Doped Fe3O4 was synthesized from electroplating sludge by hydrothermal reaction which used urea as the precipitator of FeCl2 and FeCl3.Through analyzing the effect of the doping amount

reaction time

and the reaction temperature on the synthetic Fe3O4

it indicates that when the mass ratio of iron source to electroplating sludge is 4∶1

the reaction time is 4 h and the temperature is 160 ℃

the best experimental result can be explored.And the research shows that: in the acidic leaching condition

Cu in the doped Fe3O4 has the largest leaching concentration

Ni takes the second place;Zn

Fe and Cr have a good stability

and the concentration is lower than the regulatory limit of Toxic Characteristic Leaching Procedure(TCLP) in pH range of 3～10.Therefore

the electroplating sludge enriching Cu is not suitable for doped source

and that enriching Zn and Cr is a good choice.The black doped Fe3O4 has a better magnetism

and is weakly agglomerated and equably distributed.