| This work has been undertaken to develop advanced techniques for preparing the supporting layer of ultrafiltration membrane by using Al2O3 and China clay, which are abundant and cheap, and its separating layer by using pure aluminium, which was made by electrolyzing Al2O3. This is able to supply a basal theory and techniques for preparing whole ultrafiltration membranes suitable for separating proteins in food industry.The experimental results showed that the ultrafiltration membrane composed of a supporting layer prepared by using Al2O3 and China clay, and a separating layer prepared by using pure aluminium, which was made by electrolyzing Al2O3, is practicable. The molecular-weight cutoff of the membrane is 44000 Dalton and its water flux is 7.3×10-1 m3/ (m2·h) . The conclusions are summarized as follows.1 Preparation of supporting layerThis experiment put emphasis upon studies on optimal dosage of aluminium oleate applied to the preparation of the supporting layer. The experimental results indicated that the optimal dosage of aluminium oleate used for the preparation of supporting layer is 10%(w/w). The water flux of the supporting layer prepared by using the optimal dosage of aluminium oleate is 9.96×10-1 m3/ (m2·h) with the bearing strength suitable for preparing good ultrafiltration membrane. It was found that the higher the dosage of aluminum oleate used is, the worse the bearing strength of the supporting layer is, and on the other hand, the lower the dosage of aluminium oleate used is, the lower the water flux of the supporting layer is.2 Production of aluminium by electrolyzing Al2O3The pure aluminium were produced on cathode by electrolyzing Al2O3 at 1000℃ when the direct current (voltage- 3.1V, electric current density -15KA/m2) passed through the fusion of cryolite and Al2O3 in the electrobath with carbon as anode and steel as cathode.3 Research into preparing aluminium hydroxide sol(1) It was found that the best conditions of preparing aluminium hydroxide sol through the dissolution of aluminium by nitric acid are as follows: ammonia: prepared aluminium nitrate solution:acid (1:1:0.1), adding the solutions dropwise (10ml/min), respectively at 85℃, stirring for 6h12h.(2) It was also found that the best conditions of preparing aluminium hydroxide sol through aluminium hydroxide precipitates are as follows: 1g/100ml aluminium hydroxide in the prepared gel-sol at 85℃, nitric acid:aluminium hydroxide (15ml: 1g), stirring for 6h.Comparing the two methods described above of preparing aluminium hydroxide sol, method (2) is better than method (1) in terms of time-consuming and gel-sol stability.4 The selection of the method for making ultrafiltration membraneThe experimental results showed that the overall performance of the ultrafiltration membrane made by...
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