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An EELS‐based study of the effects of pyrolysis on natural carbonaceous materials used for activated charcoal preparation
Author(s) -
JeanneRose V.,
Golabkan V.,
Mansot J. L.,
Largitte L.,
Césaire T.,
Ouensanga A.
Publication year - 2003
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.2003.01170.x
Subject(s) - pyrolysis , charcoal , carbon fibers , chemistry , bagasse , activated carbon , nitrogen , chemical engineering , adsorption , materials science , organic chemistry , composite material , pulp and paper industry , composite number , engineering
Summary Electron energy‐loss spectroscopy (EELS) has been used to characterize the electronic structure of charcoal phases at the nanoscale, thus demonstrating that the technique can be applied to environmental science. Activated charcoal is extensively used to remove pollutants from liquid and gaseous sewage. It is mainly obtained by activation of coke or charcoal produced from ligneous precursors. The present study concerns the use of by‐products of local Caribbean agriculture, such as sugar cane bagasse, fruit stones and seeds, for use as activated charcoal precursors. Charcoal phases are prepared by high‐temperature pyrolysis of lignocellulosic raw materials under a nitrogen gas flow. With the aim of optimizing the pyrolysis temperature and duration and oxygen content, the concentration of carbon sp 2 hybridized chemical bonds and structural ordering have been followed by EELS for different treatment temperatures. To quantify the carbon sp 2 content, near edge structure (NES) at the carbon K edge has been measured to determine the strength of π → π* and 1s → π* transitions. Three precursors of plant origin, shells of Terminalia catappa and Acrocomia karukerana and seeds of Psidium guajava , with the pyrolysis temperatures between 600 and 900 °C, were investigated. The fraction of carbon sp 2 bonding is found to increase when the temperature rises from 600 °C to the range 700–750 °C and becomes stable at higher temperatures. For temperatures in excess of 700 °C, structural ordering probably occurs and well‐defined 1s → σ* NES is present, whose intensity increases with increasing preparation temperature. For the highest temperature of around 900 °C, the structure of the final product is less well organized than graphitized carbon but a few per cent of a highly ordered phase is found.