Alkaline metal ion permeation through amorphous carbon membranes with varying degree of graphitization

Abstract

Amorphous carbons are prospective materials for the selective separation of alkaline metals ions due to their wide range degree of organization. To demonstrate so, a study of the drift of ion alkaline ion (H+, Li+, Na+, and K+) at different applied electric fields (0.8–3 V) for a series of amorphous carbon with different degrees of organization must be performed. Amorphous carbon membranes were synthesized from hyper cross-linked polymer precursors poly(acrylic acid) hyper cross-linked with polyvinyl alcohol. The amorphous carbon membranes were synthesized at pyrolysis temperatures of 400, 500, 600, and 700 °C. Pyrolysis temperature can cause changes in the structure of the monolithic membranes, such as changes in graphitization degree, hydrophobicity, and textural features, like pore volume and pore size. Hydrophobicity degree has also increased with the increase of pyrolysis temperature. Permeability of ions across membranes was assessed using ionic conductivity, which was calculated for chronoamperometric measurements. Besides, the influence of the electric field on the permeation of the ions was evaluated. Based on the results, amorphous carbon membranes can show great performance in lithium separation from other alkaline metal ions. In the best case, the mobility of Li+ becomes two times faster than the mobility of K+ and Na+.