Abstract: In this work, a naturally occurring illite was characterized by using FTIR and XRD technique to determine its surface functional groups and crystal structure. Sorption of ⁶⁰Co(Ⅱ) on illite as a function of contact time, pH, ionic strength, foreign ions and humic substances was studied under ambient conditions using batch technique. The results indicate that the sorption of ⁶⁰Co(Ⅱ) on illite is strongly dependent on pH values and ionic strength. A positive effect of humic substances on ⁶⁰Co(Ⅱ) sorption is found at pH<8, whereas a negative effect is observed at pH>8. At low pH, the sorption of ⁶⁰Co(Ⅱ) is dominated by outer-sphere surface complexation and/or ion exchange with Na⁺/H⁺ on illite surfaces, whereas inner-sphere surface complexation is the main sorption mechanism at high pH. From the experimental results, it is possible to conclude that illite has good potentialities for cost effective treatments of ⁶⁰Co(Ⅱ) contaminated wastewater.