Modelling molybdate and tungstate adsorption to ferrihydrite
2003 (English)In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 200, no 02-jan, 105-115 p.Article in journal (Refereed) Published
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°C. 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.
Place, publisher, year, edition, pages
Elsevier, 2003. Vol. 200, no 02-jan, 105-115 p.
Molybdenum, tungsten, hydrous ferric oxide, surface complexation, modelling, molybdenum adsorption, oxide minerals, ion adsorption, equilibria, phosphate, soils, acid
IdentifiersURN: urn:nbn:se:kth:diva-22713DOI: 10.1016/s0009-2541(03)00161-xISI: 000184511700007OAI: oai:DiVA.org:kth-22713DiVA: diva2:341411
QC 201005252010-08-102010-08-102015-03-24Bibliographically approved