SORPTION OF ANTIMONY SPECIES BY HUMIC-ACID

The retention of antimony (a potential toxin) in polluted soils or waterway sediments can involve interaction with several component phases. One of these, humic acid, has been found to adsorb antimony (In) from solutions of Sb(OH)(3) or potassium antimonyl tartrate (C8H4K2Sb2O12) in accordance with Langmuir type isotherms. Using Sb(OH)3 solutions (initial Sb levels < 10 mu M) the bonding constant value (at pH 4) was 6 x 10(5), with a calculated saturation capacity of 23 mu mol g(-1). the antimonyl tartrate systems (initial Sb levels 0.5 to 75 mu M) the bonding constant value for the sorbed species was 1.6 x 10(5) and the saturation capacity 53 mu mol g(-1). Addition of small amounts of HCl or NaOH (to vary the pH between 3.1 and 5.4) had little effect on the amount sorbed from KSbT solutions but with Sb(OH)3 solutions uptake was reduced (by about 15%). In the presence of NaCl (0.5 or 0.05M) Sb uptake increased (by about 15%). Antimony (V) (introduced as KSb (OH)(6)) was not sorbed from solutions < 10 mu M in this salt. Using more concentrated solutions, uptake gradually increased, reaching a plateau value of around 8 mu mol g(-1) with solutions initially 50 or 75 mu M.