Abstract
In this day and age there is a growing concern about the increasing number of dangerous chemicals in Agriculture. Obsolete pesticides and their metabolites represent a major threat to the environment. These compounds are highly persistent, toxic and tend to accumulate within the human body. While considerable efforts have been made to abolish stockpiles of these hazardous chemicals, the removal of their residues from soil and water sources remains problematic. Therefore, the main aim of this research project is to provide the basis for the development of a simple, cost-effective and environmentally friendly technology for the removal of obsolete pesticides from water and soil. The fundamental concept was based on Supramolecular Chemistry, which implies non-covalent interactions between "host" and "guest". Although such interactions have formed the basis of numerous fundamental studies, their application within the environmental field has yet to be assessed. Introductory physicochemical analyses of the pollutants and prospective receptors in various media such as solubility, speciation in different organic solvents as well as partition and distribution in binary organic solvent/water systems were carried out. Design of the "host" was based on the calix[4]arene framework since it provided a convenient route for chemical transformations and possesses cavities of complementary size to the guest species. The receptor was chemically converted, using synthetic resource-saving techniques that provide the best outcome, to improve its ability to remove obsolete pesticides from water and soil. In connection with the preliminary studies and the synthetic activities, extensive 1H NMR, X-ray, UV and electrochemical evaluations of interactions between a wide variety of obsolete pesticides and the receptors were carried out. As a result, the receptors were proved to interact selectively with chlorinated phenyl- and phenoxyacetic acids and their metabolites. This was followed by a detailed determination of the stability of supramolecular complexes as well as the thermodynamic parameters associated with the complexation process. Finally, aqueous samples of pollutants were subjected to extraction by the most prospective receptors. At this stage, some macrocycles were anchored to a polymeric backbone or naturally occurring materials. As such, both liquid-liquid (LLE) and solid-liquid (SLE) extraction techniques were tested and proved to be effective tools for water remediation.