Mechanism Of Charge Transfer During The Coalescence Of A Drop With A Liquid Interface

With the rapid development of science and technology,the investigation of related parameters of the coalescence of liquid-liquid（L-L）plays a very important role in many fields such as material,energy,biomedicine and so on.For example,the coalescence of drop-drop is used to break the emulsion and remove the oil.At present,although there are a lot of researches on the coalescence of L-L,there are still few researches on the charge transfer of the coalescence of L-L.Therefore,it is necessary to investigate the charge transfer during the L-L coalescence process.In this paper,a system that controls the coalescence process of a drop and air-liquid interface was set up to investigate the electrical signal and factors that influence the electrical signal.And then,that working principle is analyzed and experimental.Finally,the gas environment is detected through this system.The main research contents are as follows:（1）Measuring the charge and polarity of the gas-liquid interface of the drop by using the Faraday cup method,and analyzing the source of the charge on the surface of the drop.The experiment shows that pure water drop is positively charged,while Na Cl,Li Cl,KCl and Mg Cl₂drop is negatively charged.The reason is that Cl^-tends to the drop interface.And the relationship between the amount of charge and concentration is not a monotonous trend,but there is an inflection point near the concentration of 3.5%.（2）The system of coalescence of drop and water interface was set up to control the speed of the drop approaching the water interface by controlling the formation time of drop,and eliminate the secondary drop.The electrical signal generated by the system when the drop coalesces with the water interface is investigated.The experimental results show that the current of the system becomes larger as the volume of the drop becomes larger.And the voltage of the system is affected by the volume of drop,the type of drop,concentration of drop and the material of the needle that produces the drop.The voltage first increases and then decreases as the concentration increases in the range of 1%-10%,and the inflection point is also around 3.5%.（3）Using the system to investigate the influence of the gas environment.First,putting the system into a closed space and fill the container with the gas to be measured.The electrical signal generated by the process of coalescence of drop and water interface in different gas environments was investigated.The experiment results show that inert gas has little effect on the electric signal of the system,while reactive gas such as CO₂,NO,NO₂ will have a greater impact on the electric signal of the system.This is because the reactive gas changes the p H of the liquid,and the change of the p H will affect the liquid interface charge distribution,and the closer the p H value is,the smaller the voltage and current signal will be.The system of double-electrode of coalescence of drop and water interface is proposed in this paper provides new ideas and methods for the investigation of the charge transfer mechanism in the L-L coalescence process and the development of new gas sensors.