The purpose of this study is to investigate the sorption characteristics of chemically-modified micas (Na-mica) and Na-birnessite for the removal of radioactive species such as cesium and strontium from water and wastewater. To examine sorption capacity of Na-micas (sodium-micas), batch and column tests were carried out under single and bi-solute conditions Additionally, the effect of pH and ionic strength on the sorption capacity of Na-micas and Na-birnessite was investigated. Based on the results of this study, the following conclusions can be drawn.
Investigation using various material characterization methods such as XRD, SEM and EDS showed that the final products synthesized by the ion exchange method were Na-micas. Also, these material characterization methods indicated that manganese oxide synthesized by the redox reaction was Na-birnessite.
For single solute system, the changes in pH had no significant effect on the sorption capacity of Na-micas for cesium and strontium. This result implied that main removal mechanism of radioactive species by Na-micas was not chemisorption but ion exchange.
Kielland plots indicated that Na-micas showed selectivity for both cesium and strontium at the low concentrations. Expecially, sorption efficiency for strontium reached upto 90%. These results suggest that Na-micas can be excellent sorbent/ion exchangers for removal of strontium.
Isotherm results under bi-solute condition showed larger adsorption of cesium by Na-micas compared to strontium. However, Na-birnessite sorbed strontium more than cesium. On the other hand, the changes in pH had bigger effect on the sorption capacity of Na-mica than Na-birnessite.
Sorption capacity of cesium and strontium under bi-solute condition was lower than those under single solute condition. These experimental equilibrium data were well described by Langmuir competitive model.
According to the result of column tests, the exhaustion time for strontium was longer than cesium for both Na-micas and Na-birnessite. On the other hand, the exhaustion time for Na-micas was longer when compared to Na-birnessite for both cesium and strontium.