Hydrous titanium dioxide (HTDO) shows amphoteric character and has attracted considerable attention due to its high adsorption selectivity for certain ions. The adsorption and desorption behavior of some heavy metal ions and arsenic compounds on amorphous HTDO (Am-HTDO) was studied at different pH values. In the first part of this study, the selectivity and chromatographic behavior of metal ions were determined. The distribution coefficient increased with increasing pH. The selective sequence shows Pb > Hg :~ Cd > Ca > Mg in NaNO 3 and Pb >> Cd > Ca > Mg > Hg in NaCl. Chromatographic separation of mercury and lead from sodium, potassium, magnesium, and calcium was performed with 0.002 M nitric acid on a relatively small column (5.0 Γ 0.5 cm i.d.) of Am-HTDO in the H + form. After washing with water, mercury was eluted with 0.01 M and lead with 0.5 M HCI with high recoveries.
In the second part, the selectivity and chromatographic behavior of As anions were also studied at different pH values. For arsenic compounds, the sequence shows As(III)> As(V)> cacodylic acid [dimethyl arsenic acid (CHa)2AsO(OH)] in a solution of NaCl + NaOH with ionic strength of 0.1. The Am-HTDO in neutral media shows relatively high breakthrough capacity with 0.91, 0.90 and 2.28 mmol/g for cacodylic, As(V) and As(III) acids respectively. The arsenic compounds adsorbed can be eluted with 0.1 M NaOH as an eluant with a yield of 85, 73 and 51% for cacodylic, As(V) and As(III) acids, respectively.