Pd nanocatalyst supported on chitosan–waste oil microspheres for efficient degradation of industrial pollutants in water

Disposal of industrial pollutants is one of the most important working topics today. Pd–doped catalysts have high efficiency in the degradation of many organic pollutants. Within the scope of this study, waste engine oil (WEO) was used as activated carbon (AC) source and then AC was encapsulated with chitosan (CS) to prepared chitosan–based microbeads (CS/WEO AC) for catalyst support. After treatment with glyoxal as cross–linker, Pd nanoparticles with spherical shape and 16.8 nm diameter were decorated on the microbeads (Pd@CS/WEO AC). Efficiency of Pd@CS/WEO AC on the reduction of 4-nitrophenol (4-NP), 4-nitro-o-phenylenediamine (4-NPDA), 2-nitroaniline (2-NA), 4-nitroaniline (4-NA) as nitroarens; methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) as organic dyes; Cr(VI) and K₃[Fe(CN)₆] was examined in aqueous media. Developed Pd@CS/WEO AC nanocatalyst reduced nitroarenes, organic dyes, Cr(VI) and K₃[Fe(CN)6] in very short times (0–130 s). Based on kinetic studies, the rate constants for Pd@CS/WEO AC–catalyzed reduction reactions of 2–NA, 4–NP, 4–NA, 4–NPDA, MO, RhB, [Fe(CN)₆]^3⁻, and Cr(VI) were found to be 0.018 s⁻¹, 0.007 s⁻¹, 0.026 s⁻¹, 0.012 s⁻¹, 0.021 s⁻¹, 0.065 s⁻¹, 0.048 s⁻¹, and 0.042 s⁻¹, respectively. Additionally, it was confirmed that Pd@CS/WEO AC is a long–lasting catalyst, as it was reused for five successive runs in the reduction of 4–NP. In this study, we aim to design new materials by modifying carbon–containing waste sources with biological macromolecules and investigate the possible applications of these materials to remove some pollutants from water sources.