Criterious preparation and characterization of earthworm-composts in view of animal waste recycling. Part I. Correlation between chemical, thermal and FTIR spectroscopic analyses of four humic acids from earthworm-composted animal manure

Criterious Preparation and Characterization of Earthworm-composts in View of Animal Waste Recycling: Part II. A Synergistic Utilization of EPR and ¹H NMR Spectroscopies on the Characterization of Humic Acids from Vermicomposts

“…The RAHAr sample spectrum was simulated starting from the assumption that the experimental spectrum is a sum of the spectra of Cu-4O and Cu-4N complexes, where the Cu-4O complex is present in a larger concentration than the Cu-4N complex ( Figure 5). This hypothesis is corroborated by the attributions of ν as (OCO) bands of carboxylate groups interacting with metals at ~ 1645 cm -1 in the FTIR spectra presented in part I of this study 3 10 atoms in the equatorial plane of an axial symmetry were more evident in the experimental spectra than the same parameters values for Cu-4N complexes. This fact can be indicative of the higher concentration of Cu-4O than Cu-4N complexes in the samples as considered above.…”

“…The doublet at δ 6.59 was tentatively assigned to aromatic hydrogens or biphenolic groups, although resonance of aromatic hydrogens of rings substituted with ortho or para amine groups can also appear in this region. Other weaker signals in the δ 7.1 to 6.2 range, more abundant in the COHA 1 H-NMR spectrum, can be due to the resonance of pyrrolic or indolic type heterocyclic hydrogens, in agreement with the high nitrogen content of the samples 3 . The presence of pyrrolic hydrogens is in agreement with the existence of porphyrin structures, as suggested by the EPR parameters for the Fe 3+ and Cu 2+ 16.0 Hz), these signals can be assigned to the resonance of trans hydrogens of conjugated double bonds of groups like C(=O)R (R = alkyl, ether), present in the pyrrolic structure 36 .…”

“…VC preparations, isolation of HA, chemical analysis and Mn, Fe, Co, and Cu determinations using atomic absorption spectroscopy were previously described 3 . Extraction of HA using aqueous alkaline solution and acid precipitation was carried out only once, in order to prevent loss or modification of important organic constituents of the samples, or excessive hydrolysis of metal ions.…”

“…In a previous study 3 , thermal analysis, chemical and spectroscopic (FTIR and visible) results indicate a high nitrogen content and low carboxylic acidity, as well as a high degree of conjugated aliphatic and/or substituted or condensed aromatic structures for the humic acids (HA) extracted from these VC. The existence of peptide chains and N-heterocycles in the samples was proposed, but it could not be confirmed, and a differentiation between aliphatic conjugation and aromaticity degree was not possible.…”

“…It occurs as a result of the growing food industry activities in that region. Very recently, we proposed to study the criterious preparation and characterization of sheep (SH), cow (CO), goat (GO) and rabbit (RA) vermicompost manures, using the earthworm Eisenia foetida, forming organic fertilizers for soil amendment 3 . Each corresponding vermicompost (VC), characterized as much as possible, would be recommended for amending specific type of degraded soils, already existing in southern Brazil.…”