mmontecinos1

Hello everyone, I am trying to reproduce the surface precipitation model of Cu in HFO y HAO developed by Karthikeyan and Elliott (1999) (Surface Complexation Modeling of Copper Sorption by Hydrous Oxides of Iron and Aluminum, Journal of Colloid and Interface Science 220, 88–95 (1999). I would like to edit FeOH.dat sorption file to include equations [5] to [8] considered by the authors. However, I am not sure how due to these equations consider both sorbed and precipitated species To include eqs. [5] and [6] I was thinking of include the following species: >(s)FeOHCu(OH)2H+ charge= 1.0 mole wt.= 171.4228 4 species in reaction 1.000 >(s)FeOH -1.000 H+ 1.000 Cu++ 2.000 H2O log K= -0.7500 dlogK/dT= 0.0000 >(w)FeOHCu(OH)2H+ charge= 1.0 mole wt.= 171.4228 4 species in reaction 1.000 >(w)FeOH -1.000 H+ 1.000 Cu++ 2.000 H2O log K= -0.7500 dlogK/dT= 0.0000 but I am not sure if this is a proper way to represent this model of surface precipitation. Regarding to eq. [7] and [8], I don’t know how to include it, due to these equations represent the change in Ksp precipitation due to HFO adsorption. I would appreciate any recommendation Best regards, Mauricio Montecinos

Thanks you Brian! I followed your advice and now my results fits perfectly Best regards, Mauricio

Dear Brian, Now I am trying to model the sorption of Cu on Kaolinite through the bidentate model developed by Lund et al (2008) (Fig. 3a, blue line/dots). I created the sorption file using the FeOH.dat as a template for bidentate sorption reactions. However, when I run the program, GWB overestimate the sorption. I used the “sorbate include” option, but the result didn’t improve. Also, I would like to implement the Bidentate variable charge + ion exchange site model (no Cu sorption on ion exchange site). I created the IonEx.dat file, with the reaction for H exchange, but when I run it in React, nothing happens. I mean, there is no difference between the model with and without ion exchange site model. I would appreciate any recommendation you could give me to solve these problems. Best regards, Mauricio Montecinos 2008 - Lund_Fig2a - Bidentate.rea KOH_KGa_Bidentate.dat 2008 - Lund_Fig2a - Bidentate_IonEx.rea IonEx_H.dat thermo_editV8.dat

Hi Brian, I didn't know about the sorbate include option. I followed your instructions and now the model in GWB fits perfectly Thanks you so much! Mauricio Montecinos

Hello everyone, I am using React program of GWB 9.0 to simulate surface complexation of Copper (Cu++) on Kaolinite. I want to reproduce the modeling results of Lund et al. (2008) (T.J. Lund, C.M. Koretsky, C.J. Landry, M.S. Schaller, S. Das, Surface complexation modeling of Cu(II) adsorption on mixtures of hydrous ferric oxide and kaolinite, Geochem. Trans. 9 (2008) 9). They describe the sorption of copper at a variety of ionic strength using different Double Layer Model (e.g. Monodentate variable charge site, Bidentate variable charge site, among others). I am modeling the sorption for the system with 1E-4 M Cu, 0.01 M NaNO3 and 2 g/L of Kaolinite using a 1-site model (Monodentate) (Fig 2A, blue line in Lund et al. 2008).I created a dataset of surface reaction using file FeOH.dat as a template, but changing basis species, sorbing minerals and surface species. I also modified the thermodynamic database to include minerals and dissolved species of interest. However, when I run React, GWB underestimate the sorption of Cu for pH > 5.5. I thought it could be due to changes in the Ionic Strenght, but it increase only for low pH (<4). I also tried excluding all other species of Cu, different than Cu++ but the results didn’t improve. I would appreciate any recommendation to understand the problem. Best regards, Mauricio Montecinos 2008 - Lund_Fig2a - Monodentate.rea KOH_KGa_Monodentate.dat thermo_editV8.dat

I am trying to make a surface complexation model for Calcite according to Sø, H. et al, (2008) (Sorption and desorption of arsenate and arsenite on calcite. Geochimica et Cosmochimica Acta, 72(24), 5871). I am using the thermodynamic database “thermo.dat”, and I have no problems in load the surface data, but when run the sorption model, the program crashes. The surface database is attached below. Best regards Mauricio Montecinos A. Calcita.dat.txt