Sebbahi S.,Materials and Environment Laboratory |
El Fakir L.,Materials and Environment Laboratory |
Rghioui L.,Physicochemical team of condensed Materials |
El Hajji A.,Materials and Environment Laboratory |
And 3 more authors.
Journal of Materials and Environmental Science
This work deals with the spectroscopic characterization by attenuated total reflection (ATR) of lignin and derivative chars. The char is obtained by carbonizing the lignin. The char is then either directly activated or treated in air at 140°C and 245°C before being activated. The carbonization is carried out under nitrogen at 600°C and the activation under CO2 at 700°C. The effect of the different heat treatments on the surface functional groups have been examined. The oxygenated groups initially present in lignin are the aliphatic and cyclic ether, carbonyl, methoxyl, phenolic hydroxyl, primary and secondary aliphatic hydroxyl groups. These groups undergo a substantial loss during the carbonization except the cyclic ether group. Carbonization leads to a decrease in aliphaticity and an increase in aromaticity and the development of a thermoplastic phase by crazing. The band intensity of the various aforementioned oxygenated groups increases during the pre-treatment of coal by air. The pre-treatment in air also leads to the reformation of the carbonyl group. The presence of such groups and the increase in the pre-treatment temperature is reflected by a decrease of the thermoplastic character of the material. The carbonyl groups are formed during the activation of the raw char while they disappear during the activation of the pre-treated char in air before activation. Images taken by transmission electron microscopy (TEM) show the development of the microporosity in the first case and the plastic phase in the latter. Source