Preparation Of Functionalized Fe₃O₄ Nanoparticles And Their Applications In Oilfiled Wastewater Treatment

While the ASP flooding improving the crude oil recovery rate,it also produces a large amount of ASP flooding wastewater.Traditional water treatment methods are difficult to effectively treat ASP flooding wastewater because the ASP flooding wastewater has the characteristics of large viscosity,slow sedimentation of mechanical impurities,high oil content,high degree of oil emulsification and strong emulsification stability.In recent years,Fe3O4 nanomaterials have demonstrated unique advantages in the field of water treatment due to their unique magnetic properties and strong surface coordination activity.Moreover,the use of magnetic nanomaterials to treat ASP flooding wastewater is still a relatively new topic and needs further study.In this paper,a functionalized Fe3O4 nanoparticle is designed for the treatment of oilfield produced water,and the rapid separation of pollutants is achieved by applying an external magnetic field.Functionalized Fe3O4 nanoparticles have the advantages of high processing efficiency,fast separation speed,and easy recovery when they compared with traditional processing methods.Therefore,the development of this new type of magnetic nano-adsorbent can provide new ideas for the treatment of oilfield produced water.The main work of this thesis is as follows:1.Fe3O4 nanoparticles with different sizes and different morphologies were synthesized by polyol method through changing the mixing and dissolution of raw materials.The as-prepared Fe3O4 nanoparticles are characterized by XRD,TEM,DLS,FTIR and MPMS.The core material suitable for surface modification and water treatment was selected by comparing their colloidal stability and magnetic response ability in aqueous solution.2.Amino-functionalized Fe3O4 nanoparticles were successful synthesized by directly reacting of 3-aminopropyltriethoxysilane(APTES)with the as-prepared Fe3O4 nanoparticles.The optimal modification amount of APTES is 3 m L,the optimal modification time is 12 h and the optimal modification temperature is 70?.The successful modification of APTES has been proved by TEM,FTIR and XPS.The TEM and XPS result indicates that the APTES layers deposited on the surface of Fe3O4 nanoparticles adopt an amorphous 3D structure with thickness of 2 to 3 nm cross-linked by hydrogen bonding,Si-O bonding and/or other forces.3.It is proved that electrostatic adsorption is the main mechanism of APTESFe3O4 adsorption of HPAM by comparing the adsorption experiments of APTES-Fe3O4 nanoparticles on HPAM,PAA and CPAM.The maximum adsorption capacity of APTES-Fe3O4 at p H = 5,7,9 is 42.51 mg g-1,37.12 mg g-1,26.81 mg g-1,respectively,the adsorption capacity is 3.2 times,8.2 times and 35 times of Fe3O4 respectively.The kinetic results indicate that electrostatic adsorption is the main rate-limiting step.The isothermal adsorption curve shows that the adsorption of HPAM by APTES-Fe3O4 is more consistent with the monolayer uniform adsorption.Thermodynamic studies indicate that the adsorption of HPAM by APTES-Fe3O4 is endothermic.After 3 cycles,the adsorption of HPAM by APTES-Fe3O4 can still maintain about 90%.4.Experiments show that APTES-Fe3O4 can effectively remove HPAM and oil in produced water.The optimal dosage of APTES-Fe3O4 is 9.6 mg m L-1,the optimal flocculation time is 7.5 min,and the optimal p H range is 5-9.In addition,the increased concentration of HPAM and SDBS in the produced water will reduce the processing performance of APTES-Fe3O4.The sodium salt does not affect the processing performance of APTES-Fe3O4,and the increased concentration of calcium salt and bentonite will accelerate the flocculation and gelation of HPAM.After 3 cycles,APTES-Fe3O4 can still maintain a degreasing rate of more than 90%.