Adsorption Of Oil From Wastewater By Carrier Particles Of Supported Demulsifier:Characteristics And Mechanism

The produced water from ASP flooding has high emulsification and fine oil droplets,so it is stable and difficult to treat.After the demulsification using the conventional demulsifiers,the fine oil droplets are still difficult to coalesce and a secondary emulsification takes place.The system of produced water from ASP flooding is a system where demulsification and emulsification are co-existing and reversible.The demulsification and destabilization of fine oil droplets are crucial to improve the separation efficiency of oil and water,so it is necessary to develop a new demulsifier for the produced water from ASP flooding.The polyether polyquaternary ammonium salt supported demulsifier is a functional demulsifier which integrates demulsification and adsorption.By capturing and adsorbing the fine oil droplets after demulsification,the problem that difficult coalescence of fine oil droplets after demulsification using conventional demulsifiers can be solved,so the demusification efficiency of the produced water from ASP flooding is improved.The paper focuses on the adsorption behavior and mechanism of carrier particles for fine oil droplets after demulsification using the polyether polyquaternary ammonium salt supported demulsifier.Preparation of the simulated produced water from ASP flooding and adsorbent?the supported demulsifier?.According to the water quality analysis of the produced water from ASP flooding from the No.1 Oil Production Plant of Daqing Oilfield,the simulated water sample was prepared.The viscosity of the simulated water was tested to be 4.199 mPa·s,and the medium diameter d₅₀ of the oil droplets in water sample was 11.15?m.The polyether polyquaternary ammonium salt supported demulsifier?PPA@SiO₂?was prepared by the polymerization and grafting methods,and the reaction products and hydrophobically modified carrier particles?MPS@SiO₂?were characterized and analyzed by means of SEM,BET,contact angle measurement,TG and FTIR.The mass charge ratio of the polyether polyquaternary ammonium salt demulsifier ranged from 2684 to 12862,it was a high polymer.FTIR spectra analyses proved that it had been successfully grafted onto carrier particles.The polyether polyquaternary ammonium salt demulsifier accounts for 6%in total mass of PPA@SiO₂.MPS-SiO₂ and PPA@SiO₂ both had large specific surface area and good hydrophobicity,whose adsorption isotherms belonged to the type?adsorption isotherm.The medium diameter d₅₀ of SiO₂·nH₂O,MPS-SiO₂ and PPA@SiO₂ were21.4?m,115?m and 132?m respectively,it was inferred to be a mesoporous material from the average pore diameter.The carrier particles had a spherical shape,good dispersion and no adhesion,so they had good oil absorption properties.Study on adsorption characteristics of carrier particles of the supported demulsifier for oil droplets.The effects of oil-displacing agent concentration?alkali,surfactant and polymer?,and chemical environment of solution?temperature,pH and salt concentration?on the adsorption abilities of the carrier particles?DEM-SiO₂?were investigated.The surfactant in the oil-displacing agent had the most significant effect on the adsorption performance of DEM-SiO₂ and MPS-SiO₂.With adsorption temperature increasing,the equilibrium adsorption capacity of DEM-SiO₂ and MPS-SiO₂ decreased,and approached 330 mg/g and 312 mg/g at 20? respectively.At pH 9-11,the equilibrium adsorption capacity of DEM-SiO₂ was larger than that of MPS-SiO₂,indicating that DEM-SiO₂ was more suitable for the treatment of weak alkaline produced water from ASP flooding.The salt?NaCl?concentration had little effect on the equilibrium adsorption of MPS-SiO₂,and had no effect on the equilibrium adsorption of DEM-SiO₂.The high magnification and large depth optical microscopic results showed that fine oil droplets and coalesced oil droplets were adsorbed onto the surface of DEM-SiO₂ after demulsification,and there existed multilayer adsorption.In the conditions that the dosage was 1.0 g/L,the adsorption temperature was 20 ^oC and the adsorption time was 40 min,the equilibrium adsorption capacities of DEM-SiO₂,MPS-SiO₂ and the activated carbon powder for the oil droplets in the simulated produced water from ASP flooding were compared.The equilibrium adsorption capacity of DEM-SiO₂ reached 390 mg/g,which was 27times the adsorption capacity of specific area of the activated carbon powder.The carrier particles DEM-SiO₂ were recovered by solvent regeneration process.The results of FTIR and TG analyses showed that the recycled carrier particles were structurally-complete and had good thermal stability.Study on the adsorption mechanism of carrier particles of the supported demulsifier for oil droplets.The adsorption kinetics and thermodynamics of the carrier particles DEM-SiO₂ for oil droplets were studied.The adsorption heat effect of DEM-SiO₂ and MPS-SiO₂ on oil droplets were tested by microcalorimeter.The adsorption kinetics of the carrier particles DEM-SiO₂ showed that the adsorption process conformed to the pseudo-second-order kinetics.The intraparticle diffusion had a certain effect in the oil absorption process of the carrier particles,but it was not the major rate-determining step.In the isothermal adsorption experiment,the adsorption of DEM-SiO₂ for oil droplets could be more reasonably described by the Freundlich isotherm adsorption model.The thermodynamic study results showed that?G and?H of the adsorption process were negative,indicating that the adsorption process was a spontaneous exothermic process.And?S also was negative,indicating that the adsorption process was accompanied by a decrease in confusion degree.The values of the adsorption heat measured by the microcalorimeter were both negative and small,which further explained that the adsorption process was exothermic and a main physical adsorption progress supplemented by chemical adsorption from the actual measurements.At the same adsorbent dosage,with the adsorption temperature increasing,the adsorption heat value of the DEM-SiO₂ adsorption process dominated by?H enhanced gradually.While after reaching 40?,the adsorption heat value decreased.At the same adsorption temperature,with the content increase of DEM-SiO₂ after the demulsification of the supported demulsifier,the adsorption heat effect of the carrier particles on the oil droplets enhanced gradually.