2.3. Batch extraction experiments
2.4. Surface complexation modeling
The pH-dependent sorption of Cd(II) and U(VI) on sepiolite at I = 0.01 mol/L NaClO4 solution was fitted by surface complexation modeling. The protonation and deprotonation constants (log K+ and log K− values) of sepiolite can be given by Eqs. (2) and (3), respectively:equation(2)SOH+H+=2SOH+SOH+H+=SOH2+equation(3)SOH=SO−+H+.SOH=SO−+H+.
These constants can be obtained by fitting Sirolimus potentiometric titration of sepiolite at I = 0.01 mol/L NaClO4 solutions. In deciduous study, cation exchange (XNa) and surface complexation sites (SOH) were employed to simulate sorption data. The surface complexation reactions can be presented by Eqs. ( (4), (5) and (6)):equation(4)2XNa+M2+=X2M+2Na+2XNa+M2+=X2M+2Na+equation(5)SOH+M2+=SOM++H+SOH+M2+=SOM++H+equation(6)2SOH+M2++H2O=(SO)2M(OH)−+3H+2SOH+M2++H2O=SO2MOH−+3H+where M2 + refers to Cd2 + or UO22 + cation. These equilibrium constants can be obtained by fitting the pH-dependent sorption data.