Study On PH Response Behavior Of Microwave-magnetic Nanoparticle Coupling

The produced fluid of chemical flooding often exists in the form of emulsion,which will not only corrode pipelines and equipment,but also cause environmental pollution.In addition,in order to reach the standard of heavy oil transportation in our country（Moisture Content<1%）and realize the effect of demulsification of high efficiency and environmental protection,it is necessary to explore new demulsification technology.In our previous research,we found that microwave and magnetic nanoparticles have a synergistic effect on demulsification,but the demulsification effect is not ideal,and the separated water is turbid.Considering that the physical and chemical properties of magnetic nanoparticles are easily affected by pH,this paper first systematically studies the effect of pH on microwave-magnetic nanoparticles cooperative demulsification,the modified magnetic nanoparticles Fe₃O₄@CPAM were synthesized by water solution method,and their physical properties were characterized.Finally,the pH response behavior and mechanism of microwave-modified magnetic nanoparticles were studied,and compared with that of microwave-modified magnetic nanoparticles,so as to prove the feasibility of the modification.The experimental results show that:（1）As the mass concentration of magnetic nanoparticles increases,the water content of the emulsion first increases and then decreases,with the optimal mass concentration of 175 mg/L.Moreover,the water division rate of emulsion under Fe₃O₄@CPAM action was significantly higher than that of emulsion under the action of Fe₃O₄.（2）With the increase of pH value,the water division of the emulsion first decreases and then increases,and when the pH=3,the demulsification effect is the best,and the water separation rate of 1h under this condition reaches the highest value.This is because under acidic conditions,the negative charge of magnetic nanoparticles increases with the increase of pH value,and when it is adsorbed on the surface of oil droplets,the electrostatic repulsion between oil droplets becomes larger and the water separation effect becomes worse.Under alkaline conditions,with the increase of pH value,the negative charge of magnetic nanoparticles continues to increase,due to the electrostatic repulsion between magnetic nanoparticles at the interface of oil droplets,resulting in loose arrangement between adjacent molecules,and the mechanical strength of the interface film decreases,making oil droplets easy to agglomerate.（3）The order of water division rate of emulsion under the four demulsification methods is:microwave+Fe₃O₄@CPAM>microwave+Fe₃O₄>Fe₃O₄@CPAM>Fe₃O₄,that is,the coupling synergy between microwave and modified magnetic nanoparticles is the strongest.Mainly because after adding microwaves,polar water molecules will rotate at high speed to destroy the hydrogen bonds between water molecules,resulting in a decrease in the number of hydrogen bonds and enhanced hydrophobicity,so that magnetic nanoparticles are easily adsorbed on the oil-water interface,forming a mixed interface film and reducing the mechanical strength of the interface film;In addition,Fe₃O₄@CPAM As a magnetic flocculant,it can adsorb on the surface of negatively charged oil droplets and flocculate them through electric neutralization or complement,achieving rapid demulsification effect.In order to further explore the influence of pH value,microwave radiation time,radiation power,and concentration of magnetic nanoparticles on the water separation rate of emulsion,this paper uses SPSS software to carry out a uniform experimental design of four factors and three levels.Through variance analysis and nonlinear regression,a prediction model for the water separation rate of emulsion is obtained,and Matlab software is used to program the optimization solution.It is found that when the pH value is 3,the microwave radiation power is690W,the radiation time is 15s,and the concentration of magnetic nanoparticles is 195mg/L,the theoretical water separation rate of the emulsion can reach the maximum of 99.99%.In addition,experimental validation was conducted on significant influencing factors such as pH value,microwave radiation time,and the optimal solution,demonstrating the high accuracy and applicability of the water separation rate prediction model.