Adsorption of Cu(II) and methylene blue from aqueous solutions by magnetic humic acid nanoparticles

Magnetic humic acid nanoparticles (MHA) was prepared via coprecipitation method. Adsorptive removal of methylene blue (MB) and Cu(II) by MHA in single-component and binary systems was studied, respectively. MHA showed highly removal efficiency to MB and Cu(II). The adsorptions of MB and Cu(II) on MHA were pH dependent with uptake dropping in acidic solutions. The adsorption mechanisms of MB and Cu(II) were also different. MB is adsorbed via two mechanisms: π–π interactions and ion exchanging, while Cu(II) only involves ion exchanging. It was also proved that MHA can selectively remove MB in acidic solutions. The adsorption equilibrium and kinetic study indicated that the adsorption of MHA was in agreement with Langmuir model and pseundo-second-order model, respectively. Furthermore, MHA could be easily regenerated and reused with almost no loss of adsorption capacity. Overall, MHA is an efficient and versatile adsorbent for Cu(II) and MB.