Abstract:The sorption mass of such metal ions as Ag+, Cr3+, Cu2+, Pb2+, Zn2+, Cd2+and Ni2+ on calcite surfaces are measured by atomic absorption spectroscopy (AAS) as a function of metal ion concentration at temperature of 30℃and ion strength ofI=0.1 mol/L. The surface reaction isotherms can be classified into four types, viz.: A_type, adsorption isotherm of Langmuir (Ag+); B_type, adsorption isotherm of Freudlich (Cd2+, Ni2+); C_type, adsorption_copre_cipitation isotherm with saltation (Cu2+, Zn2+); D_type, linear sorption isotherm (Cr3+, Pb2+). The species of Ag+sorbed on calcite surface is of the form of >CO3Ag with very small surface coverage,NMex=0.01. The species of Cd2+and Ni2+sorbed on calcite surface are sin- gle nuclear complexation (>CO3MOH),NMex<0.1, or multi_nuclear complexation, 0.1< NMex<1, and subordinately single nuclear complexation (>CO3MOH); the surface species of Cu2+, Zn2+and Ni2+are precipitation products under the condition of high concentration. The species of Pb2+and Cr3+sorbed on calcite surface are mainly precipitation products and subordinately adsorption complexation products at low concentration,NMex≤0.08. The experimental results show that multi-models coexist in the surface reactions of heavy metal ions with calcite. The sorption behavior of the sorbed cations such as Cd2+, Cu2+, Zn2+ and Ni2+on calcite can be modeled by surface exchange reaction at low concentration of metal ions; they can be modeled by both surface complexation and exchange reaction, or by precipitation at high concentration of metal ions. Surface complexation or precipitation can be used to model the sorption behavior of such sorbed cations as Ag+, Pb2+ and Cr3+ on calcite.