Simazine removal

Agbekodo K.M., Legube B., Dard S. (1996), Atrazine and simazine removal mechanisms by nanofiltration Influence of natural organic matter concentration. Water Research, 30,11,2535-2542. 

Herbicides. An array of herbicides are registered for use in aquatic sites, but copper sulfate and diquat dibromide are of additional interest because they also have therapeutic properties (9,10). Copper sulfate has been used to control bacteria, fungi, and certain parasites, including Jchthjophthirius (ich). Diquat dibromide can control columnaris disease, but it also exhibits fungicidal properties (9,10). EPA recentiy proposed to limit the amount of diquat dibromide, endothaH, glyphosate, and simazine that can be present in drinking water therefore, the use of these compounds may be reduced if they cannot be removed from the effluent. 

Preferential removal of an ethyl versus an isopropyl moiety is a concept that has been suggested by Leonard (1988). DIA occurs in surface water that has received parent atrazine, simazine, or cyanazine. DEA occurs in surface water that has received atrazine or propazine. The concentrations of DEA and DIA in surface water vary with the hydrologic conditions of the basin and the timing of runoff (Mills and Thurman, 1994 Thurman et al, 1994,1998a). 

A study was designed to define the relative rates of dealkylation of selected triazine herbicides and two monodealkylated triazine degradation products in the unsaturated zone and in surface runoff. Atrazine and propazine degrade to DEA by deethylation and deisopropylation, respectively. Similarly, atrazine and simazine can both dealkylate to DIA by removal of an isopropyl and ethyl side chain, respectively (Figure 30.12). Differences in the concentration of the dealkylated degradation product from the two different sources should indicate any preferential removal of ethyl versus isopropyl side chain. Furthermore, because monodealkylated DEA and DIA have different side chains remaining, their relative rate of removal should provide additional information on the liability of the ethyl side chain versus an isopropyl side chain. 

This study showed that under field conditions, the removal of an ethyl side chain from atrazine occurred more readily than the removal of an isopropyl side chain. Furthermore, deethylation rates of atrazine and simazine were comparable, and approximately two to three times more rapid than the rates of deisopropylation from atrazine and propazine, regardless of parent triazine. Continued dealkylation of the monodealkylated degradation products at 1 m in the unsaturated zone also shows a preferential removal of ethyl side chains over isopropyl side chains. Therefore, the small concentrations of DIA commonly reported in the environment do not result purely from a smaller production of the degradation product, but from a rapid removal once produced. This substantial turnover rate or flux of DIA in the environment is evidence for the presence of a didealkylated degradation product in the unsaturated zone (Mills and Thurman, 1994 Thurman et al., 1994). 

The widespread application of herbicides in agriculture has resulted in many polluted surface waters. As a result, numerous pesticides/herbicides have been treated in bench-scale laboratory studies with 03/UV/H202 processes during the last 10 years (see Table 10). Among them, many studies focused on the treatment of atrazine and other. v-triazine herbicides (simazine, prop-azine, etc.). Atrazine is a priority pollutant that similar to other individual pesticides has a very low maximum contaminant level (MCL) (0.1 pg L 1 for the European Environmental Commission according to Directive 80/778/ EEC). In some countries atrazine cannot be used but it is still found in many surface waters. In France, for example, atrazine was banned on September 28, 2001. From applied technologies, only carbon adsorption [180] and possibly advanced oxidations can be recommended to remove some of these... 

The application of MIPs prepared using triazines as templates to the SPE of water samples requires drying of the cartridge after the sample application in order to remove water traces, which would disrupt the interactions between the analytes and the sorbent. In the protocol described by Matsui et al. [19] the aqueous sample was applied to the MIP cartridge, which was then carefully dried prior to a selective dichloromethane wash (entry D in Tables 15.1 and 15.2). HPLC-UV analysis of wastes and extracts showed that all the impurities were washed off without significant elution of simazine (4) and that the analyte was quantitatively recovered in the eluate. 

This range of compounds consists of the many chemicals that are used to control pests worldwide. Target species include insect, animal, or plant species. Examples of the hundred or so pesticides that have been studied to determine their removal during drinking water treatment processes include -5-triazines (atrazine, simazine, cyanazine, propazine), lindane, DDT, 2, 4-D, atachlor, metolachlor, asulam, hymexazol, methomyl, imidacloprid, carbaryl, linuron, thiobencarb, and diquat. 

The Lyonnaise des Eaux in France [4.116] has developed a process for the denitrification of underground waters in order to produce drinking water. This process combines a bioreactor with adsorption by powdered activated carbon, together with a hollow-fiber UF unit. This process allows the elimination of nitrates, nitrites, pesticides, and herbicides (atrazine, diethylatrazine, simazine, metabenzthiazuron, and urea derivatives, etc.) as well as taste and odor compounds. These molecules are frequently present in underground waters in Europe, as a result of past intensive agricultural practices. The UF membrane unit also disinfects the water by removing protozoa, bacteria, and viruses. 

Apart from the fact that in the presence of the natural organic matter in water MN-200 loses only 10% of its capacity for the above triazine pesticides, the regeneration of MN-200 (exhausted with simazine, chlor-otoluron, isoproturon, atrazine, and diuron) proceeds easily by simple washing of the polymer with 3—5 bed volumes of acetone, methanol, ethanol, or 1-propanol [71]. Complete removal of atrazine, benazohn, bentazone, imazapyr, and triclopyr requires about 8 BV of aqueous ethanol adjusted to pH 12 at 50°C. Regeneration of carbon F-400 presents great problems 200 BV of the above most efficient reagents comprehensively removes only benazolin and triclopyr, while the recovery of other herbicides remains below 50% [70]. 

In the preparation of the BCD complex of simazine, a mixture of 5.00 g (24.8 mmol) of technical grade simazine and 30.4 g (24.8 mmol) of BCD in 500 ml of water was heated at 100 C for 11 days. There was no significant dissolution of the simazine. Fifty ml of 1,4-dioxane was added as a co-solvent, and die mixture heated at 100 °C for 2 days, yielding a clear solution. After cooling to room temperature 392 mg of white precipitate (unreacted simazine) was isolated after refrigeration of the filtrate at 4 tT for 5 days, 12.99 g of unreacted BCD came out of solution. Removal of solvent from ti remaining solution followed by vacuum drying provided 22.12 g of BCD complex, mp 150-162 °C. Elementary analysis CTable I) of the material indicated a 2 1 5 simazine/BCD/HjO molar ratio (24.8% simazine). 

Ceramic membranes impregnated with crosslinked silylated CD polymers, i.e. organic-inorganic filters were investigated for removal of some organic pollutants from water [59]. It was established that they remove polycyclic aromatic hydrocarbons PAH, the monocyclic aromatic hydrocarbons, trihalo methanes, methyl-f-butyl ether and pesticides. Trihalomethanes are disinfection by-products, they (especially dibromochloromethane) increase the risk of cancer. The pesticides simazine and atrazine are drinking water pollutants. 

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