1,721,026 research outputs found
Adsorption and degradation of triasulfuron on homoionic montmorillonites
No full textThe adsorption and degradation of the herbicide triasulfuron [2-(2-chloroethoxy)-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide] (CMMT) on homoionic Fe3+-, Al3+-, Ca2+-, or Na+-exchanged montmorillonite in aqueous medium were studied. Ca- and Na-exchanged montmorillonite were ineffective in the adsorption and degradation of triasulfuron. The adsorption on Fe- and Al-exchanged montmorillonite was rapid, and equilibrium was attained after 5 min. Degradation of the herbicide was slow and the type of the degradation products depended on the nature of the exchangeable cations. In the presence of Fe3+-rich montmorillonite, the metabolites 2-(2-chloroethoxy)benzenesulfonamide (CBSA), 2-(2-chloroerhoxy)-N-[[(4-hydroxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide (CHMT), and 1-[2-(2-chtoroethoxy)benzene-1-sulfonyl]-7-acetyl-triuret (CBAT) were the only identified products, whereas 2-amino-3-methoxy-6-methyltriazine (AMMT), CBSA, CHMT, and CBAT were the primary metabolites fur the Al3+-rich montmorillonite. A Fourier transform infrared (FT-TR) study of montmorillonite samples after the interaction with triasulfuron in organic solution suggests that the hydrolysis mechanism involves the adsorption of the herbicide on the 2:1 layers
Adsorption and desorption of triasulfuron by soil
No full textThe adsorption and desorption of the herbicide triasulfuron [2-(2-chloroethoxy)-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide] by three soils, soil organic matter (H+ and Ca2+-saturated), and an amorphous iron oxide were studied. Adsorption isotherms conformed to the Freundlich equation. It was found that pH is the main factor influencing the adsorption in all of the systems. Indeed, the adsorption on soils was negatively correlated with pH. The highest level of adsorption was measured on soils with low pH and high organic carbon content. Moreover, it was found that humic acid is more effective in the adsorption compared with calcium humate (the pH values of the suspensions being 3.5 and 6, respectively). Experiments on amorphous iron oxide confirmed the pH dependence. Desorption was hysteretic on soils having high organic carbon content
STRUCTURAL AND SPECTROSCOPIC ANALYSIS OFBALTIC AMBER
No full textAmber is a fossilized tree resin appreciated since antiquity for its unique aesthetic qualities in the production of small decorative objects. Its chemical composition is strongly related to the origin of the resin, but Baltic amber is synonymous with the chemical name butanedioic acid (C4H6O4), more commonly known as succinic acid (Beck, 1986). C4H6O4 is also a natural constituent of plant and animal tissues which has been used in Europe as a natural antibiotic and general curative for centuries. It has been stated, for example, that succinic acid isolated from Baltic amber can stimulate human and plant organisms, and can contribute to an increase in the yield of some cultivated plants (Matuszewska and John, 2004). In the literature it was reported that not all Baltic ambers contain succinic acid (Matuszewska and John, 2004).
The primary goal of this study was to characterize succinite, a Baltic amber characterized by levels of succinic acid ranging from 3 to 8%. The selected succinite samples - (Palmnicken, Baltic Coast, and Prussia amber) consisted of opaque pale brown to nearly dark red-brown rounded masses of this amber variety. For comparative purposes, our tests were also carried out on a number of reference materials, including amber from Danzig Region, Poland, and commercial specimens. Standard gemological methods were used to document the samples’ colour, hardness, refractive indices, fluorescence to long and short-wave ultraviolet radiation, and inclusions. X-ray powders patterns were collected before and after adsorption on a Bruker D8 Advance diffractometer equipped with SOL-X detector. Thermal analyses (TG and DTA) were performed in air up to 900°C at 10°C min-1. According to Shashoua et al. (2006), IR techniques have been shown to identify the provenance of the amber beyond the basic Baltic/ non-Baltic distinction. In this study, infrared spectra collected on a Thermo Electron Corporation FT Nicolet 5700 Spectrometer FTIR spectra revealed characteristic spectral differences that make it possible to positively identify Baltic amber.
Beck C. W. (1986). Spectroscopic Investigations of Amber. Applied Spectroscopy Reviews, 22, 57-110.
Matuszewska A., Shashoua J. A. (2004). Some possibilities of thin layer chromatographic analysis of the molecular phase of Baltic amber and other natural resins. Acta Chromatographica, 14, 82-91.
Shashoua Y., Degn Berthelsen M.-B. L. & Nielsen O. F. (2006). Raman and ATR-FTIR spectroscopies applied to the conservation of archaeological Baltic amber. Journal of Raman Spectroscopy, 37, 1221–1227
Hydrolysis and adsorption of cyhalofop-butyl and cyhalofop-acid on soil colloids
No full textA study was undertaken to investigate the stability of cyhalofop-butyl (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]butylpropanoate (CyB), an aryloxyphenoxy-propionic herbicide, at different pH values. The hydrolysis of CyB was faster in nonsterile than in sterile water. In sterile medium, CyB degraded only to (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid (CyA), whereas in nonsterile water, also the metabolites (2R)-2-[4-(4-carbamoyl-2-fluorophenoxy)phenoxy]propanoic acid (CyAA) and (2R)-2-[4-(4carboxyl-2-fluorophenoxy)phenoxy]propanoic acid (CyD) were detected. The adsorption of CyB onto clays, iron oxide, and dissolved organic matter (DOM), using a batch equilibrium method, was also studied. A lipophilic bond is responsible for CyB adsorption on DOM. CyB was adsorbed on Fe-III- and Ca-clays through hydrogen bonding between the carbonyl oxygen and water surrounding the exchangeable cations. In the interlayer of K-clay, CyB was hydrolyzed to CyA, which remained adsorbed therein as a monomer. The acid CyA was adsorbed only by the Fe-oxide through complexation. The CyA-Fe-oxide complex was stable and did not undergo degradation
Zeolites for sustainable agricolture: furfural encapsulation and controlled release in ZSM-5
No full textWidespread application of synthetic nematicide on the crops aimed to fight nematode parasite could be a threat to human health and overall environmental quality. Most of synthetic nematicides have been withdrawn from the market, due to their toxicity. This had led to looking for a non-chemical alternative which must be equally effective and eco-friendly, derived from natural materials, aiming to reduce synthetic pesticide input. Recently, it has been proved that an aldehyde, namely furfural, is effective against Meloidogyne sp. (a dangerous specie of nematode) [1]. This latter biomolecule can be easily extracted from Melia azedarach fruits, a tree growing in tropical and subtropical areas.
This work is part of a wider multidisciplinary project, which aims to develop an innovative, easy to produce, and eco-sustainable nematicidal formulate by combining a botanical extract of known nematicidal activity with environmentally friendly porous materials. Specifically, an aldehyde - namely, furfural and salicylaldehyde, which is known for its occurrence in Melia azedarach (MA) tree and mainly responsible for the plant defense ability against nematodes - wase encapsulated into microporous alumina-silicate matrices (zeolites) to obtain a nematicidal formulate with a controlled release of the bioactive aldehyde. From a structural point of view, the project is focused on the study of interactions that take place between the guest nematicidal molecule and the host zeolite carrier in order to elucidate, at an atomistic level, the mechanisms that control the adsorption (encapsulation) and desorption (controlled release) properties. The first part of the project was addressed to define the zeolite with the highest encapsulation capacity and that was capable to prolong the bioactivity of the embedded products (encapsulated aldehyde). With this purpose, several zeolites (zeolite Y, mordenite, ferrierite, beta and ZSM-5) with different silica/alumina ratio (from 10 up to 500), pore architecture and type/position of adsorbing sites were tested. In this study the furfural encapsulation into microporous alumina-silicate ZSM-5 (SiO2/Al2O3 = 500) zeolite will be discussed. Furfural was encapsulated into zeolite via adsorption from water and adsorption equilibrium was monitored by adsorption kinetics. Adsorption isotherms were determined in order to define the affinity and maximal adsorption capacity and selectivity of tested zeolite for the selected nematicide. The monitoring was done by liquid chromatographic analysis (HPLC) of equilibrium solutions performed via Jasco 880-PU Intelligent and thermogravimetric analysis (25°-900°C, heating rate 10°C/min) of loaded zeolite samples. Electronic nose data were collected on AIRSENSE PEN3. After adsorption, the zeolite samples were structurally characterized with X-ray diffraction (XRD) technique (Bruker D8 Advance diffractometer equipped with SOL-X detector) - coupled with Rietveld refinements of the diffraction patterns. Structural analysis was used to prove the embedding of the aldehydes inside the zeolite pores and to define the interaction distance between the porous framework and each molecule. This combined diffractometric, chromatographic and thermogravimetric study allowed us to: 1) evaluate the maximum adsorption capacity of hydrophobic zeolite against furfural molecules ; 2) localise the biomolecules in the zeolite channel system; 3) probe the interaction between the adsorbate and the zeolite framework; 4) evaluate the release kinetics of the encapsulated molecules in gas phase.
Our results highlighted that ZSM-5 can be useful tool for nematode pest management, and may help improving environmental protection while minimizing risk to overall health.
[1] Ntalli, N. G., Cottiglia, F, Bueno, C. A., Alché, L. E., Leonti, M, Vargiu, S., Bifulco, E., Menkissoglu-Spiroudi, U., Caboni, P. (2010): Cytotoxic tirucullane triterpenoids from Melia azedarach fruits. Molecules, Ann. Appl. Biol. 15, 5866-5877
Degradation of primisulfuron by a combination of chemical and microbiological processes
No full textMicrobial degradation of the herbicide primisulfuron was investigated using enrichment cultures from contaminated soils and 20 axenic cultures. At neutral pH, no disappearance of the herbicide was detected either in the enrichment cultures or in the growth media of the axenic microbial cultures. During the growth of some of the microbial strains, however, the pH of the medium dropped below 6, resulting in the hydrolysis of primisulfuron. The rate of primisulfuron hydrolysis was clearly pH dependent; primisulfuron was more persistent in neutral or weakly basic solutions than in acidic solutions. After hydrolysis of the herbicide, four products were observed. These were identified as methyl 2-(aminosulfonyl)benzoate, 2-amino-4,6-(difluoromethoxy)pyrimidine,2-N-[[[[[4,6-bis(difluoromethoxy)-2-pyrimidinyl]amino]carbonyl] amino]sulfonyl]benzoic acid, and 2-(aminosulfonyl)benzoic acid. After hydrolysis, it was found that the fungus Phanerochaete chrysosporium mineralized 27 and 24% of C-14-phenyl- and C-14-pyrimidine-labeled products, respectively, after 24 days of incubation. Similarly, Trametes versicolor mineralized 13 and 11% of C-14-phenyl- and C-14-pyrimidine-labeled hydrolysis products, respectively. In addition, primisulfuron in a hydrolytically stable solution, at pH 7.0, was rapidly decomposed after ultraviolet irradiation, and two photolysis products were isolated [methylbenzoate and 4,6-(difluoromethoxy)pyrimidin-2-ylurea]. When C-14-phenyl-labeled primisulfuron was exposed to photolysis for 24 h, 32% of the initial radioactivity was recovered as (CO2)-C-14, whereas no (CO2)-C-14 was detected if the herbicide was labeled at the C-14-pyrimidine position. Mineralization of C-14-pyrimidine-labeled products of photolyzed primisulfuron by P. chrysosporium was similar to 25% after 24 days. These results clearly indicate that hydrolysis and photolysis of primisulfuron facilitated microbial degradation
Effect of undesalted dissolved organic matter from composts on persistence, adsorption, and mobility of cyhalofop herbicide in solis
No full textThe effect of undesalted dissolved organic matter (DOM) extracted from composts on the degradation, adsorption, and mobility of cyhalofop herbicide in soils was studied. A paddy-field sediment poor in organic matter (OM), an OM-rich forest soil, and DOM from agroindustrial or municipal waste compost were used. DOM increased the cyhalofop-acid but not the cyhalofop-butyl solubility in water. The degradation of cyhalofop-butyl in the sediment was slow, giving cyhalofop-acid as the only metabolite, whereas in forest soil, the process was faster, and three byproducts were detected. Soil pretreatment with DOM did not modify the degradation pattern but only reduced the adsorption of cyhalofop-butyl by soil, whereas it increased the adsorption of cyhalofop-acid. Among the. cationic components of DOM solutions, the potassium ion seems to be related to the increased adsorption of the cyhalofop-acid in both OM-poor and OM-rich soils, yielding reversible complexes with the former and favoring hydrophobic interactions with the latter
Influence of water on the retention of methyl t-butyl ether (MTBE) by high silica zeolites: A multidisciplinary adsorption study from aqueous solution and water vapour
No full textMethyl tertiary-butyl ether (MTBE) is a gasoline additive to increase octane ratings. MTBE is of particular concern due to its high aqueous solubility/vapour pressure and to its not readily biodegradability and potential human carcinogenicity. As suggested by U.S. EPA, it is of utmost importance the development of water remediation technologies to remove MTBE [Ref].
Zeolites are alumino-silicates of defined porosity, whose properties are related to the framework structural and chemical features. These properties can be modulated to increase their selectivity and sorbent activity. Here, the ability of two high silica zeolite (ZSM-5 and Y) to retain MTBE in the presence of water (i.e. from aqueous and gas phase) was addressed.
MTBE batch adsorption was performed and analyzed by HS-SPME-CG and TG and the exhausted sorbent investigated by XRPD. The Rietveld analysis allowed the identification of the occurrence and the positioning of MTBE-H2O clusters into the zeolite pores (see figure). The formation of clusters were also observed when the adsorption was conducted in gas phase in the presence of water vapour by variable pressure/temperature FTIR spectroscopy, thus highlightening the cooperative effect of H2O in MTBE removal by the zeolites. These findings are of certain interest for scientists working in the depollution of wastewater streams and indoor environments from oxygenated organic pollutants.
[Ref]: Braschi et al., 2012 J. Phys. Chem. C; Sacchetto et al., 2013 PCCP; Arletti et al., 2013 J. Solid State Chem.
Research funded by Research Center for Non-Conventional Energy, Istituto ENI Donegani – Environmental Technologie
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