The removal of calcium-bearing gangue minerals from diasporic bauxite is essential for improving feed quality for the Bayer process. In this study, the effects of particle size, collector type, and surface electrokinetic properties on the reverse flotation of calcium-bearing minerals from low-grade diasporic bauxite were investigated. A diasporic bauxite ore from the Morçukur deposit in Seydişehir, Türkiye, was characterized by Mineral Liberation Analysis (MLA), and zeta potential measurements were performed over a wide pH range for different particle-size fractions and collector conditions. Reverse flotation experiments were conducted using sodium oleate (NaOl) and sodium lauryl sulfate (SLS) at different collector dosages and particle sizes. The results showed that particle size strongly influenced mineral liberation, surface charge, collector adsorption, and flotation selectivity. Zeta potential measurements indicated more favorable electrokinetic conditions for reverse flotation at acidic pH values, particularly at pH ≤ 7. Among the investigated particle-size fractions, the −75+53 μm fraction exhibited the most favorable flotation response, indicating improved liberation of calcium-bearing minerals. Under the experimental conditions, SLS showed superior flotation selectivity and promoted the removal of calcium-bearing minerals, whereas NaOl provided a better statistical fit in the nonlinear regression analysis. The NaOl model yielded an R² of 0.95 and an RMSE of 5.35, compared with R² = 0.89 and RMSE = 9.23 for SLS. Conversely, SLS produced a lower MAE (2.22) than NaOl (3.88), indicating smaller average prediction errors. The results demonstrate that electrokinetic characterization combined with particle-size optimization and collector selection can improve the selective removal of calcium-bearing gangue minerals from diasporic bauxite. The findings also highlight the importance of distinguishing between flotation performance and statistical model performance when evaluating collector effectiveness.