Chlorite alteration in aqueous solutions and uranium removal by altered chlorite

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