Elemental analysis, FTIR and 13C-NMR of humic acids from sewage sludge composting

Abstract

The effect of composting on the chemical structure of humic acids extracted from a mixture of sewage sludge and straw at different times of treatment was investigated by elemental analysis, Fourier transform infrared and carbon 13-nuclear magnetic resonance. The starting material was composed of a heterogeneous mixture of etherified aromatic structures bearing peripheral long-chain lipidic, peptidic and carbohydrate structures. The results show a decrease in aliphatic compounds during composting, and an increase in aromatic structures-mainly those substituted by functional groups such as phenolic, methoxylic and carboxylic groups. These changes support the preferential oxidation of readily accessible moieties such as aliphatic side chains of lipidic and peptidic structures, leading to the production of highly functionalized aromatic macromolecules. The latter compounds are resistant to microbial degradation and are therefore preserved as part of the newly-formed humic acid structures. sewage sludge / composting / humic acids / chemical structure / humification Résumé-Caractérisation des acides humiques extraits au cours du compostage de boues résiduaires par analyse élémentaire, IRTF et 13 C-RMN. L'action du processus de compostage sur la structure chimique des acides humiques extraits de mélange de boues résiduaires de stations d'épuration et de paille a été suivie à différents stades du traitement par analyse élémentaire, spectroscopies infrarouge à transformée de Fourrier et résonance magnétique nucléaire du carbon 13. Le matériel initial est composé d'un mélange hétérogène de structures aromatiques éthérifiées sur lesquelles sont liées de longues chaînes lipidiques et des structures peptidiques et carbohydrates. Les résultats obtenus montrent une diminution, durant le processus de compostage, des composés aliphatiques, avec une augmentation relative des structures aromatiques principalement celles substituées par des groupements fonctionnels tels que phénols, méthoxyles, carboxyles. Ces transformations mettent en évidence l'oxydation préférentielle des composés facilement accessibles, comme, par exemple, les chaînes aliphatiques périphériques des structures lipidiques et peptidiques, ce qui conduit à une production de structures aromatiques riches en groupements fonctionnels. Ces dernières sont résistantes à la décomposition microbienne et sont donc préservées pour constituer une partie de la structure d'acides humiques néoformés. boues résiduaires / compostage / acides humiques / structure chimique / humification

Sorption of heavy metals from aqueous solution by dehydrated powders of aquatic plants

“…Plant cells are constructed by polysaccharide, protein, lipid composition, containing carboxyl, carbonyl, hydroxyl, amino and other functional groups which can bind with metal ions (Macfie and Welbourn 2000;Amir et al 2004). The samples of the two aquatic plants had broad absorption peaks at 3,300-3,400 cm -1 , which mainly represented -OH and -NH stretching vibration of carbohydrate, cell wall material and proteins.…”

Genesis of structural features of humic acids from the sediments of a high productive coastal zone

“…In the 145-160 ppm region, a less-resolved peak at 152 ppm is mainly an indicative of phenolic carbon, aromatic ethers and or N-substituted aromatic carbon (Amir et al, 2004;Liang et al, 1996). Remarkably, the contribution of substituted aromatic moieties to HAs structure is only near a fourth of (7.04%) the unsubstituted aromatic signals around 96-145 ppm.…”

“…Fourier transfer infrared spectroscopy has been widely used for gross characterization of humic acids since the groups (phenolic and alcoholic hydroxyls, aromatic and aliphatic carboxyls and carbonyls, aliphatic C-H, and amides) that are typical to HAs (Amir et al, 2004;Sierra et al, 2004;Stevenson, 1994) can provide valuable information on the structural and functional properties. The experimental FT-IR frequencies of HAs isolated from mudbank sediments and their assignments are given in Table 2.…”

“…Less intensive bands between 1350-1460 cm -1 assign to several chemical groups typical of OH deformation and CO stretching of phenolic OH, C-H deformation of CH 3 and CH 2 groups and C-O-O - (Amir et al, 2004;Stevenson, 1994). Existence of ionized carboxylic groups is indicated by the COO -antisymmetic stretching absorption (1454 cm -1 ) and absence of H-bonded carboxylic O-H stretching broad shoulder absorption bands at 2550 cm -1 .…”

“…Substituted aliphatic carbons usually exhibit high resonance, and the peak around 55 ppm is characteristic of N-alkyl or methoxyl groups of aromatic esters (Amir et al, 2004;Mahieu et al, 2002;Piccolo et al, 1990). Several studies (Hatcher et al, 1980;Malcolm et al, 1989; have assigned the peak at 55 ppm to methoxy groups associated with lignin and lignin-like products, and this structural characteristics make them to highly resistant to microbial degradation compared to other alkyl groups (Amir et al, 2004). The persistence of a peak at 57 ppm in Calluna vulgaris litter after a prolonged period of natural degradation of 23 years was reported by Huang et al (1998).…”