Suspension, aqueous, pesticide

Stabilization of Aqueous Pesticidal Suspensions by Graft Copolymers... 

Influence of Bentonite on the Rheology of Aqueous Pesticide Suspension Concentrates... 

Preparation of Suspensions A standard 400 g leg aqueous pesticide suspension was prepared by a wet milling process using a Dyno mill (ex. Willy. A. Bachofen, Basle, Switzerland). 40g... 

The process of UV-ozonatlon, whereby aqueous pesticide suspensions are pretreated with Intense ultra-violet radiation In the presence of oxygen prior to soil disposal, was shown to be effective In accelerating the degradation of several commonly used herbicides... 

Phase separation can also be produced from solutions of polymers in organic solvents. By addition of a nonsolvent for the polymer to the solution containing the core material the pol)mier will precipitate aroimd the emulsified core to form microcapsules (30). This can allow for the encapsulation of aqueous solutions or suspensions of pesticides. For example, such an aqueous solution can be emulsified in oil containing the dissolved polymer. Addition of the nonsolvent to the oil phase separates out the polymer, which can then form the wall around the water droplets. 

Guo et al. reported that trace amoimts of aqueous organochlorine pesticides, such as hexachlorocyclohexane (HCH), could be totally degraded and mineralized into CO2 and HCl by near-UV irradiation of a suspension of Mg/Al LDH intercalated with paratungstate anions [108]. They demonstrated that photocatalytic degradation of the pesticide occurs in the interlayer galleries. It was also found that Zn/Al/W(Mn) mixed oxides, formed by calcination of POM-intercalated Zn/Al LDHs [109], exhibited higher photocatalytic activity in the degradation of HCH compared with the POM-LDH precursors. 

The amount of adsorbed chemical is controlled by both properties of the chemical and of the clay material. The clay saturating cation is a major factor affecting the adsorption of the organophosphorus pesticide. The adsorption isotherm of parathion from an aqueous solution onto montmorillonite saturated with various cations (Fig. 8.32), shows that the sorption sequence (Al > Na > Ca ) is not in agreement with any of the ionic series based on ionic properties. This shows that, in parathion-montmoriUonite interactions in aqueous suspension, such factors as clay dispersion, steric effects, and hydration shells are dominant in the sorption process. In general, organophosphorus adsorption on clays is described by the Freundhch equation, and the values for parathion sorption are 3 for Ca +-kaoUnite, 125 for Ca -montmorillonite, and 145 for Ca -attapulgite. 

Sorption has been commonly described as an equilibrium process, in which the pesticide molecules are rapidly and readily exchanged between the sediment and aqueous phases. In this approach ( ), the equilibrium water phase concentration, (expressed relative to suspension volume) is related to the sediment phase concentration, (expressed relative to dry weight sediment), through... 

Atmospheric Vapor. As emphasized elsewhere in this volume, most forest pesticides can be expected to volatilize. Even those with seemingly low vapor pressures (less than 10 6torr) are observed to vaporize from soil, leaves, and especially from aqueous solutions and suspensions (23-25) Consequently, a significant and perhaps major proportion of applied chemicals—pesticides, solvents, and adjuvants—can be expected to move eventually into the atmosphere. 

Muneer et al. [129] examined the photocatalytic oxidation of three pesticide derivatives, propham, propachlor and tebuthiuron in aqueous TiC>2 suspensions. The rates of degradation of each compound were found to be strongly affected by the type of TiC>2 used, pH, catalyst and substrate concentration. For each compound several intermediate products were identified using GCMS. This study indicated that the photocatalytic oxidation process proceeded by reactions involving electron transfer, hydroxyl radical and superoxide radical anions. Scheme 2 displays the proposed mechanism for the photocatalytic decomposition of propham. 

Konstantinou IK, Albanis TA. Photocatalytic transformation of pesticides in aqueous titanium dioxide suspensions using artificial and solar light intermediates and degradation pathways. Appl Catal B Environ 2003 42 319-335. 

Benomyl absorbed by plants is rapidly metabolised in the tissue fluids into MBC (Sims et al., 1969 Peterson and Edgington, 1970), so that benomyl itself can be detected only rarely in the tissue fluids. Sunlight, heat and various solvents enhance the transformation. At the same time, Baude et al. (1973) showed by the chemical approach that benomyl has adequate stability in aqueous suspensions at a concentration usual in sprays. An aqueous suspension of the benomyl preparation Benlate at 23°C contained more than 90% of the original benomyl even after 48 hours. After a longer time, the larger part of the residue found on the leaves consisted of intact benomyl. No other metabolites were found in the plant in addition to MBC, even if benomyl was used in combination with alkaline pesticides (basic copper sulfate or lime sulfur solution) in the spray. Thus, because of its low solubility, the hydrolysis of benomyl in practice is not as rapid as has been measured in dilute solutions by several authors (Jhooty and Singh, 1972 Brown and Albrigo,... 

In conclusion, soil composition (pesticide residue) played an important role in controlling fabric/soll Interactions. Captan, an aqueous suspension of particles, was more difficult to remove In 100% cotton denim. This was attributed to particle size and the clay-llke nature of the materials comprising the pesticide formulation. 

Pesticides in Aqueous Titanium Dioxide Suspensions Using Artificial and Solar Light Intermediates and Degradation Pathways , Appl. Catal. B-Environ., 2003,42, 319... 

If the pesticide constituent is a solid that is not soluble in oil or water, dien either a suspension concentrate (SC) or a water dispersible granule (WG, WDG) can be evaluated. A suspension concentrate is a dispersion of active ingredient in a continuous aqueous phase. The concentrated suspension is then diluted in the spray tank prior to application. If the solid has to be dispersed in an oil phase, then the oil flowable (OD) has to spontaneously enuilsify if it is to be diluted into an aqueous spray tank. 

Pollard SJT, Fowler GD, SoUars CJ, Perry R (1992) Low-cost adsorbents for waste and wasteweiter treatment areview. Sci Total Environ 116(l-2) 31-52 Qdais HA, Moussa H (2004) Removal of heavy metals from wastewater by membrane processes a comparative study. Desalination 164(2) 105-110 Rahman MA, Muneer M (2005) Photocatalysed degradation of two selected pesticide derivatives, dichlorvos and phosphamidon, in aqueous suspensions of titanium dioxide. Desalination 181(1-3) 161-172... 

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