Kinetics of Supercritical Fluid Extraction of Zinc Ion from Aqueous Solution

• Main Authors: CHEN,SHIH-LUNG, 陳賜龍
• Other Authors: Clifford Y. Tai
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/72363359040195699650

碩士 === 國立臺灣大學 === 化學工程學研究所 === 87 === Precipitation is a conventional technique to remove heavy metals from wastewater. The disadvantage of this technique is to produce a large volume of sludge, which causes another pollution problem. Then, a fluidized—bed crystallizer has developed to remove the heavy metal ions from water as metal carbonate or sulfide pellet. This technique is used in Holland as well as in Taiwan. Recently, supercritical carbon dioxide is widely used as solvent in an extraction process. However, direct extraction of metal ions from water is impossible by using supercritical CO2, because of the charge neutralization requirements. When a chelating agent is added, metal—chelate complex will form and thus dissolve in the supercritical CO2. If the complex can be easily decomposed to recover metal and to recycle the chelating agent, the process will gain economical advantage. The aim of this study is to investigate the kinetics of metal extraction in an 1.3 liter vessel using supercritical CO2 as solvent. Operating variables, such as pressure and stirring rate are studied. The metal ion investigated in this study consists of copper, nickel and zinc .The chelating agent utilized in this study is the commercially available Cyanex 302. The results showed that the extraction rate follows the following order when cyanex 302 is used as the chelating agent.The removal rate of increases with an increase in stirring rate, but decreases with pressure.