Nanofiltration membrane is usually used to treat dye effluents. 2-piperazinecarboxylic acid functions as a monomer in thin-film composite (TFC) membranes, which are used in nanofiltration. Specifically, it works during aqueous phase in interfacial polymerization (IP) process by forming polyamide thin films on an underlying support membrane. In a recent study (Tang et al., 2023), such novel loose polyamide nanofiltration membrane is found be to more effective than conventional nanofiltration membranes in terms of treating dye effluents.
The underlying mechanism is that the carboxylic acid group in 2-piperazinecarboxylic acid has modified the properties of the membrane. First of all, the existing carboxyl group increases the polarity of the membrane, resulting in improved resistance to contamination and enhanced anti-fouling performance. Second of all, the carboxylic acid functional group reduces the reactivity of the amine sites, resulting in a looser polyamide layer with larger pore size. The balanced combination of pore size and Donnan effect can accomplish precise separation with high permeability. Last but not least, the carboxyl group provides negative surface charge on the membrane which is important to electrostatic interactions in separation.
By modifying with 2-piperazinecarboxylic acid, the resulting membrane is more capable of separating organic dyes and inorganic salts. It also exhibits higher water permeability, which is a critical metric when assessing membrane performance. Moreover, users and researchers can adjust the concentration of 2-piperazinecarboxylic acid to customize the performance of the membrane for various purposes.
Reference:
1. Tang, S., Chen, Y., Zhang, H., Zhang, T., Wang, P., & Sun, H. (2023). A novel loose nanofiltration membrane with high permeance and anti-fouling performance based on aqueous monomer piperazine-2-carboxylic acid for efficient dye/salt separation. Chemical Engineering Journal, 475, 146111. https://doi.org/10.1016/j.cej.2023.146111