Development of magnetically retrievable nanostructure Pd catalyst system supported on keratin-Schiff base and its application in catalytic and antioxidant activities

Abstract

Recently, the production of biomaterial supported metal nanoparticles has gained significant importance as an emerging field with numerous applications ranging from healthcare to sustainable environment due to their unique chemical, catalytic, physical, and biological properties. In this paper, we fabricated magnetically retrievable Schiff base modified-keratin supported nano-sized Pd catalyst (Pd@keratin/Fe₃O₄/Sch) to investigate its catalytic and antioxidant characteristics. The design procedure for Pd@keratin/Fe₃O₄/Sch is as follows: (1) extraction of keratin from goose feathers, (2) loading of Fe₃O₄ onto keratin (keratin/Fe₃O₄), (3) amino-functionalization of keratin/Fe₃O₄ (keratin/Fe₃O₄/APT), (4) Schiff base modification of keratin/Fe₃O₄/APT (keratin/Fe₃O₄/Sch), and (5) preparation of the nano-structured Pd catalyst. Diverse analytical methods, bearing FT-IR, TEM, EDS, XRD, TGA, XPS, BET and FE-SEM were utilized to substantiate production of Pd nanoparticles. TEM results indicated that the formed Pd nanoparticles had an average particle size of 20 nm. The catalytic behavior of Pd@keratin/Fe₃O₄/Sch was then studied in the catalytic reduction of nitroaromatics (p-nitrophenol (p-NP), p-nitro-o-phenylenediamine (p-NPDA), o-nitroaniline (o-NA), p-nitroaniline (p-NA)) and organic dyes (rhodamine B (RhB), methyl orange (MO) and methylene blue (MB)). The Pd@keratin/Fe₃O₄/Sch successfully reduced p-NP, p-NPDA, p-NA, and o-NA rapidly with rate constants of 0.018 s⁻¹, 0.013 s⁻¹, 0.039 s⁻¹, and 0.034 s⁻¹, respectively. In addition, it promptly reduced MB, while it reduced MO and RhB with rate constants of 0.023 s⁻¹ and 0.054 s⁻¹, respectively. The Pd@keratin/Fe₃O₄/Sch was readily recovered due to its magnetic nature and was reused up to six cycles. The stability of Pd@keratin/Fe₃O₄/Sch was confirmed through EDS and ICP analyses conducted after the reusability tests. The samples obtained after each step in the Pd@keratin/Fe₃O₄/Sch production were also investigated for their antioxidant activities. The order of antioxidant activity was found to decrease in the following sequence: keratin/Fe₃O₄, Pd@keratin/Fe₃O₄/Sch, keratin/Fe₃O₄/APT, keratin/Fe₃O₄/Sch and keratin, respectively. The fabricated Pd@keratin/Fe₃O₄/Sch is an ideal catalyst system for remediating wastewater contaminants and biological applications with excellent catalytic and antioxidant capacity, easy recovery, and good stability.