Pd@SA/β-CD/FeO: Pd nanoparticles on sodium alginate hydrogel beads reinforced with β-cyclodextrin and FeO particles for effective reductive elimination of organic pollutants.

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 FeO 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/FeO 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/FeO was then evaluated for the reduction of MO, MB, RhB, p-NA, p-NP, o-NA, and p-NPDA using NaBH, and the reductions were monitored by UV-Vis analyses. Pd@SA/β-CD/FeO 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 for p-NP, 0.022 s for o-NA, 0.012 s for p-NPDA, 0.018 s for p-NA, 0.054 s for RhB, and 0.01 s for MO. Thanks to its magnetic nature, Pd@SA/β-CD/FeO was easily recovered and reused up to six cycles, affirming its potential as a practical, economical, and sustainable catalyst.