Mineral surface charge development in mixed electrolyte solutions

- Charge development at goethite surfaces was tracked in mixed NaCl/NaClO4 solutions.
- Cl− promotes charge development more than ClO4-.
- Molecular dynamics show that perchlorate broadens the interfacial region.
- Surface charge data are modeled using a thermodynamic adsorption model.
- A combination of ion-specific compact layer capacitances predicts surface charge.