Analytical Constraints on Pb(II) Adsorption Studies at the γ-Alumina–Water Interface

Abstract

Analytical observations constrain different aspects of adsorption and should not be treated as interchangeable evidence. This reassessment of Pb(II)/γ-Al2O3 connects solid-phase energy-dispersive X-ray fluorescence (EDXRF), a buffered contact protocol, fluorescence quenching, and existing surface-complexation summaries. The protocol used 10 g L–1 alumina in 0.025 mol L–1 acetate buffer at pH 5.5 and 25 °C. Lead-glass reference-material results show relative differences of +4.03% for PbO and +446.75% for Al2O3; the corresponding absolute differences are 0.9671 and 0.5638 percentage points. Thus, relative agreement depends on both analyte response and reference concentration. Four fluorescence series retain distinguishable optical responses, although their individual sodium dodecyl sulfate (SDS) concentration assignments are unresolved. The maximum initial Pb loading gives a reproducible dose ceiling of 0.190 mmol g–1, distinct from a measured adsorption capacity. Recorded model residual statistics describe numerical alternatives, not independently identified surface structures. A measurement-to-inference map identifies the additional evidence needed to connect these observations to mass balance and coordination chemistry. The contribution is a case-based assessment of analytical consistency at an oxide–water interface. Missing concentration records and direct surface characterization preclude a validated capacity or a unique inner- or outer-sphere assignment.