Preparation And Sepration Performance Study Of Nano-porous Anodic Alumina Membrane

Inorganic membrane in food separation and other fields often involved in protein products,such as recycling and sterilization,but it is very difficult to study the membrane separation performance in quantitatively because of the complexity of pore structure of membrane.Anodic alumina membrane with strictly parallel pore path and perpendicular to the membrane surface,an adjustable aperture(a few hundred nanometer to several nanometers) and narrow distribution range can be used in many areas,such as nano-materials stuffing and precision-filled membranes.It is important for alumina membrane to overcome its own fragile and find a suitable body of support in order to improve its strength and get better application future.This experiment studied influence on the quality of electrochemical polishing using of perchloric acid and ethanol mixture with different operation conditions,such as concentration, temperature,voltage,duration,with or without stirring.The results obtained appropriate condition scope:the volume ration(HClO₄:C₂H₅OH) is 1:4～1:6;polishing temperature is 10～20℃;voltage is 16～20V;duration is 2～3min;magnetic stirring.This experiment didn't divest membrane,but directly prepared a new type of anodic alumina membrane supported by macroporous aluminum.This membrane which had good toughness and strength was used for filtration analysis of bovine serum albumin(BSA) solution to research separation performance of membrane.The experimental results showed that,membrane flux decreased and rejection increased with increasing of anodic oxidation time.In the beginning of filtration,with the decreasing of oxidation voltage,membrane flux decreased,rejection increased;in the late,membrane flux(smallest oxidation voltage) is maximum,membrane rejection(highest oxidation voltage) is maximum.Membrane flux increased and rejection decreased with the increasing of preparation duration of support. With the increasing of etching time,flux increased,rejection decreased.After secondary anodic oxidation,membrane flux was slightly larger than once oxide film,but the rejection hasn't obvious difference.This experiment also examined the influence of operating conditions on the performance of membrane separation,and a preliminary study of membrane separation model was conducted.The experimental results showed that,with the increasing of the BSA solution temperature,membrane flux first increased and then decreased,in contrary to rejection,it is best at around 20℃.In the beginning,flux decreased with the increasing of concentration,in the late,stable flux of system with larger concentrations is higher.With the creasing of solution PH value,flux first decreased and then increased,the flux is least when PH is 4.7; after the static adsorption,the membrane flux is less.With the increasing of operating pressure,the initial flux increased gradually,and the rejection first decreased and then increased;to a certain extent,the stable flux increased with the increasing of pressure,but decreased if it would continue;under the same operating pressure,rejection increased with the increasing of filtration time,it was proper at 0.15MPa.Simulated by three blocked models, middle blocked model was suitable to separation process of BSA solution.Restoration rate of the flux decreased with the increasing of backwash times,and increased with the increasing backwash pressure(＜0.15MPa);flux can also be restored by ultrasonic cleaning.