Surface characterization of chitosan and cellulose-derived porous carbons with K2CO3 activation and its application to water and ethene adsorption

Porous carbons were prepared by the K2CO3 activation of polysaccharides, cellulose and chitosan, to develop an adsorbent that can be used to keep fruits and vegetables fresh during long-distance transportations. Their water, ethene, and carbon dioxide adsorption behaviors and pore properties (i.e., pore surface area and volume and surface functional groups) were investigated using a volumetric adsorption apparatus and Boehm titration method. The time courses of ethene adsorption by the carbons at room temperature were measured through gas chromatography. Chitosan-derived carbons did not have only oxygen-containing functional groups but also nitrogen-containing ones that provided the carbon surface with a higher affinity to water molecules than cellulose-derived carbons. These functional groups significantly decomposed at 900 °C and developed fine pores that were not detectable by nitrogen adsorption measurement. The K2CO3 activation provided ultramicropores suitable for ethene adsorption than carbon dioxide one to the carbons. The presented carbons indicated a high ethene-removal rate comparable to that of commercially available ethene adsorbent.