| 摘要 |
<p>The aqueous waste sludge suspension is treated at 20-80 DEG C and pH values between 4 and 13, preferably from pH 6-7, of 1.0-3.0. As a result of the chlorination, chromium is converted into the hexavalent form. Copper, zinc and nickel are present as dissolved sulphates and interfering components, such as calcium sulphate, iron sulphate and silica, are present as insoluble residues. After filtration, the chromium is first separated off from the solution in a fixed-bed anion exchanger. The copper is separated off from the remaining solution by liquid-liquid extraction with hydroxyphenone oxime diluted with petroleum as the extractant and then the zinc with di-(2-ethylhexyl) phosphate diluted with petroleum as the extractant. The aluminium is precipitated from the remaining solution as the hydroxide and is separated off, and finally the nickel is separated off by liquid-liquid extraction with sodium di(2-ethylhexyl) phosphate diluted with an aromatic solvent as the extractant. Yields of up to 99.5 % of the valuable nonferrous metals present in the waste hydroxide sludges are obtained.</p> |
