Electrosorption of β-naphthol on graphite

Isotherms for the adsorption of β-naphthol from a buffered aqueous solution of 0.5 M K₂SO₄ onto graphite were detemrined over a range of potential of 1.27 V. The adsorbent was a packed bed of -100 + 120 mesh graphite powder. Sufficient surface area was available to calculate accurately the amount adsorbed by measuring spectrophotometrically the change in adsorbate concentration in the bulk solution. At all potentials, a Langmuir adsorption isotherm, modified for the displacement of solvent molecules, was followed up to 60-65% of monolayer coverage. The ratio of projected areas of β-naphthol and water molecules was consistent with the experimentally derived number of solvent molecules displaced, six. The largest amount of adsorption observed, 2.5×10^-10 mol cm^-2, agreed with the calculated monolayer coverage of β-naphthol molecules lying in flat orientation on the graphite surface. Adsorption increased at more positive potentials. Over the range of potential investigated, the adsorbability constant increased sixfold. Desorption was only partially reversible.