PMC

Initial rates with respect to Fe(II)(aq) production as a function of pH. The reported orders with respect to [H⁺] were calculated from the straight lines connecting successive pairs of points.

Effects of (a) the voltage scan rate at pH 7 and (b) pH from 5 to 8 on illustrative CVs measured with 821 µM PYO in 0.1 M KCl aqueous solution buffered with 10 mM CH₃C(O)ONH₄-MOPS.

(a) Fe(II)(aq) production as a function of time and (b) UV–visible spectra collected at 0.85, 2.2, 4.2, 16, 45, 109, and 170 min, during the reaction between 100 µM Fe(OH)₃(am, s) and 50 µM reduced PYO at pH 6. Arrows indicate peak growth as the reaction progresses.

Initial rates with respect to Fe(II)(aq) production for reactions of reduced phenazines with Fe(OH)₃(am, s) (filled symbols) and α-Fe₂O₃(s) (open symbols) as a function of the half-wave potential (E_1/2) of the phenazine redox couples. R₀ values (in the top panels) were derived from the time course plot illustrated in . R_A (in the bottom panels) corrects for differences in surface area loading for the two (hydr)oxides by dividing R₀ by the surface area (in m² g⁻¹), the formula weight (in g/mol Fe), and the suspension concentration (in moles Fe/L). All E_1/2 values were measured in this study and are listed in , except for PCA and PCN at pH 8, where their E_1/2 values were derived from (see text) using the values measured at pH 7.