Adsorption of Molybdate Anion (MoO42−) By Sodium-Saturated Kaolinite

Patrick J. Phelan and Shas V. Mattigod
Department of Soil and Environmental Sciences University of California, Riverside, California 92521

Abstract: Adsorption of Mo(VI) on 2−0.2-µm size fraction of sodium-saturated kaolinite at 25 ± 2°C and at a constant pH of 7.00 ± 0.05 was studied. The kaolinite sample was pretreated to remove any surface oxide and hydroxide coatings. The initial concentrations of Mo in solution ranged from 1 to 11 mg/liter in a NaClO4 background electrolyte at a constant ionic strength of 0.09 ± 0.01. Calculations of speciation using the GEOCHEM computer program indicated that under experimental conditions Mo(VI) was mainly in the MoO42− form. The experimental conditions were also shown to fulfill the requirements for applying the Langmuir equation in interpreting adsorption data. The Langmuir parameter for the adsorption maximum, n0 and the affinity parameter, KMoO42−-ClO4 were computed to be 3.33 × 10−4 mole/mole of adsorbent and 5.969 × 105, respectively. The large affinity parameter indicated that the Nasaturated kaolinite surface has a very high affinity for MoO42− ions relative to ClO4 ions.

Key Words: Adsorption • Electrolyte • Kaolinite • Molybdate ion • Speciation

Clays and Clay Minerals; February 1984 v. 32; no. 1; p. 45-48; DOI: 10.1346/CCMN.1984.0320106
© 1984, The Clay Minerals Society
Clay Minerals Society (www.clays.org)