Cationic pesticides, properties

Cationic Compounds. Cationic pesticides readily dissolve and dissociate in aqueous solutions to form cationic species. Physical and chemical properties for several cationic pesticides are given in Table II. The herbicides, diquat and paraquat, are the only compounds that have been studied much concerning reactions with soil colloids. Morfamquat is a herbicide related to diquat and paraquat chlormequat and phosphon are plant growth regulators. Phenacridane chloride is a fungicide, and Hyamine is a germicide. The remaining compounds were included for comparative purposes. 

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. 

Ionic surfactants may cause complications with water during application. For example, in hard water, there is an excess of Ca++, Mg++, Fe++, S04, and other inorganic ions. These will react with the anionic or cationic ions of the surfactant to form insoluble salts that precipitate, removing the surfactant from the spray solution. This will result in reducing the surface active properties of the surfactant. For this reason, pesticide formulators often use both ionic and nonionic surfactants in their formulations. Because the latter agents do not ionize, they are not as likely to react with the constituents of hard water. 

Properties M.w. 469.67 cationic Uses Emulsifier for pesticides and solvent cleaners... 

Such modification results in an alteration in the surface properties so much that the hydrophilic zeolites (i.e., with Si/Al < 10) are converted into hydrophobic zeolites (i.e., with Si/Al > 10) which can absorb molecular diameters (e.g., organic cations) larger then water [5, 8]. With this in view, it has been reported that the adsorption capacities of different surface modified zeolites can increase with the increase in their Si/Al ratio [8]. This can be attributed to the corresponding increase in their uniform pore size and their adsorption capacities which can follow the increasing order such as CLI > Ca-Y > Ca-X > Ca-A > Na-Y > Na-X > Na-A as presented in Table 2.10 [8, 62]. The adsorption capacity of zeolites can become a tool for proving the superiority of one zeolite over another for application point of view e.g., removal of pesticides from the environment [8, 62]. 

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