Chlorite alteration in aqueous solutions and uranium removal by altered chlorite

Chlorite alteration and the U removal capacity of altered chlorite were investigated. Batch kinetic dissolution tests using clinochlore CCa-2 were conducted for 60 days in aqueous solutions of various pHs and ionic strengths. Batch sorption tests using these altered chlorite samples were conducted for 48 h with natural groundwater containing 3.06 × 10⁻⁶ M U. Chlorite dissolution was influenced more by pH_o than by the ionic strength of the solution. TEM analysis revealed Fe(oxy)hydroxide aggregates in the solid residue from the batch dissolution test with 0.1 M NaClO₄ solution at pH_o = 10. The U removal capacity of the reacted chlorite samples at pH_o = 6–10 was higher than that of the reacted chlorite samples at pH_o = 3. The degree of dissolution of chlorite samples reacted at pH_o = 3–8 was inversely proportional to the U removal capacity, but that of chlorite samples reacted at pH_o = 10 was proportional to the U removal capacity. The positive correlation between the U removal capacity and degree of chlorite dissolution at pH_o = 10 might be due to the formation of Fe-containing secondary minerals and changes in the reactive sites.