Modeling the Chemical Evolution of Porewater in the Palfris Marl, Wellenberg, Central Switzerland

ABSTRACTThe chemical evolution of groundwater in the Palfris marl at Wellenberg has been simulated using a reactive transport model. The results were tested against the chemical and stable carbon isotopic composition of water samples from exploratory boreholes. Water chemistry is constrained by mineral and cation exchange equilibria. To reproduce measured CO2(tot) and δ3C values requires H+ ion exchange. Matching measured ratios between Cl– and other dissolved constituents constrains the relative amounts of reacting water and rock to porosities between I and 10%. NaHCO3 waters sampled from the Palfris are formed by replacement of the initial Na-Cl water by one to five pore volumes of infiltrating Ca-HCO3 recharge water. To entirely exhaust the exchange capacity of the formation so that Ca-HCO3 water persists requires several hundred to several thousand pore volumes of flow. The agreement between model results and measured water chemistry demonstrates a quantitative understanding of the geochemical processes controlling the chemistry of water naturally present in the Palfris marl. These processes will also determine the behaviour of material that might emanate from a repository. In addition, the modelling provides water flow information of use in testing groundwater flow models.

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Correction of ground-water chemistry and carbon isotopic composition for effects of CO2 outgassing

Geochimica et Cosmochimica Acta ◽

10.1016/0016-7037(78)90235-1 ◽

1978 ◽

Vol 42 (12) ◽

pp. 1799-1807 ◽

Cited By ~ 42

Author(s):

F.J. Pearson ◽

Donald W. Fisher ◽

L.N. Plummer

Keyword(s):

Isotopic Composition ◽

Water Chemistry ◽

Ground Water ◽

Carbon Isotopic Composition ◽

Carbon Isotopic

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Modeling of Ion Exchange Processes to Optimize Metal Removal from Complex Mine Water Matrices

Water ◽

10.3390/w13213109 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3109

Author(s):

Angela Isabel Pedregal Montes ◽

Janith Abeywickrama ◽

Nils Hoth ◽

Marlies Grimmer ◽

Carsten Drebenstedt

Keyword(s):

Ion Exchange ◽

Mine Water ◽

Reactive Transport ◽

Metal Removal ◽

Transport Model ◽

Breakthrough Curves ◽

Exchange Capacity ◽

Operating Conditions ◽

Mine Waters ◽

Exchange Processes

The modeling of ion exchange processes could significantly enhance their applicability in mine water treatment, as the modern synthetic resins give unique advantages for the removal of metals. Accurate modeling improves the predictability of the process, minimizing the time and costs involved in laboratory column testing. However, to date, the development and boundary conditions of such ion exchange systems with complex mine waters are rarely studied and poorly understood. A representative ion exchange model requires the definition of accurate parameters and coefficients. Therefore, theoretical coefficients estimated from natural exchange materials that are available in geochemical databases often need to be modified. A 1D reactive transport model was developed based on PhreeqC code, using three case scenarios of synthetic mine waters and varying the operating conditions. The first approach was defined with default exchange coefficients from the phreeqc.dat database to identify and study the main parameters and coefficients that govern the model: cation exchange capacity, exchange coefficients, and activity coefficients. Then, these values were adjusted through iterative calibration until a good approximation between experimental and simulation breakthrough curves was achieved. This study proposes a suitable methodology and challenges for modeling the removal of metals from complex mine waters using synthetic ion exchange resins.

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