Three-Dimensional Rice Straw-Structured Magnetic Nanoclay-Decorated Tripolymeric Nanohydrogels as Superadsorbent of Dye Pollutants

Herein, a simple eco-friendly route was adopted to synthesize three-dimensional (3D) rice straw-structured poly(vinyl alcohol) (PVA)/ chitosan (Cs)/agar-agar (Agr), tripolymer-based magnetic nanohydrogels with incorporations of Cloisite30B and magnetite (Fe3O4) nanoparticles via sulfate-induced quick gelation approach. The 3D rice straw structures of nanohydrogels were evolved due to the rolling of exfoliated clay platelets during transformation of PVA/Cs/Agr hydrogel network, whereas the situation of exfoliation was achieved because of long time ultrasonication and strong repulsive interactions between positively charged tripolymeric chain and interstitial quaternary ammonium ions of nanoclays. Synthesized nanohydrogels were characterized with Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and thermogravimetric analysis/differential thermogravimetry along with their rheological measurements to interpret the viscoelastic behaviors. The suitability of these nanohydrogels was investigated in detail for removal of rhodamine B (RhB) and methylene blue (MB) dyes from aqueous solution with variation of contact time, initial dye concentration, adsorbent dosage, temperature, and pH, which were observed to be fitted well with pseudo-second-order kinetic and Langmuir isotherm models with revealing endothermic physisorption nature of adsorption. The low-cost, large-scale production, high adsorption capacities (q(max)@RhB: 780 mg.g(-1); q(max)@MB: 800 mg.g(-1)), easiness of regeneration, biocompatibility, and high magnetization value (38.16 emu.g(-1)) may explore the synthesized PVA/Cs/Agr@Clay/Fe3O4 nanohydrogels as potential scavenger of organic dyes.