Adsorption of pesticide

Gerstl Z, Helling CS. 1987. Evaluation of molecular connectivity as a predictive method for the adsorption of pesticides by soils. J Environ Sci Health B22 55-69. 

Because of the large volume of water Involved, Incineration Is not a preferred method. Adsorption of pesticides onto media such as activated charcoal, as well as biological and chemical treatment, are feasible methods, but they require frequent monitoring and maintenance. Evaporation ponds and soil pits have the advantages of less maintenance, applicability to a broad range of chemicals, and the ability to reduce the volume of waste via water evaporation. (1-3). In addition, these latter two methods have been estimated to be the least expensive on a per gallon basis of waste (J ). This Is of considerable Importance because the wastes are... 

Surface water Adsorption of pesticides from 2 L of water onto XAD-2 and XAD-7 resins. Elution with methylene chloride, water removal and use of K-D to reduce volume. GC/chemical ionization ion trap MS 0.0005 ppb (0.5 ppt) 103.8 (14% CV) at 1 ppb level Mattern et al. 1991... 

The flux of DOC from terrestrial landscapes to surface runoff has wide-ranging consequences for aquatic chemistry and biology. DOC affects the complexation, solubility, and mobility of metals (Perdue et al., 1976 Driscoll et al., 1988 Martell et al., 1988 see Chapter 8) as well as the adsorption of pesticides to soils (Senesi, 1992 Worrall et al., 1997). Formation of trihalomethanes when drinking water is disinfected with chlorine, a worldwide threat to water supplies, is also linked to DOC concentrations (Siddiqui et al., 1997). DOC attenuates ultraviolet-B (UV-B) radiation and thus provides some protection to aquatic biota from exposure to harmful UV radiation (e.g., Williamson and Zagarese, 1994). Finally, DOC affects the heat balance and thus stratification in lakes, which is an important constraint for aquatic organisms with limited habitats (Schindler et al., 1996, 1997). 

Acheta domestlcus. toxicity of aminocarb, 218-20 Additives for spray dispersion performance, 100-15 ecotoxicity, 351-61 Adsorption of pesticides in aquatic sediment, 267 in soil, 195-96 Aerial applicators, exposure monitoring, 323-29... 

Moreale, A., Van Bladel, R. (1976) Influence of soil properties on adsorption of pesticide-derived aniline and p-chloroaniline. J. Soil Sci. 27, 48-57. 

Objectives of this study were to investigate the adsorption of several of the important classes of organic pesticides and to establish precise physical and thermodynamic parameters. An effort has been made to shed some light on the relatively neglected question of rates of adsorption of pesticides. Further, initial attempts to correlate chemical structure with rate and capacity for adsorption have been made. 

As Table I illustrates, the chemical classes represented by the pesticides studied include thiophosphates [0,0-diethyl-o-p-nitrophenyl phos-phorothioate], carbamates [1-naphthyI-N-methylcarbamate], dinitrophe-nols [2,4-dinitro-o-sec-butylphenol and 2,4-dinitro-o-cyclohexylphenol], and chlorophenoxy acids [2,4-dichlorophenoxyacetic acid, 2,4,5-trichloro-phenoxyacetic acid, and 2-(2,4,5-trichlorophenoxy)propionic acid]. In addition, a number of molecularly related nitrophenols have been studied to establish the effects of molecular geometry and substituent groups on adsorption of pesticide-type materials. 

Representative rate data for 2,4,5-T and parathion for the experiments on adsorption of pesticides on active carbon are presented in Figures 1 and 2. The (C0 — C)/m values in these plots represent the amount of solute, both in micromoles and milligrams, removed from solution per gram of carbon. Good linearization of the data is observed for the experiments, in accord with expected behavior for intraparticle-transport rate control. Similar linearization was obtained also for data for the other pesticides. The linear traces facilitate comparison of relative rates of adsorption of pesticides, and such comparison is made in column 1 of Table III, using the square f the slope pf each plot as the relative rate constant for the experiment. 

Molecularly Related Nitrophenols. To define more explicitly the relative influences of molecular structure and hydrophobic character upon rate of adsorption of pesticide materials by porous carbon, a number of pure dinitrophenols molecularly related to DNOSBP and DNOCHP have been studied. The molecular structures of DNOSBP, DNOCHP and the molecularly related dinitrophenols—DNP, DNC, DNT, and DNPCHP —are illustrated in Figure 5. 

Soil type is one of the most important factors influencing the adsorption of pesticides by soils. Of special importance are the clay and organic matter. 

Soil temperature influences chemical degradation, microbial decomposition, and volatilization. For example, no aldrin or heptachlor was lost from frozen soils, but at 6°C, 16-27% of the dose applied to soil was lost in 56 days at 26°C, 51-55% disappeared and at 46°C, 86-98% was lost. Diazinon was also degraded faster at higher temperatures than at low ones (Edwards, 1973b). Temperature also influences the adsorption of pesticide in soils because adsorption is a exothermic process, so that increased temperatures decrease adsorption and release pesticides. 

Gerstl, Z. and Helling, C.S. (1987). Evaluation of Molecular Connectivity as a Predictive Method for the Adsorption of Pesticides by Soils. J.Environ.Sci.Health, B22,55-69. 

The extent to which an organic compound partitions out of water onto soil is determined by physical-chemical properties of both the soil and the compound. The soil s organic matter content is the single best characteristic for estimating the amount of soil adsorption of pesticides and other organic molecules. The partition, or sorption, coefficient of the organic molecule Koc (equal to ATp/SOM) is rather independent of soil type. This suggests that SOM is the principal soil component responsible for pesticide sorption and that the role of SOM is similar in different soils. 

The BET equation has been applied to ion adsorption from soil solutions, although the extended Langmuir equation (Eq. 9.11) would seem to apply as well. The BET equation has also been used to study the adsorption of pesticides having relatively high vapor pressures. 

Several mathematical models have been proposed for representing the overall adsorption of pesticides by soils. The most comprehensive one appears to be that of Lambert et al. (9), in which the partition of pesticides between soil water and soil is represented by a linear adsorption equation similar to the Langmuir equation. In this model they have assumed that the active adsorbent for pesticides in soils is the soil organic matter. This approach has been successful in modeling the adsorption of nonionic pesticides on soils (12), Lambert (13) has introduced an index of soil adsorption of pesticides which is intended to indicate the amount of active organic matter in a soil and therefore may be used to compare the adsorption capacity of one soil with that of another. Lambert states that the index is independent of the pesticide being adsorbed. 

Supercritical Fluid Regeneration of Activated Carbon for Adsorption of Pesticides EPA Report 600/2-80-054 1980. 

Chemical effects relate to exchange capacity, buffering capacity, supply and availability of macro- and micronutrients, adsorption of pesticides and other chemicals, etc. 

It is apparent from the perusal of the literature that the investigations concerning the adsorptive removal of different pesticides from water have generally been directed toward determining the efficiencies of powdered and granulated activated carbons for their removal. None of the studies have discussed the effect of such parameters as the surface area, pore-size distribution, or the chemistry of the carbon surface on the adsorption and its mechanism. Only in one paper Prakash indicated that the adsorption of diquat and paraquat depended on the surface area of the carbon. Thus, there is need to study the influence of these parameters on the adsorption of pesticides. 

Because of their unique layered structure and highly tunable chemical composition based on different metal species and interlayer anions, LDHs have many interesting properties, such as unique anion-exchanging ability, easy synthesis, high bond water content, memory effect, nontoxicity, and biocompatibility. Based on these properties, LDHs are considered as very important layered crystals with potential applications in catalysis [6], controlled drugs release [7], gene therapy [8], improvement of heat stability and flame retardancy of polymer composites [9], controlled release or adsorption of pesticides [10], and preparation of novel hybrid materials for specific applications, such as visible luminescence [11], UV/photo stabilization [12], magnetic nanoparticle synthesis [13], or wastewater treatment [14]. 

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