We developed an organic-inorganic hybrid material for selective removal of Hg~(2+) ion from water,by immobilizing rhodamine derivative onto the surface of core /shell Fe_3O_4@SiO_2 nanospheres (Fe_3O_4@SiO_2-R6G).With a saturation magnetization of 26.1 emu?g~(-1),the Fe_3O_4@SiO_2-R6G could be simply re-collected from water by an external magnet within a few minutes.Moreover,the Fe_3O_4@SiO_2-R6G showed high selectivity for adsorbing Hg~(2+) over other metal ions in aqueous solution.The maximum adsorption capacity for Hg~(2+) was 40.15 mumol?g~(-1).It could be easily recovered by treatment with a solution of tetrabutylammonium hydroxide and used repeatedly
