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Van Thuan T.,Nguyen Tat Thanh University | Ho V.T.T.,Hochiminh City University of Natural Resources and Environment | Trinh N.D.,Nguyen Tat Thanh University | Thuong N.T.,Nguyen Tat Thanh University | And 2 more authors.
Carbon - Science and Technology | Year: 2016

Highly porous KOH-activated carbon was successfully synthesized from rice husk by chemical activation with KOH. The products were characterized by IR, SEM, and BET. The response surface methodology (RSM) was employed to determine the optimum fabrication conditions of AC with respect to the simultaneous effects of activation temperature (T), impregnation rate (IR) and activation time (t) to maximize the yield of activated carbon and removal efficiency of Ni2+. The optimum synthesis conditions were T = 522°C, IR = 1.3 and t = 360 min with a maximum AC yield of 28.5 % and a maximum Ni2+ removal of 28.5 %. The results indicated that highly porous structure, high surface area as well as the surface functional groups are key impacts in the adsorptive capacity of activated carbons for Ni2+. © Applied Science Innovations Pvt. Ltd., India.

Van Thuan T.,Nguyen Tat Thanh University | Quynh B.T.P.,Nguyen Tat Thanh University | Nguyen T.D.,Nguyen Tat Thanh University | Ho V.T.T.,Hochiminh City University of Natural Resources and Environment | Bach L.G.,Nguyen Tat Thanh University
Surfaces and Interfaces | Year: 2017

This study aims at optimizing the adsorption of heavy metal ions onto banana peel derived activated carbon (AC) using response surface methodology (RSM) involving central composite design (CCD). The cheap, non-toxic and locally available banana peel was subjected to carbonization and subsequently KOH-activation to produce the porous AC, which was then characterized by SEM and FTIR analyses. In RSM study, the individual and interactive effects of three critical variables including heavy metal ion concentration, pH of solution and AC dosage on the adsorption capacity were optimized. The maximum adsorption capacity appeared to follow the order: Cu2+ (14.3 mg/g) < Ni2+ (27.4 mg/g) < Pb2+ (34.5 mg/g) that agreed well with the verification experiments, revealing the reliability and suitability of the optimization approach. In addition, the results of isotherm study show that the Langmuir model can be used to best describe the adsorption behavior of Cu2+ and Ni2+ onto the banana peel derived activated carbon. © 2016 Elsevier B.V.

Tran V.T.,Nguyen Tat Thanh University | Nguyen D.T.,Nguyen Tat Thanh University | Ho V.T.T.,Hochiminh City University of Natural Resources and Environment | Hoang P.Q.H.,University of Food Industry | And 2 more authors.
Journal of Materials and Environmental Science | Year: 2017

The removal of Ni2+ in aqueous solution was investigated by adsorption process on activated carbons fabricated from rice straw (RSAC) and tea waste (TWAC). The samples were characterized by XRD, SEM, N2 adsorption (BET), and TGA. The response surface methodology was employed to optimize the maximum percentage of Ni2+ removal. The results showed that the surface area of TWAC was about four times greater than that of RSAC and thus the TWAC exhibited higher adsorption capacity for Ni2+. The adsorption isotherms were also evaluated by Langmuir, Freundlich and Temkin equations revealed that both monolayer and multilayer adsorption were effective in the uptake process of metal ions. By the optimization using the RSM-based quadratic regression equations, the impact of independent variables including metal ion concentration, pH and AC dosage on the removal of Ni2+ was statistically investigated.

Ho V.T.T.,Hochiminh City University of Natural Resources and Environment | Giang Bach L.,Nguyen Tat Thanh University | Thanh T.,Nguyen Tat Thanh University | Giang Nguyen N.,National Taiwan University of Science and Technology | Hong L.-S.,National Taiwan University of Science and Technology
Molecular Crystals and Liquid Crystals | Year: 2015

We present the first experimental comparisons of growth of Ga-doped ZnO (GZO) thin films through metalorganic chemical vapor deposition (MOCVD) using Triethylgallium (TEG) and Trimethylgallium (TMG) as dopant sources with qualified opt-electrical properties. Interestingly, we found the GZO films growth by using TEG source exhibited the preferred orientation of (100) and (110) planes which (100) plane is the dominant orientation as well as the formation of pyramidal texture on the film surface compared to the one using TMG source that is highly (002)-orientated ZnO films and formation of planar structure. Additionally, the total C incorporation into GZO films prepared by TEG is slightly lower than that of using TMG source, indicating the formation of stable C2H4 species during reaction when using TEG source can reduce the C incorporation of GZO films compared to the less stable CH3 species by using TMG source. It also found that the doping efficiency by using TEG as a dopant source was much lower than that of using TMG source due to the different thermal decomposition between two sources. These results indicate clearly that the Ga dopant source is crucial to determine the morphology, structure, carbon incorporation as well as the doping efficiency of GZO films that can motivate further research in this field by using various materials. © 2015 Taylor & Francis Group, LLC.

Ho V.T.T.,Hochiminh City University of Natural Resources and Environment | Bach L.G.,Nguyen Tat Thanh University | Thanh T.,Nguyen Tat Thanh University | Nguyen N.G.,National Taiwan University of Science and Technology | Hong L.-S.,National Taiwan University of Science and Technology
Molecular Crystals and Liquid Crystals | Year: 2015

The vertically-aligned GaN nanowires (NWs) were grown on Au coated α-Al2O3(001) and GaN(002)/α-Al2O3(001) substrates by metal organic chemical vapor deposition technique using trimethygallium and tertiarybutylhydrazine (TBHy) as sources. The growth tempearuture of the GaN NWs were reduced to under 700°C due to the low decomposition temperature of TBHy. The vertically-aligned GaN NWs were grown by controlling diameter of Au droplets in the nucleation stage. The GaN NWs grown on α-Al2O3 exhibited (101) preferred orientation, while GaN NWs on the GaN(002)/α-Al2O3(001) substrate retained [0001] growth direction. © 2015 Taylor & Francis Group, LLC.

Bach L.G.,Nguyen Tat Thanh University | Bui Q.T.P.,Nguyen Tat Thanh University | Cao X.T.,Pukyong National University | Ho V.T.T.,Hochiminh City University of Natural Resources and Environment | Lim K.T.,Pukyong National University
Polymer Bulletin | Year: 2016

A facile strategy for growing the poly(2-hydroxyethyl methacrylate) encapsulated on the surface of SiO2 nanoparticles (SiO2/PHEMA) as a molecular host matrix for the luminescent Tb3+ via a combination of surface-initiated reversible addition fragmentation chain transfer polymerization and coordination chemistry was successfully developed. The structure, morphology and fluorescence properties of the materials were investigated using relevant physical and spectral techniques. The core–shell structure and uniform dispersion of SiO2/PHEMA and SiO2/PHEMA:Tb3+ complexes were found according to SEM and TEM analyses while their surface bonding characteristics were determined via FT-IR analysis. In photoluminescence measurement, the SiO2/PHEMA:Tb3+ nanoparticles showed characteristic emissions of Tb3+ with the strongest (5D4 → 7F5) green emission without detectable emissions of ligands, demonstrating that SiO2 framework covalently bonded with PHEMA segments acting as an efficient matrix for sensitization of fluorescent Tb3+ ions. © 2016 Springer-Verlag Berlin Heidelberg

Dinh N.T.,Hochiminh City University of Natural Resources and Environment | Hatta K.,Tokyo Institute of Technology | Kwon S.H.,Tokyo Institute of Technology | Rollon A.P.,University of the Philippines at Diliman | Nakasaki K.,Tokyo Institute of Technology
Biomass and Bioenergy | Year: 2014

Granular sludge from a full-scale methane reactor treating brewery wastewater was used as a seed for the treatment of glycerol in a laboratory-scale repeated-batch methane reactor, and the change in the microbial community during the acclimation stages was examined. Two types of substrate solutions, a glucose, sodium acetate, and lactic acid mixture, as well as glycerol, were prepared and fed by mixing the two solutions to increase the ratio, in a stepwise manner, of glycerol from 0% to 100%, while keeping a loading of COD at 2.5kgm-3d-1 throughout the fermentation process. Vigorous methane gas production, approximately 580dm3m-3d-1, was observed during the acclimation stages. Microbial analysis revealed that both bacterial and archaeal communities changed significantly; bacteria (genus Trichococcus and family Syntrophomonadaceae) became dominant rapidly after the start of acclimation, and archaea belonging to the hydrogenotrophic methanogens (genera Methanobacterium and Methanospirillum), increased gradually with the progress of acclimation. © 2014 Elsevier Ltd.

Hoang T.T.T.,Hochiminh City University of Natural Resources and Environment | Tu L.T.C.,Hochiminh City University of Natural Resources and Environment | Le N.P.,Hochiminh City University of Natural science | Dao Q.P.,Institute for Environment and Resources | Trinh P.H.,Institute for Environment and Resources
Wetlands Ecology and Management | Year: 2012

Vietnamese coastal wetlands have traditionally been used for shrimp farming, but with the expansion of commercial shrimp farming and the associated clearance of mangroves, these valuable ecosystems have been rapidly degraded. The application of veterinary antibiotics in shrimp culture is one of the major threats to Vietnamese mangroves. These antibiotics are released into the environment through wastewater streams from shrimp ponds and cause environmental problems as well as the occurrence of antibiotic resistant bacteria. However, there is only a limited amount of information available on the occurrence and fate of antibiotics in Vietnamese mangroves. Ciprofloxacin and norfloxacin are two of most commonly fluoroquinolones used in shrimp culture. Laboratory experiments were therefore carried out using saline shrimp pond water to investigate the fate of both antibiotics in a coastal wetland ecosystem. Furthermore, two wetland plant species (Ceratophyllum demersum and Chrysopogon zizanioides), were used for studying phytoremediation of both antibiotics through a hydroponic experiment. Both ciprofloxacin and norfloxacin were photodegradable but at a slow rate, whereas the biodegradation seemed to be insignificant. If given at an initial concentration of 5 or 10 mg/L, a higher removal of antibiotics was achieved using C. demersum: 40 % for norfloxacin and 44-39 % for ciprofloxacin, respectively. With C. zizanioides, ciprofloxacin and norfloxacin were reduced by 40-38 and 36-34 %, respectively. These results indicated that phytoremediation could be effective in the removal of both antibiotics. © 2012 Springer Science+Business Media B.V.

Thuy H.T.T.,Hochiminh City University of Natural Resources and Environment | Loan T.T.C.,Hochiminh City University of Natural Resources and Environment
Water, Air, and Soil Pollution | Year: 2014

Ciprofloxacin, griseofulvin, and rifampicin are three human antibiotics that are also widely used in the shrimp culture of Cangio coastal wetland (Vietnam, 10° 24′ 38″ N, 106° 57′ 17″ E). They have been detected in shrimp larvae pond and receiving water bodies. However, the environmental fate of these antibiotics in coastal wetland milieu is currently unknown. The aim of this study was to determine the degradation potential of these antibiotics in water and sediments from Cangio coastal wetlands. The effects of light, microbial activities, and presence of sediments on the degradation of all three antibiotics were investigated in "water-only" and "water-sediment" experiments. Results indicate that the environmental fate of those antibiotics was quite complex. Photodegradation seemed to play a major role in "water-only" system, since shorter t1/2 was observed for ciprofloxacin, griseofulvin, and rifampicin, with light than in the dark, for both sterile and non-sterile conditions. Biodegradation played a minor role in the disappearance of the antibiotics and was overlaid by photodegradation. In addition, sorption to sediment was of major importance for antibiotics, especially for ciprofloxacin and rifampicin. The t1/2 of these antibiotics in aqueous phase of "water-sediment"system was higher than for "water-only" experiments, indicating that a part of antibiotics were adsorbed by sediment. The biodegradation did not play a major role on sediment sorption of CIP and RIF, since no statistically significant differences between non-sterile and sterile conditions were observed. Only for GRI, the impact of the biodegradation to the sediment sorption could be found and led to the weak affinity to sediment sorption of this antibiotic. All three antibiotics were more sensitive to photodegradation than to biodegradation; however, the degradation rate was low. In addition, the sorption by sediment occurred also with a slow rate, so these antibiotics could recalcitrant persist in the coastal wetland environment. © Springer International Publishing 2014.

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