Reasearch On A New Type Of Anodic Alumina Membrane Supported By Aluminum

Porous anodic alumina membrane enjoys a number of advantages such as uniform diameter, higher pore density, parallel aperture, so it can be made of new type of ultra-precision membrane, and it has great potential applied value in separation filed. But the anodic alumina membrane is easily broken in the process of removing back aluminum and separation for its brittleness and lack of support. So it is very difficult to produce with large area, and it has only been used in laboratory.In this paper, we chose orthogonal experiment, and anodic alumina membranes were fabricated by one-step anodizing process. The effects of oxidation temperature, time and voltage on membrane thickness, pore diameter and orderly degree were investigated. Experimental result showed that the maximum influencing factor on membrane thickness was oxidation time, followed by temperature and voltage, and the maximum influencing factor on pore diameter and orderly degree was voltage, followed by temperature and time. The best parameters of the techniques were obtained as follows: 13℃, 2 hours , 130V. The effect of oxidation processes on orderly degree was analyzed quantitatively by mathematical method.In this paper, we fabricated through-hole porous anodic alumina membranes supported by macropore aluminum by electrochemical method, which based on one-step anodic alumina membranes. We studied the effects of several influencing factors on membrane. The results showed that the membrane had better mechanical intensity and tenacity, which could be curved to 180 degree and was not broken under 0.3MPa and brittleness of membrane was improved in a certain extent. Mean pore diameter of membrane and pure water flux increased with the increase of etching time, while rejection of membrane for PEG 20000 decreased, which had little effect on porosity. Pure water flux of membrane decreased with the increase of oxidation time, while rejection of membrane increased; Pure water flux and PEG flux of membrane decreased with the increase of filter time. Compared with phosphoric acid membrane, the pore diameter of oxalic acid membrane was smaller, and the thickness of oxalic acid membrane was thicker; Under the same pressure, the stable pure water flux of oxalic acid membrane was smaller than phosphoric acid membrane, while the rejection of oxalic acid membrane was higher than the latter. The stable pure water flux of membrane increased with the increase of anodic reaction time, while it had little effect on the rejection of membrane. The pure water flux and PEG 20000 flux increased with the increase of operation pressure.In this paper, we studied the anticorrosion property of membranes with and without annealing by anticorrosion experiment, and investigated the surface morphology and composition of membranes by using SEM and XRD. The results showed that the membranes were completely anticorrosion in neutral environment without annealing, and they had better anticorrosion property in acid environment than alkaline environment. When pH was above 12, the membranes could be corrupted. The membranes were transformed from amorphous phase toα-Al₂O₃ crystalline phase by 5 hours annealing at 800℃and 910℃. At the same time, aluminum and amorphous alumina were found by XRD patterns. The membrane had little change in front side after 5 hours annealing at 800℃, while the back side was transformed from ruleless distributing to cluster distributing. The membranes were completely anticorrosion in neutral and violent acid environment with annealing at 800℃, and the anticorrosion property of membranes had greater improved in violent alkaline solution.