Fig. 3

Purification performance of the nanoparticles towards oilfield wastewater. Photographs of deionized water, oilfield wastewater before and after treated with a Fe₃O₄@SiO₂-MPS-AM-DMC-AMPS and c Fe₃O₄ under external magnet field, respectively, and the corresponding desalination efficiency of b Fe₃O₄@SiO₂-MPS-AM-DMC-AMPS and d Fe₃O₄ for each ion