Highly Robust Alginate-based Magnetic Nanosorbents of Pd Catalysts for the 4-Nitrophenol Reduction

Abstract

This work presents the synthesis of alginate-coated magnetite nanoparticle (MNP) containing amino-enriched moieties for the immobilization of palladium (Pd), and its use as a recyclable catalyst for the reduction of 4-nitrophenol (4NP) in water. The alginate grafted onto the surface of MNP contained carboxylate anions that served as coordination sites for Pd. Additionally, the incorporation of amino-enriched components, such as poly(vinyl amine) (PVAm) and 2-(dimethyl amino)ethyl methacrylate (DMAEMA), onto the alginate-coated MNPs resulted in additional interactions, including the formation of carboxylate-ammonium salts. In this study, the influence of these amino groups on the efficiency of Pd immobilization, catalytic activity and reusability of nanosorbents for 4NP reduction was investigated. The existence of Pd in the nanosorbents was detected by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, and energy-dispersive X-ray techniques. The average size of MNPs was approximately 12.3 ± 2.9 nm, and for Pd, it was about 3.9 ± 0.8 nm. It was found that the incorporation of these amino-enriched moieties into the particles significantly enhanced the catalytic activity of the nanosorbents. Notably, MNP containing extended DMAEMA units exhibited excellent tolerance to 4NP reduction, with an insignificant loss of catalytic performance even after 20 consecutive reuses, maintaining a conversion of over 98 %. HIGHLIGHTS Synthesis of alginate-based magnetite nanoparticle for the immobilization of Pd and its use as a catalyst for the reduction of 4-nitrophenol in water were presented The carboxylate groups in alginate provided the coordinating sites for Pd immobilization and improved the particle dispersibility in water The incorporation of amino-enriched components to the particle reduced the degree of Pd aggregation on the particle surface The catalysts had high catalytic performance for the reduction of 4-nitrophenol in water and exhibited highly robust properties with excellent reusability for up to 20 cycles with insignificant changes in their performance GRAPHICAL ABSTRACT