engleski

Electrochemical insights into spatial complexity of hematite - dicarboxylate interactions at the interface

Adsorption of soil organic matter (SOM) at minerals surface is very important phenomena in the environment resulting in organic matter (OM) protection against degradation. Hematite is known to play important role in carbon accrual in the on Earth, however its role may be reversed in some conditions. To shed light on the interactions of organic matter with iron oxides, we investigated the properties of the hematite/electrolyte electrical double layer in the presence of dicarboxylate ions. Here by combining of three electrochemical descriptors (surface charge density (σ0), surface potential (Ψ0) and electokinetic potential (ζ) we gain new insight into pH-dependent malonates interactions with hematite surface in the solution. Malonates adsorb to hematite surface in a wide pH range between 3 and point of the zero charge (pHpzc = 8.7). However, the mode of coordination depends on a pH value. We distinguished two different malonates complexation types: inner-spherical complexes at pH below 4 and outer-spherical above pH 5. The surface charge and potential are sensitive to malonate concentration in acidic conditions. As the pH increases, we only observe the zeta potential sensitive to malonate ions as a response to their accumulation in the shear plane. The transition from the inner to the outer sphere geometries is smooth, suggesting that both types of complexes geometries exist simultaneously with a ratio depending on the pH.

Adsorption of soil organic matter (SOM) ; minerals surface ; hematite ; hematite/electrolyte electrical double layer ; diarboxylate ions ; surface charge density ; surface potential ; electokinetic potential

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