Neutron Imaging of Paramagnetic Ions: Electrosorption by Carbon Aerogels and Macroscopic Magnetic Forces

TL;DR

This study demonstrates the use of neutron imaging to observe electrosorption of paramagnetic Gd$^{3+}$ ions in carbon aerogels and explores magnetic field effects on ion confinement and desalination.

Contribution

It introduces a novel neutron imaging approach to study ion electrosorption and shows how magnetic forces influence ion behavior in porous electrodes.

Findings

Neutron imaging visualizes Gd$^{3+}$ ion uptake in aerogels.

Magnetic field gradients induce convective flow and ion confinement.

Method enables desalination of paramagnetic ions from solutions.

Abstract

The electrosorption of Gd$^{3+}$ ions from aqueous 70 mM Gd(NO$_3$)$_3$ solution in monolithic carbon aerogel electrodes was recorded by dynamic neutron imaging. The aerogels have a bimodal pore size distribution consisting of macropores and mesopores centered at 115 nm and 15 nm, respectively. After the uptake of Gd$^{3+}$ ions by the negatively charged surface of the porous structure, an inhomogeneous magnetic field was applied to the system of discharging electrodes. This led to a convective flow and confinement of Gd(NO$_3$)$_3$ solution in the magnetic field gradient. Thus, a way to desalt and capture paramagnetic ions from an initially homogeneous solution is established.