Effect of an eco-friendly o/w emulsion stabilized with amphiphilic sodium alginate derivatives on lambda-cyhalothrin adsorption-desorption on natural soil minerals.

The effects of amphiphilic O/W emulsions, stabilized by the alkyl polyglycoside (APG) or cholesterol-grafted sodium alginate (CSAD)/APG systems, on lambda-cyhalothrin adsorption/desorption mechanisms on natural soil minerals (i.e., illite and kaolinite) were investigated. Sorption and desorption of lambda-cyhalothrin onto soil minerals was studied via batch equilibration to give insight into the adsorption equilibrium, kinetics, and thermodynamics of lambda-cyhalothrin adsorption onto minerals. The results indicate the following: (i) The adsorption processes for the APG system and CSAD/APG system include: rapid adsorption, slow adsorption, and adsorption equilibrium. The adsorption kinetics of pesticide on illite and kaolinite are in accordance with the Ho and McKay model, and the adsorption isotherm conforms to the Freundlich model. In addition, the adsorption processes of pesticide for the two systems on minerals were spontaneous and feasible (ΔG0 < 0), endothermic (ΔH0 > 0), and mainly involved chemical bonding (ΔH0 > 60). (ii) The equilibrium adsorption percentages of the pesticide on illite for the APG system and CSAD/APG system were 42.4% and 64.8%, and the corresponding equilibrium adsorption percentages on kaolinite were 40.8% and 61.8%, respectively. Moreover, the pesticide adsorption rate K2-CSAD/APG was faster than K2-APG, and its adsorption capacity Kf-CSAD/APG was greater than Kf-APG. Meanwhile, the pesticide desorption Kfd in the CSAD/APG system was smaller than that in the APG system. As a result, this eco-friendly O/W emulsion based on amphiphilic sodium alginate derivatives might provide a green pesticide formulation, since it could reduce the amount of lambda-cyhalothrin entering aquatic systems to threaten non-target fish and invertebrate species.