pH Dependence of ferrous sorption onto two smectite clays
- Resource Type
- Article
- Authors
- Schultz, Chris; Grundl, Tim
- Source
- Chemosphere. Dec2004, Vol. 57 Issue 10, p1301-1306. 6p.
- Subject
- *SMECTITE
*CLAY minerals
*ADSORPTION (Chemistry)
*IRON
*HYDROGEN ions
- Language
- ISSN
- 0045-6535
This work examines the abilities of two smectite minerals (SWa-1 and Wyoming montmorillonite) to adsorb ferrous iron at concentrations from 0.037mM (2ppm) to 2.5mM (240ppm) over a range of pHs from 4.0 to 8.0. Both sorption isotherm and sorption edge data are presented. Ferrous sorption (mM) to both SWa-1 and Wyoming montmorillonite over the pH range 4.0–6.75 is relatively constant at ∼1000lkg−1 for both minerals. Sorption in this pH range is attributed to the cation exchange capacity of the clay along the basal surfaces. At pH values above 6.75 the amount of ferrous iron sorbed increases dramatically. At pH 8, sorption (mM) reaches 6600lkg−1 and 8000lkg−1 for Swa-1 and Wyoming montmorillonite respectively. This is attributed to the specific interaction between ferrous ions and surface sites along mineral edges. The overriding geochemical implication is that in reduced sediments containing more than a few percent clay, the pool of sorbed ferrous iron is vast. This pool of reduced iron is both redox labile and bio-available and is not readily indicated by simple measurement of dissolved Fe2+. [Copyright &y& Elsevier]