Ferrocene as an efficient and recyclable heterogeneous catalyst for catalytic ozonation in water

Light-driven reversible charge transfers from ITO nanocrystals

The combination of semiconductors and redox active molecules for light-driven energy storage systems has emerged as a powerful solution for the exploitation of solar batteries. On account of this, transparent conductive oxide (TCO) nanocrystals (NCs) demonstrated to be interesting materials, thanks to the photo-induced charge accumulation enabling light harvesting and storage. The charge transfer process after light absorption, at the base of the proper use of these semiconductors, is a key step, often resulting in non-reversible transformations of the chemicals involved. However, if considering the photocharging through TCO NCs not only as a charge provider for the system but potentially as part of the storage role, the reversible transformation of the redox compound represents a crucial aspect. In this paper, we explore the possible interaction of indium tin oxide (ITO) NCs and typical redox mediators commonly employed in catalytic applications with a twofold scope of enhancing or supporting the light-induced charge accumulation on the metal oxide NC side and controlling the reversibility of the whole process. The work presented focuses on the effect of the redox properties on the doped metal oxide response, both from the stability point of view and the photodoping performance, by monitoring the changes in the optical behavior of ITO/redox hybrid systems upon ultraviolet illumination.

The influence of ferrocene anchoring method on the reactivity and stability of SBA-15-based catalysts in the degradation of ciprofloxacin via photo-Fenton process

The study is aimed at evaluation of the impact of ferrocene (Fc) anchoring method on the efficiency of its incorporation on the surface of mesoporous silica SBA-15, as well as the reactivity and stability of these hybrid organic-inorganic materials in degradation of ciprofloxacin (CIP) via photocatalytic, Fenton and photo-Fenton processes. For this purpose, Fc was anchored on SBA-15 supports via three different methods: (i) Schiff base formation, (ii) Friedel-Crafts alkylation, and (iii) click reaction (azide-alkyne cycloaddition). The as-prepared materials were characterized by powder X-ray diffraction, nitrogen physisorption, infrared spectroscopy and inductively coupled plasma optical emission spectrometry, as well as UV-visible and X-ray photoelectron spectroscopies. The highest efficiency of Fc anchoring was obtained when applying the Friedel-Crafts alkylation, while the least effective was the Schiff base formation. As concerns the catalysts activity, all materials exhibited negligible reactivity in the photocatalytic process, but were capable of degrading CIP in the presence of H2O2 (Fenton process). For all materials, the highest efficiency of CIP removal was observed for the photo-Fenton reaction. When expressed as the activity of a single Fc site, the most reactive were Fc species from the catalyst prepared by the click reaction. All materials, irrespectively of the ferrocene anchoring method, were deactivating over the reaction time because of Fc leaching. The highest stability in three subsequent reaction cycles was observed for the catalyst prepared by the azide-alkyne cycloaddition. Thus, the click reaction was found to be the best method for the preparation of Fc-containing catalysts for CIP degradation.

Closed Bipolar Electrode-Enabled Electrochromic Sensing of Multiple Metabolites in Whole Blood

We report a closed bipolar electrode (CBE)-based sensing platform for the detection of diagnostic metabolites in undiluted whole human blood. The sensor is enabled by electrode chemistry based on: (1) a mixed layer of blood-compatible adsorption-resistant phosphorylcholine (PPC) and phenylbutyric acid (PBA), (2) ferrocene (Fc) redox mediators, and (3) immobilized redox-active enzymes. This scheme is designed to overcome nonspecific protein adsorption and amplify sensing currents in whole human fluids. The scheme also incorporates a diffusing mediator to increase electronic communication between the immobilized redox enzyme and the working electrode. The use of both bound and freely diffusing mediators is synergistic in producing the electrochemical response. The sensor is realized by linking the analyte cell, containing the specific electrode surface architecture, through a CBE to a reporter cell containing the electrochromic reporter, methyl viologen (MV). The colorless-to-purple color change accompanying the 1e^- reduction of MV²⁺ is captured using a smartphone camera. Subsequent red-green-blue analysis is performed on the acquired images to determine cholesterol, glucose, and lactate concentrations in whole blood. The CBE blood metabolite sensor produces a linear color change at clinically relevant concentration ranges for all metabolites with good reproducibility (∼5% or better) and with limits of detection of 79 μM for cholesterol, 59 μM for glucose, and 86 μM for lactate. Finally, metabolite concentration measurements from the CBE blood metabolite sensor are compared with results from commercially available FDA-approved blood cholesterol, glucose, and lactate meters, with an average difference of ∼3.5% across all three metabolites in the ranges studied.

Degradation of amaranth by persulfate activated with zero-valent iron: influencing factors, response surface modeling

In this study, zero-valent iron (ZVI) is applied to activate persulfate (PDS) for the degradation of amaranth (AMR). The effects of PDS concentration, ZVI concentration, solution pH  , temperature, and reaction time on the degradation of AMR by the ZVI/PDS advance oxidation process are investigated. Sulfate and hydroxyl radicals are involved in the main reaction pathway of AMR and sulfate radical acts as a dominant oxidant. The CCD (central composite design) plan is chosen to build the RSM model for the prediction of AMR degradation. ANOVA analysis shows that the secondary fitting model had great fitness with R2 = 0.997, $$R_{{{\text{adj}}}}^{2}$$ R adj 2  = 0.936, p-value of lack of fit = 0.107. Optimum conditions for 98% AMR removal given by RSM are PDS concentration = 7.33 mM, ZVI dosage = 17.79 mM, initial pH   4.62, temperature = 59.49 °C, reaction time = 9.88 min which is proved to be very closed to the real removal rate of 96.78%. Sensitivity analysis indicates that the relative importance of the influencing parameters is of the following order: temperature, PDS concentration, pH  , ZVI dosage, and reaction time. The PDS/ZVI system shows an acceptable RSE of about 75% and TOC removal of 85% on AMR oxidation. Finally, the possible pathway of AMR degradation is proposed.

Ferrocene-modified Uio-66-NH2 hybrids with g-C3N4 as enhanced photocatalysts for degradation of bisphenol A under visible light

Designing graphitic carbon nitride (CN) based heterostructured photocatalysts with high catalytic activity is highly desired for peroxymonosulfate (PMS) activation to degrade organic pollutants from water. Herein, a novel heterostructured composite (U-F@CN) consisting of ferrocene-modified Uio-66-NH₂ (U-F) and CN was synthesized. The U-F@CN exhibited superior photocatalytic performance to degrade bisphenol A (BPA) in the presence of PMS under visible light. The experimental results indicated that BPA could be removed entirely by U-F@CN within 60 min under visible light irradiation. In addition, the outstanding photocatalytic activity could be maintained at high level in a wide pH range, appropriate temperature region and natural water condition. Benefiting from the good chemical stability, outstanding optical property and in-situ generation of interfacial heterojunction of U-F@CN, the interfacial transport of photogenerated charges could follow the Z-scheme mechanism, which can accelerate the charge separation and transport to yield abundant reactive active species (ROS) to efficiently active PMS and under visible light. This work provides a novel approach to design CN-based heterostructured photocatalysts with high stability and superior photocatalytic activity for environmental remediation.

Ferrocene anchored activated carbon as a versatile catalyst for the synthesis of 1,5-benzodiazepines via one-pot environmentally benign conditions

1,5-Benzodiazepine is considered as one of the central moieties in the core unit of most drug molecules. Construction of such moieties with a new C–N bond under solvent-free and mild reaction conditions is challenging. Herein, we present a benign protocol for one pot synthesis of 1,5-benzodiazepine derivatives by using ferrocene (FC) supported activated carbon (AC) as a heterogeneous catalyst. The catalyst FC/AC was characterized by several analytical and spectroscopic techniques to reveal its physicochemical properties and for structural confirmation. The synthesized catalyst FC/AC was explored for its catalytic activity in the synthesis of 1,5-benzodiazepines through condensation of o-phenylenediamine (OPDA) and ketones (aromatic and aliphatic) under solvent-free conditions. The robust 10 wt% FC/AC catalyst demonstrated appreciable activity with 99% conversion of diamines and 91% selectivity towards the synthesis of the desired benzodiazepine derivatives under solvent-free conditions at 90 °C in 8 h. Additionally, several reaction parameters such as catalyst loading, reaction temperature, effect of reaction time and effect of different solvents on selectivity were also studied and discussed in-depth. To understand the scope of the reaction, several symmetrical and unsymmetrical ketones along with different substituted diamines were tested with the synthesized catalyst. All prepared reaction products were obtained in good to efficient yields and were isolated and identified as 1,5-benzodiazepines and no side products were observed. The obtained catalyst characterization data and the activity studies suggested that, the synergetic effect occurred due to the uniform dispersion of ferrocene over the AC surface with numerous acidic sites which triggered the reaction of diamine and ketone to form the corresponding benzodiazepine derivative and the same was illustrated in the plausible mechanism. Furthermore, the synthesized catalyst was tested for leaching and recyclability, and the results confirmed that catalyst can be used for up to six consecutive cycles without much loss in the catalytic activity and its morphology which makes the process sustainable and economical for scale-up production. The present method offered several advantages such as an ecofriendly method, excellent yields, sustainable catalytic transformation, easy work-up and isolation of products, and quick recovery of catalyst.

1,5-Benzodiazepine is considered as one of the central moieties in the core unit of most drug molecules.

Catalyst development for tar reduction in biomass gasification: Recent progress and the way forward

Biomass valorization via catalytic gasification is a potential technology for commercizalization to industrial scale. However, the generated tar during biomass valorization posing numerous problems to the overall reaction process. Thus, catalytic tar removal via reforming, cracking and allied processes was among the priority areas to researchers in the recent decades. This paper reports new updates on the areas of catalyst development for tar reduction. The catalyst survey include metallic and metal-promoted materials, nano-structured systems, mesoporous supports like zeolites and oxides, group IA and IIA compounds and natural catalysts based on dolomite, palygorskite, olivine, ilmenite, goethite and their modified derivatives. The influence of catalyst properties and parameters such as reaction conditions, catalyst preparation procedures and feedstock nature on the overall activity/selectivity/stability properties were simultaneously discussed. This paper not only cover to model compounds, but also explore to real biomass-derived tar for consistency. The area that require further investigation was identified in the last part of this review.

Ozonation catalysed by ferrosilicon for the degradation of ibuprofen in water

The search for optimal catalysts to improve the working efficiency of ozonation has always been an important issue in the research field of advanced oxidation processes. In this study, a novel catalyst, ferrosilicon, was selected as the catalyst in heterogeneous catalytic ozonation to degrade ibuprofen (IBP) in water and treat real pharmaceutical wastewater. During the procedure, 45^#ferrosilicon exhibited the best catalytic activity. Under the optimized experimental conditions, the IBP removal reached 75%, which was a great improvement compared to the 37% removal by ozone alone. The 45^#-ferrosilicon-catalysed ozonation also achieved 68% TOC removal for real pharmaceutical wastewater, which was 31% higher than that by ozone alone. The degradation pathway of IBP was proposed using GC/MS. The EPR test proved that the main active species in the system were free active radicals •OH, and the measured accumulative •OH amount was 102 μmol. The characterization results show that the nascent metallic oxides, hydroxides, and hydroxyoxides on the ferrosilicon surface facilitated the decomposition of ozone molecules and generation of free active radicals. The removal of target organic contaminants in the water was mainly attributed to the oxidization of these highly active species.

Modified Ferrocenes as Primary Driers for Formulations of Alkyd Paints

The effect of modification of benzoylferrocene periphery on catalytic activity toward drying of alkyd resins has been investigated by the combination of experimental techniques. A series of substituted ferrocenes have been synthesized and characterized by analytical and spectroscopic tools including X-ray diffraction analysis on single crystals. The electrochemical behavior of the ferrocene derivatives has been elucidated by cyclic voltammetry and rotation disk voltammetry. The activity toward room temperature curing of alkyd resin has been evaluated by standard mechanical tests on coated plates, which enabled to establish a structure/catalytic activity relationship. Fast drying of test coatings has been observed for formulations of (3-methoxybenzoyl) ferrocene. Time-resolved infrared spectroscopy in combination with attenuated total reflectance sampling technique enabled to reveal the kinetic origin of the improved performance for this ferrocene derivative.

The catalytic ozonation of diazinon using nano-MgO@CNT@Gr as a new heterogenous catalyst: the optimization of effective factors by response surface methodology

In this research, the degradation of the insecticide diazinon was studied using a new hybrid catalyst consisting of magnesium oxide nanoparticles (nano-MgO), carbon nanotubes (CNTs), and graphite (Gr), nano-MgO@CNT@Gr, under various experimental conditions. This study shows the optimization of the nano-MgO@CNT@Gr/O3 process for diazinon degradation in aqueous solutions. Box-Behnken experimental design (BBD) and response surface methodology (RSM) were used to assess and optimize the solo effects and interactions of four variables, pH, catalyst loading, reaction time, and initial diazinon concentration, during the nano-MgO@CNT@Gr/O3 process. Analysis of regression revealed an adequate fit of the experimental results with a quadratic model, with R 2 > 0.91. Following the collection of analysis of variance (ANOVA) results, pH, catalyst loading, and reaction time were seen to have significant positive effects, whereas the concentration of diazinon had a considerable negative impact on diazinon removal via catalytic ozonation. The four variables for maximum diazinon removal were found to be optimum (82.43%) at the following levels: reaction time, 15 min; pH, 10; catalyst dosage, 1.5 g L-1; and diazinon concentration, 10 mg L-1. The degradation of diazinon gave six kinds of by-products. The mechanism of diazinon decomposition was considered on the basis of the identified by-products. According to these results, the nano-MgO@CNT@Gr/O3 process could be an applicable technique for the treatment of diazinon-containing wastewater.

The corrosion inhibition of stainless steel by ferrocene–polyoxometalate hybrid molecular materials – experimental and first principles studies

The corrosion inhibition mechanism for SS316 coated with FcPMo hybrid material is shown.

Ferrocene-modified iron-based metal-organic frameworks as an enhanced catalyst for activating oxone to degrade pollutants in water

Ferrocene (Fc) has been regarded as a useful catalyst for activating Oxone to generate sulfate radicals (SR) in degradation of organic pollutants. Nevertheless, direct usage of Fc molecules in aqueous solutions may lead to difficult recovery and aggregation. While a few attempts have immobilized Fc on several substrates, these substrates exhibit very low surface areas/porosities and, especially, do not offer significantly additional contributions to catalytic activities. In this study, a Fe-containing metal organic frameworks (MOFs), MIL-101, is particularly selected for the first time as a support to immobilize Fc chemically. Through the Schiff base reaction, ferrocenecarboxaldehyde can react with amine-functionalized MIL-101 (namely, MIL-101-NH₂) to form Fc-modified MIL-101 (Fc-MIL). As Fc-MIL consists of both Fe from MIL-101 and Fc and also exhibits high surface areas, it appears as a promising catalyst for activating Oxone. Catalytic activities for Oxone activation by Fc-MIL are studied using batch-type experiments of amaranth dye degradation. Fc-MIL shows higher catalytic activities than its precursor MIL-101-NH₂ owing to the modification of Fc, which equips with MIL-101 with more catalytic sites for activating Oxone. Besides, Fc-MIL also outperforms the benchmark catalyst of Oxone activation, Co₃O₄, to degrade amaranth. In comparison to the other reported catalysts, Fc-MIL shows the much smaller activation energy for amaranth degradation, proving its advantage over other catalysts. The synthesis technique proposed here can be also employed to develop other Fc-modified MOFs for other environmental catalysis applications.

Ferrocene functionalized graphene based electrode for the electro-Fenton oxidation of ciprofloxacin

Ferrocene functionalized graphene based graphite felt electrode was firstly investigated for heterogeneous electro-Fenton oxidation of ciprofloxacin in neutral pH condition. Electrochemical reduction of Ferrocene functionalized graphene oxide (Fc-ErGO) was performed by cyclic voltammetry technique. At neutral pH condition, Fc-ErGO electrode (0.035 min^─1) exhibited ∼3 times and ∼9 times higher removal rates in comparison with plane ErGO (0.010 min^─1) and plane graphite felt (0.004 min^─1) electrodes respectively. The effect of pH and applied potential were studied for the degradation of ciprofloxacin in Fc-ErGO based electrode. Higher removal rate was observed at acidic pH (0.222 min^─1), whereas alkaline pH showed lower removal efficiency (0.014 min^─1). > 99% removal of ciprofloxacin was achieved with in 15 min and 120 min of reactions period at pH 3.0 and pH 7.0, respectively. H₂O₂ generation was found to be high in plane ErGO electrode system in all of the pH conditions. Owing to the high redox ability of ferrocene, Fc-ErGO electrode generated high concentration of OH radicals (426 μM pH 3.0; 247 μM pH 7.0; 210 μM pH 9.0) than ErGO and plane graphite felt electrodes; The electrode reusability study was performed to understand the electrode stability. There was no significant change in removal efficiency even after the 5th cycle of reusability study at both acidic and neutral conditions. The possible mechanism of oxidation in Fc-ErGO based electro-Fenton process was also proposed based on the continuous monitoring of H₂O₂ and OH radicals generated in the system.