Dear David, Could you please help me? I have a question. Is it possible to use the inverse modeling with PHREEQC for explanation of formation of brines with very high ion strength (through evaporation, mixing and reactions)? What may be the arguments? For studying the influence of complexes at low ion strengths, I tried to model addition of Na2CO3 to concentrated Gypsum solution (formed in equilibrium with Gypsum). At Na2CO3 amount required for the complete CaCO3 precipitation (without taking into consideration complexes), (CaSO4)0 concentration in the final solution was not nil. It became very small only at strong Na2CO3 excess. Does it mean that inverse modeling is impossible without taking into consideration complexes? I"ll very appreciate your help. Sincerely, Michael ------------------------------------------ Dr. Michael Zilberbrand Hydrological Service of Israel Research Division P.O.B. 36118, Jerusalem 91360 Israel
TITLE Complexes and Calcite precipitation SELECTED_OUTPUT -reset false -file Complexes-Calcite_prec_res.prn -molalities Ca+2 CaSO4 SOLUTION 1 Temp 20 pH 7.0 EQUILIBRIUM_PHASES 1 Gypsum 0.0 SAVE SOLUTION 2 END USE SOLUTION 2 REACTION 1 Na2CO3 1.0 0.01532 moles SAVE SOLUTION 3 END USE SOLUTION 3 EQUILIBRIUM_PHASES 1 Calcite 0.0 END # RESULTS at Na2CO3 1 mol # m_Ca+2 m_CaSO4 # 0.0104 0.0049 After equilibration with CaSO4 # 0.0011 4.53E-05 After addition of Na2CO3 # 2.89E-07 1.21E-08 After equilibration with Calcite # RESULTS at Na2CO3 0.01532 moles (0.0104+0.0049) # 1.0365e-02 4.9486e-03 # 4.9106e-03 2.2413e-03 # 1.4375e-04 9.0900e-05
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