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Treatment and Recovery of Valuable Materials from Aluminum Dross by Leaching
Thuy Nhi Nguyen Thi,이만승 한국자원리싸이클링학회 2017 資源 리싸이클링 Vol.26 No.5
White and black dross are resulted from the recycling of aluminum. There are no established processes to recover valuable materials from black dross. Hydrometallurgical processes seem to be suitable for the treatment of aluminum dross. The salts in the black dross are recovered by dissolving with water. The residues are treated by either alkaline or acid leaching. Although the leaching rate of alumina by NaOH is lower than that by acid, its intermediates are more suitable to the production of aluminabased materials. The future direction for the treatment and recovery of valuable materials from aluminum dross is discussed.
Thi Thuy Nhi Nguyen,이만승 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.3
Aluminum dross results from the re-melting of used aluminum cans, and is a valuable resource containing alumina. In general, aluminum dross contains oxides of Al, Ca, Fe, Mg, Si and Ti and some salts. As a continuation of the previous work to recover pure alumina from the dross, the effect of employing ultrasound wave in the NaOH solution was investigated to improve the leaching percentage of alumina from the mechanically activated dross. The use of ultrasound improved the leaching percentage of alumina from 35% to 60% and resulted in a leaching solution where the purity of aluminate ion was 99%. Among the optimum conditions (5 M NaOH, 50 oC, 4 h, pulp density of 100 g/L and ultrasonic power 100 W), leaching time had a remarkable effect on the dissolution of alumina in the presence of ultrasound. The combined effect of ultrasound and the addition of CaCl2 and organic acids to the NaOH solution was also investigated. Roasting of the black dross with CaCl2 followed by ultrasound leaching did not improve the leaching percentage of alumina. The presence of organic acids in the NaOH solution increased the leaching percentage of alumina as well as silica, and thus was not favorable for recovering pure aluminate solution from the black dross.
Recovery of Alumina from Sodium Hydroxide Leaching Solution by Precipitation with Hydrogen Peroxide
Thi Thuy Nhi Nguyen,이만승 한국자원리싸이클링학회 2019 資源 리싸이클링 Vol.28 No.4
In order to recover pure alumina from balck dross, precipiatation experiments were done to the NaOH leaching solution of mechanically activated black dross. In this work, hydrogen peroxide was added to the synthic solution as a precipitating agent. Among some variables, the concentration of H2O2 and the volume ratio of H2O2 to solution showed a remarkable effect on the precipitation of aluminum hydroxide. At the optimum conditions, most of the aluminate was precipitated. Calcination of the aluminum hydroxide at 1200o C led to the formation of θ and α-alumina. The charactistics of the synthesized activated alumina was measured by XRD and EDS. The average particles size of the alumina was 3.73 μm.
Speciation of alumina in aqueous solution and its interaction with silicate ion
Thi Thuy Nhi Nguyen,이만승 한국자원공학회 2019 Geosystem engineering Vol.22 No.4
Several aluminum (Al) species can be formed by the dissolution of Al-containing minerals. The distribution of Al-containing species depends on the total concentration of aluminum, solution pH, and the presence of complex-forming ligands. Polymeric species exists as Al-3(OH)(4)(5+), Al-13(OH)(32)(7+) when solution pH is 3-5. The mole fraction of these species is proportional to the concentration of Al (III). Al3+ exists at pH < 4 and Al(OH)(2+) exists in the pH range between 4 and 6, while Al(OH)(4)(-) is predominant at pH > 8. The reaction between Al (III) and impurity (silica) results in the formation of some new species. These data might be employed to develop a hydrometallurgical process for recovery of alumina from primary and secondary resources containing alumina.
Leaching of Black Dross by Hydrochloric Acid Solutions
Thi Thuy Nhi Nguyen,Thi Hong Nguyen,이만승 한국자원리싸이클링학회 2017 資源 리싸이클링 Vol.26 No.6
Leaching of black dross with HCl solution was conducted to find a suitable process to recover valauble materials. In this work, the leaching behavior of the components was compared between black dross and the residues after water treatment. All the components except TiO2 in the black dross were dissolved by HCl solution in the experimental ranges. Treatment of the black dross with water to recover the salts has negative effect on the leaching of Al2O3, MgO and SiO2. The reactions occuring during the leaching were discussed. At an optimum leaching condition of 3 M HCl and 90oC, the leaching percentage of Al2O3, MgO and SiO2 was 85, 100 and 40%, respectively.
Minh Sang VO(Minh Sang VO ),Minh Quoc PHAM(Minh Quoc PHAM ),Thuy Bao Thu LE(Thuy Bao Thu LE ),Le Kim Ngan NGUYEN(Le Kim Ngan NGUYEN ),Xuan Tung DAO(Xuan Tung DAO ),Huynh To Nhi PHAM(Huynh To Nhi PHAM 한국유통과학회 2023 The Journal of Asian Finance, Economics and Busine Vol.10 No.2
The study aims to evaluate the impact of corporate social responsibility on customers’ repurchase intention in Vietnam’s fast-moving consumer goods (FMCG) industry. This study employs primary data surveyed from 417 Vietnamese consumers, and the sample is selected based on the willingness to participate in providing information. The results show corporate social responsibility’s positive impact on repurchase intention in the FMCG industry in the Vietnam market. There are three components of corporate social responsibility, including ethical responsibility, legal responsibility, and economic responsibility have a positive impact on repurchase intention. The economic responsibility component has the greatest effect on repurchase intention. There is not enough statistical basis for the philanthropic responsibility component of corporate social responsibility to recognize its impact on repurchase intention. The findings of this study suggest that companies dealing in the FMCG industry in Vietnam need to invest more in further developing their corporate social responsibility, it not only helps to improve their customer loyalty to businesses but also contributes to promoting the country’s economic and social development in a better and more sustainable direction.
Hydrochloric Acid Leaching Behavior of Mechanically Activated Black Dross
Thi Hong Nguyen,Thi Thuy Nhi Nguyen,이만승 한국자원리싸이클링학회 2018 資源 리싸이클링 Vol.27 No.3
Effect of ball milling treatment on the hydrochloric acid leaching performance of black dross was investigated to recover alumina. Ball milling time and speed showed limited effect on the leaching behavior of the alumina in the mechanically dross. Under the optimum mechanical activation condition (for 1h at 700 rpm), the leaching of alumina in hydrochloric acid solution was significantly affected by leaching time and reaction temperature. MgO was completely dissolved in most of the leaching conditions, while a small amount of Ca, Fe, Si and Ti oxides was dissolved. Although 80% of alumina was dissolved, the dissolved minor components such as Ca, Fe, Mg, Si and Ti oxides should be separated to recover pure alumina solution.
Dinh Tram Anh PHAN,Thi Thuy Ngan NGUYEN,Thi Khanh Nhi NGUYEN,Tran Thien An NGUYEN,Van Si Dan PHAN,Ngoc Phuong Thao HO,Kim Xuan DO,Trong Luan NGUYEN 한국유통과학회 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.5
The outbreak of the COVID-19 pandemic has had a significant impact on the Vietnamese economy. In the midst of a complex disease that compelled people to limit their interaction, customers’ shopping habits shifted from “offline” to “online” transactions. Mobile payments have also grown in popularity. The goal of this study is to figure out what factors influence the use of mobile payments by hotel clients in Can Tho after COVID-19. The research team also examines how those factors influence customers’ willingness to use mobile payment and makes recommendations to better the current situation. Primary data was collected from 227 persons using online surveys and processed with SPSS software for this study. To analyze the correlation relationship between the elements determining the intention to use, the Cronbach alpha, EFA, Correlation, and Regression methods used to assess the scale are applied. Perceived Trustworthiness, Perceived Usefulness, and Perceived Ease of Use all have positive effects on customers’ propensity to use, according to the findings. Perceived Security, on the other hand, has no bearing. The findings of this study have significant theoretical and practical implications for the development of mobile payment services in Can Tho, particularly following the implementation of COVID-19.
Tan Dat Trinh,Pham The Bao,Le Nhi Lam Thuy,Ikuko Shimizu,김진영,Pham The Bao 한국전기전자학회 2019 전기전자학회논문지 Vol.23 No.2
In this study, a novel hierarchical approach is investigated to extract coronary vessel from X-ray angiogram. First, we propose to combine Decimation-free Directional Filter Bank (DDFB) and Homographic Filtering (HF)in order to enhance X-ray coronary angiographic image for segmentation purposes. Because the blood vesselensures that blood flows in only one direction on vessel branch, the DDFB filter is suitable to be used toenhance the vessels at different orientations and radius. In the combination with HF filter, our method cansimultaneously normalize the brightness across the image and increases contrast. Next, a coarse-to-finestrategy for iterative segmentation based on Otsu algorithm is applied to extract the main coronary vessels indifferent sizes. Furthermore, we also propose a new approach to segment very small vessels. Specifically,based on information of the main extracted vessels, we introduce a new method to extract junctions on thevascular tree and level of nodes on the tree. Then, the window based segmentation is applied to locate andextract the small vessels. Experimental results on our coronary X-ray angiography dataset demonstrate thatthe proposed approach can outperform standard method and attain the accuracy of 71.34%.