Abstract: A magnetic microspheres (Calcium Alginate@Fe₃O₄/Biochar) was prepared using calcium alginate (CA) encapsulated biochar (BC) and Fe₃O₄ as the green adsorbent for Co(Ⅱ) removal from aqueous solution. The effects of the initial Co(NO₃)₂ concentration, initial pH value of Co(Ⅱ) solution and equilibrium contact time were investigated on CA@Fe₃O₄/BC. The isothermal thermodynamic datas of the CA@Fe₃O₄/BC conformed to the Langmuir model. The maximum adsorption capacity of the CA@Fe₃O₄/BC from the Langmuir equation is 16.23 mg·g^-1 at pH=6. It appears a synergistic effect between biochar and Fe₃O₄ in CA, which enhances the maximum adsorption capacity of Co(Ⅱ) ion. The presence of the magnetic particles in magnetic microsphere allows easy isolation of the material from aqueous solutions by using a magnet. The adsorptions of Co(Ⅱ) by the CA@Fe₃O₄/BC are in good agreement with pseudo-second-order kinetic. The mechanism studies for Co (Ⅱ) removal by the CA@Fe₃O₄/BC show that the nature of Co(Ⅱ) abstraction takes place through the ion exchange between Ca(Ⅱ) and Co(Ⅱ) as well as the formation of coordination complex.