Transboundary Movement of Recyclable Waste in Vietnam: Opportunity or Loss

( Trung-hai Huynh ),( Duc-quang Nguyen ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-

Together with the development of economy, the industrial recycling activities at large scale (formal sector), especially for the steel, paper and plastic recycling has developed in Vietnam. At the present time, the recyclable waste flow run through the formal sector is much larger than it does through informal sector. The statistics shown that Vietnam is still depended on the imported recyclable scrap, and trends to increase each year, despite of its efforts on utilization of domestic waste and scrap on the waste management system, as well as on the development of support industry. The legislation system for recyclable waste is considered relatively adequate in Vietnam at the moment. Nevertheless, the efficiency of legislation has not been clear as expected, leads to many obstacles for not only the management system but also for the recycling industry of the country. Some of obstacles can be listed as: (1) the increase of imported recyclable waste leads to the increase of illegal imported waste flow; (2) the hanging/stacking of imported recyclable waste flow in the national seaport; (3) the sensitivity of recycling industry to any change on the transboundary movement of recyclable waste; and (4) the depending of country to imported scrap causes the increase of untreated domestic waste flow. The opportunity for transboundary movement of recyclable waste, then easily change into loss of the country, if the authority does not improve its management system to deal with the increase of imported recyclable waste, and to increase the effective of the collection and classification system of waste in Vietnam

Approaching Circular Economy in the Plastic Recycling in Vietnam

( Huynh Trung Hai ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-

Leaching of yttrium and europium from fluorescent lamp phosphor powder using nitric acid: kinetics and optimization

Huynh Trung Hai,Ha Vinh Hung,Vu Minh Trang 한국자원공학회 2022 Geosystem engineering Vol.25 No.3

Rare earth elements (REEs) are recognized as one of the most critical elements and considered essential for the development of sustainable energy technologies, lasers, electronics, alloys, catalysts, and other applications. In order to meet the increasing demand to ensure those essential usages, the supply of REEs is however limited from the primary sources. Recovery of REEs from secondary resources, such as discarded electrical and electronic equipment, referred to as electronic waste (e-waste) is consequently crucial. Fluorescent lamps among such wastes are of special concern due to the high quantity of REEs present in them. This article discusses a potential hydrometallurgical method for recovering REEs (yttrium and europium) from fluorescent lamp waste via nitric acid leaching. The effects of leaching factors including acid concentration and temperature were examined. To assist the leaching yields of those metals, the effect of alkaline fusion was specifically examined. The kinetics of both processes, direct- and alkaline fusion-assisted leaching were investigated based on the shrinking core model. In the case of direct leaching, the metal dissolution was controlled by surface chemical reaction with apparent activation energies of 43.9 and 48.1 kJ/mol for yttrium and europium, respectively, in the temperature range 303–333 K. Pretreatment, viz., the alkaline fusion changed the subsequent leaching mechanism to diffusion control with apparent activation energies of 7.4 and 9.5 kJ/mol for the respective metal in the same temperature range. Optimization of the alkaline fusion-assisted acid leaching process was undertaken by applying response surface methodology (RSM) based on the central composite design (CCD). Under the alkaline fusion conditions such as soda/fluorescent powder mass ratio of 0.65 g/g, temperature of 1223 K and reaction time of 7200 s followed by acid leaching (nitric acid concentration – 3.5 M, temperature-323 K, pulp density – 30 g/L and leaching duration – 1200 s), the leaching efficiencies of 92.6% and 99.5% for yttrium and europium, respectively, could be achieved.

Situation of End-of-Life Vehicles Management and Initial Assessment of the Material Flow from ELV in Vietnam

( Duc-quang Nguyen ),( Trung-hai Huynh ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-

End-of-life vehicles (ELV) can be considered as a specific waste source in Vietnam that is out of the Government control. With high amount of material and valuable parts, ELV is now handled and dismantled by the informal sector, with three main outputs including usable parts (mirror, speaker, etc.) that can be reused or refurbished, dismantled common materials (metals, plastic, rubber, leather and glass) that can be recycled, and unusable materials that contained a lot of hazardous waste is discharged directly to environment. This research is the initial research in Vietnam for the determination of material flow from ELV using network model. In the model, 5 main stake holders have been defined including customer, dismantler, recycler, automobile service and waste processor. It is found that more than a half of an ELV (57 %, in weight) can be reused in Vietnam, including mostly engine parts, wheels, air bag, speaker, chassis or mirror. These parts, then can cause the secondary disposal of replaced parts with similar volume (that will be recycled or disposed at the landfill site). About one third (32 %) can be recycled as secondary material resources, including mostly metal parts, some types of plastic and rubber. The rest (11 %) that cannot be reused or recycled is disposed without control at the dismantling site. While ELV is classified into groups of equipment that are needed to retrieve and treat by the producer under Decision 16/2015/QĐ-TTg, Vietnam do not have any proper legislation to control this waste flow, as well as any formal facility to treat it. Thus, it is still hanging for Vietnamese Government to improve the legislation for the application of Extended Producer Responsibility, not only for this type of waste but the other groups of waste that are needed to retrieve and treat by producer.

Efficient Recycling of WC-Co Hardmetal Sludge by Oxidation Followed by Alkali and Sulfuric Acid Treatments

Dong-hyo Yang,Rajiv Ranjan Srivastava,Min-seuk Kim,Dao Duy Nam,Jae-chun Lee,Hai Trung Huynh 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5

We present a process to recycle strategic metals, viz. tungsten and cobalt, from a WC-Co hardmetal sludge (WCHS) via oxidation followed by a two-step hydrometallurgical treatment with alkali and acid solutions. The oxidation of WCHS was investigated in the temperature range of 500 to 1000 °C and optimized at 600 °C to transform the maximum WC into an alkali-soluble WO3. The conditions for the selective dissolution of WO3 in stage-I were optimized as follows: 4.0 M NaOH, pulp density of 175 g/L, and temperature of 100 °C for 1 h, yielding maximum efficacy. Subsequently, in the second step, the optimal conditions for cobalt leaching from the alkali-treated residue were established as follows: 2.0 M H2SO4, 25 g/L pulp density, and 75 °C temperature for 30 min. Downstream processing of the obtained metal ions in solutions was also easier, as the only impurity of dicobaltite ions with the Na2WO4 solution was precipitated as Co(OH)3 under atmospheric O2; meanwhile, the CoSO4 solution obtained through the second step of processing can be treated via electrolysis to recover the metallic cobalt. The present process is simpler in operation, and the efficient use of eco-friendly lixiviants eliminates the previously reported disadvantage.

Bacterial Cyanide Generation in the Presence of Metal Ions (Na⁺, Mg²⁺, Fe²⁺, Pb²⁺) and Gold Bioleaching from Waste PCBs

Tran, Chi Dac,Lee, Jae-Chun,Pandey, Banshi Dhar,Jeong, Jinki,Yoo, Kyoungkeun,Huynh, Trung Hai The Society of Chemical Engineers, Japan 2011 Journal of chemical engineering of Japan Vol.44 No.10

<P>As an alternative using cyanide chemicals for gold extraction, the application of a cyanogenic bacterium <I>viz.</I> <I>Chromobacterium violaceum</I> (<I>C. violaceum</I>) in YP medium has been investigated. The catalytic roles of metal ions such as Na<SUP>+</SUP>, Mg<SUP>2+</SUP>, Fe<SUP>2+</SUP>, and Pb<SUP>2+</SUP>, as well as the effect of Na<SUB>2</SUB>HPO<SUB>4</SUB> nutrient addition on the cyanide generation efficiency of the bacterium in this medium have been elucidated. While MgSO<SUB>4</SUB> and FeSO<SUB>4</SUB> added to the medium were equally effective for cyanide generation, improved efficiency was obtained in the presence of Na<SUB>2</SUB>HPO<SUB>4</SUB> and Pb(NO<SUB>3</SUB>)<SUB>2</SUB>. In order to examine the effectiveness of <I>C. violaceum</I> cultured in YP medium for the generation of cyanide ions, the dissolution of gold and copper from waste mobile phone printed circuit boards (PCBs), a good source of gold and copper in alkaline conditions, was tested at 30°C, for various pH values and metal ion contents. Gold leaching was found to be 11% in 8 d at pH 11.0 in presence of 4.0 × 10<SUP>−3</SUP> mol/L MgSO<SUB>4</SUB>, whereas; copper recovery was high (11.4%) at pH 10.0. Addition of 1.0 × 10<SUP>−2</SUP> mol/L Na<SUB>2</SUB>HPO<SUB>4</SUB> and 3.0 × 10<SUP>−6</SUP> mol/L Pb(NO<SUB>3</SUB>)<SUB>2</SUB> to the YP medium increased copper leaching to 30.3% and 38.1%, respectively, at pH 10.0 in 8 d. However, this effect was not observed for gold leaching.</P>