LAUSR

In the present study we have shown that polypyrrole functionalized magnetic $$\hbox {Fe}_{3}\hbox {O}_{4}$$Fe3O4 nanoparticle can be used for the removal of Ni(II) and Cr(VI) from industrial effluent. The magnetic sorbent was synthesized by co-precipitation method ($$\hbox {Fe}_{3}\hbox {O}_{4}$$Fe3O4) and then subsequently chemical oxidative polymerization of polypyrrole to deposit thick layer of polypyrrole. The resultant polypyrrole-protected magnetic nanoparticles were characterized by various instrumental methods including SEM, XRD, FT-IR, and vibrating sample magnetometer. The polypyrrole modified magnetic nanoparticles were utilized as adsorbent for the removal of metal ions such as Ni(II) and Cr(VI) by batch method. The various experimental parameters such as pH, adsorbent dosage and contact time on the adsorption of metal ions onto $$\hbox {Ppy}@\hbox {Fe}_{3}\hbox {O}_{4}$$Ppy@Fe3O4 were studied. The optimum adsorption equilibrium time and pH of the medium were 150 min at pH 6 for Ni(II) ions and 60 min at pH 2 for Cr(VI) ions. Kinetic studies showed that the adsorption followed a pseudo-second-order model. The experimental data were analyzed using linear optimization techniques such as Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms and nonlinear optimization techniques (error functions). It is observed that the experimental data were found to have a good fit with Langmuir isotherm for both metal ions. The maximum adsorption capacity was found to be 19.92 and $$344.82\,\hbox {mg g}^{-1}$$344.82mgg-1 for Ni(II) and Cr(VI) ions, respectively.