| Summary: | 碩士 === 逢甲大學 === 環境工程與科學所 === 97 === Liquid－liquid extraction to remove contaminants from water is a traditional technique and has been criticized for some shortcomings. For the past decade, a large amount of organic solvent such as benzene, toluene, hexane, dichloromethane, and trichloroethene are widely used. However, the common features of these solvent are easily volatile, toxic, and extremely harmful to the environment and humans. Therefore, a new type of green solvent called room temperature ionic liquids (RTILs) was developed in recent years to replace the conventional organic solvent. Ionic liquid owns some superior properties such as low volatile, non-flammable, a wide range of liquid temperature, low toxicity, and miscible with organic compounds. This studies focused on using ionic liquid as an extraction solvent to remove Cr(VI), Co2+, and Cu2+ which chelating with ammonium pyrolidium dithiocarbamate (APDC) from aqueous solution. The chelation chemistry, best experimental conditions and the extraction efficiency are clearly discussed.
In this study, firstly, two different concentrations (i.e.1mg/L and 10mg/L) were prepared for each of metal ion. Then an adequate dosage of chelating agent APDC was added to form metal chelates at suitable pH ranges. The extraction efficiency depends mainly upon the pH for each extracted metal. Secondly, an aqueous solution containing metal chelate was mixed with ionic liquid called 1-butyl-1-methylpyrrolidinium bis-(trifluoromethylsulfonnyl) imide which was abbreviated as [bmpy][Tf2N]. The metal chelate contained in the water was centrifuged for couple minutes and distributed themselves in relation to their solubilities in the two solvents. The percent removal of metal from water was analyzed by graphite electro-thermal atomic absorption spectrometry. For Cr(VI), the extraction efficiency was up to 99% at pH 3 by [bmpy][Tf2N]. A comparison study was made by using chloroform, the solubility of Cr(APDC)3 in chloroform was poor and the extraction efficiency was less than 50%. The extraction efficiency of Co(APDC)2 by [bmpy][Tf2N] was close to 100% at pH 2-10. It was found that that Cu(APDC)2 was extracted stabilized below pH 6 and the extraction efficiency was more than 99% in the same pH condition.
Keywords: Ionic liquid, [bmpy][Tf2N], Green solvent, Chelating agent, APDC, Extraction efficiency
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