Study On The Preparation Of Magnetic Fluid And Separation Properties

Magnetic liquid is a kind of liquid functional materials,which is composed of magnetic particles,carrier liquid and surfactant,having both the magnetic properties and the flowability.Magnetic liquid will show the magnetic properties,viscosity,magnetic suspension property,magneto optical characteristics,magneto optical properties,thermo magnetic properties and other properties under amagnetic field which make the magnetic liquid widely used in the field of Biological,chemical,medical,sealing,damping,aerospace,metallurgy,mineral processing,wastewater treatment and sensor.Coprecipitation was used to prepare Fe3O4.The effects of reaction temperature and time,material ratio,and dosing rate on the size of Fe3O4 were studied.Sodium oleate and sodium dodecyl benzene sulfonate(SDBS)were used as surfactants to wrap Fe3O4 up.TEM,XRD,IR,VSM,Malvern mastersizer and zetasizer nano were used to study the dispersion,size,the material composition,reaction between the surfactant and Fe3O4 and magnetic properties.the stability of the products of the direct and indirect modification were compared.Results showed that the best condition of preparing Fe3O4 was that at 80?,Fe3+:Fe2+ is 1.4,the concentration of Fe3+and Fe2+ is 0.5 mol/L,NaOH concentration is 2 mol/L,excess coefficient of NaOH is 1.3,adding NaOH into mixing ferric salt solution quickly,reaction for 20min.Under this condition,the size of Fe3O4 was 0.790?m.Then wash the foreign ion away,make the concentration of Fe3O4 to 16mg/mL,adjust the pH to 5.5,weigh sodium oleate as heavy as 20%of Fe3O4,keep suspension fluid of Fe3O4 in the ultrasonic cleaner for 20min,make it stirring in the water bath for 30min at 80?,cool to the room temperature,then add SDBS as heavy as 10%of Fe3O4 to the suspension,keep reacting for 10min.Under this condition,the size of Fe3O4 in the magnetic fluid was 125nm detected by the Malvern Zetasizer Nano,where there was no obvious stratification after 30 days,which indicated that the magnetic fluid had a better stability after modification.The relatively complete crystal is obtained after crystallization 90min.Besides,Effect of indirect modification was better than the indirect one in stability.TEM results showed that Fe3O4 modified by sodium oleate and SDBS had a better dispersion and its size was about lOnm.XRD test results showed that the product prepared by coprecipitation was Fe3O4,with a crystallization structure,whose size was 14nm.IR spectrums indicated that the sodium oleate and SDBS adsorb on the surface of Fe3O4.and the adsorption layer of sodium oleate was firmer than SDBS.The hysteresis regression curve of magnetic fluid passed through the origin and there was no magnetic remanence and coercivity,indicating that the magnetic fluid had superparamagnetism.The result of Zeta potential showed that algebraic value of Zeta potential of Fe3O4 increased after modification by odium oleate and SDBS,which met the colloid stability theory that the higher the surface potential,the stabler the colloid.The force of magnetic fluid on different size of the quartz,pyrite,and tourmaline were studied under different magnetic intensity in different concentrations of magnetic fluid.The results showed that in the magnetic field,the deposition rate of the three minerals in the magnetic fluid was slower than that without the magnetic field.The higher the magnetic fluid concentration and the stronger the magnetic intensity,the slower the deposition rate,which indicated that the apparent density of magnetic fluid increased with the increase of the magnetic intensity and the magnetic fluid concentration.The force on minerals from the magnetic fluid in the magnetic field was obtained,Fm =according to the continuous equation,Maxwell's equations,the generalized Ohm's law,the Bernoulli equation of magnetic fluid and conservation of momentum and energy conservation equations.Magnetic buoyancy was similar to that.The visual density of magnetic fluid was that.The resultant force of the mineral particles was that.When F>0,mineral particles will move up,when F<0,will move down;when F = 0,will keep static in a position in magnetic liquid.