Separation of heavy metals from industrial waste streams by membrane separation technology

Abstract

Industrial membrane technology is becoming increasingly attractive as a low-cost generic separation technique for volume reduction, recovery, and/or purification of the liquid phase and concentration and/or recovery of the contaminant or solute. It offers outstanding future potential in the reduction and/or recycling of hazardous pollutants from waste streams. Membrane separation technology may include: (1) commercial processes such as electrodialysis, reverse osmosis, nanofiltration, and ultrafiltration and (2) the development of hybrid processes such as liquid membranes, Donnan dialysis, and membrane bioreactor technology. Membrane separation technology as applied to waste treatment/reduction and environmental engineering problems has several advantages over conventional treatment processes. In contrast to distillation and solvent extraction membrane separation is achieved without a phase change and use of expensive solvents. The advantages of this technology are (1) low energy requirements; (2) small volumes of retentate that need to be handled; (3) selective removal of pollutants with the use of complexing agents and biocatalysts or by membrane surface modification; (4) the possibility for achieving zero discharge'' with reuse of product water, binding media and target, compounds; (5) continuous operation; (6) modular design without significant size limitations; (7) discrete membrane barrier to ensure physical separation of contaminants; and (8) minimal labor requirement.