SURFACE CHEMICAL STUDIES OF ANODICALLY OXIDIZED ALUMINUM MEMBRANES

X-ray photoelectron spectroscopy (XPS) and fast atom bombardment secon dary ion mass spectrometry (FAB-SIMS) have been used to study the surf aces of inorganic microfiltration membranes produced by controlled rem oval 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/phosph oric acid electrolyte. Both techniques established that phosphates wer e concentrated on the surface of membranes formed in phosphoric acid a nd oxalic/phosphoric acid and that oxalate ions were present on the su rfaces of membranes formed in oxalic acid. The low intensity of the Al O(x)- fragments implies that all of the aluminium ions in the surface are coordinated to phosphates or oxalates. However, any differences it s the chemical state of the aluminium on the different membranes were not detectable by either technique.