Efficient purification processes that separate impurities from air and water are necessary to sustain life on Earth. To this end, carbon materials have long been used for deodorizing, separating, and removing harmful anion impurities by adsorption. So far, the detailed mechanism by which carbon purifies water has remained a mystery. Additionally, it is not known if the aqueous solution adsorbed on the carbon material is acidic, alkaline, or neutral.
source https://www.lifetechnology.com/blogs/life-technology-science-news/acidic-layer-in-single-walled-carbon-nanotubes-facilitates-confinement-of-anion-impurities
