HOLLOW-FIBER SOLVENT-EXTRACTION REMOVAL OF TOXIC HEAVY-METALS FROM AQUEOUS WASTE STREAMS

This study is concerned with the applications of the immobilized interface-based techinques to reversible chemical complexation-based solvent extraction of toxic heavy metals from industrial wastewaters using microporous hydrophobic hollow fiber (MHF) modules. Toxic heavy metals studied were copper and chromium(VI). Each metal was individually removed in separate once-through experiments from a synthetic wastewater by organic extractants flowing in the shell-side countercurrent to wastewater flowing in the fiber bore. The organic extractant used for copper extraction was 5-20 % v/v LIX 84 diluted in n-heptane, and that for chromium extraction was 30 % v/v TOA (tri-n-octylamine) diluted in xylene. A mathematical model was developed to predict the extent of copper extraction from the aqueous synthetic wastewater by the MHF module. The equilibrium constant for copper was determined to be 1.7 from experimental partitioning data. The experimental data on copper extraction in the MHF module are described well by the model if the forward interfacial chemical reaction rate constant is 9.0 x 10(-6) cm/s.