Abstract

The environmental geochemistry of molybdenum and tungsten is not well known. To enable predictions of Mo and W concentrations in the presence of ferrihydrite (hydrous ferric oxide), batch equilibrations were made with MoO42-, WO42-, o-phosphate (PO43-) and freshly prepared ferrihydrite suspensions in 0.01 M NaNO3 in the pH range from 3 to 10 at 25 The results showed that WO42- is adsorbed more strongly than MoO42-, and that both ions are able to displace PO43- from adsorption sites at low pH. Two models, the Diffuse Layer Model (DLM) and the CD-MUSIC Model (CDM), were tested in an effort to describe the data. In both models, the adsorption of MoO42- and WO42- could be described with the use of two monodentate complexes. One of these was a fully protonated complex, equivalent to adsorbed molybdic or tungstic acid, which was required to fit the data at low pH. This was found to be the case also for a data set with goethite. In competitive systems with PO43-, the models did not always provide satisfactory predictions. It was suggested this may be partly due to the uncertainty in the PO43- complexation constants. (C) 2003 Elsevier Science B.V. All rights reserved.

Keywords

molybdenum; tungsten; hydrous ferric oxide; surface complexation; modelling

Published in

Chemical Geology
2003, Volume: 200, number: 1-2, pages: 105-115
Publisher: ELSEVIER SCIENCE BV

UKÄ Subject classification

Geochemistry


Publication identifier

DOI: https://doi.org/10.1016/S0009-2541(03)00161-X

Permanent link to this page (URI)

https://res.slu.se/id/publ/69497