Abstract: Magnetite particles were coated on layered double hydroxides by one-step co-precipitation method,then the prepared solids were calcined to obtain magnetic metal oxides,which were used to remove humic acid from aqueous solution.The results show that magnetic calcined Zn-Al LDHs (M·Zn-Al LDO) performed a effective adsorption for humic acid removal.The effect of preparation conditions on the removal of humic acid was investigated,and the preparation conditions were optimized by orthogonal test.The results of adsorption of humic acid by M·Zn-Al LDO show that the humic acid removal rate is obtained 97.96% with the M·Zn-Al LDO dosage of 0.2 g/L at 30 min in initial humic acid concentration of 20 mg/L.The adsorbent is characterized using X-Ray,FT-TR,TG-DSC and SSA analysis,the results demonstrat that typical layered structure of hydrotalcite is not affected by introducing a certain amount of magnetic substrates which are Fe3O4 and γ-Fe2O3.The calcined products are metal oxides and still held excellent magnetic property,whose specific surface area is 80.00 m2/g.The humic acid removal by M·Zn-Al LDO is performed by surface adsorption and intercalation of small size functional groups in humic acid when the structure of hydrotalcite built again on memory effect.

Key words: magnetic layered double hydroxides;calcination;humic acid;adsorption