Microwave pyrolysis of pecan nut shell and thermogravimetric, textural and spectroscopic characterization of carbonaceous products

In the present work, the pyrolysis of pecan nut shell was studied using microwave technology at different input power and exposure time. The carbonaceous products were characterized using elemental analysis, potentiometric titration, thermogravimetric analysis, N2 adsorption isotherms at −196 °C and FT-IR spectroscopy. The characteristics of microwave carbonaceous products were compared with carbons prepared by conventional heating and commercial carbons and finally, the interaction of textile dyes with the carbonaceous materials was studied. The results are indicating that it is possible to obtain carbonaceous materials with similar textural parameters in conventional and microwave systems, but for microwave heating the processing times are short (3 min). Also, the exposure time of 2 min of microwave are not enough for the complete depolymerization of the lignocellulosic matrix of the pecan nut shell and significant amount of cellulose and hemicelluloses remain in char after microwave treatment. Finally, all the carbons obtained by microwave heating are microporous materials with a high number of basic groups on their surface and the high molecular size of dyes is controlling the adsorption on these materials