NMR investigation on the occurrence of Na species in porous carbons prepared by NaOH activation

Application studies of activated carbon derived from rice husks produced by chemical-thermal process—A review

“…The use of alkali hydroxides (special NaOH and KOH) as activating agents for the production of microporous activated carbons has attracted great interest due to the valuable properties of the materials produced by this process [47]. The most frequently reported results indicate the formation of alkali carbonate, hydrogen, and the alkaline metal, according to the overall reaction:…”

Characteristics of microporous/mesoporous carbons prepared from rice husk under base- and acid-treated conditions

“…Physical activation involves the carbonization of a precursor using a gaseous activating agent such as steam or CO 2 [5]. Chemical activation first mixes the precursor with a chemical activating agent such as phosphoric acid (H 3 PO 4 ), zinc chloride (ZnCl 2 ) or alkali hydroxides (NaOH and KOH) and then heats it in an inert gas [6][7][8][9]. A comparison of chemical activation with physical activation shows that chemical activation * Corresponding author.…”

A multiple-field 23Na NMR study of sodium species in porous carbons

“…This subject has been intensively studied in recent years using modern textural and spectroscopic techniques, as well as theoretical methods [1][2][3][4][5]. The presence of oxygenated surface Na groups in the porous network of carbon materials has been recently demonstrated by 23 Na NMR measurements in activated carbons prepared by reaction with NaOH [6]. Similar Na groups were detected also in raw coal samples naturally containing sodium in their mineral fraction [7,8].…”

“…After extensive washing with distilled water, which led to the removal of all carbonates and silicates, the material showed well-developed porosity, as revealed by nitrogen adsorption measurements. Further details about samples preparation and basic characterization of the activated samples can be found elsewhere [6,20].…”

“…After water and/or acid washing the carbonate is removed, leaving a porous structure and thus producing materials with increased surface area and microporous volume [9][10][11]. However, Na + ions remain bound to the carbon surface even after washing, in a disordered arrangement with chemical environments usually associated with oxygenated surface groups [6,8].…”