Palladium nanoparticles anchored on NiO particles-modified micro-size chitosan spheres: A promising, active, and retrievable catalyst system for treatment of environmental pollutants.

Efficient treatment of toxic organic pollutants in water/wastewater by using innovative, cost efficient, and simple technologies has recently become an important issue worldwide. Remediation of these pollutants with chemical reduction in the presence of a nano-sized catalyst and a reducing agent is one of the most useful methodologies. In the present study, we have designed a promising heterogeneous catalyst system (Pd@CS-NiO) by easy and efficient stabilization of palladium nanoparticles on the surface of microspheres composed of chitosan (CS)-NiO particles (CS-NiO) for the reduction of organic pollutants. The nano-structure of the developed Pd@CS-NiO was successfully validated using FE-SEM, XRD, EDS, TEM, and FTIR/ATR and its particles size was determined as 10 nm. The catalytic power of Pd@CS-NiO was then assessed in the reduction of 4-nitro-o-phenylenediamine (4-NPDA), 4-nitrophenol (4-NP), 4-nitroaniline (4-NA), 2-nitroaniline (2-NA), and some organic dyes, namely methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) in aqueous medium at room temperature. The reductions were thoroughly studied spectro-photometrically. The tests displayed that the synthesized Pd@CS-NiO was a highly active and useful catalyst that reduced these pollutants in 0-145 s. Moreover, the rate constants for 2-NA, 4-NP, 4-NA, 4-NPDA, MO, and RhB were found to be 0.017 s-1, 0.011 s-1, 0.006 s-1, 0.013 s-1, 0.023 s-1, and 0.03 s-1, respectively. Moreover, the recycling test indicated that Pd@CS-NiO may be recovered easily thanks to its micro size nature and could be used up to seven steps, confirming its practical application potential.

Gas-Phase Regeneration of Metal-Poisoned V2O5-WO3/TiO2 NH3-SCR Catalysts via a Masking and Reconstruction Strategy.

Renewing metal-poisoned NH3-SCR catalysts holds great potential for mitigating environmental pollution and utilizing hazardous wastes simultaneously. Ionic compounds containing heavy metals often exhibit limited solubility due to their high polarizability, making traditional washing techniques ineffective in removing heavy metal poisons. This study presents a gas-based method for regenerating heavy-metal-poisoned V2O5-WO3/TiO2 catalysts employed in NH3-SCR techniques. The regeneration is achieved by employing a masking and reconstruction strategy, which involves the in situ formation of NO2 to mediate the production of SO3. This enables the effective bonding of Pb and triggers the reconstruction of active VOx sites. In situ spectroscopy confirms that the sulfation of PbO restores acidity, while the occupied effect resulting from the sulfation of TiO2 promotes the formation of more polymeric VOx species. Consequently, the regenerated catalyst exhibits enhanced activity and superior resistance to metal poisons compared with the fresh catalyst. The innovative method offers a promising solution for extending the lifespan of poisoned catalysts, reducing waste generation, and enhancing the efficiency of NH3-SCR systems.

In Situ Preparation of Metallic Copper Nanosheets/Carbon Paper Sensitive Electrodes for Low-Potential Electrochemical Detection of Nitrite.

In the realm of electrochemical nitrite detection, the potent oxidizing nature of nitrite typically necessitates operation at high detection potentials. However, this study introduces a novel approach to address this challenge by developing a highly sensitive electrochemical sensor with a low reduction detection potential. Specifically, a copper metal nanosheet/carbon paper sensitive electrode (Cu/CP) was fabricated using a one-step electrodeposition method, leveraging the catalytic reduction properties of copper's high occupancy d-orbital. The Cu/CP sensor exhibited remarkable performance in nitrite detection, featuring a low detection potential of -0.05 V vs. Hg/HgO, a wide linear range of 10~1000 µM, an impressive detection limit of 0.079 µM (S/N = 3), and a high sensitivity of 2140 µA mM-1cm-2. These findings underscore the efficacy of electrochemical nitrite detection through catalytic reduction as a means to reduce the operational voltage of the sensor. By showcasing the successful implementation of this strategy, this work sets a valuable precedent for the advancement of electrochemical low-potential nitrite detection methodologies.

Chitosan-sunflower meal biochar hydrogel incorporated with green synthesized NiO nanoparticles for enhanced catalytic reduction of anthropogenic water pollutants.

Anthropogenic activities have been one of the crucial driving factors for water pollution globally, thereby warranting a sustainable strategy for its redressal. In this study, we have developed a hydrogel-biochar nanocomposite for catalytic reduction of water pollutants. To begin with, green synthesis of nickel oxide nanoparticles (NiO NPs) was accomplished from waste kinnow peel extract via the environmentally benign microwave method. The formation of NiO NPs was affirmed from different analytical techniques namely ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive spectroscopy (EDS). The FESEM images revealed spherical nature of NiO NPs. The average particle size was found to be 15.61 nm from XRD data. A novel hydrogel-biochar nanocomposite comprising the green NiO NPs, sunflower meal biochar and chitosan was prepared (Cs-biochar@ NiO) and explored as a nanocatalyst towards catalytic reduction of pollutants such as 4-nitrophenol, potassium hexacyanoferrate (III) and organic dyes methyl orange (MO), Congo red (CR), methylene blue (MB) in the presence of a reducing agent, i.e. NaBH4. Under optimized conditions, the reduction reactions were completed by 120 s and 60 s for 4-NP and potassium hexacyanoferrate (III) respectively and the rate constants were estimated to be 0.044 s-1 and 0.110 s-1. The rate of reduction was found to be faster for the dyes and the respective rate constants were 0.213 s-1 for MO, 0.213 s-1 for CR and 0.135 s-1 for MB. The assessment of the nanocatalyst in the reduction of binary dye systems depicted its selectivity towards the anionic dyes CR and MO. The nanocatalyst displayed effective reduction of dyes in real-water samples collected from different sources. Taken altogether, this study validates the design of sustainable hydrogel-biochar nanocatalyst for the efficient reduction of hazardous anthropogenic water pollutants.

Exploring the potential of surface-modified alginate beads for catalytic removal of environmental pollutants and hydrogen gas generation.

In this study, hydrogel beads were fabricated using alginate (Algt) polymer containing dispersed nickel phthalocyanine (NTC) nanomaterial. The viscous solution was poured dropwise into a divalent Ca2+ ions, resulting in the formation of hydrogel beads known as NTC@Algt-BDs. The surface of the NTC@Algt-BDs was further modified by coating them with different types of metal ions, yielding metal-coated M+/NTC@Algt-BDs. The adsorbed metal ions i.e., Cu+2, Ag+, Ni+2, Co+2, and Fe+3 were subsequently reduced to zero-valent metal nanoparticles (M0) by NaBH4. The prepared beads were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) (XPS). Initially, M0/NTC@Algt-BDs were examined for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Among them, the Cu0/NTC@Algt-BDs catalyst exhibited the highest reduction rate and therefore, investigated for reduction of different nitrophenols (NPs) and dyes, including 2-nitrophenol (2-NP), 2,6-dinitrophenol (2,6-DNP), methyl orange (MO), potassium ferrocyanide (PFC), congo red (CR), and acridine orange (ArO). The highest reduction rates of 2.019 and 1.394 min-1 were observed for MO and 2-NP, respectively. Furthermore, the fabricated catalysts were employed for the efficient production of H2 gas by NaBH4 methanolysis. Among which the Ag0/NTC@Algt-BDs catalyst showed excellent catalytic production of H2 gas, exhibiting the lowest activation energy (Ea) of 25.169 kJ/mol at ambient temperature. Furthermore, the impact of NaBH4 amount, and catalyst dosage on the reduction of 2-NP and H2 gas production was conducted whereas the effect of temperature on methanolysis of NaBH4 for evolution of H2 gas was studied. The amount of H2 gas was confirmed by GC-TCD system. Additionally, the recyclability of the catalyst was investigated, as it garnered significant research interest.

Facile synthesis of copper nitroprusside chitosan nanocomposite and its catalytic reduction of environmentally hazardous azodyes.

One of the biggest issues affecting the entire world currently is water contamination caused by textile industries' incapacity to properly dispose their wastewater. The presence of toxic textile dyes in the aquatic environment has attracted significant research interest due to their high environmental stability and their negative effects on human health and ecosystems. Therefore, it is crucial to convert the hazardous dyes such as methyl orange (MO) azo dye into environmentally safe products. In this context, we describe the use of Copper Nitroprusside Chitosan (Cu/SNP/Cts) nanocomposite as a nanocatalyst for the chemical reduction of azodyes by sodium borohydride (NaBH4). The Cu/SNP/Cts was readily obtained by chemical coprecipitation in a stoichiometric manner. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy were applied to investigate chemical, phase, composition, and molecular interactions. Additionally, Scanning electron microscope (SEM) was used to examine the nanomaterial's microstructure. UV-vis spectroscopy was utilized for studying the Cu Nitroprusside Chitosan's catalytic activity for the reduction of azodye. The Cu/SNP/Cts nanocomposite demonstrated outstanding performance with total reduction time 160 s and pseudo-first order constant of 0.0188 s-1. Additionally, the stability and reusability study demonstrated exceptional reusability up to 5 cycles with minimal activity loss. The developed Cu/SNP/Cts nanocomposite act as efficient nanocatalysts for the reduction of harmful Methyl orange azodye.

Catalytic reduction of nitroarenes by palladium nanoparticles decorated silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) hybrid microgels.

Conversion of toxic nitroarenes into less toxic aryl amines, which are the most suitable precursors for different types of compounds, is done with various materials which are costly or take more time for this conversion. In this regards, a silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) Si@P(CS-NIPAM-MAA) Si@P(CNM) core-shell microgel system was synthesized through free radical precipitation polymerization (FRPP) and then fabricated with palladium nanoparticles (Pd NPs) by in situ-reduction method to form Si@Pd-P(CNM) and characterized with XRD, TEM, FTIR, SEM, and EDX. The catalytic efficiency of Si@Pd-P(CNM) hybrid microgels was studied for reduction of 4-nitroaniline (4NiA) under diverse conditions. Different nitroarenes were successfully transformed into their corresponding aryl amines with high yields using the Si@Pd-P(CNM) system as catalyst and NaBH4 as reductant. The Si@Pd-P(CNM) catalyst exhibited remarkable catalytic efficiency and recyclability as well as maintaining its catalytic effectiveness over multiple cycles.

Preparation of nanocellulose/reduced graphene oxide matrix loaded with cuprous oxide nanoparticles for efficient catalytic reduction of 4-nitrophenol.

The paper reports on the preparation of cellulose nanocrystals/reduced graphene oxide matrix loaded with cuprous oxide nanoparticles (CNC/rGO-Cu2O) through a simple solvothermal method and its application for 4-nitrophenol reduction to 4-aminophenol using sodium borohydride. The CNC/rGO-Cu2O nanocomposite was formed chemically by first mixing CNC and graphene oxide (GO) followed by complexation of the negatively charged functional groups of CNC/GO with Cu2+ ions and subsequent heating at 100°C. This resulted in the simultaneous reduction of GO to rGO and the formation of Cu2O nanoparticles. The as-elaborated nanocomposite was firstly characterized using different techniques such as atomic force microscopy, scanning electron microscopy, transmission electron microscopy, UV-Vis spectrophotometry, Raman spectroscopy and x-ray photoelectron spectroscopy. Then, it was successfully applied for efficient catalytic reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride: the reduction was completed in about 6 min. After eight times use, the catalyst still maintained good catalytic performance. Compared to CNC/rGO, rGO/Cu2O and free Cu2O nanoparticles, the CNC/rGO-Cu2O nanocomposite exhibits higher catalytic activity even at lower copper loading.

Decolorization of methylene blue by silver/reduced graphene oxide-ethylene diamine nanomaterial: synthesis, characterization, and optimization.

In this study, ethylene diamine-coated reduced graphene oxide-supported silver composite (Ag/rGO-ED) was synthesized and used as an efficient catalyst for the decolorization of methylene blue (MB) in the presence of NaBH4. The morphology of the obtained material was elucidated using field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The influences of four parameters (MB concentration (mg/L), NaBH4 amount (mM), catalyst amount (g/L), and contact time (s)) on the decolorization process were appraised and optimized via response surface methodology (RSM). For the decolorization of MB, the optimum solutions were obtained as Co of 32.49 mg/L, NaBH4 amount of 152.89 mM, catalyst amount of 0.83 g/L, and 101.39 s contact time with MB decolorization efficiency of 97.73%. MB, a pollutant in wastewater, was decolorized rapidly by Ag/rGO-ED with an efficiency of approximately 97%. The exploration of kinetics and thermodynamics was another major emphasis of the work. The activation energy (Ea) and rate constant (k) for the decolorization of MB were obtained as 37.9 kJ/mol and 0.0135 s-1, respectively. The obtained results show that the catalyst, a new composite material in the literature, is promising for decolorization of wastewater.

Silver nanoparticle-decorated cellulose beads: Eco-friendly catalysts for efficient 4-nitrophenol reduction and antibacterial performance.

This study presents an innovative and environmentally friendly method to produce fibrous cellulose beads by mechanically stirring natural fibers in an aqueous medium. Date palm fibers are transformed into uniform beads with a diameter of 1.5 to 2 mm through chemical treatment and mechanical agitation. These beads are then decorated with silver nanoparticles (Ag0 NPs) in a one-step synthesis, giving them catalytic capabilities for the reduction of 4-nitrophenol (4-NP) and antibacterial activities. Characterization techniques such as FTIR, XRD, SEM, EDX, and TGA confirmed the successful synthesis and deposition of Ag0 NPs on the cellulose beads. Tests showed complete conversion of 4-NP to 4-AP in just 7 min, with pseudo-first-order kinetics and a Kapp of 0.590 min-1. Additionally, Ag0@CB demonstrated exceptional recyclability and stability over five cycles, with minimal silver release. The beads also showed strong antibacterial activity against Escherichia coli and Staphylococcus aureus, effectively eradicating bacterial colonies in 30 min. In summary, Ag0@CB exhibits multifunctional capabilities for degrading organic pollutants and biomedical applications, offering promising potential for large-scale production and practical use in water treatment and antibacterial coatings.

Green NiO nanoparticle-integrated PVA-alginate hydrogel: potent nanocatalyst for efficient reduction of anthropogenic water pollutants.

Hydrogel nanocatalyst composed of nickel oxide (NiO) nanoparticles embedded in PVA-alginate hydrogels were potentially explored toward the reduction of anthropogenic water pollutants. The NiO nanoparticles was accomplished via green method using waste pineapple peel extract. The formation of the nanoparticles was affirmed from different analytical techniques such as UV-Vis, FTIR, XRD, TGA, FESEM, and EDS. Spherical NiO nanoparticles were obtained having an average size of 11.5 nm. The nano NiO were then integrated into PVA-alginate hydrogel matrix forming a nanocomposite hydrogel (PVALg@ NiO). The integration of nano NiO rendered an improved thermal stability to the parent hydrogel. The PVALg@ NiO hydrogel was utilized as a catalyst in the reduction of 4-nitrophenol (4-NP), potassium hexacyanoferrate (III), rhodamine B (RhB), methyl orange (MO), and malachite green (MG) in the presence of a reducing agent, i.e., NaBH4. Under optimized conditions, the reduction reactions were completed by 4.0 min and 3.0 min for 4-NP and potassium hexacyanoferrate (III), respectively, and the rate constant was estimated to be 1.14 min-1 and 2.15 min-1. The rate of reduction was found to be faster for the dyes and the respective rate constants were be 0.17 s-1 for RhB, MG and 0.05 s-1 for MO. The PVALg@ NiO hydrogel nanocatalyst demonstrated a recyclability of four runs without any perceptible diminution in its catalytic mettle. The efficacy of the PVALg@ NiO hydrogel nanocatalyst was further examined for the reduction of dyes in real water samples collected from different sources and the results affirm its high catalytic potential. Thus, this study paves the path for the development of a sustainable hydrogel nanocatalyst for reduction of hazardous pollutants in wastewater treatment.

Selective catalytic oxidation of DMF over Cu-Ce/H-MOR by modulating the surface active sites.

Selective catalytic oxidation of the hazardous DMF exhaust gas presents a significant challenge in balancing oxidation activity and products selectivity (CO, NOx, N2, etc.). It is found that Cu/H-MOR demonstrates superior performance for DMF oxidation compared to CuO on other supports (γ-Al2O3, HY, ZSM-5) in terms of product selectivity and stability. The geometric and electronic structures of CuO active sites in Cu/H-MOR have been regulated by CeO2 promoter, leading to an increase in the ratio of active CuO (highly dispersed CuO and Cu+ specie). As a result, the oxidation activity and stability of the Cu/H-MOR catalyst were enhanced for DMF selective catalytic oxidation. However, excessive CuO or CeO2 content led to decreased N2 selectivity due to over-high oxidation activity. It is also revealed that Ce3+ species, active CuO species, and surface acid sites play a critical role in internal selective catalytic reduction reaction during DMF oxidation. The 10Cu-Ce/H-MOR (1/4) catalyst exhibited both high oxidation activity and internal selective catalytic reduction activity due to its abundance of active CuO specie as well as Ce3+ species and surface acid sites. Consequently, the 10Cu-Ce/H-MOR (1/4) catalyst demonstrated the widest temperature window for DMF oxidation with high N2 selectivity. These findings emphasize the importance of surface active sites modification for DMF selective catalytic oxidation.

Generalized ratiometric surface-enhanced Raman scattering biosensor for okadaic acid in food based on Au-triggered signal amplification.

BACKGROUND: Reliability and robustness have been recognized as key challenges for Surface-enhanced Raman scattering (SERS) analytical techniques. Quantifying the concentration of an analyte using a single characteristic peak from SERS has been a controversial topic because the Raman signal is susceptible to highly concentrated electromagnetic hotspots, inhomogeneity of SERS substrate, or non-standardization of measurement conditions. Ratiometric SERS strategies have been demonstrated as a promising solution to effectively balance and compensate for signal fluctuations caused by matrix heterogeneity. However, it is not easy to construct ratiometric SERS sensors with monitoring the ratio of two different signal intensities for target analysis. RESULTS: An attempt has been made to develop a novel ratiometric biosensor that can be applied to detect okadaic acid (OA). Aptamer-anchored magnetic particles were first combined with gold-tagged short complementary DNA (Au-cDNA) to create heterogeneous nanostructures. When the target was present, the Au-cDNA was dissociated from nanostructures, and 4-nitrothiophenol (4-NTP) was initiated to reduce to 4-aminothiophenol (4-ATP) in the presence of hydrogen sources. The SERS ratio change of 4-NTP and 4-ATP was finally detected by AuNPs-coated film. OA was successfully quantified, and the detection limit was as low as 2.4524 ng/mL. The constructed biosensor had good stability and reproducibility with a relative standard deviation of less than 4.47%. The proposed method used gold nanoparticles as an intermediate to achieve catalytic signal amplification and subsequently increased the sensitivity of the biosensor. SIGNIFICANCE AND NOVELTY: Catalytic reaction-based ratiometric SERS biosensors combine the multiple advantages of catalytic signal amplification and signal self-calibration and provide new insights into the development of stable, reproducible, and reliable SERS detection techniques. This ratiometric SERS technique offered a universal method that is anticipated to be applicable for the detection of other targets by substituting the aptamer.

A MOF@Metal Oxide Heterostructure Induced by Post-Synthetic Gamma-Ray Irradiation for Catalytic Reduction.

Metal-organic framework (MOF) based heterostructures, which exhibit enhanced or unexpected functionality and properties due to synergistic effects, are typically synthesized using post-synthetic strategies. However, several reported post-synthetic strategies remain unsatisfactory, considering issues such as damage to the crystallinity of MOFs, presence of impure phases, and high time and energy consumption. In this work, we demonstrate for the first time a novel route for constructing MOF based heterostructures using radiation-induced post-synthesis, highlighting the merits of convenience, ambient conditions, large-scale production, and notable time and energy saving. Specifically, a new HKUST-1@Cu2O heterostructure was successfully synthesized by simply irradiating a methanol solution dispersed of HKUST-1 with gamma ray under ambient conditions. The copper source of Cu2O was directly derived from in situ radiation etching and reduction of the parent HKUST-1, without the use of any additional copper reagents. Significantly, the resulting HKUST-1@Cu2O heterostructure exhibits remarkable catalytic performance, with a catalytic rate constant nearly two orders of magnitude higher than that of the parent HKUST-1.

Metal nanoparticles decorated mint-cellulose acetate composite as an efficient catalyst for the reduction of methyl orange.

Water contamination caused by toxic compounds has emerged as one of the most severe challenges worldwide. Biomass-based nanocomposites offer a sustainable and renewable alternative to conventional materials. In this study, a nanocomposite of mint and cellulose acetate (Mint-CA) was prepared and employed as a supportive material for Cu nanoparticles (CuNPs) and Ag nanoparticles (AgNPs). The selectivity of CuNPs@mint-CA and AgNPs@mint-CA was assessed by comparing their performance in the reduction reaction of various dyes solutions. AgNPs@mint-CA exhibited superior catalytic performance, with a removal of 95.2 % for methyl orange (MO) compared to 68 % with CuNPs@mint-CA. The absorption spectra of MO exhibited a distinct peak at 464 nm. The reduction reaction of MO by AgNPs@mint-CA followed pseudo-first-order-kinetic with a rate constant of k = 0.0063 min-1 (R2 = 0.928). The highest removal of MO was achieved under the following conditions: a catalyst weight of 40 mg, an initial MO concentration of 0.07 mM, the addition of 0.5 mL of 0.1 M NaBH4, and a temperature of 25 °C. Furthermore, the AgNPs@mint-CA catalyst exhibited exceptional reducibility even after five use cycles, highlighting its potential for efficiently removing MO.

Enhanced photocatalytic degradation of organic pollutants by green-synthesized gold nanoparticles using polysaccharide for environmental remediation.

The recent rise in textile dye wastewater discharge into the environment has detrimental effects on living organisms and human health. The present study reports a facile approach to green-synthesized AuNPs employing sesbania gum for catalytic and photocatalytic degradation of organic pollutants. The obtained AuNPs were characterized by various techniques such as UV-vis, FT-IR, SEM, TEM, AFM, zeta potential, LC-MS, and XPS. The XRD patterns revealed a highly crystalline and face-centered cubic structure. XPS and EDX analysis defined the chemical composition and product purity of SBG-AuNPs. Photocatalytic degradation of hazardous dyes congo red and safranin-O using SBG-AuNPs showed a rapid decomposition rate with 94.69 % under visible light irradiation. The effect of pH, dye concentration, and catalyst dose on photodegradation and recyclability was also studied. The kinetic plots were used to calculate the rate constant, showing a pseudo-first-order reaction. Scavenger trap experiments confirmed the role of h+ and superoxide(.O2-) as active species, and LCMS analysis was used to identify the degradation intermediates. The catalytic reduction of SBG-AuNPs was studied for brilliant green (BG) and methylene blue (MB) in the presence of NaBH4, resulting the degradation efficiency of 90.37 % and 84.52 %, respectively. This study presents an innovative approach for designing highly efficient photocatalysts for environmental remediation and wastewater treatment from textile dyes.

Silver oxide doped iron oxide/alginate nanocomposite coated cotton cloth for selective catalytic reduction of potassium ferricyanide.

Silver oxide doped iron oxide (Ag2O-Fe2O3) nanocatalyst was prepared and coated on cotton cloth (CC) as well as wrapped in sodium alginate (Alg) hydrogel. Ag2O-Fe2O3 coated CC (Ag2O-Fe2O3/CC) and Ag2O-Fe2O3 wrapped Alg (Ag2O-Fe2O3/Alg) were utilized as catalysts in reduction reaction of 4-nitrophenol (4-NP), congo red (CR), methylene blue (MB) and potassium ferricyanide (K3[Fe(CN)6]). Ag2O-Fe2O3/CC and Ag2O-Fe2O3/Alg were found to be effective and selective catalyst for the reaction of K3[Fe(CN)6]. Further amount of catalyst, K3[Fe(CN)6] quantity, amount of NaBH4, stability of catalyst and recyclability were optimized for the reaction of K3[Fe(CN)6] reduction. Ag2O-Fe2O3/Alg and Ag2O-Fe2O3/CC were appeared to be the stable catalysts by maintaining high activity during recyclability tests showing highest reaction rate constants (kapp) of 0.3472 and 0.5629 min-1, correspondingly. However, Ag2O-Fe2O3/CC can be easily recovered as compared to Ag2O-Fe2O3/Alg by simply removing from the reaction which is the main advantage of Ag2O-Fe2O3/CC. Moreover, Ag2O-Fe2O3/Alg and Ag2O-Fe2O3/CC were also examined in real samples and found useful for K3[Fe(CN)6] reduction involving real samples. The Ag2O-Fe2O3/CC nanocatalyst is a cost and time saving material for economical reduction of K3[Fe(CN)6] and environmental safety.

Synergistic reduction of nitrophenols by Au-CDs nanoconjugates with NaBH4.

Developing sustainable and innovative approaches for the efficient reduction of nitrophenols is crucial for environmental remediation, for managing health concerns posed by their widespread presence as hazardous pollutants in industrial effluents and contaminated water. We report the use of 12.9 ± 1 nm (TEM data) sized gold carbon dot nanoconjugates (Au@CDs) for catalytic conversion of o, m, p-nitrophenols to aminophenols by sodium borohydride. A simple approach was followed to synthesize ultra-small and highly stable Au@CDs, using citric acid and PEG as reducing and stabilizing agents. X-ray diffraction analysis verified the formation of nano-crystalline nanoconjugates. These nanoconjugates showed a remarkable catalytic activity in the range of 0.22-0.33 s-1(varying with nanoconjugate concentration) which was much higher compared to conventional chemical methods of reduction. All the catalytic reaction experiments were performed at room temperature (27 ± 2 °C). Furthermore, an increase in rate constant was observed with increasing concentration of nanoconjugates. The catalytic activity of Au@CDs nanoconjugates was observed to be in order of m-nitrophenol > o-nitrophenol > p-nitrophenol with apparent rate constant (kaap) values of 0.068, 0.043 and 0.031, respectively. Comparative analysis with GNPs, CDs and Au@CDs nanoconjugates stated that the nanoconjugates had superior catalytic activity. The research can have significant implications in the development of new strategies for environmental remediation and biomedical applications.

Tailoring Iridium Valence States on ZSM-5 for Enhanced Catalytic Performance in CO Selective Catalytic Reduction of NO under Oxygen-Enriched Environments.

Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir to maintain an active metallic state, thereby preventing a decrease in catalytic activity in the CO-SCR reaction. Moreover, the Ba modification increased the NO adsorption of the catalyst, further improving the catalytic activity. Owing to the better anti-oxidation ability of Ir0 in IrBa0.2/ZSM-5(27) than in Ir/ZSM-5(27), IrBa0.2/ZSM-5(27) showed better stability than Ir/ZSM-5(27). Considering that all samples in the present study were tested to simulate actual flue gases (such as sintering flue gas and coke oven flue gas), NH3 was introduced into the reaction system to serve as an extra reductant for NOx. The NOx conversion to N2 (77.1%) was substantially improved using the NH3-CO-SCR system. The proposed catalysts and reaction systems are promising alternatives for treating flue gas, which contains considerable amounts of NOx and CO in oxygen-enriched environments.

Electron transfer enhanced catalytic activity of nitrogen doped reduced graphene oxide supported CuCo2O4 towards the fast reduction of 4-nitrophenol in water.

There has been a growing interest in the design and development of graphene based composite materials with superior performances for environmental catalytic applications. But in most of the studies the synthesis conditions require elevated temperatures and expensive working setups (high temperature furnaces, autoclaves, inert atmosphere conditions etc.). In this reported work, the nitrogen doped reduced graphene oxide supported CuCo2O4 (NG/CuCo2O4) composites were prepared through a simple one pot synthesis method under mild conditions (∼95 °C and air atmosphere) and successfully employed as catalysts for the reduction of toxic 4-nitrophenol (4NP). The characterization results revealed the successful formation of NG/CuCo2O4 composites with a possible charge transfer interaction between nitrogen doped reduced graphene oxide support of CuCo2O4. The NG/CuCo2O4 hybrids exhibited robust catalytic activity in 4NP reduction with an activity factor of 261.5 min-1 g-1. A 4NP conversion percentage which is as high as 99.5% was achieved within 11 min using the NG/CuCo2O4 catalyst. The detailed kinetic analysis confirmed the Langmuir-Hinshelwood model for the NG/CuCo2O4 catalysed 4NP reduction. The nitrogen doped reduced graphene oxide support modified the electronic levels of CuCo2O4 nanoparticles through electron transfer interactions and enhanced the catalytic activity of CuCo2O4 in NG/CuCo2O4 through improved adsorption of reactant ions and effective generation of active hydrogen species. The good reusability and stability along with profound activity of NG/CuCo2O4 catalyst makes it a promising material for wide scale catalytic applications.