Cmbf. Maia et al., Spectroscopic characterization of organic structures and organic-inorganicinteractions in paper mill sludge, ACT HYDR HY, 28(7), 2001, pp. 372-377
The organic composition and organic-inorganic interaction in paper mill slu
dge (PS) solvent extracts (hexane, ethyl acetate, acetone and ethanol) and
humic fractions, humic acid (HA) and humin (HU) were studied by electron pa
ramagnetic resonance spectroscopy (EPR), proton and carbon-13 nuclear magne
tic resonance spectroscopy (H-1 NMR; C-13 NMR), Fourier-transformed infrare
d spectroscopy (FTIR), and ultraviolet-visible spectroscopy (UV-vis). The s
trategy of fractionating the PS, sequentially, with organic solvents of inc
reasing polarity is a reliable analytical procedure for humic substance sam
ple separation because it results in more purified fractions. FTIR, H-1 NMR
and C-13 NMR results showed that hexane extract consisted mainly of alipha
tic hydrocarbon structures. Their contents in the extracts decreased as the
polarity of the extracting solvent increased and the content of oxygen fun
ctional groups increased. Carboxylic and carboxylate functional groups were
found in the acetone extract, and ester and ether functions were predomina
ntly found in the ethanol extract. EPR spectra revealed some Fe3+ complexes
with rhombic structure (g(1) = 4.3; g(2) = 9.0) in the humic fractions and
in all solvent extracts, except hexane. Quasi-octahedral Fe3+ complexes (g
= 2.3; DeltaH(pp) less than or equal to 400 G) were found in the HU fracti
on and in the acetone extract. The organic free radical content in the HA f
raction was higher than the non-fractionated PS sample and HU fraction.