Isolation and Characterization of Gramineae and Fabaceae Soda Lignins.
Some agricultural residues such as wheat or barley straw, as well as certain fast-growing plants likeLeucaena leucocephalaandChamaecytisus proliferus, could be used as raw materials for the paper industry as an alternative to traditional plants (eucalyptus, pine, etc.). In the present study, four types of lignin obtained from the spent liquors produced by the pulping processes using the abovementioned feedstocks were isolated and characterized. Lignin samples were acquired through an acid precipitation from these spent liquors. The characterization of the precipitated lignin samples were performed using a Fourier transform infrared spectroscopy (FT-IR) and both liquid- and solid-state nuclear magnetic resonance spectroscopy (NMR) to analyse the chemical structure, and thermogravimetric analysis (TGA) for determining the thermal properties. Additionally, chemical composition of lignin fractions was also measured. Even though they were of different botanical origin, all the studied samples except for wheat straw lignin had a similar chemical composition and thermal behaviour, and identical chemical structure. Wheat straw lignin showed a greater amount of Klason lignin and lower carbohydrate content. Furthermore, this lignin sample showed a higher thermal stability and significantly different cross-peak patterns in the 2D-NMR experiments. The molecular structures corresponding top-coumarate (PCA), ferulate (FA) and cinnamyl aldehyde end-groups (J) were only detected in wheat isolated lignin.
Chemical Engineering Department, Faculty of Science, University of Córdoba, Building Marie-Curie, Campus of Rabanales, 14014 Córdoba, Spain. z42doroj@uco.es.
Juan
J
Domínguez-Robles
Chemical Engineering Department, Faculty of Science, University of Córdoba, Building Marie-Curie, Campus of Rabanales, 14014 Córdoba, Spain. q92saser@uco.es.
Rafael
R
Sánchez
Chemical Engineering Department, Faculty of Science, University of Córdoba, Building Marie-Curie, Campus of Rabanales, 14014 Córdoba, Spain. a02esvie@uco.es.
Eduardo
E
Espinosa
Centro Interdipartimentale di Ricerca sulla Risonanza Magnetica Nucleare per l'Ambiente, l'Agro-Alimentare ed i Nuovi Materiali (CERMANU), Via Università 100, 80055 Portici, Italy. davide.savy@unina.it.
Davide
D
Savy
Centro Interdipartimentale di Ricerca sulla Risonanza Magnetica Nucleare per l'Ambiente, l'Agro-Alimentare ed i Nuovi Materiali (CERMANU), Via Università 100, 80055 Portici, Italy. pierluigi.mazzei@unina.it.
Pierluigi
P
Mazzei
Centro Interdipartimentale di Ricerca sulla Risonanza Magnetica Nucleare per l'Ambiente, l'Agro-Alimentare ed i Nuovi Materiali (CERMANU), Via Università 100, 80055 Portici, Italy. alessandro.piccolo@unina.it.
Alessandro
A
Piccolo
Chemical Engineering Department, Faculty of Science, University of Córdoba, Building Marie-Curie, Campus of Rabanales, 14014 Córdoba, Spain. a.rodriguez@uco.es.
Alejandro
A
Rodríguez
D007887:Fabaceae / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry* / Q000302:isolation & purification*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D064209:Phytochemicals / Q000737:chemistry / Q000302:isolation & purification; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification; D006109:Poaceae / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013818:Thermogravimetry
D064209:Phytochemicals; D010936:Plant Extracts; D008031:Lignin
agricultural residues; alkaline extraction; physico-chemical properties; soda lignin; spent liquors; structural elucidation