Separation of heavy metal ions from water by supercritical carbon dioxide

• Main Authors: Song-bo Chen, 陳松柏
• Other Authors: Clifford Y. Tai
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/81571820346513092160

碩士 === 國立臺灣大學 === 化學工程學研究所 === 89 === ABSTRACT There is a large amount of wastewater produced by electroplating and chemical plants every year in Taiwan. Precipitation is a conventional technique to remove heavy metal ions from wastewater. The method will generate another pollutant of sludge, so it is necessary to develop a new technique for separating metal ions. Because of its nontoxicity, nonflammability, and affordable price , carbon dioxide is the most frequently used solvent in supercritical fluid extraction(SFE). However, direct extraction of metal ions from water is impossible because of the charge neutralization requirements. When a chealating agent is added, metal-chealate complex will form and thus dissolve in the supercritical CO2. The aim of this study is to remove metal ion or to separate a mixture of metal ions from aqueous solution. First, we studied the extraction efficiency of Cyanex302 for different metal ions. Second, we separated metal ions of Cu2+ and Zn2+ from water. Third, different chealating agent were tested to extract Co2+ and Ni2+, they do not react with Cyanex302. The results indicate that Cu2+、Zn2+、Pb2+、Ag+、Fe3+ can be extracted by Cyanex302 and Al3+、Co2+、Ni2+、Mn2+ can not. Cu2+ and Zn2+ can be separated by Cyanex302 at the following operating conditions：Cu2+ initial concentration 140ppm、Zn2+ initial concentration 70ppm, and chealating agent 4ml. At the conditions, Cu2+ will be extracted first and then the concentration of Zn2+ will decrease when Cu2+ concentraction is below 10ppm.