Selective removal of chromium, copper, nickel, and zinc from waste streams /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Environmental regulations and liabilities are forcing industries to investigate waste minimization. One aspect of waste minimization is recycling a waste so that it may be reused as a process feedstock. Waste minimization efforts by metal finishing and printed circuit board manufacturing industries have been hampered by the presence of multiple metals. It is desirable to selectively remove each metal so they may be recycled. Current metal removal techniques such as precipitation do not allow selective metal removal. One technique that allows selective metal removal is solvent extraction by chelation or complexation. These two reactions can be controlled by pH and ligand concentration, respectively. The purpose of this study was to investigate the feasibility of selectively extracting chromium(III), chromium(VI), copper, nickel, and zinc, which are common metals in aqueous waste streams. Two extracting agents were employed, dithizone for selectively extracting copper, nickel, and zinc as a function of pH; and Aliquat 336 for selectively extracting chromium(III) and chromium(VI) as a function of chloride concentration. Individual and multiple metal solutions were extracted with dithizone-chloroform and Aliquat 336-chloroform solutions. The optimum pH values for extracting copper, nickel, and zinc were pH 1.0, pH 4.8, and pH 7-8, respectively. Chromium(III) was not extracted by Aliquat 336. The least chloride concentration minimized the co-extraction of other metals besides chromium(VI) when extracted with Aliquat 336. A 0.1 M Aliquat 336 solution did not completely extract chromium(VI) in a single extraction. Copper, nickel, and zinc were selectively separated by dithizone at their optimum pH values based on differences in the reaction equilibria and reaction rates. The presence of chromium(VI) destroyed the metal separation capability of dithizone by possibly oxidizing the dithizone. The copper-, nickel-, and zinc-dithizone extraction constants and apparent reaction rates were measured and used in a simple model which simulated the results. The model was also used to optimize the pH and dithizone concentration for selective removal of copper, nickel, and zinc. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemical Engineering." |
| Physical Description: | xv, 293 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |