Research progress in ion selective nano-ions channels for water treatment

Abstract

Selective ion removal technology becomes an emerging water treatment method for nutrient recovery in wastewater, water softening, extraction of key minerals from brine, and utilization of industrial wastewater. Biological ion channels have efficient single ion selectivity,and both nanoscale and sub-nanoscale ion channels have been successfully prepared to simulate biological ion channels in the past two decades. This paper mainly introduces the conceptual and theoretical framework of natural ion channel, reviews the current materials and preparation methods of nano ion channel membranes, and summarizes the selectivity of nano ion channels for typical water pollution ions as well as their advantages, disadvantages and research directions. The difference of ion size, charge and hydrophilicity between univalent and multivalent ions can be measured, so the basis for constructing ion selective channels is the adjustment of channel size, surface charge and hydrophilicity. Whereas the size difference between univalent ions is not significant, specific ion binding interactions are introduced into sub 1 nm channels to achieve single ion selectivity. This paper analyzes how to construct an ideal nano ion channel, and proposes that the selectivity of target ions usually depends on the physical and chemical properties of the channel, including pore size, channel dimension, surface charge, functional sites and channel wall polarity. By changing or optimizing these factors, the selective separation of target ions by membrane can be improved. Finally, the prospect of combining membrane technology with nano ion channel for ion selective removal is presented.

Keywords

• nanoscale ion channels
• ion selective membrane
• membrane treatment technology
• solute-solute separation