Nanoparticles Regulating Electrokinetic Flow Of Interface And Its Application

The ship carries 80%of world trade traffic.The direct discharge of a large amount of oil-contaminated sewage generated during the operation of a ship would endanger the marine environment and human health,and the ecological balance will be destroyed.Coalescence and ultrafiltration membrane separation methods can meet the mandatory requirements of the ship handling emulsified oil,but in practice the coalescence filter and the filter are easy to be clogged by the oil while retaining the emulsified oil droplets.It is of great significance to study the electrokinetic flow of the solid-liquid interface regulated by nanoparticles to restrain the adhesion of the oil droplets on the surface of the oily wastewater treatment material.In addition,the development of a new type of highly efficient and green marine oil wastewater treatment technology is the key to solve this problem fundamentally based on the principle that nanoparticles regulate liquid-liquid interface electrokinetic flow to enhance coalescence of oil droplets.Based on the large specific surface area and strong adsorption capacity of nanoparticles,this paper aims to develop a novel green and efficient marine oil wastewater treatment technology by changing the zeta potential distribution at the interface of solid-liquid interface and liquid-liquid interface to change the interface electrokinetic flow.The influence of inhomogeneous distribution of zeta potential at PDMS microchannel wall and oil-water interface on electroosmotic flow is investigated by means of numerical simulation and experimental verification.And the influence law of the inhomogeneous distribution of the interfacial zeta potential on the vortex is found.In addition,Al₂O₃ nanoparticles reinforcing coalescence of oil droplets under DC electric field is also studied.Specifically,the main contents of this paper include:（1）Fe₃O₄ nanoparticles regulating the electrokinetic flow of the solid-liquid interfaceThe effects of the inhomogeneous distribution of Fe₃O₄ nanoparticles on the surface electrokinetic flow of PDMS microchannels are investigated by numerical simulation and experimental verification.First,a straight microchannel model of electroosmotic flow is established.Numerical simulation is performed to study the influence of length ratio of inhomogeneous zeta potential distribution in the microchannel coated by Fe₃O₄ nanoparticles on the vortex generation.Tracing particle method is used to verify the simulation results.The results show that the best treatment time of microchannels with 2mg/mL Fe₃O₄ nanoparticle suspension is 20min.Under the same electric field strength,the coating length ratio of Fe₃O₄ nanoparticles in straight microchannels is different,and the number of vortexes is also different.The experimental results are in good agreement with the simulation results.Under the same coating length ratio condition,the position of vortexes does not change with the change of the strength of the DC electric field,indicating that the charge at the solid-liquid interface does not shift.（2）Al₂O₃ nanoparticle regulating the electrokinetic flow of the liquid-liquid interfaceThe effects of the inhomogeneous distribution of Al₂O₃ nanoparticles on the electrokinetic flow at the oil-water interface are investigated by numerical simulation and experimental verification.First,an oil drop surface electroosmotic flow model is established.The effect of the distribution angle of inhomogeneous zeta potential on the surface of the oil droplet is studied by numerical simulation.Tracing particle method is used to verify the simulation results.The results show that the response coverage area ratio of Al₂O₃ nanoparticles decreases with the increase of oil droplet diameter under the same electric field.The coverage area ratio of Al₂O₃ nanoparticles coated on the oil droplet with the same size decreases with the increase of electric field strength.The magnitude of the electric field strength has no effect on the shape,size and position of the vortexes,but the rotational speed of the vortexes is proportional to the electric field strength.The experimental and simulation results agree well.（3）Coalescence of oil droplets enhanced by Al₂O₃ nanoparticles under DC electric fieldThe experimental system for forming fixed oil droplets of controlled size and position is designed and set up.The effects of droplet size and electric field strength on the coalescence velocity of droplet are investigated experimentally.The strengthening effect of Al₂O₃ nanoparticle on coalescence of oil droplets under DC electric field is studied.The results show that DC electric field can accelerate the coalescence of oil droplets in water.When the electric field intensity is constant,the coalescence time of oil droplets decreases with the increase of oil droplet diameter.When the oil droplet diameter is constant,the coalescence time of oil droplets decreases with the increase of electric field strength.In the case of the same strength and oil droplet diameter,the coalescence time of the oil droplets coated with nanoparticles are shorter than that of the oil droplets uncoated with nanoparticles.The research of this paper is of certain reference significance for the development of a new type of efficient and green marine oil sewage treatment plant and the improvement of oil wastewater treatment efficiency.