Indium recovery from aqueous solution containing oxalic acid – Enhancement by using hydrophobic membranes
Journal
Separation and Purification Technology
Journal Volume
235
Date Issued
2020
Author(s)
Abstract
The work studied a separation process scheme combining extraction and stripping with membrane oil–water separators. By using hydrophobic membrane modules as oil–water separators, the extractant–containing organic solution could move forward and backward between extraction and stripping vessels while the passage of aqueous solutions (feed and strip solutions) was prevented by membrane hydrophobicity. Therefore, the feed and strip solutions did not contact each other, but the ion-extractant complexes flowed from the extraction vessel to the stripping vessel to allow for extractant regeneration and the regenerated extractant then flowed back to the extraction vessel to enhance extraction efficiency. Compared to the supported liquid membrane process that used hydrophobic membranes as oil–water contactors, the present scheme used the dispersion of aqueous solution in organic solution to provide the major surface area for extraction and the need for membrane surface area could be reduced. The process was applied to recovery of indium from aqueous feed solution containing oxalic acid, which could form complex with indium ions and thus reduced the extraction efficiency. The results show that the studied process effectively enhanced the indium recovery efficiency: for 360 ml of 160 ppm indium aqueous solution (containing 2 wt% of oxalic acid), 99% removal of indium ions was accomplished in 30 min of operation, with 0.08 M of Di-(2-ethylhexyl) phosphoric acid (D2EHPA) in the organic solution, while 20 ppm of indium still remained in the feed using the traditional solvent extraction process with the same organic solution and D2EHPA concentration.
Type
journal article