Role of ferrihydrite in adsorption of three imidazolinone herbicides.
Adsorption of the imidazolinone herbicides imazapyr, imazethapyr, and imazaquin on synthetic ferrihydrites, either freeze-dried or not-freeze-dried, has been studied. The synthetic ferrihydrites were characterized by X-ray diffraction, scanning electron micrographs, and specific area determination. On each ferrihydrite, adsorption was found to be strongly dependent on pH. The highest extent of adsorption took place at pH values close to the pK(a) of the carboxylic group of the herbicides. No adsorption was observed at pH > 8. The freeze-drying process reduced the adsorptive capacity of the ferrihydrite by formation of larger aggregates provoking a decrease of the surface area. The chemical differences between the herbicides did not strongly affect the adsorption process of the herbicides. However, imazaquin was more adsorbed than the other two herbicides, in particular at pH close to its pK(a).
Leone
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Dipartimento di Valorizzazione e Protezione delle Risorse Agroforestali (DI.VA.P.R.A.) - Chimica Agraria, Università degli Studi di Torino, Via Leonardo da Vinci 44, 10095 Grugliasco, Italy.
Gennari
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M
Nègre
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M
Boero
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V
D000327:Adsorption; D005290:Ferric Compounds; D005293:Ferritins / Q000737:chemistry; D005612:Freeze Drying; D006540:Herbicides / Q000737:chemistry / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry / Q000302:isolation & purification*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D009525:Niacin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification*; D009539:Nicotinic Acids / Q000737:chemistry / Q000302:isolation & purification*; D011804:Quinolines / Q000737:chemistry / Q000302:isolation & purification*; D014961:X-Ray Diffraction
D005290:Ferric Compounds; D006540:Herbicides; D007093:Imidazoles; D009539:Nicotinic Acids; D011804:Quinolines; D009525:Niacin; C093630:imazethapyr; C076656:imazapyr; C092844:ferric oxyhydroxide; C057728:imazaquin; D005293:Ferritins