| Summary: | 碩士 === 國立臺北科技大學 === 環境工程與管理研究所 === 103 === Due to the rapid development of science and technology, people rely on high-tech product are increasing year by year. Nowadays rare earth elements stand a high place on technologies, however, rare earth mining has greatly impact on our environment, such as soil erosion, radioactive pollution and drinking water pollution, etc. Hence, rare earth mining had been banned in many countries, and China becomes a most important supplier in the world. China supplies 30% of rare earth resources annually and having 90% of the whole world market. In recent years, China has posted policies, which restricted the exploitation of rare earth and limit its exports. Thus many countries begin to develop techniques for recovery rare earth, however, environmental impacts of different recovery technologies were overlooked.
This study intends to explore environmental impacts and carbon footprints of recovering Cerium, Gadolinium and Lanthanum from Solid Oxide Fuel Cell Electrode. Results of three different kinds of leaching solvents (they are nitric acid, hydrochloric acid and sulphuric acid) were compared. In this study, LCA software SimaPro 8.0.2 was used and IMPACT 2002+ and IPCC 2007 GWP 100a were applied for assessing environmental impacts and carbon footprints, respectively.
By using 0.326 mg Cerium recovery as a reference for comparison, the results indicate that using nitric acid for recovering rare earth has the highest environmental impact, especially on climate change and resources use which are ten times higher than the other two leaching solvents. Carbon footprints of leaching solvent processes are 37.3 KgCO2eq, 3.66 KgCO2eq and 3.56 KgCO2eq for nitric acid, hydrochloric acid and sulphuric acid, respectively. Regarding carbon footprints, nitric acid is also the highest one, however, is has the lowest recovery efficiency. This will increase the amount of raw materials and operation time to achieve the same amount of Cerium recovery and creates higher environment impacts and carbon emissions. Finally, hot spots for reducing environmental impacts and carbon footprints were identified and suggestions were provided in the conclusion.
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