Recyclable polymer microgel stabilized rhodium nanoparticles for reductive degradation of para-nitrophenol

Abstract

The purpose of present work is to fabricate rhodium nanoparticles in Poly(N-isopropylmethacrylamide-acrylic acid) [p(NMAA)] microgel system. Synthesized polymer [p(NMAA)] microgels and rhodium nanoparticles loaded [Rh-p(NMAA)] microgels were analyzed by FTIR (Fourier Transform Infra-red) spectroscopy, XRD (X-ray Diffraction) analysis and UV/Vis (Ultraviolet–Visible) spectroscopy. Catalytic reductive conversion of P-nitrophenol (P-Nph) into P-aminophenol (P-Aph) via Rh-p(NMAA) was used to evaluate the catalytic activity of the hybrid microgel [Rh-p(NMAA)]. Kinetic study of catalytic reductive conversion of P-Nph was explored by considering various reaction parameters. It was found that the value of first order observed rate constant (k obs) was varied from 0.019 to 0.206 min−1 with change in concentration of sodium borohydride (SBH) from 3 to 14 mM at given temperature. However, further increment in concentration of SBH from 14 to 17 mM, reduced the value of k obs from 0.206 to 0.156 min−1. The similar dependence of k obs on concentration of P-Nph was observed at specific concentration of SBH and Rh-p(NMAA) at constant temperature. Kinetic study reveals that conversion of P-Nph to P-Aph takes place on the surface of rhodium nanoparticles (RhNPs) by adopting different reactions intermediates and obeys the Langmuir-Hinshelwood mechanism. Reduction efficiency of recycled Rh-p(NMAA) catalytic system was also measured and no significant reduction in the percentage catalytic activity was obtained up to four cycles for P-Nph conversion into P-Aph.

Fabrication of NIPMAM based polymer microgel network assisted rhodium nanoparticles for reductive degradation of toxic azo dyes

“…Though, the components of the p-(NIPMAM-co-AA-AAm) microgels are visible to electromagnetic radiation in the UV visibility range [ 11 ]. The surface Plasmon resonance of rhodium NPs in the microgel network was assigned to the unique peak at 220 nm [ 9 ]. Fig.…”

“…Hybrid microgels were fabricated at room temperature by in situ reduction of metal ions in a microgel network. It has been reported in the literature that rhodium nanoparticles were prepared by reducing rhodium ions in a microgel network [ 9 ]. For hybrid microgel preparation, the 7.5 mL prepared microgel was mixed with 12.5 mL distilled water, poured into three round-bottom flask and stirred for 30 min while supplying nitrogen to remove the dissolved oxygen from the dispersion.…”

“…A main drawback of previously used techniques such as coagulation and flocculation [ 8 ] is that it leads to secondary contamination due to the overuse of coagulant [ 3 ]. The catalytic reduction method by using metal nanoparticles is considered the best method for the decomposition of harmful azo dyes among all the above-mentioned methods due to its extensive surface area, strong catalytic activity, high efficiency and exceptional capacity to transport electrons [ 9 ]. The decomposition of azo dyes, in the presence of nanocatalysts, is the most excellent approach for removing azo dyes from aqueous media [ 10 ].…”

“…Rhodium NPs are extra stable than Ag and Au NPs, and their surface does not oxidize easily in water. For this reason, Rhodium nanoparticles are frequently used as catalysts in aqueous media [ 9 ]. To the best of our knowledge, no studies of the catalytic degradation of azo dyes in the presence of hybrid microgels with Rh NPs based on p-(NIPMAM-co-AA-AAm) have been published in the literature.…”

Multifunctional Core-Shell Microgels as Pd-Nanoparticle Containing Nanoreactors With Enhanced Catalytic Turnover

“…Moreover, aggregation of nanoparticles can lead to another major challenge as it reduces the accessible surface area and catalytic activity (Ingham et al, 2011;Hansen et al, 2013). Both problems can be minimized by incorporating the nanoparticles into suitable carrier systems such as polyelectrolytes (Wunder et al, 2010;Battistoni et al, 2017;Du et al, 2019;Ding et al, 2021), inorganic nanocontainers (Zhang et al, 2009;Ding et al, 2011;Priebe and Fromm, 2014), or organic polyacrylamide-based microgels (Lu and Ballauff, 2011;Brändel et al, 2019b;Inui et al, 2020;Naseem et al, 2020;Oberdisse and Hellweg, 2020;Sabadasch et al, 2020;Iqbal et al, 2021). The latter systems offer a wide range of parameters to tune the catalytic activity of the embedded nanoparticles due to their versatile responsiveness triggered by temperature (Liu et al, 2009;Friesen et al, 2021), ionic strength (Karg et al, 2008) or pH (Snowden et al, 1996;Hoare and Pelton, 2004;Hoare and Pelton, 2006).…”