2-aminopyridine functionalized magnetic core–shell Fe3O4@polypyrrole composite for removal of Mn (VII) from aqueous solution by double-layer adsorption

Abstract

• Fe 3 O 4 @PPy-AP composite is synthesized for rapid Mn (VII) adsorption from solution. • The maximum adsorption capacity of the composite is 781.25 mg g-1 at 318.15 K. • Both the N atoms in PPy and AP can adsorb Mn (VII) through coordination effect. 2-aminopyridine functionalized magnetic core–shell Fe 3 O 4 @polypyrrole structure (Fe 3 O 4 @PPy-AP composite) is fabricated to remove Mn (VII) from water. The adsorbent fully combines the easy magnetic separation of Fe 3 O 4 microspheres, the excellent corrosion resistance of PPy, as well as double-layer adsorption for Mn (VII) of PPy and AP. The effects of time, temperature and pH on the adsorption performances and adsorption mechanism are investigated in detail, for which the significance of structure of Fe 3 O 4 @PPy-AP composite is elucidated. It is clear that the adsorption process is chemical adsorption. The adsorption kinetics and isotherm is more suitable for pseudo-second order model and Freundlich model. The initial adsorption rate is 67.43 min g mg −1 , and the maximum adsorption capacity can reach 781.25 mg g −1 at 318.15 K. The film diffusion dominates the speed of the entire adsorption process. Adsorption thermodynamic calculations show that ΔS and ΔH are 198.33 J mol −1 K −1 and 37.88 kJ mol −1 , respectively, and the decreased ΔG with increasing temperature indicates that the adsorption process is endothermic and spontaneous. The Fe 3 O 4 @PPy-AP composite only loses less than 1% of Mn (VII) adsorption capacity after each adsorption–desorption cycle. This Fe 3 O 4 @PPy-AP composite with good magnetic properties and dual adsorption properties has broad application prospects in the rapid separation and adsorption of heavy metal ions.