Fe3O4-FeMoS4: Promise magnetite LDH-based adsorbent for simultaneous removal of Pb (II), Cd (II), and Cu (II) heavy metal ions

Highlights: • Fe₃O₄-FeMoS₄ based LDH adsorbent was synthesized by hydrothermal technique. • Fe₃O₄/FeMoS₄/MgAl-LDH showed ultrafast and ultrahigh adsorption performance toward to Pb (II), Cd (II) and Cu (II). • The Pb (II), Cd (II) and Cu (II) adsorption was dominated by electrostatic attraction and inner-sphere surface complexation. • The Fe₃O₄/FeMoS₄/MgAl-LDH is a low-cost intercalation and promising material for pollution remediation. There have always been numerous challenges to designing a cost-effectiveness, reusable and robust adsorbents for simultaneous heavy metal ion remediations from wastewaters. Herein, a novel kind of nanocomposite relying on the synergic impact of magnetic Fe₃O₄, FeMoS₄⁻², and magnesium-aluminum layered double hydroxide (MgAl-LDH) using loading the FeMoS₄⁻² on protonated Fe₃O₄ and adhered to the surface of Mg/Al-LDH (Fe₃O₄/FeMoS₄/MgAl-LDH). The nanocage structures adsorbent was characterized via FT-IR, XRD, FE-SEM, EDX, and VSM techniques and demonstrated having an efficient adsorption capability to common cationic pollutants (Pb (II), Cd (II) and Cu (II) by batch experiments. Disparate chief parameters affecting adsorption performance, including Fe₃O₄/FeMoS₄/MgAl-LDH mass, metal ion concentrations, solution pH, and contact time were considered and optimized through central composite design (CCD) in detail. Its supreme adsorption efficiency toward Pb (II), Cd (II), and Cu (II) accounted for 190.75, 140.50, and 110.25 mg g⁻¹, respectively, which acquired by the Langmuir model under the parameter set at 60 min contact time, solution pH at 5, 0.03 g the Fe₃O₄/FeMoS₄/MgAl-LDH and metal ion concentrations ranging from 10 to 300 mg L⁻¹. Such enhancement stemmed from the coordinated complexes in the LDH interlayer region and electrostatic attraction between Fe₃O₄/FeMoS₄/MgAl-LDH and metal ions. Furthermore, the adsorption conducts were more consistent with the pseudo-second-order model and the Langmuir isotherm model, respectively. Likewise, the features such as the superior regeneration and reusability allow the Fe₃O₄/FeMoS₄/MgAl-LDH nanocomposite to constitute as one of the promising materials for heavy metals remediation in wastewater.