An IR study to investigate the structural relationship of lignin-like matter and lignosulphonates obtained from animal–vegetable wastes

Lignin-like matter (I) from rice hull residues and humin-like matter and (II) from rice hull-fecal matter compost yield, upon sulphonation by SO3, the lignosulphonates III and IV, respectively. The solid state IR spectra of I and II are analysed and interpreted based on the functional groups content values obtained for III and IV by solution NMR spectroscopy. IR absorbance values at five selected wavelengths for I and II correlate well with functional groups content values for III and IV according to Beer’s law. It is concluded that the sulphonated derivatives, aside from the −SO3H content, reflect well the chemical structure of the parent materials. No side reaction of I or II with SO3, other than C sulphonation, is apparent. The above correlation may be useful for waste management purposes.