Preparation Of Magnetic Hyperbranched Cationic Polymers And Application Of Ternary Composite Flooding In Wastewater Treatment

With the continuous deepening of oilfield development and the application of tertiary oil recovery technology,oilfield ternary composite flooding wastewater containing alkali,surfactant,polymer,microemulsion droplets,and solid impurities is generated after oil-water separation,which urgently needs to be effectively treated.The wastewater from ternary composite flooding contains oil,suspended solids,anionic polymers,and surface active substances,with high viscosity and Zeta potential,resulting in difficulties in demulsification,flocculation,and slow separation and sedimentation.In response to the problem of difficult treatment of oilfield ternary composite flooding wastewater,magnetic branched core（FSN）was prepared using tetraethyl silicate（TEOS）,nano Fe₃O₄,and aminopropyl triethoxysilane（APTES）,and then reacted with polyamines and methyl acrylate to synthesize magnetic hyperbranched molecule FSNMN with demulsification ability.A cationic polymer long chain（CAMHA）with flocculation ability was synthesized using acrylamide（AM）,acryloyl oxyethyltrimethyl ammonium chloride（DAC）,and maleic anhydride（MA）.The cationic polymer long chain was grafted with FSNMN to obtain a magnetic hyperbranched cationic polymer（FSNMN-C）,which has good demulsification and rapid flocculation ability for ternary composite flooding wastewater.CAMHA polymer was synthesized using acrylamide（AM）,acryloyl oxyethyltrimethyl ammonium chloride（DAC）,and maleic anhydride（MA）.The optimal reaction conditions were as follows:the molar ratio of AM:DAC:MA was 3:1:0.0025,the reaction temperature was50℃,the first stage reaction time was 6 hours,the second stage reaction time was 0.5 hours,the molecular weight was over 4 million,and the cationic degree was about 21%.CAMHA has a good flocculation effect on suspended solids,with a gravity settling time of 30 minutes and a flocculation efficiency of 91.12%.Its flocculation performance was analyzed based on flocculation experiments.CAMHA has weak ability of electrostatic demulsification for negatively charged lotion,and the maximum oil removal rate is only 54%after 30 minutes of treatment.Finally,FSNMN was grafted onto CAMHA to obtain FSNMN-C magnetic hyperbranched cationic polymer.The reaction surface method was used to analyze the graft synthesis conditions of CAMHA onto the third generation magnetic hyperbranched molecules of five polyamines.The removal rate of suspended solids was taken as the response value,and the optimal graft synthesis conditions were obtained,that is,the molar ratio of reactants was 1:1,the reaction temperature was 40℃,and the reaction time was 4h.The average molecular weight of the optimal 3-FSNMN4-C graft product was 4.7 million,the cationic degree was 20.5%,and the saturation magnetization was 20 emu/g.A 20 mg/L dosage in the magnetic field can be used to treat simulated wastewater for 30 minutes,achieving a removal rate of 93.82%for oil and91.95%for suspended solids.Experimental evaluation of the demulsification and flocculation ability of the third and fourth generation FSNMN-C products on ternary composite flooding wastewater,comparative analysis of the performance of FSNMN-C in treating simulated fluid and ternary composite flooding wastewater,and summary of the demulsification and flocculation mechanism of FSNMN-C molecules on oilfield ternary composite flooding wastewater:adsorption and replacement of oil-water interface surfactants,destruction of oil-water interface;Reduce the Zeta potential of suspended colloidal particles and disrupt electrostatic stability;Interacting with colloidal particles to produce flocs,reduce system viscosity,capture flocculation through nets,and enhance the ability to clean suspended solids and oil droplets;Force the aggregation of particles under magnetic drive,enhancing flocculation and demulsification capabilities.Hyperbranched polymers have broad application prospects in the field of ternary composite flooding wastewater treatment.The research and application of magnetic hyperbranched cationic polymer type demulsifiers and flocculants can provide new ideas and reference methods for the treatment of ternary composite flooding wastewater.