Improvement of the desorption of the pesticide 2,4-D via complexation with HP-?-cyclodextrin

Inclusion complex formation of 2,4-dichlorophenoxyacetic acid (2,4-D) with hydroxypropyl-β-cyclodextrin (HP-β-CD) has been proposed as a way of modifying the behaviour of the pesticide in the soil environment. The present study assesses the effect of complex formation on 2,4-D physicochemical properties (aqueous solubility, crystallinity and dissolution rate) and its behaviour on soils. The solid complexes were prepared using different methods (spray drying, kneading and heating in a sealed container). To confirm the complex formation in the solid state differential scanning calorimetry, hot stage microscopy and x-ray diffraction techniques were employed. Complex formation in solution was studied by phase solubility. The presence of HP-β-CD increased the 2,4-D solubility nine times approximately. The apparent stability constant was determined as 98.6 M −1. The dissolution rates of the 2,4-D/HP-β-CD complexes were examined and compared with that of the pure pesticide. The results indicated that the complex may have great utility as a rapid way of dissolving the pesticide. Batch experiments were performed to study the adsorption–desorption of 2,4-D on soils and the influence of the HP-β-CD over these processes. The results showed that HP-β-CD could increase the desorption of 2,4-D previously adsorbed on soils.