Magnetic magnetite (Fe3O4) nanoparticle synthesis and applications for lead (Pb2+) and chromium (Cr6+) removal from water

• Fe3O4 was synthesized by coprecipitation using TMAOH and thoroughly characterized.
• Magnetite nanoparticles successfully remediated aqueous Cr6+ and Pb2+.
• Magnetite Langmuir adsorption capacities of ∼35 (Cr6+) and ∼53 (Pb2+) mg/g were obtained.
• Likely Cr6+ and Pb2+ sorption mechanisms versus pH were described.
• Kinetics were pseudo-second order, rate dependent on the number of surface sites.

Magnetic magnetite (Fe3O4) nanoparticles synthesized by chemical co-precipitation were characterized using XRD, TEM, SEM-EDX, FT-IR, ED-XRF, PPMS, point of zero charge (pHpzc) and surface area measurements. As-prepared Fe3O4 nanoparticles were successful for aqueous Cr6+ and Pb2+ removal. Batch adsorption experiments systematically investigated the influence of pH, temperature, contact time and adsorbate/adsorbent concentration on Cr6+ and Pb2+ adsorption. Maximum Cr6+ and Pb2+ removal occurred at pH 2.0 and 5.0, respectively. Sorption data fit pseudo-second order kinetics, indicating a chemical adsorption. The Freundlich, Langmuir, Redlich–Peterson, Toth, Radke and Sips adsorption isotherm models were applied to describe equilibrium data. The Sips and Langmuir models best described Cr6+ and Pb2+ adsorption on magnetite nanoparticles, respectively. The maximum Langmuir adsorption capacities were 34.87 (Cr6+) and 53.11 (Pb2+) mg/g at 45 °C, respectively. Fe3O4 nanoparticles are promising potential adsorbents and exhibited remarkable reusability for metal ions removal in water and wastewater treatment.

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