Investigation Of Radionuclide60Co Sorption On Solid-Water Interface

60Co, one of the most common radionuclides, is widely utilized in industrial, agriculture and medical applications.60Co is characterized by emission of high gamma energy which can cause alopecia, reproducibility obstacle of anemia and leukemia. Therefore, the removal of60Co from wastewater is of great significance for human health and environment protection.This work contributes to the sorptions of60Co on kaolinite, montmorillonite, goethite, titanium dioxide and eggshell derivative as a function of contact time, pH, ionic strength, temperature and foreign ions in the absence and presence of humic acid using a batch technique. Sorption mechanisms of60Co on materials above are determined through the dynamics data, thermodynamics research and model fitting. The results show that:The effects of pH, ionic strength and foreign ions on sorptions of60Co on kaolinite and montmorillonite are obvious. The sorptions of60Co on the two clays above decrease with increasing ionic strength at low pH values. However, the sorptions of60Co on the two clays above are independent of ionic strength at high pH values. The sorptions of60Co on the two clays above under the same pH values are in the following sequence:Li+>Na+>K+, indicating that the cations can alter the surface properties of the two clays and thus influence the sorptions of60Co. The presence of FA enhances60Co sorptions on the two clays above at low pH, but suppresses60Co sorptions at high pH. Outer-sphere surface complexation and/or ion exchange are the main mechanisms of60Co sorptions on the two clays above at low pH values, whereas inner-sphere surface complexation is the main adsorption mechanism at high pH values.The effects of ionic strength on sorptions of60Co on goethite and titanium dioxide are different. The sorption of60Co on goethite decreases with increasing ionic strength at low pH values, and is independent of ionic strength at high pH values. However, the sorption of60Co on titanium dioxide is independent of ionic strength at any pH values. The presence of FA enhances60Co sorptions on goethite and titanium dioxide at low pH values, but reduces60Co sorptions at high pH values. The sorption mechanisms of60Co on goethite and titanium dioxide are different. Surface complexation and/or ion exchange are the main mechanisms of60Co sorption on goethite, whereas inner-sphere surface complexation is the single sorption mechanism of60Co sorption on titanium dioxide.The effects of pH, ionic strength and foreign ions on sorption of60Co on hydroxyapatite are similar to that on the two clays above. However, the effect of FA on sorption of60Co on hydroxyapatite is different from that on other materials above. The presence of FA suppresses60Co sorption on hydroxyapatite at low pH, but has no effect on60Co sorption at high pH. Outer-sphere surface complexation and/or ion exchange are the main mechanisms of60Co sorption on hydroxyapatite at low pH values, whereas inner-sphere surface complexation is the main sorption mechanism at high pH values.Kaolinite, montmorillonite, goethite, titanium dioxide and eggshell derivative can be used to remove60Co from wastewater on a large scale, due to their low cost and better sorption capacity of60Co.