Nanofiltration (NF) membranes have begun to displace some traditional membranes in Reverse Osmosis (RO) filtration systems because they offer better solute rejection under lower pressure. NF membranes have higher water recovery rates than conventional membranes while reducing consumptive energy use. However, NF membranes are not perfect. The active layer in NF/RO membranes are manufactured through an interfacial polymerization process. The organic plastics incorporated into the membranes often have high surface roughness and do not completely cross-link. The surface roughness leads to premature fouling of the membranes, while the incomplete linking leaves gaps in the active layer thus reducing the rejection of solutes.
To address these challenges with NF/RO membranes, researchers have developed a novel new material for the active membrane layer. Researchers have incorporated dendrimers into the active layer made from the same Polyamide (PA) polymers the first generation active layers were composed. Dendrimers are artificially synthesized polymers manufactured from interconnected branched chains of monomers. They can be designed to selectively bond with elements in ionic compounds through chemical reactions. Dendrimers can be used in the active layer of NF membranes to selectively bond to solutes like arsenic or boron when filtering fresh or saltwater. These dendrimers have been shown to absorb 100% of a solute when minimum concentrations relative to solute concentrations are met. Additionally, these dendrimers can be renewed through simple processes involving cleaning with an acid solution. The active layer of the NF/RO membranes can be customized per application, allowing these filtration systems to target specific contaminants.
These filters can be used to filter out natural chemicals in salt or fresh water. Additionally, these filters can be used to target pharmaceuticals or pesticides in treated water. Finally, dendrimers have a number of uses in nanotechnology, including the manufacture of nanoscale batteries, nanopesticides, drug delivery platforms, nanocatalysts and as standalone nanomachines.
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There are relatively few risks associated with this technology. The manufacture of dendrimers is a tightly controlled chemical process, so the risks in the manufacturing process are simple and well understood. Beyond the manufacturing process, the dendrimer active layers are contained within the NF and RO membrane layers, nearly eliminating their potential for release into the environment.