zixuan

Recently, I have been trying my reactive model to simulate the transport of Sb and Cr in the binary mineral system. But I found when I change the wt% of HFO, the model could not converge. Therefore, I enhanced the Na and Cl concentrations in both wastewater and clean fluids from 0.1 M to 1M. The wastewater (0~1yr.) can be run, but the clean fluids cannot get converge. I attempted to use react and spce8 to find the reason, but I still do not know how to deal with this problem. I also tried to reduce the velocity of clean fluids from 0.2m/d to 0.002m/d, but the clean fluids cannot desorb Sb and Cr at extremely low velocities. 1999.tdat KLN fit 1999.sdat HFO fit 1999.sdat simplest RTM.x1t

Dear Wang, Thanks for your reply. It is helpful. I solved this problem with your suggestions. Best regards, Zhang

Dear Wang, Thanks for your reply! I used two liquids to infiltrate the soil. In stage 1 (t=0~0.5 yr.), wastewater was introduced, the soil would be contaminated. In stage 2(t>0.5 yr.), clean fluid was introduced and the soil was cleaned. But I found the Breakthrough Curves of stage 1 seemed different with or without stage 2. I wondered why stage 2 would have some influence on stage 1. That's my question. Eg. I attached another X1t file, If I simulated the transport of Sb and Cr with or without stage 2 [NaCl (pH=9) solution], stage 1 would be different like this. The left one is without NaCl solution The left one is with NaCl solution simplest RTM.x1t 1999.tdat HFO fit 1999.sdat KLN fit 1999.sdat

Sorry, as for the X1T, I have a new question: when I used the "components in fluid" in the last node to represent the breakthrough curves, the first 60 days' breakthrough curves would have some differences with or without NaOH addition stage after the 60th day. I wonder about the reason for this difference. How can I modify it? I will be appreciated it if anyone can give me some suggestions. check transport.x1t 1999.tdat KLN fit 1999.sdat HFO fit 1999.sdat

Dear Wang, Thanks for your help. After I revised the concentrations and units to 1e-12 mg/L, and changed the balance species from Cl- to HCO3-, this program successfully ran in X1T and SpecE8. Because there was no related data about some trace ions, I assumed it would be no problem to set any negligible value for these ions.

Excuse me. There is another problem on X1t. I want to use wastewater flow to contaminate the soil and then apply acid rainwater to the soil. I have checked all ions composition in the initial pore water system and both inlet fluids. (This data was provided by previous studies. If there is no data about specific ions, it would be assigned to 1e-24, which could be ignored.) But it showed that there was a large residual. Solving for initial state of each nodal block. Residuals too large, 855-th interation Largest residual(s): Resid Resid/Totmol Cbasis --------------------------------------------------------- CrO4-- -8.314e-29 1.964e+200 3.028e-238 --------------------------------------------------------- I assumed this was caused by some mistakes in initial pane or something, because I used another solution containing only NaCl, and the same problem happened. But I am still wondering about the specific reason. In my initial plane, the chromate was closed to zero. Or it caused by the shortage of some important ion concentrations? But I checked the charge balance in SpeCE8. I attached my x1t and sorbing surface files. I really appreciate if you can help me. transport.x1t Kaolinite 2Cr.sdat HFO.sdat thermo.tdat

Jia, Thanks for your reply. I have solved it with your approach. That's really helpful! Best regards, Zhang

Sorry, I mean the sorbing surface file by "model". Thanks!

Hello, Recently I am applying the surface complexation model in X1t. But when I added my model, it showed the following information. After I clicked YES, the model still cannot be added to the program. But I tried other models offered by official software, there is no problem. And I checked the X1t has read the proper thermo database My model is also in the same situation, and it could be added to React program.

Dear Wang, Thanks for your reply. It helped me. But I found when I included the sorbate in options, the system seems not include preadsorbed antimonate because the total Sb concentration is the value after pickup instead of 1e-5M. I want to research the result after twice adsorption.

Hello Wang, Here I have a new question. I'm researching about the influence of sequence of addition on adsorption rates of Sb and Cr on HFO. I have mentioned my operation steps before: But when I checked the outcome file, I found the total amount of chromium was larger than what I set. For example, I used 0.05g/L HFO to adsorb 1e-5M Sb at pH=3. And then the 1e-5M CrO4-- will be added. Why the later addition ions will be larger than what it should be? I'm confused. Elemental composition In fluid Sorbed total moles moles mg/kg moles mg/kg ------------------------------------------------------------------------------- Chromium 7.115e-05 1.004e-05 0.5220 6.111e-05 3.177 Hydrogen 111.0 111.0 1.119e+05 0.0001504 0.1516 Iron 0.0004698 1.008e-12 5.629e-08 Nitrogen 0.0009833 0.0009827 13.76 6.302e-07 0.008826 Oxygen 55.51 55.51 8.881e+05 0.0002830 4.527 Potassium 0.001008 0.001008 39.41 8.086e-09 0.0003161 antimony 9.227e-06 1.700e-07 0.02070 9.057e-06 1.103 SC.rea IN6+OU1 num2.sdat thermo.tdat

Hello Wang Jia, I really appreciate your reply. I will update it. You reminded me of another important things. Thanks!

Hello Wang, Thanks for your reply. I downloaded the filed uploaded, and combined them. It still turned out wrong with same error at pH=7.5 and 8. Now that there wasn't an error in your examination, I think it may because of my steps. Steps: 1. run the program directly to get an endpoint of adsorption of Cr 2. run→pickup→system→entire 3. add Sb，swap it to Sb(OH)6- in aqueous (C=1e-4M) 4. run the program I'm not sure which step or setting is wrong.

Sorry, I got in a new problem. When I attempted to find the adsorption rates of Sb and Cr on HFO at pH=7.5 and 8, the error that "pivot: diagonalization failed" came out. It was assumed HFO adsorbed Cr firstly, and then the Sb(V). So after adsorption os Cr(VI), the Sb(V) was added into the react files. I checked some references, but cannot find the reasons. C=1e-4M.rea IN6+OU1 num2.sdat thermo.tdat

I'm really grateful for your help. I want to investigate the pH influence, so perhaps before it, I need to do a simulation of kinetics to confirm the possibility of adsorption B. I think your suggestions are really helpful. Thanks!