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Improvement in rare earth element recovery from waste trichromatic phosphors by mechanical activation

Song, Guanghan, Yuan, Wenyi, Zhu, Xuefeng, Wang, Xiaoyan, Zhang, Chenglong, Li, Jinhui, Bai, Jianfeng, Wang, Jingwei
Journal of cleaner production 2017 v.151 pp. 361-370
X-ray diffraction, electronic wastes, leaching, microstructure, particle size, rare earth elements, recycling, scanning electron microscopy, sulfuric acid, temperature
This research introduced a pretreatment process -mechanical activation- for extracting rare earth elements (REE) from waste trichromatic phosphors separated from e-waste. The effects of mechanical activation on the physicochemical properties of waste trichromatic phosphors were investigated using multiple methods by scanning electron microscopy (SEM), Brunauer-Emmett-Teller measurement (BET), particle size analysis, and X-ray diffraction (XRD). The results show that mechanical activation has noticeable effects on the microstructure of waste trichromatic phosphors. Increasing the rotational speed could cause the changes of SA, structural defects, and breakage of the crystalline network, which could significantly improve in REE extraction rates. Specifically, changes in the crystalline degree of disorder caused by mechanical activation played a crucial role in enhancing the REE leachability from waste trichromatic phosphors. In addition, the sulfuric acid leaching behaviors of the activated waste trichromatic phosphors were studied by varying several parameters, including leaching time, liquid-to-solid ratio, acid concentration, heating temperature, and various activation conditions: Y, Eu, and Ce recovery rates reached approximately 96.3%, 91.1%, and 77.3%, respectively, from waste trichromatic phosphors activated for 60 min at the rotational speed of 550 rpm (by ball mill) compared with 46.7%, 42.3%, and 31.2%, respectively, from the raw sample. The method is promising to be put into practice to promote the recycling REE from various waste electric and electronic products.