image: Uranium extraction from seawater at a viable cost is a long-term quest in the sustainable future development of nuclear power. Radiation-modified polyethylene fiber is considered to be the most suitable adsorbent found in seawater in terms of adsorption efficiency, mechanical strength and corrosion resistance. A scheme for extracting uranium from seawater on a pilot/plant scale consists of preparing an amidoxime-based ultra-high molecular-weight polyethylene (UHMWPE) fibrous adsorbent with a radiation- induced graft copolymerization of acrylonitrile and acrylic acid and the subsequent conversion of cyano groups to amidoxime groups on the graft chains. The resultant UHMWPE fibrous adsorbent braids are plaited and planted on the sea floor, where they stand like seaweed. After a soaking period of 30 to 60 days underwater, uranyl and other metal ions are adsorbed by the amidoxime functional groups on the surface of the plaits. Last, the adsorbent braids are recovered from the testing site by a ship on which the elution and collection of uranium and the regeneration of the adsorbent material can be completed. The end product, U3O8, is produced in the form of yellowcake and the adsorbent material can be reused (see the article by XING Zhe, HU JiangTao, WANG MouHua, ZHANG WenLi, LI ShiNeng, GAO QianHong & WU GuoZhong in SCIENCE CHINA Chemistry 2013 No. 11 issue, page 1504�). view more
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2013 No.11 issue of SCIENCE CHINA Chemistry published a special topic on extraction of uranium from Seawater recently.
Owing to the fast economic growing and the concern over greenhouse gases and air pollution, the development of nuclear energy is one important option to meet the expanded energy consumption in our future. To achieve that goal, continuing and reliable supplies of uranium are critical to future nuclear power projects. As is well known, global terrestrial reserves of uranium are limited and the deposits in China are relatively small. Given the projected big growth in nuclear power in the future, reliable supply of uranium at a reasonable price is essential for China. Extraction of uranium from seawater faces a great challenge but has received attention for more than sixty years. It is described by American scientists recently as a"game-changing" approach if it can be realized at economic viable costs. Encouraged by the global aggressive nuclear power development plans in the past years, although the pace was slow down by Fukushima accident in Japan in 2011, extraction of uranium from seawater has been emerging as a potential approach to overcome the shortage of nuclear fuel.
Japan is playing a leading role in the research of uranium extraction from seawater; it has collected more than one kilogram of uranium from seawater by immersing functionalized polyethylene fibers in ocean. The United States Department of Energy (DOE) supported a program in 2010 to start a project for uranium extraction from seawater, some universities and institutions have been engaged in such project. Almost at the same time, a project was supported by the Chinese Academy of Sciences (CAS), although in a small budget, to evaluate the feasibility of extracting uranium from seawater and salt lake. This could be considered as a new era for the research on uranium extraction from seawater in China. CAS and DOE have now established a tight collaboration mechanism for uranium extraction from seawater.
Besides some institutions of CAS, many research groups in universities and institutions of China have also shown great interests or already joined the work on uranium extraction from seawater. Since uranium is present in very low concentrations in ocean (3.3-3.5 ppb), the collection of uranium from seawater economically is far more difficult than any usual collection process of metal ion from aqueous solution. Therefore, many approaches should be taken to design and synthesize functional ligands, develop advanced sorbents, understand the coordination mechanism, and find suitable elution process. To make the extraction of uranium from seawater more economically competitive, mass production of high performance adsorbents at a reasonable cost and good durability of adsorbent in seawater are two most important issues.
In March 25-26, 2013, the workshop on extraction of uranium from seawater was held in Shanghai, with more than eighty attendees from China and five delegates from the US. This workshop was initiated by Prof. Zhifang Chai at Institute of High Energy Physics of CAS, and financially supported by the National Natural Science Foundation of China, Shanghai Institute of Applied Physics (CAS), and China Academy of Engineering Physics. There were four invited talks and twelve oral presentations. The numbers of attendees and presentations are much higher than expected. The topics presented at the workshop cover a wide range of areas, including computer modeling, synthesis of nanoparticle with large surface area, radiation induced grafting of polymer fiber and following amidoximation, sorption and elution processes, marine test, etc. This workshop could be considered as the first one on the topic of uranium extraction from seawater in recent twenty years in China.
After the workshop, the organizing committee invited five research groups to make contributions and decided to publish them in a special mini-issue in Science China Chemistry. These five excellent contributions show us the ongoing of project in different approaches.
The special topic is available for free viewing at: http://chem.scichina.com:8081/sciBe/EN/volumn/current.shtml#
Science China Press Co., Ltd. (SCP) is a scientific journal publishing company of the Chinese Academy of Sciences (CAS). For 50 years, SCP takes its mission to present to the world the best achievements by Chinese scientists on various fields of natural sciences researches.