Study On The Preparation Of Membranes With Adaptable Wettability And Oil/water Separation Mechanism

The treatment of large quantities of polymer-containing,surfactant-containing,highly water-containing produced fluid in the middle and late stages of oilfield development is a hot issue that needs to be addressed at this stage of oilfield development.At present,the treatment of produced fluid mainly includes pretreatment based on gravity settling and hydrocyclone separation and deep treatment with the addition of chemical agents or high frequency electric field for emulsion breaking.Pretreatment methods based on density difference cannot independently and selectively separate oil/water according to demand,and existing deep treatment methods have problems such as high energy consumption,secondary pollution and single demulsification type.To address this challenge,membranes with adaptable wettability modified with polydopamine(PDA)and functionalized amphiphilic polymers as a new method for oil/water separation of produced fluid were proposed in this paper.The membrane surface wettability can be automatically switched by adapting to the contact environment.The selectively separation characteristics of membranes with adaptable wettability applied to oilwater mixtures and multiple types of emulsions were investigated.The chemical probe AFM technique and the simplified model of microchannel were combined for the first time to quantitatively analyze the force properties of the oil-water separation process,revealing the mechanism of selectively oil/water separation and demulsification.The use of membrane separation with adaptable wettability for the separation of produced fluid is of dual significance for oilfield environmental protection and cost reduction and efficiency gains.Synthesis of functionalized amphiphilic polymers via RAFT controlled polymerization reaction.The metal membrane and microfiltration membrane with adaptable wettability are prepared by dip-coating method for the separation of oil-water mixture and emulsion,respectively.Comprehensive analysis of the microscopic morphology,chemical properties and macroscopic wettability of membrane surfaces to investigate the adaptable wettability of PDA/polymer modified membranes.The separation characteristics of oil-water mixtures and multiple types of emulsions have been investigated separately through oil/water separation experiments.Study of the formation of physical/chemical bonds during the construction of multimeshed polymer network and the structure of polymer networks in specific environments based on the theory of intermolecular interactions.Principle for the generation of adaptiable wettability phenomena following the construction of polymer networks on membrane surfaces by surface free energy thermodynamics.The change in force during oil phase contact with the surface is analysed by the chemical probe AFM technique,Further analysis of the act mechanism of oil/water selectively separation and emulsion breaking in conjunction with comprehensive force analysis within a simplified model of membrane microchannel.The results show that the functionalized amphiphilic polymers synthesized contain both hydrophilic and hydrophobic chains as well as mussel-inspired adhesion groups.Because of the construction of rough structure and polymer network,PDA/ polymer modified membranes have excellent adaptively wettability and can switch autonomously.Modified membranes offer high efficiency,high throughput,tolerance to harsh conditions and reusability in the separation of mixtrues and multiple types of emulsions.Nanomechanical experiments were conducted to quantify the adhesion or repulsion of the oil phase in contact with the membrane surface.Combined with the force analysis in the simplified model of membrane microchannels,the act mechanisms of selectively separation and demulsification were further clarified,the direction of capillary additional pressure produced by differential wetting is opposite,which leads to the different energy needed to overcome when oil and water pass through the microchannel,thus realizing the selectively oil/water separation.In the microchannel,when the strength of the external force on the emulsion droplet is greater than the cohesive strength of its oil-water interface,leading to the breaking of the emulsion.