RETENTION OF VANADIUM (V) BY 3 FINNISH MINERAL SOILS

Retention of V(V) by three Finnish mineral soils from 10(-4) M and 10( -5) M sodium vanadate solutions was investigated at room temperature i n the pH range 2.3-7.5. In adsorption experiments, 0.02 M KCl was used as ionic medium, and the samples were left to equilibrate for 72 h. T he solid: solution ration was 1 : 100 (m:v). Maximum adsorption occurr ed at pH approximately 4, where 70-80% of the added V (350-400 mug g-1 from 10(-4) M solution and 25-40 mug g-1 from 10(-5) M solution) was retained by each soil. Retention was significant even at pH 6, where a dsorption of a similar anion, molybdate, is negligible. Desorption of the retained V was measured by adding 50.0 cm3 of 0.02 M KCl into weig hed soil samples and shaking for 17 h in a mechanical stirrer. Only a minor part of retained V could be removed from each soil by the KCl tr eatment. Retention of different ionic species of V from 10(-5) M solut ion is approximated using values of log K obtained from the literature . In these calculations, kaolin is used as a reference material.