Modification of the Textural Properties of Chitosan to Obtain Biochars for CO2-Capture Processes

Abstract

Three chitosans with different morphologies have been used (commercial chitosan powder, chitosan in film form and chitosan in globular form synthesized by the freeze-dried method) for the synthesis of biochars. The pyrolytic treatment has revealed that the biochar synthesized from the chitosan formed by the freeze-dried method reaches the highest CO2-adsorption capacity (4.11 mmol/g at 0 °C and a pressure of 1 bar) due to this adsorbent is highly microporous. Moreover, this biochar is more resistant to the pyrolytic treatment in comparison to the biochars obtained from the commercial chitosan and chitosan in the form of film. CO2-adsorption studies at different temperatures have also shown that the adsorption capacity diminishes as the adsorption temperature increases, thus suggesting that the adsorption takes place by a physical process.

Valorization of wipe wastes for the synthesis of microporous carbons and their application in CO2 capture, gas separation and H2-storage

“…3 ), the textural properties are quite sensitive: higher pyrolysis temperatures lead to an increase in microporosity and the equivalent surface area. These results agree with those reported for other biochars obtained from cellulose residues [ 6 , 30 ] where the thermal treatment generates a physical activation forming microcavities in the biochars, which may have great potential to adsorb small molecules such as CO 2 .…”

“…From these data, it is expected that the formation of an ordered graphite should require a much higher pyrolysis temperature. However, the application of a higher temperature can cause a collapse of the porous structure [ 29 , 30 ], diminishing its microporosity so its application in gas adsorption processes would not be beneficial. On the other hand, a broad band located between 2300 and 3000 cm −1 is also observed.…”

“…The analysis of the W-500 sample shows a main peak located about 126 cm −1 as well as a shoulder at 140 cm −1 [ 16 , 32 ]. These bands are ascribed to C-species with sp 2 hybridization [ 16 , 30 ]. The set of bands with maxima at about 40 cm −1 is assigned to the existence of aliphatic carbons, while the set of bands located at about 220 cm −1 are attributed to the presence of carbonyl bands [ 33 ].…”

“…In a previous study, biochars synthesized from agricultural cellulosic wastes (cotton, wheat or linen) have shown an adsorption capacity of 2.5 mmol/g at a pressure of 760 mm Hg and a temperature of 25 °C [ 6 ]. Biochars obtained from chitosan, whereby a hydroxyl group is substituted by an amine group, reached a CO 2 -adsorption capacity between 1.8 and 2.0 mmol/g, except for those materials prepared by freeze-drying method where a higher CO 2 -adsorption capacity was observed due to the higher microporosity of the latter materials [ 30 ]. On the other hand, biochars synthesized from fruit shells such as coconut or almond achieve a CO 2 -adsorption uptake between 2.5 and 2.7 at 760 mm of Hg at 25 °C [ [36] , [37] , [38] ].…”

Biopolymeric Nanocomposites for CO2 Capture

“…Limited solubility in water at neutral pH, requiring acidic conditions for dissolution [102] Biocompatible, biodegradable, and non-toxic Mechanical properties possibly affected by moisture absorption [99] Antimicrobial properties Challenging solution processing due to high viscosity [92] Forms films, gels, and fibers with excellent mechanical properties Sensitive to enzymatic degradation by chitinases [107][108][109] Can be chemically tailored to introduce specific functionalities [107,109]…”