2016-Sustainable Industrial Processing Summit
SIPS 2016 Volume 8: Non-ferrous, Rotary Kiln, Ferro-alloys, Rare Earth, Coal
| Editors: | Kongoli F, Xueyi G, Shumskiy V, Kozlov P, Capiglia C, Silva AC, Turna T |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2016 |
| Pages: | 350 pages |
| ISBN: | 978-1-987820-50-8 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Mechanism of CeMgAl11O19:Tb3+ structure decomposition during alkaline fusion process
Shengen Zhang1; Yifan Liu2;1INSTITUTE FOR ADVANCED MATERIALS & TECHNOLOGY, UNIVERSITY OF SCIENCE AND TECHNOLOGY BEIJING, Beijing, China; 2INSTITUTE FOR ADVANCED MATERIALS & TECHNOLOGY, UNIVERSITY OF SCIENCE AND TECHNOLOGY BEIJING, Beijing, China;
Type of Paper: Regular
Id Paper: 215
Topic: 6
Abstract:
The alkaline fusion process is a useful pretreatment for rare earth elements (REEs) recycling from the blue phosphor (CeMgAl11O19:Tb3+, CMAT). But the lack of basic theory affects the further development of alkaline fusion process. In our previous work, Free Oxoanion Theory (FOAT) has been summarized to elucidate the structure decomposition process of blue phosphor (BaMgAl10O17:Eu2+, BAM). In this paper, alkaline fusion experiments were performed to describe the CMAT structure decomposition mechanism. Different substances (KOH, NaOH, Ca(OH)2, NaCl, Na2CO3, and Na2O2) were chosen to react with CMAT to explain alkaline fusion process, only KOH, NaOH, Na2CO3, and Na2O2 can damage the CMAT structure. Cerium, terbium and magnesium ions were bonded with free oxoanion (OH-, CO32-, O22-) preferentially to escape from the CMAT structure. The remaining structure of aluminate eventually decomposed into aluminate in air. Cations (Na+, K+) were introduced to bond with the aluminate ions to maintain the charge balance of reaction system. It¡¯s clear that FOAT can be used to elucidate the structure decomposition process of aluminate phosphors (both BAM and CMAT) during the alkaline fusion process. Furthermore, the activation energy of CMAT reaction with NaOH was determined by three model-free methods. The calculated activation energy variation tendency versus conversion factor agrees with the proposed mechanism.
Keywords:
RareEarth; Recycling;References:
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