The effect of humic acid addition on the capacity of inorganic sorbents to sorb radioactive cesium and strontium was studied
on montmorillonites in a calcium and potassium form. The Sips isotherm for humic acid sorption and multisite distribution
model of ion sorption was found to suit well for the description of mobility of ions as a function of equilibrium humic acid
concentration as a single variable at given pH and type of silicate. Complexation of the ions was of minor importance at the
conditions investigated. Influence of humic acid on the specific radiocesium interception potential (SRIP) was also evaluated.