An extractant having a strong affinity for heavy metal ions, bis(2,4,4trimethylpentyl) monothiophosphinic acid (Cyanex 302, HA), was encapsulated in the alginate polymer matrices. The emulsification of HA extractant in microcapsules (MCs) resulted in a considerable reduction in the size of oil drops. The uptake rates of Cd2+ for MCs were enhanced compared to those for the matrices of CaALG and BaALG, and a large difference in uptake rate was observed within 10 h. The uptake of Cd2+ by MCs attained equilibrium within 20 h and Cd2+ ions were preferentially adsorbed on MCs even in the presence of 0.1 M HNO3 and 1 M NaOH. The uptake (%) of heavy metal ions, Ag, Cd, Pb and Cu, for HA-CaALG was above 96%, suggesting a simultaneous removal of soft metal ions. The uptake ability of Cd2+ for MCs is superior to that of conventional resins. The successive removal of Cd2+ ions was accomplished by a column packed with granular MCs. Various shapes of MCs such as fiber and film are also obtained. The microencapsulation techniques with alginate polymer are thus applicable to environmental remediation.