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Recovery of Valuable Metals from Polishing Powder Wastes by Hydrometallurgical Process
( Namil Um ),( Woo-il Kim ),( Hyo-hyun Choi ),( Cheol-woo Yoon ),( Ji-young Lee ),( Sun-kyoung Shin ),( Gil-jong Oh ),( Tetsuji Hirato ) 한국폐기물자원순환학회(구 한국폐기물학회) 2014 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2014 No.-
The main feature of rare earth polishing powder waste (REPPW) is the significant content of CeO<sub>2</sub> content in solid solutions of rare earth oxides. La, Pr, and Nd, like Ce, are used in polishing as well as dyes in polishing industry and also contained in REPPW. In addition, non-rare earth metals such as Ca, Al, Si, Ba, Mg, and F account for some proportion of REPPW, depending on the type of polished material. The leaching process using sulfuric acid solution can be proposed as a process for the recovery of rare earths from REPPW because it is easy and inexpensive to implement the treatment of REPPW. However, it also has some demerits in terms of separation and recovery. Undesired species are dissolved along with the materials of interest in the solution and another method is needed to separate these materials. Therefore, this study suggested that the leaching process with two steps based on the dissolution characteristics of the considered element-H<sub>2</sub>SO<sub>4</sub>-H<sub>2</sub>O solutions is needed for cerium recovery from REPPW by sulfuric acid leaching. The two steps of the leaching process consist of case 1 with La<sub>2</sub>O<sub>3</sub>, Pr<sub>2</sub>O<sub>3</sub>, Nd<sub>2</sub>O<sub>3</sub>, and CaO and case 2 with CeO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub>. this classification can be useful for developing the total process for cerium recovery from REPPW via two-stage acid leaching based on experimental results. In addition, a k-T (reaction rate constant-reaction temperature) diagram that permits rational extraction of CeO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> was devised according to the kinetics data fitted by a shrinking core model.
UM, Namil,HIRATO, Tetsuji Elsevier 2016 Journal of rare earths Vol.34 No.5
<P>This study described a hydrometallurgical method to investigate the separation of rare earth elements (REEs) from rare earth polishing powder wastes (REPPWs) containing large amounts of rare earth oxides with a major phase of CeO2 and minor phases of La2O3, Pr2O3, and Nd2O3 using a process devised by the authors. The suggested approach consisted of five processes: the synthesis of NaRE(SO4)(2)center dot xH(2)O from rare earth oxides in Na2SO4-H2SO4-H2O solutions (Process 1), the conversion of NaRE(SO4)(2)center dot xH(2)O into RE(OH)(3) using NaOH (Process 2), and the oxidation of Ce(OH)(3) into Ce(OH)(4) using air with O-2 injection (Process 3), followed by Processes 4 and 5 for separation of REEs by acid leaching using HCl and H2SO4, respectively. To confirm the high yield of NaRE(SO4)(2)center dot xH(2)O in Process 1, experiments were carried out under various Na2SO4 concentrations (0.4-2.5 mol/L), sulfuric acid concentrations (6-14 mol/L), and reaction temperatures (95-125 degrees C). In addition, the effect of the pH value on the separation of Ce(OH)(4) in HCl-H2O solutions with Ce(OH)(4), La-, Pr-, and Nd(OH)(3) in Process 4 was also investigated. On the basis of above results, the possibility of effective separation of REEs from REPPWs could be confirmed.</P>
Um, Namil,Kang, Young-Yeul,Kim, Ki-Heon,Shin, Sun-Kyoung,Lee, Youngkee Elsevier 2018 Waste management Vol.82 No.-
<P><B>Abstract</B></P> <P>This study examines the new policy framework, which includes effective environmental assessment procedure to manage waste in Korea.</P> <P>Concept of this framework pursues the important strategies toward the waste reduction, preservation of landfill area, stabilization and removal of hazardous substance in wastes, and optimal treatment for energy and material recovery from wastes. Therefore, it has begun on three points. First, activating the effective recycling system to reuse wastes will be essential to waste reduction. Second, the utilization of substitute resource can be expected through the optimal transforming the wastes into the recycled product, raw material, thermal energy, etc. Third, the characteristics of waste must be evaluated by strategic environmental assessment.</P> <P>To realize this concept, the strategic environment assessment with reinforcement of hazardous property, categorization of recycling type, and classification of environmental assessment procedure depending on the recycling type was provided. In addition, based on this environment assessment, the new policy framework was built through the established and revised Wastes Control Act by focusing on simple systematic procedure for decision of the possible recycling and strengthening the safety of the wastes to a higher level with promoting recycling activities.</P> <P><B>Highlights</B></P> <P> <UL> <LI> New policy framework for effective waste management in Korea was examined. </LI> <LI> New policy framework includes the national strategic environmental assessment. </LI> <LI> Strategy pursues waste reduction, preservation, stabilization, and optimal use. </LI> <LI> Government applied the new framework to establish and revise the Wastes Control Act. </LI> </UL> </P>
( Namil Um ),( Jin-mo Yeon ),( Hee-sung Lee ),( Seong-kyeong Jeong ),( Min-young Choi ),( David Chung ),( Tae-wan Jeon ),( Sun-kyoung Shin ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-
This study investigated the dissolution kinetics of insoluble chloride in MSWI bottom ash under physical condition with submerged particle via accelerated carbonation. The water-to-solid ratio was controlled by the condition, 10 dm<sup>3</sup>/kg, and the CO<sub>2</sub> concentration was kept constant at 30%. The reaction temperature was varied from 20℃ to 40℃ for dissolution kinetics. The result of an XRD analysis indicated that insoluble chloride (Friedel’s Salt) in untreated bottom ash could combine with CO<sub>2</sub> to form mainly an amorphous Al-rich material and calcite. In addition, the theoretical model was fitted well to the kinetics data pertaining to the dissolved insoluble chloride as the carbonation process proceeded; in the theoretical model, the product-layer diffusion was predominant. The variation of the rate constant upon dissolution with the temperature obeyed the Arrhenius equation with activation energy of 24.61 kJ/mol.
수출입 폐기물 관리체계 개선을 위한 앞으로의 방향에 대한 고찰
엄남일 ( Namil Um ),박윤수 ( Yoon-soo Park ),김우일 ( Woo-il Kim ),박선오 ( Sun-oh Park ),김용준 ( Yong-jun Kim ),김기헌 ( Ki-heon Kim ),이영기 ( Youngkee Lee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2018 No.-
폐기물의 국가 간 이동 시 선진국 등 자국의 폐기물에 대한 엄격한 규제를 피하기 위해서 부적정 처리를 진행해 왔으며 이러한 이슈는 국제문제로 대두되었다. 특히 1976년 이탈리아 소베소에서 발생한 다이옥신 유출사고 때 증발한 폐기물이 1983년 그린피스에 의해 프랑스의 한 마을에서 발견되었고, 그 후 1987년 6월 ‘유해폐기물의 환경적이고 건전한 관리를 위한 타이로 지침과 원칙’이 채택된 카이로 지침을 바탕으로 1989년 3월 스위스 바젤에서 세계 116개국 대표가 참석한 가운데 바젤협약(1992년 5월 협약 발효)이 채택되었다. 이에 따라 우리나라는 1994년 바젤협약에 가입함에 따라 폐기물국가간이동법을 제정하여 수출입 폐기물을 바젤협약의 분류체계로 전환하였으며, 최근에는 수출입 규제폐기물과 관리폐기물로 구분하여 관리하고 있다. 최근 들어 바젤협약 당사국총회에서는 국가 간 수출입 폐기물 규제와 효율적인 관리를 위한 제도마련을 회원국들에 요구하고 있으며, 우리나라(환경부 및 국립환경과학원)에서도 이에 맞추어 수입 및 수출되는 폐기물의 통관절차·이동·유통·저장 및 재활용 처리 등 전 부분에 걸쳐 관리체계의 개선에 대해 효과적인 방안을 모색하고 있다. 그럼에도 불구하고 규제 및 관리폐기물 판단기준 부제, 폐기물과 중고제품 구분의 모호성, 수출입 폐기물 품목 세부 분류의 필요성 등 많은 문제점이 나타나고 있는 것도 사실이다. 이에 대해 본 연구에서는 수출입 폐기물 관리체계 개선을 위한 문제점과 이를 극복할 앞으로의 해결 방안에 대해 언급하고자 하였다.
Factors Affecting the Crystal Growth of Scalenohedral Calcite by a Carbonation Process
Thriveni, Thenepalli,Um, Namil,Nam, Seong-Young,Ahn, Young Jun,Han, Choon,Ahn, Ji Whan The Korean Ceramic Society 2014 한국세라믹학회지 Vol.51 No.2
In the present work, we report a novel microstructure of scalenohedral calcite synthesized without any additives by a simple and ecofriendly carbonation process carried out in a liquid-gas system as well as the effects of experimental conditions on the crystal growth of the scalenohedral calcite phase. Various process parameters, pH, temperature, $Ca(OH)_2$ concentration, $CO_2$ flow rates, and the total volume concentration, were investigated to enhance the sensitivity of the process. The highest average length of the scalenohedral calcite was obtained at pH 6.0, temperature of $45^{\circ}C$, $Ca(OH)_2$ concentration of 0.2M, $CO_2$ flow rate of 80mL/min, and total volume of 1L. The synthesized calcite was characterized by XRD, SEM, and FTIR to identify the phases and surface morphology.