RESUMEN
Composite particles have been made by combining nanosized polymer particles with magnetite microparticles using a ball-mill process. The magnetite particle cores were included to facilitate the composite particles separation by use of a magnetic field. Polymer particles carried carboxylic groups as ion-exchange vehicles. The composite particles were used in the extraction/stripping of Zn, Cu, Ni, and Cr from aqueous solutions in a stirred batch reactor of laboratory scale. The extraction behavior of these metals was studied as a function of initial metal concentrations of up to 25 mM, ionic strength at pH (5-7), and temperature (1-80 degrees C). Experimental results showed that the process was very fast and yielded complete metal removal when the initial concentrations of metals were very low. The selectivity series was Cu > Cr > Zn > Ni. The effect of ionic strength was immaterial at pH 7. However, extraction decreased with increasing ionic strength at pH 5. Extraction increased with increasing temperature. A series of extraction/ stripping experiments indicated that the particles can be reused without significant loss in their extraction capacity.