Supplementary materials for "Ba attachment and detachment fluxes to and from barite surfaces in variable [Ba$^{2+}$]/[SO$_{4}$$^{2-}$] solutions near solubility equilibrium"

Abstract

We measured barium attachment and detachment fluxes from and to barite crystal surfaces in solutions with [Ba]/[SO$_{4}$] ratios from 0.06 to 52. The doping of $^{137}$Ba in starting experimental solutions allowed measurements of unidirectional fluxes near solubility equilibrium (Q/K  1.0) in batch reactors. Both attachment and detachment fluxes increase with [Ba]/[SO$_{4}$] ratios, with an “S” shape function with a plateau at [Ba]/[SO$_{4}$]>1.5 and a low plateau at [Ba]/[SO$_{4}$]<1. As expected, the attachment and detachment fluxes were found to be equal as the solutions were near solubility equilibrium (|SI| ≈0.0n).