Abstract
Oil droplets containing surfactants and pesticides are expected to spread on a water surface, under the Marangoni effect, depending on the surfactant. Pesticides are transported into water through this phenomenon. A high-speed video camera was used to measure the movement of Marangoni ridges. Gas chromatography with an electron capture detector was used to analyze the concentration of the pesticide in water at different times. Oil droplets containing the surfactant and pesticide spread quickly on the water surface by Marangoni flow, forming an oil film and promoting emulsification of the oil–water interface, which enabled even transport of the pesticide into water, where it was then absorbed by weeds. Surfactants can decrease the surface tension of the water subphase after deposition, thereby enhancing the Marangoni effect in pesticide-containing oil droplets. The time and labor required for applying pesticides in rice fields can be greatly reduced by using the Marangoni effect to transport pesticides to the target.
Highlights
In 1871, the Italian physicist Carlo Marangoni took a sponge soaked in oil and threw it into a pond
The hydrophilic group of S500 is benzenesulfonate, which is a short hydrophilic chain and cannot form hydrogen bonds in reverse micelles as in the case of hydrophilic oxyethylene chains. It is more difficult for S500 to form reverse micelles than it is for S601, and the stability of the formed reverse micelles is weaker than that of nonionic surfactants
The micelle relaxation time of the micelles related to the micelle formation/disintegration kinetics is shorter, the micellar disintegration process is faster, the concentration of surfactant monomer is supplemented in time, and it is easier for S500 monomer adsorbs to the interface faster, generating a stronger Marangoni effect
Summary
In 1871, the Italian physicist Carlo Marangoni took a sponge soaked in oil and threw it into a pond He observed surface movement caused by the difference in surface tension between oil and water phases and measured the speed of wave propagation. When oil droplets or surfactant solutions are deposited on the liquid subphase (water surface), molecules from the oil or surfactant will migrate to the air–water interface and move on the subphase surface, resulting in a surface tension gradient that generates Marangoni stress. This causes the Marangoni flow from the low surface tension area to the high surface tension area [7,8,9,10,11,12,13,14].
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