Equilibrium and kinetic simulation of groundwater demanganation and deironing

Analysis of chemical equilibria among iron and manganese aqueous species at various Eh-pH conditions and aqueous CO2 concentration is done. Thermodynamic and equilibrium-kinetic simulation of iron and manganese aqueous species oxidations is developed for groundwater demanganation and deironing. Numerical simulation of chemical interactions in the system groundwater-aqueous oxygen-rock minerals-aqueous carbon dioxide is shown that deironing is effective enough but aqueous manganese(II) concentration is increased. It occurs because (Fe,Mn)CO3 solubility rate is too slow and (Fe,Mn)CO3 dissolution and removal of aqueous iron species results in secondary MnCO3 formation. Using published experimental data on carbonate dissolution kinetics, iron and manganese oxidation kinetics and the critical values of rate constants of iron and manganese homogenous oxidation, iron and manganese carbonates solubility, manganese homogenous catalytical oxidation on iron hydroxide suspension are chosen. The kinetics-thermodynamics model of underground oxidation of iron and manganese by dissolved oxygen have been developed. By numerical simulation of chemical interactions in the system groundwater saturated by oxygen-stratal water-intake rock minerals shows that deironing occurs effective enough but aqueous manganese concentration increased. It happens due to aqueous manganese slow oxidation and dissolution of (Fe,Mn)CO3. Also secondary MnCO3 formation is possible due to removal of aqueous iron specis. So underground demanganation is possible if there is no (Fe,Mn)CO3 among intake rock minerals or inconvenience of water contact with it.