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Two sorbing surfaces for Ni and Zn


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Hellow Brian. My name is Abel. I want to model sorption of heavy metals onto iron and manganese oxides. I know React considerate only Fe oxides. I already set my data base for Mn oxides and runs well. I obtained heavy metals sorption onto this oxides. However, my modelling considerate both oxides (Fe and Mn) acting together in the solution. Is there a possibility to include both surfaces in the programme? As far as Im told, only one sorbing surface can be included at a time.

Thank you very much.

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Hi Abel,

The GWB apps come installed with example datasets for surface complexation on iron oxyhydroxides, but you can account for any number of different sorbing surfaces in React and the other GWB programs. You simply supply a dataset for each surface. The graphical thermo data editor TEdit can be used to quickly construct surface datasets.

To use multiple surfaces in a model, each surface dataset that’s loaded should have a different “surface type”. The surface type is simply a descriptive label that appears in the third line of the surface dataset. For example, the label in FeOH.sdat, which describes sorption to hydrous ferric oxide, is HFO. If you prepare a separate dataset for Mn oxide sorption, you might use “Mn oxide” for the surface type. 

A separate requirement for using multiple surface datasets simultaneously is that species must have unique names. For example, an uncomplexed site in FeOH.sdat is >(w)FeOH, so you can’t reuse that name in your Mn oxide dataset. Instead, you might use something like >MnOH. 

That’s really all you need to do. For an example of a model incorporating multiple surfaces, check out Colloid.X1t, installed with the software in the Script folder. The example uses a Kd surface dataset to describe partitioning of Pb++ between the solution and sediments in an aquifer, and a two-layer surface complexation dataset to describe Pb++ complexation with a ferric hydroxide colloid that flows into the aquifer. 

Hope this helps,

Brian Farrell
Aqueous Solutions 

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