Nanofiltration (NF) is a membrane-based filtration method with pore sizes between 1 and 10 nanometers, much smaller than in ultrafiltration, but still larger than in reverse osmosis. 

Nanofiltration membranes are typically thin-film composite (TFC) membranes, arranged as spiral-wound, tubular, or hollow-fiber (capillary) modules based on polyamide or cellulose acetate.  

The extremely small pore size of NF retains the tiniest particles that would not be stopped even by tight ultrafiltration. The process does require higher operational pressure and crossflow operation to minimize fouling by concentration polarization. The separation mechanism is defined between pore size separation and solution diffusion separation.

Nanofiltration systems generally run at pressures of 5 to 20 bar, depending on the application. 

In water treatment at Pentair, NF finds at this time its main applications in the removal of humic substances and color from surface water and groundwater. The fine pores also allow for synthetic dye removal and water decolarization without impact on the mineral balance of the water.

As a gentle molecular separation process, compared to centrifugation or distillation, NF finds an increasing number of applications in the chemical and and pharmaceutical industries. NF is applied in solvent exchange at room temperature, gas condensate purification, catalyst recovery, fractionation and extraction processes, and product polishing. The dairy industry makes use of NF’s capability to simultaneously concentrate and (partially) demineralize in continuous large-volume processing. 

If you have any questions, please contact us.

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