Innovations in separations technology for the recycling and re-use of liquid waste streams

As the costs of wastewater disposal increase more emphasis is being placed upon the recovery and recycling of valuable chemicals contained within thes e streams. In this article, we review three separations technologies that f acilitate such recycling. Solvent extraction is an established technique fo r recovery of heavy metals and other pollutants and is most useful in large and medium scale operations when solute concentrations are high. Membrane technology is a more recent development that can be used in conjunction wit h extraction solvents to extend the range of conditions under which such pr ocesses are viable. Finally, adsorption and ion-exchange processes provide the means for extracting valuable contaminants when the concentrations of s uch so lutes are low. (C) 2001 Elsevier Science B.V. All rights reserved.