SURFACE CHEMICAL STUDIES OF ANODICALLY OXIDIZED ALUMINUM MEMBRANES

X-ray photoelectron spectroscopy (XPS) and fast atom bombardment secondary ion mass spectrometry (FAB-SIMS) have been used to study the surfaces of inorganic microfiltration membranes produced by controlled removal of anodic films formed on aluminium in phosphoric and oxalic acid electrolytes. The results are compared with those of similar analyses of membranes produced from anodic films formed in mixed oxalic/phosphoric acid electrolyte. Both techniques established that phosphates were concentrated on the surface of membranes formed in phosphoric acid and oxalic/phosphoric acid and that oxalate ions were present on the surfaces of membranes formed in oxalic acid. The low intensity of the AlO(x)- fragments implies that all of the aluminium ions in the surface are coordinated to phosphates or oxalates. However, any differences its the chemical state of the aluminium on the different membranes were not detectable by either technique.