Fig. 8 Diffuse reflectance infrared Fourier transformed (DRIFT) spectra of Al oxide with adsorbed CO₃ and/or SO₄. These difference spectra are the result of subtraction of a spectrum of Al oxide with only NaCl from a spectrum of Al oxide with adsorbed CO₃ and/or SO₄. The pHs of the Al oxide suspensions were 6.5 ± 0.1