An experimental study of sepiolite dissolution and growth rates as function of the aqueous solution saturation state at 60 °C

Clay mineral growth can directly affect the chemistry and permeability of many natural systems, including soils, marine sediments, Earth surface waters, geothermal powerplants carbon dioxide storage sites. Notably, sluggish precipitation clay minerals has been hypothesised to hinder weathering rates. To date, there are limited data on rate effect aqueous solution saturation states these In this study we quantify dissolution rates sepiolite, a 2:1 layered Mg-phyllosilicate (Mg4Si6O15(OH)2 * 6H2O) as function state in series mixed flow experiments. Results both experiments consistent with r=-10-14.801-expΔGrσRT, where r refers area normalized sepiolite units mol/cm2/s, ΔGr denotes Gibbs Free energy reaction, which is <0 for undersaturated solutions, 0 at equilibrium >0 supersaturated σ Temkin’s stoichiometric number, R stands gas constant T symbolizes absolute temperature. This equation suggests that transition theory concept micro-reversibility. The relative decrease Mg2+ Si concentrations outlet solutions experiments, X-Ray diffraction patterns precipitates collected from confirm crystalline sepiolite. results longer-term suggest over time. Such associated poisoning or destruction reactive Calculations coupled either forsterite enstatite dissolution, based laboratory measured primary rate-limiting step during most systems. These results, however, contradict fluids such observed Icelandic clays strongly supersaturated, whilst phases relatively close equilibrium. discrepancy may be due consumption sites time systems controlled by slow nucleation new surface.