抄録
Solvent extraction has been studied as a useful method to recover metals from wastewater. The conventional extraction process generally requires large quantity of organic solvent, and should be improved into the safe and environment-friendly process. In the present work, the commercial chelate extractant 5-dodecyl salicylaldoxime (LIX860-I) was immobilized in the polyvinylalcohol (PVA) gel beads and the gel beads prepared were used for recovering copper in a model wastewater containing 0.5 wt% CuSO4·5H2O. The gel beads of 4 to 6 mm in diameter were packed in a column of 5.4 cm in diameter and 8.2 cm in height for extracting copper from the water to the gel beads without direct contact of the solvent with the wastewater. The extraction was carried out by circulating the copper-containing water through the column at 180 ml/h. It was found that copper in the water was almost completely extracted into the gel beads, although the process required relatively long time due to the diffusion resistance of copper in gel phase. A practical extraction process was suggested to employ the initial stage of the extraction process where the rate was relatively high. The copper extracted in the gel particles was recovered by back-extraction with a high concentration of H2SO4 solution. The gel beads could be reused at least three times with negligible leakage of the LIX860-I and no damage to the beads. In conclusion, it was shown that the LIX860-I-entrapping PVA gel beads could be utilized repeatedly to recover copper in wastewater without using organic solvent.
