Preparation Of Polysulfonate Ultrafiltration Membrane And Application On Oil Decolorization

Adsorption methods are traditionally used in the plant oil decolorization process, in which activated clay is often used as absorbent. As heating is essential, this method is high energy consumption and toxic substance may be resulted, at the same time reactions between activated clay and oil can lead to the deterioration in quality of the oil. On the other hand, this method is expensive because of the high price of activated clay and oil absorbed in the clay which is difficult to be recovered. As the result, new techniques and methods which can overcome the shortcomings mentioned above are the focuses of researchers. Ultrafiltration membrane technology is one of the new methods, which has many advantages as followed: mild process conditions, low energy consumption, no poisonous and harmful substance, easy operation, no oil waste, environmental friendly. In this study, the new organic-inorganic ultrafiltration membranes were prepared and applied in oil decolorization process.Polysulfone (PS)/silicon dioxise (SiO₂) hybrid ultrafiltration membrane was prepared by phase invertion process. PS was used as organic membrane material and SiO₂ was used as inorganic membrane material. The influence of PS concentration, evaporation time, concentration of inorganic additive, concentration of Polyvinyl Pyrrolidone (PVP), the ratio of dimethyl acetylamide (DMAC) and methylpyrrolidone (NMP) on the permeability fluxes and decolorization rate of membranes were investigated. The optimum process conditions of membrane manufacture were as followed: PS concentration 18%, PVP concentration 5%, evaporation time 40s, SiO₂ concentration 0.3%, NMP and DMAC ratio 1∶1. Surface and cross-sectional structure of membranes were observed by SEM.Polyethersulfone (PES)/inorganic additive hybrid ultrafiltration membrane was prepared by phase invertion process. The influence of PES concentration, evaporation time, concentration of inorganic additive (SiO₂,Al₂O₃ or nano-SiO₂), PVP concentration, reaction temperature, evaporation temperature and membrane thickness on the permeability flux the decolorization rate of membranes were investigated. The optimum process conditions of membrane preparation were identified in this experiment as follows: PES concentration 18%, PVP concentration 8%, evaporation time 90s, reaction temperature 40℃,evaporation temperature 35℃, inorganic additives concentration 0.6% respectively. Surface and cross-sectional structure of optimal membranes were observed by SEM.Decolorization experiments of oil were carried out in lab with six kinds of ultrafiltation membrane prepared, which were polysulfone membrane, polysulfone/ SiO₂ hybrid membrane, polyethersulfone membrane, polyethersulfone/SiO₂ membrane, polyethersulfone/Al₂O₃ membrane and polyethersulfone/nano-SiO₂. Influences of operation pressure and oil concentration on permeate flux and decolorization rate were evaluated. Decolorization rate were compared among six kinds of membranes. Aperture, porosity and the anti-fouling performance of membranes were measured. The mechanisms of Sieve and Hole model responsible for permeate flux were investigated. New processing of oil decolorization was proposed.The research provides a certain reference for the preparation of polysulfonate ultrafiltration membrane and the decolorization of oil.