Fe3O4 embedded κ-carrageenan/sodium alginate hydrogels for the removal of basic dyes

Here, we introduce κ-carrageenan and sodium alginate based hydrogel (CAG-NaAlg-cl-polyAA) and hydrogel nanocomposite (CAG-NaAlg-cl-polyAA/Fe3O4) through a free radical crosslinking method using acrylic acid/ N,N′- methylenebisacrylamide as a monomer/crosslinker system. The hydrogel is stimuli-responsive and its water absorption efficiency is enhanced through the optimization of synthesis parameters. The synthesized superabsorbents have been sequentially characterized through HR-TEM, powder XRD, FTIR, SEM-EDS, and XPS analysis. The average particle size of Fe3O4 nanoparticles stabilized through the CAG-NaAlg-cl-polyAA hydrogel matrix is 10.7 ± 2.5 nm. The CAG-NaAlg-cl-polyAA hydrogel exhibited > 95 % dye removal efficiency for the removal of basic dyes (auramine O, crystal violet and malachite green), whereas the % dye removal potential of CAG-NaAlg-cl-polyAA/Fe3O4 is enhanced upto 99 % after the incorporation of Fe3O4 nanoparticles. Langmuir adsorption is the most favorable adsorption isotherm with R2 = 0.992 (auramine O, AU), 0.989 (malachite green, MG), and 0.974 (crystal violet, CV). Kinetic studies indicate that the adsorption of AU, CV, and MG follows pseudo 2nd order kinetics. Moreover, the reusability of the fabricated samples upto five consecutive cycles further explores its potential for the separation of basic textile dyes from industrial wastewater.