Acid–base properties of a goethite surface model: A theoretical view

摘要: Abstract Density functional theory is used to compute the effect of protonation, deprotonation, and dehydroxylation different reactive sites a goethite surface modeled as cluster containing six iron atoms constructed from slab model (1 1 0) surface. Solvent effects were treated at two levels: (i) by inclusion up water molecules explicitly into quantum chemical calculation (ii) using additionally continuum solvation for long-range interactions. Systematic studies made in order test limit fully hydrated surfaces monomolecular layer. The main finding that three types hydroxyl groups (hydroxo, μ-hydroxo, μ3-hydroxo), hydroxo group most active protonation whereas μ- μ3-hydroxo undergo deprotonation more easily. Proton affinity constants (pKa values) computed appropriate protonation/deprotonation reactions all investigated compared results obtained multisite complexation (MUSIC). approach was validated consecutive [Fe(H2O)6]3+ complex solution good agreement between calculated experimental pKa values found. prediction pristine point zero charge, pHPPZN. value 9.1 fits well with published 7.0–9.5.