Demulsification Of Oil-in-Water Emulsion Through Hydrophilic Microfiltration Membrane

The microfiltration membrane demulsification technique has the merits of high separation efficiency, low energy consumption, no pollution, relatively simple installment, broad versatility and so on, compared with the traditional emulsion breaking technology. This thesis studied the break-up of O/W emulsion by mixed cellulose ester membrane and polytetrafluororthylene(PTFE) membrane, researched membrane cleaning and fouling. The experimental results showed that the hydrophilic membranes can be used for demulsification of the oil-in-water emulsion. The flux of mixed cellulose ester membrane can achieve 5.798m³Â·m^-2·h^-1, demulsification efficiency 67% under the optimal demulsification condition , membrane pore size 0.45μm, transmembrane pressure 0.3MPa, volumetric ratio of aqueous phase to internal oil phase 4: 1, the surfactant concentration 0.1%. The used membrane was soaked about 30min with 0.5%(wt%) NaOH, then blowed 5min with the compressed air. Under this condition, demulsification efficiency may achieve 33.0%, the membrane flux recover coefficient is 28.7%. The flux of polytetrafluororthylene(PTFE) membrane can achieve 0.948m³Â·m^-2·h^-1, demulsification efficiency 62.4% under the optimal demulsification condition , transmembrane pressure 0.25MPa, volumetric ratio of aqueous phase to internal oil phase 4: 1, the surfactant concentration 0.1%. The used membrane was soaked about 1h with 1% (wt%)NaOH, then blowed 5min with the compressed air. Under this condition, demulsification efficiency may achieve 39%, the membrane flux recover coefficient is 33.0%. Compared with polytetrafluororthylene(PTFE) membrane, mixed cellulose ester membrane has the advantages of high flux, high demulsification efficiency and low cost and so on.The membrane fouling analysis indicated that the membrane itself resistance approximately was the total drag 10%, the resistance that can be removed by cleaning was the total drag 70% approximately, but still 20% resistance could not be removed.The demulsification mechanism was simulated that the continuous phase of O / W emulsion wetted and coalesced on the surfaces and pore walls of membrane, migrated in the pores after deformation by pressure firstly, as the result the internalphase droplets contacted, coalesced, collided and then formed a bigger droplet, emulsion was not stabilized and formed two separated phase.