(a) Binding isotherms of Pb2+ ions to synthetic-eumelanin-coated discs, hair-extract-coated discs, and blank PVDF discs; pH uncorrected titrations of Pb(NO3)2 in H2O. (b) Linearized Langmuir isotherm representation of the data for synthetic-eumelanin- and hair-extracted-coated discs in (a), . (c) Binding isotherms to Pb2+ ions to synthetic-eumelanin-coated discs; titrations of Pb(NO3)2 in 50 mM NaNO3 (aq.) at initial pH 5.50, 4.75, and 4.00. (d) Binding isotherms to Pb2+ ions to hair-extract-coated discs; titrations of Pb(NO3)2 in 50 mM NaNO3 (aq.) at initial pH 5.50, 4.75, and 4.00. (a–d) Data are average values from at least three independent titrations, each with different discs; error bars represent one standard deviation.
