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RISS 인기검색어
- 검색키워드
- 저자 : ( Tetsuji Hirato ) (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
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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>
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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.
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