Yang Li,Feifei Yang,Jing Xiong,Kejia Liu,Wanhai Xiao,Tao Qi,Zhipeng Dong,Yong Wang
Rare earth polishing powder waste (REPPW) usually contains lanthanum (La) and cerium (Ce) with content over 50 %, thus its recovery is important for the cyclic utilization of rare earth. In the traditional acid leaching process, La and Ce are simultaneously leached and required further separation. Based on their leaching behavior difference, a two-stage hydrochloric acid leaching process was proposed in this study to recover and primarily separate La and Ce in REPPW. With the optimal operation conditions, La enriched solution with a relative purity of 91.11 % and Ce enriched solution with a relative purity of 92.85 % were obtained and their recovery ratio were 59.47 and 85.15 %, respectively. After precipitation and calcination, products of La 2 O 3 with purity of 83.67 % and CeO 2 with purity of 93.38 % were obtained. Besides, individual leaching kinetics of La and Ce in low-acid leaching were studied using various shrinking core models. Based on the analysis of phase components and micromorphology evolution of REPPW during the leaching process, the leaching mechanism of REPPW was determined. Combined the leaching regularity with the fitting results, the leaching process of La was controlled by interfacial transfer and product layer diffusion, and the Ce was by product layer diffusion. The apparent activation energies of the LaOF and CeO 2 leaching reactions were 89.97 kJ/mol and 79.03 kJ/mol, respectively.
Kai Gao,Xingyu Liu,Shaochun Hou,Guoguang Zhang,Zongyang Da,Shengfeng Ma,Chunlei Guo,Weihua Guan
The concentration of rare earth elements (lanthanum, cerium, and praseodymium) within rare earth polishing powder waste (REPPW) typically exceeds 50 %, with the majority of impurities comprised of silicon and aluminum-related compounds. Transforming REPPW into recycled rare earth polishing powders that adhere to polishing standards in an eco-friendly and economically viable way presents a significant challenge in the industry. Traditional acid or alkaline processes predominantly recover rare earth elements as oxides, which are underutilized due to their high costs. Considering the varying forms of impurities and rare earth compounds found in REPPW, this research introduces a novel physicochemical decontamination and continuous chemical transformation process aimed at producing regenerated rare earth polishing powders. Under optimal conditions, the physicochemical two-step decontamination process achieved a rare earth recovery rate surpassing 92 %, while silicon and aluminum removal rates reached 86.12 %. During the continuous chemical transformation of REPPW, the rare earth phases in an alkaline setting followed the sequence REOF (CeO 2 ) → RE(OH) 3 → RECO 3 OH→RECO 3 F→CeLa 2 O 3 F 3 (CeO 2 ), which not only facilitated phase reorganization but also enhanced the particle surface structure. Notably, these chemical transformations did not disrupt the rare earth distribution; instead, they indirectly boosted product purity and uniformly dispersed within the regenerated polishing powder particles, thereby improving polishing efficiency. Consequently, the adoption of this innovative regeneration process for polishing powders holds substantial importance for the sustainable utilization of rare earth resources.
The growing market demand for glass polishing leads to the production of a significant amount of waste known as rare earth polishing powder waste (REPPW), which poses environmental risks. This study is expected to achieve the waste treatment and comprehensive utilization of rare earth resources. A simple direct and low-cost gravity settling-hydrofluoric acid (HF) leaching process is proposed to regenerate rare earth polishing powder from the glass polishing waste. Firstly, dilute and stir the waste slurry evenly before letting it stand. The next gravity settling step removes most of the large impurity particles, and the acid-leaching process restores the aggregated polishing powder particles to their original size while removing the SiO 2 impurities to obtain the regenerated polishing powder. The optimal conditions for the HF leaching process are 0.25 M, 10 min, and 25 °C. The powder regenerated reaches a rare earth content of 95.3% and can be directly used for glass polishing. Particularly, ultra-precision surface roughness is achieved and the materials removal rate reaches 119.4% of the pristine polishing powder. The regeneration mechanism of the HF leaching process is proposed. The material flow and mass balance of the products obtained during the regenerating process indicate that the recycling of 1000 kg REPPW slurry yielded approximately 658 kg regenerated polishing powder, and it provides a total economic value of 2438.7 US dollars in the regenerating process.
危险品化学品经营许可证（带存储）