Magnetite@poly(p-phenylenediamine) core-shell composite modified with salicylaldehyde for adsorption and separation of Mn (VII) from polluted water

Magnetite@poly-p-phenylenediamine (Fe3O4@PpPD) composite modified with salicylaldehyde (SA) was fabricated as adsorbent to remove Mn (VII) from wastewater. The Fe3O4 microspheres endow the adsorbent with the ability of rapid solid–liquid separation. The PpPD with acid and alkali resistance can protect Fe3O4 from corrosion while introducing a large amount of N atoms to adsorb Mn (VII). The introduction of SA increases the specific surface area and adsorption sites of the adsorbent. The effects of pH, time and temperature on the adsorption process were studied. At pH = 2, the maximum adsorption capacity (Q) is as high as 148.34 mg g−1, which is attributed to the complexation/chelation and electrostatic interaction between amino and hydroxyl groups and Mn (VII). It is found that the adsorption process conforms to the pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamics studies demonstrate that the adsorption is a spontaneous endothermic process. After four adsorption cycle tests, the adsorption capacity losses only 1%. Moreover, high adsorption efficiency in river water and mixed metal ions’ solution prove that the prepared Fe3O4@PpPD-SA composite possesses excellent Q in removing Mn (VII).