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(129)Xe NMR studies of morphology and accessibility in porous biochar from almond shells

M. Farina, M. Mauri, G. Patriarca, R. Simonutti, K. T. Klasson, H. N. Cheng
RSC Advances 2016 v.6 no.105 pp. 103803-103810
adsorption, almond shells, biochar, byproducts, carbon, diffusivity, filtration, heat treatment, nitrogen, nuclear magnetic resonance spectroscopy, porous media, scanning electron microscopy, xenon
Micro and mesoporous materials are often used in catalysis, purification, composite filler, and other applications. Almond shell is an important agricultural byproduct that can be transformed to microporous and mesoporous carbon. In this work, we produced biochar from almond shell using a thermal treatment procedure in an inert atmosphere and characterized the pores with nitrogen adsorption, environmental SEM, and (129)Xe NMR. The latter technique differentiates adsorbed and nonadsorbed xenon and permits the correlation of different processing conditions with xenon adsorption and diffusivity. The relevance of removing the ash produced during the charring process has been included in the study. Moreover, the xenon exchange between meso- and micro-pores has been directly observed by (129)Xe NMR, demonstrating that after ash removal by water the materials have high accessibility of the pores by external fluids, thus increasing the usefulness as filtration or adsorption material.