Synthesis and Characterization of Magnetic Superadsorbent Fe3O4-PEG-Mg-Al-LDH Nanocomposites for Ultrahigh Removal of Organic Dyes

Abstract

Considering the huge demands for economical and reliable eco-remediation applications, the goal of the present work is to synthesize cost-effective and functionally efficient magnetic layered nanocomposite adsorbents for the effective adsorption of dyes followed by easy separation from wastewater. This would ensure good reusability of adsorbents without altering its adsorption capacity in a relatively short time manner. To achieve this, different molecular weights of polyethylene glycol (PEG)-modified Fe3O4 combined with Mg-Al-layered double hydroxides (MAN-LDH) were synthesized and characterized using powder X-ray diffraction, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, differential thermal analysis, energy-dispersive X-ray, and inductively coupled plasma optical emission spectroscopy. The efficacy of various adsorption parameters for the removal of methyl orange (MO) from water using Fe3O4-PEG-Mg-Al-LDH (FPL) adsorbents with different molecular weights of PEG (2FPL, 4FPL, and 6FPL) were investigated, and the results were compared. The maximum adsorption capacities of 2FPL, 4FPL, and 6FPL for MO were found to be 775.19, 826.44, and 833.33 mg/g, respectively. Detailed adsorption studies confirm that the higher adsorption capacity of 6FPL is due to the fast exchange of anions (NO3-) by MO in the interlayers of MAN-LDH, larger surface area, hydrogen bonding, and electrostatic interaction between adsorbate and adsorbent. The thermodynamic data indicate that the adsorption behavior is spontaneous and endothermic in nature. The reusability of all FPL adsorbents is observed to be excellent. The MAN-LDH recoated after the 31st-cycle nanocomposites show a recovery of 100% adsorption efficiency, similar to the freshly prepared 6FPL. Such systematic studies greatly help in advancing the applications of newly functionalized nanomaterials toward eco-remediation approaches.