Characterization and comparison of two ligno-cellulosic substrates by 13C CP/MAS NMR, XPS, conventional pyrolysis and thermochemolysis

Abstract

Ligno-cellulosic substrates (LCSs) isolated from wheat straw and bran exhibit high complexing capacities and may have important applications for metal removal from industrial effluents. These two LCSs were examined in the present work by spectroscopic and pyrolytic methods (solid state cross polarization magic angle spinning (CP/MAS) (13)C NMR, XPS, conventional Curie pyrolysis (Cupy)/GC/MS, and TMAH thermochemolysis/GC/MS). This combined study highlighted the limitation of some of the above methods when applied to ligno-cellulosic materials and the resulting biases and the usefulness of TMAH thermochemolysis. A large difference in composition was observed between bran- and straw-LCS due to a much higher contribution of alkyl moieties in the former. These moieties correspond to fatty acids esterified to the ligno-cellulosic macromolecular structure and such carboxylic functions should play an important role for metal complexation.

Use of a NICA–Donnan approach for analysis of proton binding to a lignocellulosic substrate extracted from wheat bran

“…These data are in accordance with the presence of an intense band at 30 ppm in the 13 C NMR spectrum, which was attributed to non-substituted alkyl (e.g. lipids), with IR bands at 2920 and 2850 cm -1 , and with pyrolysis GC-MS studies [26]. Atomic O/C ratios deduced from elemental (0.58) and XPS analysis (0.41) are slightly different, possibly because of preferential arrangement of the oxidized groups inside the solid.…”

“…Q max1 exceeded Q max2 , which was somewhat surprising because lignin is rich in phenol groups and contains few carboxyl functions [31]. Carboxyl functions might also originate from the presence of fatty acids [26]. The relatively high value of logK -1 , compared with those found by other authors [6,18,32] for humic substances, is consistent with the presence of fatty acids.…”

Gone or just out of sight? The apparent disappearance of aromatic litter components in soils

“…The common approach used to quantify the relative contribution of different C types to SOM is to integrate and compare peak areas of different spectra regions without considering any non-proportional signal responses (e.g., Kögel-Knabner, 2002). It has been shown that this approach underestimates lignin vs. cellulose in ligno-cellulose isolated from wheat (Gauthier et al, 2002).…”

Biosorption of Cu(II) and Zn(II) onto a lignocellulosic substrate extracted from wheat bran

“…Nowadays, it has no real application, which constitutes a serious handicap for the rentability of the industrial treatment of wheat bran. Previous characterizations had revealed that the structure of the lignocellulosic substrate is composed of lignin and cellulose as its major constituents and a non-negligible proportion of fatty acid (Gauthier et al 2002). Lignin and fatty acids bear functional groups such as alcohol, ketone, and carboxylic groups, which can be involved in complexation reactions with metallic cations.…”