Professor Zhu Baoku from Zhejiang University "ACS Nano": A new type of PA nanomembrane is used for the high precision and high

It is reported that membranes that can be used to separate sub-nanometer-sized low/high valence ions need to have extremely high separation accuracy and selectivity.
Currently, this demand is often met by constructing well-designed ion-selective nanochannels in pressure-driven membranes.
The interfacial polymerization (IP) method, as the most mature and energy-saving defect-free polyamide (PA) membrane preparation technology, is often used to construct ion-selective nanochannels.
However, due to the polydispersity, the size of tens of nanometers, the poor interface compatibility with the PA matrix, and the lack of sufficient ionizable groups for traditional nanomaterials, it is difficult to construct ion selectivity with high permeability and high separation accuracy.
Nano channel.
To solve this problem, Professor Zhu Baoku from Zhejiang University and Professor Claus Hélix-Nielsen from the Danish University of Engineering and Technology introduced ionic polyamidoamine (PAMAM) dendrimers into PA membranes to prepare new PA membrane materials through interfacial polymerization.
The separation of sub-nano-sized ions with high precision, high efficiency and high stability is realized.
Here, the author also analyzed the ion screening/transport mechanism.
The work was published on "ACS Nano" with the title "Ionic Dendrimer Based Polyamide Membranes for Ion Separation".
? Figure 1 (a) Schematic diagram of the synthesis of ionic PAMAM dendrimers.
(b) Schematic diagram of the screening/transport mechanism of low- and high-valent ions through PA membranes (PA membranes without PAMAM dendrimers and PA membranes with PAMAM G5-NH2, PAMAM G5-TAC and PAMAM G5-PS, respectively , Expressed as PIP-only, G5NH2/PIP, G5-TAC/PIP and G5-PS/PIP).
Highlights of the article: 1.
The membrane contains internal (intramolecular voids) and external (interfacial voids between ionic PAMAM dendrimers and PA matrix) nanochannels, which can be used for the rapid transport of water molecules.
2.
The sub-10 nanometer size of the ionic PAMAM dendrimer and its gradient distribution in the PA nanofilm are the key factors for the successful formation of defect-free PA nanofilms.
figure 2 The cross-sectional transmission electron microscope characterization diagram of the PA membrane? 3.
The ionizable PAMAM dendrimer attaches the ionizable group to the outside of the nanochannel, which enhances the Donnan effect during ion screening/transmission and reduces the ion separation performance on the pore size.
Sensitivity to change.
4.
Compared with the current state-of-the-art membranes, the resulting ionic PAMAM dendrimer PA membrane has higher mono-salt selectivity, high efficiency, long-term stability and chemical cleaning resistance, and can be applied to various practical applications.
Application areas, such as water purification, healthcare, energy conversion and chemical industry.
? Figure 3 The field emission scanning electron microscope characterization diagram of the front and back morphology of the PA nano film and the schematic diagram of the PA film structure.