RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

The acid-base chemistry of Gaomiaozi Na-bentonite (Na-BNT) was studied by using continuous potentiometric titrations at ionic strengths of 0.01, 0.1, 0.5 mol/L NaCl. The adsorption of Eu(Ⅲ) on Na-BNT was studied at 22±2 ℃ by a batch technique. The ionic strength was from 0.001 to 0.5 mol/L, Eu(Ⅲ) concentration from 10^-9 to 10^-4 mol/L, and pH from 3 to 10.5. A double-layer model and a non-electrostatic model for describing macroscopic data were compared by considering surface reactions on layer sites and edge sites. The double-layer model well describes the acid-base chemistry of Na-BNT and the adsorption results of Eu(Ⅲ) at 0.1 mol/L ionic strength but can not interpret Eu(Ⅲ) adsorption at other ionic strengths. In comparison, the non-electrostatic model reasonably describes all Eu(Ⅲ) adsorption results but is not satisfactory for the acid-base chemistry of Na-BNT at pH>8. The present study provides an alternative model for describing and predicting the adsorption of +3 valent lanthanides and actinides on Na-BNT.