Slow-release formulations of sulfometuron incorporated in micelles adsorbed on montmorillonite

The design and tests of slow-release formulations of sulfometuron (SFM), an anionic sulfonylurea herbicide, are described. The formulations are based on incorporation of the herbicide in octadecyltrimethylammonium (ODTMA) micelles, which adsorb on a clay mineral, montmorillonite. An optimization of herbicide/micelle clay ratios yielded high adsorption of SFM (95%), and at a 1% (w/w) water suspension only 0.5% of the adsorbed SFM was released at times varying from hours to 9 days. An analytical test in Seville soil showed that under excessive irrigation (400 mm) 100% of the commercial formulation leached, whereas the micelle-clay formulations showed only 50-65% elution. A plant bioassay in Rehovot soil showed that the commercial dispersible granule formulation (Oust, 75% ai sulfometuron methyl) yielded only 23% root elongation inhibition at the top 5 cm of the soil, whereas complete inhibition was achieved with the micelle-clay formulation. The detected concentration of SFM for the micelle-clay formulation at a depth of 15-20 cm was half of that detected for the commercial one, indicating a reduction in leaching when applying the micelle-clay formulation. A 10-fold reduction in the applied dose of SFM in the micelle-clay formulations resulted in good herbicidal activity of 60-87% inhibition. These characteristics make the new formulation promising from the environmental and economic points of view.Peer Reviewe

Sulfometuron incorporation in cationic micelles adsorbed on montmorillonite

The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption of hexadecyltrimethylammonium (HDTMA) and octadecyltrimethylammonium (ODTMA) on montmorillonite was studied above and below their critical micelle concentrations (CMC). At concentrations above the CMC, the loading exceeded the clay's cation exchange capacity (CEC) and indicated higher affinity of the cation with the longer alkyl chain. An adsorption model could adequately simulate adsorption at concentrations below the CMC, and yield fair predictions for the effect of ionic strength. The model indicated that above the CMC adsorbed micelles contributed significantly to the amount of ODTMA adsorbed. Evidence for adsorption of ODTMA micelles on montmorillonite was provided by X-ray diffraction, freeze-fracture electron microscopy, and dialysis bag measurements. SFM was not adsorbed directly on the clay mineral, and adsorbed at low levels, when the organic cation was adsorbed as monomers. In contrast, a large fraction of SFM adsorbed on the clay mineral when incorporated in micelles that adsorbed on the clay.Peer Reviewe

Factors affecting the design of slow release formulations of herbicides based on clay-surfactant systems. A methodological approach

9 pages, 7 figures, 6 tables, 39 references.A search for clay-surfactant based formulations with high percentage of the active ingredient, which can yield slow release of active molecules is described. The active ingredients were the herbicides metribuzin (MZ), mesotrione (MS) and flurtamone (FL), whose solubilities were examined in the presence of four commercial surfactants; (i) neutral: two berols (B048, B266) and an alkylpolyglucoside (AG6202); (ii) cationic: an ethoxylated amine (ET/15). Significant percent of active ingredient (a.i.) in the clay/surfactant/herbicide formulations could be achieved only when most of the surfactant was added as micelles. MZ and FL were well solubilized by berols, whereas MS by ET/15. Sorption of surfactants on the clay mineral sepiolite occurred mostly by sorption of micelles, and the loadings exceeded the CEC. Higher loadings were determined for B266 and ET/15. The sorption of surfactants was modeled by using the Langmuir-Scatchard equation which permitted the determination of binding coefficients that could be used for further predictions of the sorbed amounts of surfactants under a wide range of clay/surfactant ratios. A possibility was tested of designing clay-surfactant based formulations of certain herbicides by assuming the same ratio between herbicides and surfactants in the formulations as for herbicides incorporated in micelles in solution. Calculations indicated that satisfactory FL formulations could not be synthesized. The experimental fractions of herbicides in the formulations were in agreement with the predicted ones for MS and MZ. The validity of this approach was confirmed in in vitro release tests that showed a slowing down of the release of a.i. from the designed formulations relative to the technical products. Soil dissipation studies with MS formulations also showed improved bioactivity of the clay-surfactant formulation relative to the commercial one. This methodological approach can be extended to other clay-surfactant systems for encapsulation and slow release of target molecules of interest.This research was supported by the projects CTM2009-07425 and PRI-PIBAR-1393 from the Spanish Ministry of Economy and Competitiveness, and Junta de Andalucía Project P09-RNM4581. These projects received funding by the European Social Fund. M.C. Galán-Jiménez acknowledges a research contract from Junta de Andalucía in the frame of the project P09-RNM4581.Peer reviewe

Aproximación metodológica para el desarrollo de formulaciones de liberación lenta de herbicidas usando complejos sepiolita-surfactantes

3 páginas.-- 3 figuras.-- 1 tabla.-- Comunicación presentada en el Workshop de Mineralogía Aplicada Homenaje al Prof. Emilio Galán, Sevilla 16-17 Enero 2014Los minerales de arcilla se usan en numerosas aplicaciones industriales tales como soportes y plantillas en la producción de papel y plásticos; aislantes de calor en la industria de la construcción, pigmentos nacarados, agentes contra la corrosión en recubrimientos, agentes protectores contra UV y calor en pinturas, etc. En las últimas décadas se ha desarrollado un interés creciente por el uso de arcillas en tecnologías de vectores de principios activos a fin de conferir propiedades de liberación lenta, lo que es de particular interés en la industria farmacéutica y agroquímica.Esta investigación recibió financiación a través de los proyectos PRI-PIBAR-2011-1393-y CTM2009-07425.Peer Reviewe

Formulaciones arcilla-liposomas de sulfometurón para reducir la lixiviación del herbicida

2 páginas, 1 figura, 1 tabla, 1 referencia.-- Publicado en el Capítulo IV: Contaminación y Medio Ambiente.-- Trabajo presentado a la XVII Reunión Científica de la Sociedad Española de Arcillas, celebrada en Elche (Alicante) y Castellón, del 27-29 de noviembre de 2002.La movilidad de herbicidas en suelos es de gran interés desde hace mucho tiempo, por muchas razones entre las que se incluye (1): (i) su potencial para contaminar aguas subterráneas; (ii) reducción en su eficacia cuando el herbicida lixivia por debajo de la zona raíz de las malas hierbas, que puede potencialmente dañar la cosecha tratada; (iii) su potencial para volver a la superficie del suelo con el consiguiente peligro para posteriores cultivos. Las formulaciones de liberación controlada de herbicidas (FLCs) proveen una liberación lenta del ingrediente activo a una velocidad adecuada, reduciéndose de esta forma la cantidad de producto químico necesario para un control eficiente de las malas hierbas. El presente estudio demuestra que el uso de liposomas es una nueva herramienta para el diseño de formulaciones de liberación controlada de sulfometurón (SFM), un herbicida de la familia de las sulfonilureas. El herbicida se incorpora en vesículas formadas por cationes de aminas cuaternarias, dimetildidodecilamonio (DDAB) y dimetildioctadecilamonio (DDOB), que son posteriormente adsorbidos sobre una montmorillonita estándar (SWy-2). La concentración inicial en las soluciones vesiculares del herbicida era de 0.6 mM y del catión orgánico 6 mM.Peer reviewe

A novel system for reducing leaching from formulations of anionic herbicides: clay-liposomes

A new approach was developed for reducing leaching of herbicides and contamination of groundwater. Liposome-clay formulations of the anionic herbicides sulfometuron and sulfosulfuron were designed for slow release by incorporating the herbicide in positively charged vesicles of didodecyldimethylammonium (DDAB), which were adsorbed on the negatively charged clay, montmorillonite. Freeze fracture electron microscopy demonstrated the existence of DDAB vesicles and aggregated structures on external clay surfaces. X-ray diffraction results for DDAB with montmorillonite imply the existence of DDAB bilayers with an oblique orientation to the basal plane within the clay interlayer space at adsorbed amounts beyond the cation exchange capacity of the clay. Adding DDAB with sulfometuron or sulfosulfuron to montmorillonite yielded 95% or 83% adsorption of the herbicide at optimal ratios. Liposome-clay formulations exhibited slow release of the herbicides in water. Analytical measurements in soil columns demonstrated 2-10-fold reduction in leaching of the herbicides from liposome-clay formulations in comparison with commercial formulations. Percents of root growth inhibition of a test plant in the upper soil depths were severalfold higher for the liposome-clay formulations than for the commercial ones. Consequently, liposome-clay formulations of anionic herbicides can solve environmental and economical problems by reducing their leaching.Financial funding by the Spanish Ministry of Science and Technology (Projects REN2000-1540 and AGL2002-00993); The Hebrew University of Jerusalem through a grant from the Wolfson Foundation for Scientific Research, Matching-Bergman; and Grant G-641-106.8/1999 from the German-Israeli Foundation for Research and Development. T. Undabeytia also acknowledges the Spanish government for a Ramón y Cajal research contract.Peer Reviewe

Coagulation-flocculation of Microcystis aeruginosa by clay-polymer based composites (Comunicacion Congreso)

2 páginas.- 1 figuras.- 1 tabla.- 1 referencia.- Abstract extendido de la comunicación oral presentada en la XXVI Reunión Científica de la Sociedad Española de Arcillas.- Enlace a la revista https://www.semineral.es/websem/PdfServlet?mod=archivos&subMod=publicaciones&archivo=MACLA%2026%20V5.pdfCyanobacteria blooming episodes in water bodies are increasing due to global warming and nutrient enrichment arising from anthropogenic activities. Their presence in water poses a risk for the environment and human health due to release of toxins. Coagulation-flocculation has been proved to be a key treatment for removal of cyanobacterial cells along Drinking Water Treatment plants avoiding the release of endotoxins by cell lysis. The combined use of cationic polymer and clay minerals can be a good approach for their use in coagulation-flocculation of cyanobacterial suspensions, relative to more conventional chemicals used. In the current work, clay-polymer complexes were examined for removal of Microcystis aeruginosa in suspensions. These complexes were prepared from polymers derived of quaternized poly-4-vinylpyridine (PVP), which were sorbed and grafted on the surface of the clay mineral montmorillonite. Quaternization was performed by introducing methyl and hydroxyethyl moieties on the pyridinic N.The authors acknowledge the Ministry of Science and Innovation for financial support (grant CTM2016-77168-R).N

Dissolved organic matter adsorption from surface waters by granular composites versus granular activated carbon columns: An applicable approach

42 páginas.- 9 figuras.- 1 tabla.- referencias.- Appendix A. Supplementary dataMany new sorbents have been introduced as an alternative for granular activated carbon (GAC), the most common sorbent for dissolved organic matter (DOM) removal. In the current study, we developed an applicable granular composite based on a flocculant commonly employed for drinking water treatment adsorbed to montmorillonite. DOM adsorption from surface waters, Lake Kinneret and Suwannee River, with low and high specific ultraviolet absorption (SUVA), respectively, by composite and GAC columns, was studied. Adsorption of DOM from Suwannee River was significantly higher by the composite column, in comparison to the GAC column, while an opposite trend was obtained for the adsorption of DOM from Lake Kinneret. In-situ regeneration of the columns with a brine solution was extremely efficient and inefficient for the composite and GAC columns, respectively. Adsorption, of both waters, post-regeneration by the composite column was not compromised, while GAC effectiveness decreased. The opposite trend in DOM adsorption from Suwannee River and Lake Kinneret was explained by the different affinities of the sorbents towards various DOM molecules. Distinguishing between different DOM components adsorbed by GAC and the composite was supported by 13C NMR and direct pyrolysis-GC-MS measurements. Furthermore, we demonstrated that the kinetics and adsorption at the equilibrium of five organic molecules to the composite and GAC can be correlated to their chemical-physical properties. Indeed, combining the properties of both sorbents, by integrating them into a single column, yielded higher DOM removal than by the individual columns. Furthermore, since DOM removal by GAC and by the composite, increases, and decreases with temperature, respectively, the integrated column, mitigates the changes in removal, stabilizing the adsorption performance. Such an integrated filter may minimize additional seasonal and water quality fluctuations.Peer reviewe

Coagulation-flocculation of Microcystis aeruginosa by polymer-clay based composites

9 páginas.- 6 figuras.- 2 tabla.- 1 referencia.- Supplementary data to this article can be found online at https://doi. org/10.1016/j.jclepro.2023.136356Coagulation-flocculation is a critical treatment to reduce operational problems at Drinking Water Treatment Plants (DWTPs), created by episodes of cyanobacterial blooms in surface waters. There is a need for the search of good coaguflocculants that avoid release of intracellular toxins for a safer sustainable production. Clay-polymer interactions were examined for the development of efficient composites for their use as coaguflocculants for Microcystis aeruginosa (M. aeruginosa) suspensions. Polymers derived from poly-4-vinylpyridine (PVP) were quaternized on the pyridinic N by introducing methyl and hydroxyethyl moieties. These polymers were toxic per se; however, composites prepared either from their sorption or grafting on the clay surface of a montmorillonite exhibited null toxicity, The combination of infrared and X-ray diffraction data with thermal analysis showed a train conformation of the sorbed polymers on the clay surface whereas a brush conformation was elucidated for the grafted polymers. Only the composite prepared from grafting and subsequent quaternization with methyls was an efficient coaguflocculant, due to its high positive surface potential (+39 mV) which allowed a close contact between the quaternary moieties of the brushes and the negative cell wall. A patch flocculation mech-anism was involved, with the riks of resuspension of the coagulated cells if the composite added in excess. The optimum ratio between the amount of coagulated cyanobacteria and this composite expressed as equivalent to polymer content was 7.2 x 107 cells/mg polymer. This ratio was determined in axenic cultures of M. aeruginosa, but was reduced 5-fold in natural surface waters due to natural organic matter (NOM) content and heterogeneity. This study has demonstrated the relevance of the type of modification of the clay mineral surface with polymers to obtain good coaguflocculants of cyanobacterial cells, that can be extended to other microorganisms.This work has received financial support from the Spanish Ministry of Science and Innovation (project CTM2016-77168-R). The authors also acknowledge the Services of the University of Seville (CITIUS) of Biology for flow cytometer analysis, and of Microanalysis and Functional Characterisation for determination of zeta potentials, loading of the polymers and MC-LR analysis. They also acknowledge the Micro-scopy Service of the CIC Isla de la Cartuja.Peer reviewe

Organo-clay formulations of pesticides: Reduced leaching and photodegradation

Adsorption of organic cations on several clay minerals is reviewed with an emphasis on the effect of ionic strength and modeling. The clay exchanged with suitable organic cations forms a basis for ecologically acceptable formulations of herbicides with reduced leaching, ground water contamination and enhanced weed control efficacy. Incomplete neutralization of the clay surface charge by an organic cation may be advantageous in achieving maximal adsorption of hydrophobic herbicides. One conclusion from these studies is that optimization of clay-based herbicide formulations requires a selection of structurally compatible organic cations preadsorbed on the clay at optimal coverage. New experimental results are presented for alachlor formulations, which significantly reduce herbicide leaching under conditions of heavy irrigation. We were able to demonstrate that organo-clay formulations of alachlor and metolachlor can increase crop yields in a 1-year field experiment. The photostabilization of pesticides is reviewed and improved organo-clay formulations of the herbicides trifluralin and norflurazon are described. A pillared clay, nanocomposite micro- and/or meso porous material, was effective in reducing leaching and in conferring photostabilization, without added organic cations.Peer Reviewe