Characterization of surface properties of nitrogen-enriched activated lignites by spectroscopic and chromatographic coupled with LSER modelling measurements

One investigated way to prepare selective adsorbents towards mixtures of volatile organic compounds (VOCs) is to modify lignite by nitrogen-enrichment. These chemically modified coals are prepared by condensation of urea with the lignite before the carbonization/activation steps. This study describes a set of analytical tools able to explain in term of surface composition and of quantitative molecular interaction parameters the evolution of the selective behavior of three adsorbents. For this purpose, the evolution of the surface chemistry and the selectivity with three percentage of burn-off of a nitrogen-enriched lignite is followed by infrared and X-ray photoelectron spectroscopies and gas chromatography (GC)/linear solvation energy relationship (LSER) method. Then, the selectivity of these materials towards two test-pairs of VOCs is discussed. This QSBR investigation reveals the complementarity of these methods linking composition data of the active carbons and their selective properties.