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In the present work, nanocomposite of bentonite clay with MgFe 2 O 4 nanoparticles (NPs) was synthesized by sol-gel route. It was studied for the sequestration of Pb(II) and Ni(II) ions from the aqueous solution. The nanocomposite was analysed using X-ray diffraction, vibrating sample magnetometry, scanning electron microscopy equipped with energydispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and Brunauer-Emmett-Teller (BET) as analytical tools. The lower value of saturation magnetization (M s) of nanocomposite (5.70 emu g −1) as compared with pristine MgFe 2 O 4 NPs (12.32 emu g −1) is due to the presence of non-magnetic bentonite clay. BET studies further revealed higher surface area for nanocomposite (75.43 m 2 g −1) than MgFe 2 O 4 NPs (62.51 m 2 g −1). The presence of bentonite clay during sol-gel synthesis of MgFe 2 O 4 NPs prevented particle growth. The adsorption data were modelled using Temkin, Freundlich, Dubinin-Radushkevitch and Langmuir adsorption isotherms. Comparative evaluation of adsorption potential of nanocomposite for Pb(II) and Ni(II) ions confirmed higher affinity of Pb(II) ions (q max = 90.90 mg g −1) towards the nanocomposite as compared with Ni(II) ions (q max = 76.92 mg g −1). The results were explained on the basis of their hydration enthalpy. Thermodynamic analysis confirmed endothermic and spontaneous nature of adsorption process with H o values of 48.67 and 21.54 kJ mol −1 for Pb(II) and Ni(II) ions, respectively. Kinetic studies confirmed that a pseudo-second-order kinetic model was followed. The obtained results suggested that adsorption capacity of nanofabricated composite for Pb(II) and Ni(II) ions was higher than that of pristine MgFe 2 O 4 NPs and bentonite clay. The saturated adsorbent was magnetically retrievable and easily regenerated with 0.1 M HCl solutions. It can serve as a potential composite adsorbent for the remediation of heavy metal ions.

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