NTE: Removal of Toxic Metal Ions from Contaminated Water by Dendrimer Enhanced Ultrafiltration

Howard University, Washington DC

Investigators

Abstract

ABSTRACT Proposal No.: CTS-0086727 Proposal Type: New Technologies for the Environment Initiative (00-49) Principal Investigators: Mamdou S. Diallo Institution: Howard University NTE: Removal of Toxic Metal Ions from Contaminated Water by Dendrimer-Enhanced Ultrafiltration The discharge of toxic metal ions into publicly owned water-treatment works (POTWs), surface water bodies, aquifers and coastal water systems has caused a major water contamination problem throughout the world. Polymer-enhanced ultrafiltration (PEUF) is emerging as a promising process for treatment of water contaminated by toxic metal ions. In PEUF, a water-soluble polymer with strong binding affinity for toxic metal ions is added to contaminated water. The resulting solution is passed through an ultrafiltration (UF) membrane with pore sizes smaller than those of the metal-ion-laden polymer. Highly purified permeates have been obtained using PEUF. This project exploits recent advances in nanoscopic chemistry such as the invention of dendrimers to develop more efficient and cost effective functional materials for PEUF. Dendrimers are highly branched polymers with controlled composition and architecture consisting of three components: a core functionality, interior branch cells, and terminal branch cells. Critical properties of dendrimers such as size, shape, core chemistry, surface chemistry and polydispersity can be controlled by a judicious choice of synthetic building blocks and reaction conditions. For example, the terminal groups of a dendrimer can be designed to be compatible or incompatible with a specific surface, while its core may act as receptor for metal ions. The overall objective of this project is to evaluate the feasibility of Dendrimer Enhanced Ultrafiltration (DEUF) as an efficient, environmentally acceptable, and cost effective process for treating water contaminated by toxic metal ions. Commercial dendrimers are being modified chemically to determine the effectiveness of various forms in separating copper, zinc, and cadmium ions. The tendency of the dendrimers to foul UF membranes is also being tested. The Metal Products and Machinery (MP&M) industry is the first target for the application of DEUF. Approximately 40,000 of the 70,000 companies of the MP & M industry generate wastewater contaminated by toxic metal ions. Under current regulations, the MP& M industry is required to treat its contaminated wastewater prior to discharge into POTWs. EPA is in the process of issuing new and more stringent effluent concentration limitations for the MP&M industry. The additional costs of compliance to these new regulations using the best practicable control technology currently available are estimated to range from 1.95 to 3.59 billion dollars per year. A preliminary evaluation by EPA of the PEUF process shows it to be cost effective compared to chemical precipitation, the wastewater treatment baseline technology in the MP& P industry. Because the metal-ion binding capacity of dendrimers is significantly larger than that of linear polymers currently used in PEUF, the use of DEUF should result in more efficient water purification and significant savings for the MP& M industry.