Preparation of Berberine-montmorillonite-metolachlor formulations from hydrophobic/hydrophilic mixtures

Metolachlor which is a pre-emergent hydrophobic herbicide with moderate solubility, was detected in several water wells in agricultural and even urban areas. This study aims for the preparation of organoclay platforms which could release metolachlor in a more controlled pattern, thus - reducing the leaching to groundwater. The adsorption of metolachlor to organoclays based on difenzoquat, diquat or berberine added up to neutralizing the original charge of the clay mineral was tested. The adsorption loadings of metolachlor on berberine-montmorillonite were found to be more than 30% of the compound, whereas for difenzoquat- and diquat-montmorillonite the amounts were only 3.8% and 4.9%, respectively. Consequently, further experiments were conducted focusing on berberine-montmorillonite. Loading of preadsorbed berberine was crucial to the hydrophobicity of the platforms and it had also influence on the adsorption of metolachlor in mixed immiscible phases experiments. The exact procedure of preparation was also a key issue on determining final metolachlor amounts on the formulation: Preparation of the formulation from suspended organoclay which was not dried after preadsorbing the berberine, and was mixed with metolachlor dissolved in chloroform gave the highest percentages of adsorbed herbicide. Release from organoclay formulation was at a more controlled fashion than for commercial herbicide, or commercial herbicide mixed with non-modified montmorillonite, leaving a relatively constant concentration of herbicide after several desorption cycles. (C) 2007 Elsevier B.V. All rights reserved.