Enhanced Solubility of Herbicide Diuron in Aqueous Solution by Micellisation

Surfactants are substances widely used in agricultural sprays to improve the solubility and mobility of pesticides across crops. This study investigates the micellar properties of two ionic surfactants sodium dodecyl sulfate (SDS) and tetramethylammonium tetrafluoroborate (TMATFB) with respect to their ability to solubilize the herbicide diuron in aqueous solution. Conductometric measurements were performed in aqueous media over a temperature range of 298 to 331 K to analyze the micellization behavior and evaluate the efficiency of solubilization. From the conductivity data the critical micelle concentration (CMC), and degree of ionization were obtained at various temperatures. Concentration and temperature effect on the CMC have been studied and the different thermodynamic parameters were evaluated. The critical micellar concentration (CMC) values of surfactants decreased with increasing temperature, indicating enhanced micelle formation under thermal influence. Additionally, the solubility of diuron varied significantly across different surfactant micelles concentration, suggesting that specific interactions occur between the surfactant head groups and the pesticide. The standard Gibbs free energy (∆G°) for the diuron–surfactant mixtures was attained to be negative throughout the study suggesting spontaneous micellization process. The enthalpy (∆H°) and entropy (∆S°) were also evaluated, offering additional insight into the thermodynamic driving forces involved. The obtained thermodynamic parameters showed that |TΔS°| is greater than |ΔH°|, suggesting that the micellization process is controlled by entropy.