Use of bentonite and humic acid as modifying agents in alginate-based controlled-release formulations of imidacloprid

✍ Scribed by González-Pradas, E; Fernández-Pérez, M; Villafranca-Sánchez, M; Martínez-López, F; Flores-Céspedes, F

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 107 KB
• Volume: 55
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199905)55:5<546::aid-ps938>3.0.co;2-p

✦ Synopsis

In order to prepare a formulation to be used for controlled release, imidacloprid was incorporated into alginate granules by using calcium chloride as gellant. The formulation prepared (alginate±imidacloprid±water) was modi®ed by the addition of different sorbents. The effects on release rate of the addition of natural bentonite desiccated at 105 °C, untreated, acid-treated with sulfuric acid solutions over a concentration range between 0.5 mol dm À3 and 2.5 mol dm À3 , and a commercial humic acid, were studied by immersion of the granules in water under static conditions. The time taken for 50% of the active ingredient to be released into water, (T 50 ), was calculated from the data obtained.

On the other hand, the sorption±desorption processes of imidacloprid from a 0.01 M aqueous calcium chloride solution at 25 °C, by natural, acid-treated bentonite samples, and humic acid, have been studied by using batch experiments in order to evaluate the potential of these materials for their application in controlled-release formulations of pesticides. The experimental data have been ®tted to the Freundlich equation in order to calculate the adsorption capacities (K f ). K f values ranged from 1.76 mg kg À1 for the untreated bentonite up to 126.9 mg kg À1 for the humic acid.

A correlation study was performed with T 50 , the surface area (S) and the Freundlich parameter (K f ) of the bentonite samples in order to know the factors that affect release rate of imidacloprid from bentonite granules. A linear correlation of the T 50 values and both S and K f parameters was observed.