Pd@SA/β-CD/Fe₃O₄: Pd nanoparticles on sodium alginate hydrogel beads reinforced with β-cyclodextrin and Fe₃O₄...

The increased use of toxic organic pollutants, such as organic dyes and nitroaromatics, in various industrial applications has led to their leak into wastewater. The inability to remove these toxic pollutants, which are non-biodegradable and stable, from wastewater poses a threat to many living organisms, from human health to the environment. Therefore, the effective removal of these pollutants from water/wastewater is crucial. In this study, we designed heterogeneous catalyst system composed of palladium nanoparticles decorated on sodium alginate (SA) hydrogel beads reinforced with β-cyclodextrin (β-CD) and Fe₃O₄ for the catalytic elimination of organic dyes (methylene blue (MB), methyl orange (MO), and rhodamine B (RhB)) and nitroaromatics (p-nitro-o-phenylenediamine (p-NPDA), (p-nitroaniline (p-NA), p-nitrophenol (p-NP), and o-nitroaniline (o-NA)). Morphological and structural confirmation of Pd@SA/β-CD/Fe₃O₄ was conducted using TEM, FE-SEM, FT-IR, EDS, BET, TG, and XRD analyses. FE-SEM and TEM analyses confirmed that the prepared Pd NPs had a spherical shape with a particle size of 10 nm, while EDS, BET, TG, FT-IR, and XRD analyses confirmed their magnetic properties and chemical structure. The catalytic capability of Pd@SA/β-CD/Fe₃O₄ was then evaluated for the reduction of MO, MB, RhB, p-NA, p-NP, o-NA, and p-NPDA using NaBH₄, and the reductions were monitored by UV-Vis analyses. Pd@SA/β-CD/Fe₃O₄ with 10 nm particle size served as an effective nanocatalyst, facilitating the reduction of these contaminants within a short reaction time (0-105 s). Kinetic studies were conducted, and the rate constants (k) were determined as 0.009 s^-1 for p-NP, 0.022 s^-1 for o-NA, 0.012 s^-1 for p-NPDA, 0.018 s^-1 for p-NA, 0.054 s^-1 for RhB, and 0.01 s^-1 for MO. Thanks to its magnetic nature, Pd@SA/β-CD/Fe₃O₄ was easily recovered and reused up to six cycles, affirming its potential as a practical, economical, and sustainable catalyst.