Weng Hanqin, Wang Yi, Li Fuhai, Muroya Yusa, Yamashita Shinichi, Cheng Sheng
School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026, China; Department of Beam Material Science, SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan; Nuclear Professional School, School of Engineering, The University of Tokyo, 2-22 Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1188, Japan.
School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026, China; Reactor Operation and Application Research Sub-Institute, Nuclear Power Institute of China, Chengdu, Sichuan 610041, China.
J Hazard Mater. 2023 Sep 15;458:131852. doi: 10.1016/j.jhazmat.2023.131852. Epub 2023 Jun 15.
Recovery of platinum group metals (PGMs) including palladium (Pd), rhodium (Rh), and ruthenium (Ru) from high-level radioactive liquid waste (HLLW) possesses enormous environmental and economic benefits. A non-contact photoreduction method was herein developed to selectively recover each PGM from HLLW. Soluble Pd(II), Rh(III), and Ru(III) ions were reduced to insoluble zero-valent metals and separated from simulated HLLW containing neodymium (Nd) as a representative for lanthanides, another main component in HLLW. Detailed investigation on the photoreduction of different PGMs revealed that Pd(II) could be reduced under 254- or 300-nm UV exposure using either ethanol or isopropanol as reductants. Only 300-nm UV light enabled the reduction of Rh(III) in the presence of ethanol or isopropanol. Ru(III) was the most difficult to reduce, which was only realized by 300-nm UV illumination in isopropanol solution. The effects of pH was also studied, suggesting that lower pH favored the separation of Rh(III) but hindered the reduction of Pd(II) and Ru(III). A delicate three-step process was accordingly designed to achieve the selective recovery of each PGM from simulated HLLW. Pd(II) was reduced by 254-nm UV light with the help of ethanol in the first step. Then Rh(III) was reduced by 300-UV light in the second step after the pH was adjusted to 0.5 to suppress the Ru(III) reduction. In the third step, Ru(III) was reduced by 300-nm UV light after isopropanol was added and the pH was adjusted to 3.2. The separation ratios of Pd, Rh, and Ru exceeded 99.8%, 99.9%, and 90.0%, respectively. Meanwhile, all Nd(III) still remained in the simulated HLLW. The separation coefficients between Pd/Rh and Rh/Ru exceeded 56,000 and 75,000, respectively. This work may provide an alternative method to recover PGMs from HLLW, which minimize the secondary radioactive wastes compared with other approaches.
从高放废液（HLLW）中回收包括钯（Pd）、铑（Rh）和钌（Ru）在内的铂族金属（PGMs）具有巨大的环境和经济效益。本文开发了一种非接触光还原方法，用于从高放废液中选择性回收每种铂族金属。可溶性的Pd(II)、Rh(III)和Ru(III)离子被还原为不溶性的零价金属，并从含有钕（Nd）作为镧系元素代表的模拟高放废液中分离出来，钕是高放废液中的另一种主要成分。对不同铂族金属光还原的详细研究表明，使用乙醇或异丙醇作为还原剂，在254纳米或300纳米紫外线照射下，Pd(II)可以被还原。只有300纳米的紫外线能够在乙醇或异丙醇存在的情况下还原Rh(III)。Ru(III)最难还原，只有在异丙醇溶液中通过300纳米紫外线照射才能实现。还研究了pH值的影响，结果表明较低的pH值有利于Rh(III)的分离，但会阻碍Pd(II)和Ru(III)的还原。因此，设计了一个精细的三步过程，以实现从模拟高放废液中选择性回收每种铂族金属。第一步，在乙醇的帮助下，用254纳米紫外线还原Pd(II)。然后，在将pH值调节到0.5以抑制Ru(III)还原后，第二步用300纳米紫外线还原Rh(III)。在第三步中，加入异丙醇并将pH值调节到3.2后，用300纳米紫外线还原Ru(III)。Pd、Rh和Ru的分离率分别超过99.8%、99.9%和90.0%。同时，所有的Nd(III)仍留在模拟高放废液中。Pd/Rh和Rh/Ru之间的分离系数分别超过56000和75000。这项工作可能为从高放废液中回收铂族金属提供一种替代方法，与其他方法相比，该方法可将二次放射性废物降至最低。
