SPECIFIC SORPTION OF ANTIMONY(III) BY THE HYDROUS OXIDES OF MN, FE, AND AI

The hydrous oxides of Mn, Fe, and Al avidly sorbed Sb from μM Sb(OH), solutions, with uptake levelling off as initial Sb concentration increased. Capacity values decreased along the sequence MnOOH > Al(OH)3 > FeOOH. The amount sorbed by each substrate decreased gradually at pH values > 6. Addition of 0.4M CH3COONa to the aqueous phase (to minimise retention of weakly bound Sb) had little effect on MnOOH uptake capacity (∼160 mmol, kg-1 at pH < 7) but retention dropped rapidly at higher pH. With the other two substrates (pH 6-7) the calculated capacity values for specific Sb sorption were ∼ 45 mmol kg-1 FeOOH and ∼ 33 mmol kg- Al(OH)3; about a third of the total capacity values. On these substrates specific Sb sorption tended to peak in the pH 7 to 8 region. The pH response pattern was modified using Sb tartrate sorbate solutions. Factors influencing Sb sorption included substrate surface charge, chemical form of Sb and surface interactions. Formation of a sparingly soluble metal coating was indicated by the uptake plateaus observed when increasing amounts of solid were added to Sb solutions containing acetate. © 1990 Kluwer Academic Publishers.