Chapter 15 - Water Treatment by Dendrimer-Enhanced Filtration: Principles and Applications

Abstract

Pressure-driven membrane processes such as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF) are emerging as key components of water purification systems throughout the world. The bulk of the capital and operating costs of membrane systems is associated with the high pressure needed to remove dissolved contaminants (e.g., monovalent ions and small organic molecules). RO and NF are very effective at removing dissolved ions and organic solutes. However, high pressures (100-1000psi) are required to operate RO and NF membranes. Conversely, UF and MF membranes require much lower pressure (5-60psi). Unfortunately, they are not effective at retaining dissolved ions and organic solutes. The author of this chapter has developed a dendrimer-enhanced filtration (DEF) process that can remove dissolved substances using UF and MF. Dendrimers are highly branched 3D globular nanopolymers with controlled composition and architecture. They have many reactive functional sites and binding pockets per molecule, and their globular shape and large size makes them easier to filter than linear polymers. The DEF process works by combining dendrimers with conventional membrane filtration. Functionalized dendrimers are added to an incoming aqueous solution and bind with the target contaminants. For most dissolved solutes (e.g., cations and anions), a change in solution acidity causes the dendrimers to bind or release the target solutes. Thus, a two-stage filtration process can be used to recover and concentrate a variety of dissolved ions in water. This concentrated solution is then collected for disposal or subsequent processing or disposal, whereas the dendrimers are recycled. The DEF process has many applications including the recovery of toxic metal ions (e.g., copper) from industrial wastewater, the extraction of valuable metals (e.g., uranium) from aqueous solutions generated during in situ recovery mining, and the remediation of groundwater contaminated by anions (e.g., perchlorate).