Poly piperazine

NS-300 Membrane. The NS-300 membrane evolved from an effort at North Star to form an interfacial poly(piperazine Isophthala-mide) membrane. Credali and coworkers had demonstrated chlorine-resistant poly(piperazineamide) membranes in the asymmetric form (20). The NS-lOO, NS-200, and PA-300 membranes were all readily attacked by low levels of chlorine in reverse osmosis feedwaters. In the pursuit of a chlorine-resistant, nonbiodegra-dable thin-fiim-composite membrane, our efforts to develop interfaclally formed piperazine isophthalamide and terephthalamide membranes were partially successful in that membranes were made with salt rejections as high as 98 percent in seawater tests. 

This membrane demonstrated a vastly improved flux compared with the poly(piperazine isophthalamide) membrane, but its seawater salt rejection was low — in the range of 60 to 70 percent. A reverse osmosis test with a magnesium sulfate feedwater showed greater than 99 percent salt retention, however, dispelling the possibility that low sodium chloride rejections were due to defects in the polyamide barrier layer. The piperazine polyamide was soon concluded to have the following structure (see Reaction 111). 

Reverse osmosis test conditions 0.5% salt concentration, 200 psi, 25 C, poly(piperazine trimesamide) membrane. 

Figure 3e. SEM photomicrograph of composite membranes surface view of the poly(piperazine trimesamide) version of the NS-300 membrane.

Rasmussen and Smith [59] have reported the preparation in the bulk of several copolymers based on poly(piperazine sebacamide) and poly(oxypropyl-ene) diamine. The reaction was carried out at high temperature (220-245°C), partly under nitrogen flow and partly in vacuum. Other copolymers were successfully prepared, using a copolyether based on a mixture of ethylene oxide and propylene oxide, as well as the addition of a fatty dimer diamine. 

Others Poly(quinoxalines) Poly(benzimidazoles) Poly(piperazines) Poly(anhydrides) Poly(thiophenes)... 

FIGURE 4.2 Membrane surface atomic force microscopy images (a) PES pure membrane and (b) poly(piperazine-amide) composite membrane. (Reprinted with permission from Jahanshahi, M. et al, Desalination 257, 129-136, 2010.)... 

Jahanshahi, M., A. Rahimpour, and M. Peyravi. 2010. Developing thin film composite poly (piperazine-amide) and poly( vinyl-alcohol) nanofiltration membranes. Desalination 257 129-136. 

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