Influences of hydrophobic tail length tuning of linear aliphatic di-cation functioned anion exchange membrane on electrodialysis desalination

Abstract

We successfully prepared a series of highly ionized anion exchange membranes (AEMs) with the equivalent modifications of the linear aliphatic di-cation appending different flexible and hydrophobic alkyl tails (named QPT-Cn, n is the number of carbon atoms in the tails). Due to the synergistic interaction between the domain-limiting of the intermediate unit ethyl group of the di-cation and the hydrophobicity of the tails, QPT-Cn membranes are endowed with different microphase separation structures and exhibit various mechanical and electrochemical properties. The well complement of the C12 tails and the dense di-cations offer QPT-C12 the well-tuned microphase structure, manifesting better mechanical and electrochemical properties at the wet state. Owing to the greatly improve electrochemical properties, QPT-C12 shows the comprehensive ED performances significantly better than those of commercial AMX with an increase of 7.97 % in current efficiency (η), a reduction of 21.70 % in energy consumption, and η remaining rates of more than 98.76 %. The above results confirm that the complementary enhancement strategy of combining appropriately sized hydrophobic alkyl tails with dense linear aliphatic di-cation is an effective method to develop the advanced ED AEMs. The excellent ED performances of QPT-C12 are of competitive in the ED desalination applications.