothiazine Derivative as Organic Photocatalyst for Metal Free Atom Transfer Radical Polymerization

Hoan Minh Tran,Lan Ngoc Tan Phan,Thang Van Le,Thuy Thuy Truong,Tam Huu Nguyen,Khuong Tung Truong,Le-Thu T. Nguyen,Mai Thanh Phong,Ha Tran Nguyen 한국고분자학회 2019 폴리머 Vol.43 No.4

A novel organic photocatalyst, 4-(10H-phenothiazin-10-yl)-N,N-diphenylaniline (PDPA) has been successfully synthesized from triphenylamine and phenothiazine moiety via Buchwald-Hartwig C-N coupling. The chemical structure of catalyst was characterized via proton nuclear magnetic resonance (1H NMR) and the optical properties were investigated via UV-vis spectroscopy. The PDPA has been applied as an organic photocatalyst for metal free atom transfer radical polymerization (O-ATRP). The well-controlled molecular weights of polymethacrylates have been obtained with high yield of 95% and narrow polydispersity index (Đ).

Fabrication and modification of cellulose aerogels from Vietnamese water hyacinth for oil adsorption application

La Nam Phat,Tran Quoc Thang,Huynh Cam Nguyen,Dang Thi My Duyen,Dao Xuan Tien,Bui Dang Dang Khoa,Pham Tan Khang,Nguyen Thi Huong Giang,Hoang Minh Nam,Mai Thanh Phong,Nguyen Huu Hieu 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.11

Recycling biomass to cellulose aerogel (Cell-A) provides a promising approach to develop adsorbent materials for spilled-oil recovery. In this work, Cell-A was fabricated from Vietnamese water hyacinth via crosslinking methods using PVA as a crosslinker and freeze-drying process. Various cellulose to PVA ratios were investigated to obtain the optimal synthesis condition. The Cell-A was additionally modified by dip-coating in poly(dimethylsiloxane) (PDMS) and pyrolyzing to form PDMS-coated cellulose aerogels (Cell-AP) and carbon aerogels (CA), respectively. Results of the oil adsorption tests show that pyrolysis produced aerogels with greater adsorption capacity with an optimal mass ratio of 15 : 1 cellulose to PVA. Furthermore, the pseudo-second-order model was found to be more accurate than the pseudo-first-order model for the study of oil absorption kinetics. As a result, the modified cellulose aerogel is promising for replacing earth-unfriendly polymer-based oil sorbents due to their high oil absorption capacity.