Fig. 4

Sorption isotherms of glycolate (a), threonate (b), tartrate (c), gluconate (d), and glucarate (e) determined in the gibbsite/ACPW system at pH 13.3. Fitted isotherm functions (lines): glycolate and gluconate: composite Langmuir–Freundlich (parameters: Table 8), threonate: Langmuir (parameters: Table 7), tartrate and glucarate: two-site Langmuir. The data correspond to equilibrium concentrations. Isotherm parameters for tartrate: X²/DOF: 1.39, r²: 0.96, K_L1: 6.6 ± 2.2 L mmol⁻¹, C_sat1: 16.1 ± 2.7 mmol kg⁻¹, K_L2: 0.007 ± 0.002 L mmol⁻¹, C_sat2: 228 ± 33 mmol kg⁻¹. Isotherm parameters for glucarate: X²/DOF: 1.66, r²: 0.97, K_L1: 1.0 ± 0.5 L mmol⁻¹, C_sat1: 36 ± 13 mmol kg⁻¹, K_L2: 0.03 ± 0.01 L mmol⁻¹, C_sat2: 154 ± 14 mmol kg⁻¹