Abstract: The ionic sieve adsorbent Rb8Nb22O59·8H2O was prepared by extracting Rb+ from precursor Rb8Nb22O59，which was synthesized by solid state reaction at high temperature，in HNO3 solution.As-prepared  Rb8Nb22O59·8H2O and Rb8Nb22O59 were characterized by XRD，TG-DSC，and SEM.The exchange capacity of adsorbent for Na+ and K+ was investigated and the opti- mal preparation conditions for precursor Rb8Nb22O59 were proposed as well: calcinating the mixture of Rb2CO3 and Nb2O5 at 1 200 ℃ for 12 h.Results indicated that the structure of precursor Rb8Nb22O59 under above conditions was similar to that of prepared adsorbent Rb8Nb22O59·8H2O after acid treatment.Around 97% of Rb+ of precursor could be extracted by acid elution，while the lost amount of niobium ions was negligible（less than 0.04%），showing a good capability of regeneration.In addition，the absorption capacity of Rb8Nb22O59·8H2O for K+ and Na+ was evaluated in high concentrated sodium chloride solution（amount-of-substance ratio of Na+ to K+ was 500∶1）.The adsorbent Rb8Nb22O59·8H2O had a higher distribution co- efficient for K+ with separation factor of 43 rather than for Na+ at pH ranging from 2 to 8.Meanwhile，it was found that distribution coefficients of Rb8Nb22O59·8H2O for Na+ and K+ were stable when calcination time reached over 6 h.

Key words: ionic sieve；Rb8Nb22O59·, 8H2O；Na+；K+；ion exchange