Synergistic Effects Of Metals Research Articles

Synergistic effect of metals and cross linkers on surface modification of iron aluminum oxyhydroxide‐PVA polymer films for enhanced catalytic activity in transesterification reaction

AbstractIron‐incorporated aluminum oxyhydroxide polyvinyl alcohol films (Fe‐Al‐PVA) were synthesized using the sol–gel method. The influence of cross‐linking agents on the aluminum oxyhydroxide films was investigated by incorporating glutaraldehyde into the synthesized films. Various characterization techniques were employed to understand the physico‐chemical properties that affect the catalytic and adsorptive behavior of the self‐supported films. The liquid phase transesterification of terpenes was used to test the catalytic activity of the films for the synthesis of industrially important terpene esters. The products were analyzed using GC, GC–MS, and NMR techniques, and optimization studies were carried out under different experimental conditions. The reaction scope was expanded to a wider range of organic compounds, and a possible reaction mechanism was proposed. This study demonstrates the design and modification of efficient bimetallic polymer film catalyst for organic transformations.

Synthesis of efficient light harvesting Cr, N Co-doped TiO2 nanoparticles for enhanced visible light photocatalytic degradation of xanthene dyes; eosin yellow and rose bengal.

To solve the problem of water pollution, using environment friendly and cost effective method in short time is the need of hour. In this work, chromium (Cr) and nitrogen (N) co-doped TiO2 nanoparticles were synthesized and were used for the photocatalytic degradation of dyes under visible light. The synergistic effect of metal and non-metal co-dopants added would result in appropriate reduction of band gap {from 3.2 eVof TiO2 to 2.67eV}, decrease in recombination rate of charge carriers by trapping electrons and holes, and in better light harvesting capacity. Nanoparticles were synthesized by sol-gel method and characterized using ultraviolet-visible (UV-VIS) spectroscopy, fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), zeta potential, X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET)analysis, field emission scanning electron microscopy (FE-SEM), and RAMAN spectroscopy. Eosin yellow (EY) and rose bengal (RB) were subjected to photocatalytic degradation under solar light to check the photocatalytic activity of the synthesized nanoparticles. Effects of dye concentration, the concentration of nanoparticles, time, and pH were investigated to optimize the parameters. The results obtained were remarkable for 20ppm EY solution took 10min using 1 gL-1 NPs at pH 3 and 10ppm RB solution took 5min using 0.75 gL-1 NPs at pH 5.78 (original pH) for complete degradation. Kinetics studies were also performed and both dyes followed pseudo-second-order kinetics with R2 values 0.99312 and 0.99712 for EY and RB, respectively. The study of degraded products was conducted using high-performance liquid chromatography (HPLC) hyphenated with electron spray ionization mass spectroscopy (ESI-MS) (LC-MS) and possible degradation pathways were made for both dyes. A reusability test was also performed showing the efficiency of the particles was up to 88% after 3 cycles of use. These notable results can be attributed to the efficient removal of organic pollutants using the proposed dopants in this study.

Quantitative synergy between metal and acid centers over the Ni/Beta bifunctional catalyst for methyl laurate hydrodeoxygenation to bio-jet fuel

The synergistic effect of metal and acid centers influences performance of bifunctional hydrodeoxygenation (HDO) catalyst significantly. However, seldom work concerning this point has been performed quantitatively. Herein, the Ni/Beta catalysts were prepared for HDO of methyl laurate to bio-jet fuels. The ratios of metal to acid centers (nNi/nA) were used to quantitatively express the synergistic effect and correlated to the HDO performance. The transformation of methyl laurate mainly stagnates at fatty acid over the mono-functional catalyst (nNi/nA = 0), while the acid centers are indispensable for the efficient transformation of methyl laurate at relatively mild reaction conditions. The TOF and selectivity to C11 and C12 alkanes increase and then keep constant with the increasing nNi/nA. The turning point at the nNi/nA of 0.67 implies that one nickel center over the Ni/Beta catalyst can balance ca. 1.5 acid centers in the HDO of methyl laurate. Besides, the higher nNi/nA favors the HDO reaction pathway compared with the decarbonylation or decarboxylation ones. It increases the selectivity to C12 alkanes and improves efficiency of atomic utilization during the hydrodeoxygenation of methyl laurate. This work provides a deeper insight into the quantitative synergy of active sites over the bifunctional HDO catalyst for production of bio-fuels.

Evaluation of the developmental effects of a glyphosate-based herbicide complexed with copper, zinc, and manganese metals in zebrafish.

The use of glyphosate-based herbicides (GBH) has increased dramatically, being currently the most used herbicides worldwide. Glyphosate acts as a chelating agent, capable of chelate metals. The synergistic effects of metals and agrochemicals may pose an environmental problem as they have been shown to induce neurological abnormalities and behavioural changes in aquatic species. However, as their ecotoxicity effects are poorly understood, evaluating the impacts of GBH complexed with metals is an ecological priority. The main objective of the study was to evaluate the potentially toxic effects caused by exposure to a GBH (1 μg a.i. mL−1), alone or complexed with metals (Copper, Manganese, and Zinc (100 μg L−1)), at environmentally relevant concentrations, during the early period of zebrafish (Danio rerio) embryo development (96 h post-fertilization), a promising model for in vivo developmental studies. To clarify the mechanisms of toxicity involved, lethal and sublethal development endpoints were assessed. At the end of the exposure, biochemical and cell death parameters were evaluated and, 24 h later, different behavioural responses were assessed. The results showed that metals induced higher levels of toxicity. Copper caused high mortality, low hatching, malformations, and changes in biochemical parameters, such as decreased Catalase (CAT) activity, increased Glutathione Peroxidase (GPx), Glutathione S-Transferase (GST), reduced Glutathione (GSH) and decreased Acetylcholinesterase (AChE) activity, also inducing apoptosis and changes in larval behaviour. Manganese increased the activity of SODs enzymes. Zinc increased mortality, reactive oxygen species (ROS) levels, superoxide dismutase activity (SODs) and caused a decrease in AChE activity. Embryos/larvae exposed to the combination of GBH/Metal also showed teratogenic effects during their development but in smaller proportions than the metal alone. Although more studies are needed, the results suggest that GBH may interfere with the mechanisms of metal toxicity at the biochemical, physiological, and behavioural levels of zebrafish.

Preparation of Fe/C-Mt composite catalyst and ofloxacin removal by peroxymonosulfate activation

In recent years, montmorillonite (Mt) has started to be used as a carrier for catalysts and widely utilized inexpensive adsorbent due to its unique structure. However, the used Mt might cause solid-waste pollution without proper dispose. In order to realize the resource utilization of solid waste, a new strategy for preparing high-performance catalysts was proposed using waste Mt-based materials as precursor, providing a new way to reuse abandoned Mt materials. In this study, the waste Mt was obtained by using iron hydroxide oxide (FeOOH) and hexadecylpyridinium chloride (CPC) to simulate the process of adsorption of contaminants (tetracycline, TC) on the montmorillonite composite. The iron oxide/Carbon-Montmorillonite (Fe/C-Mt) composite catalysts were successfully prepared at 700 °C pyrolysis temperature, reconstructing metal and carbon catalytic sites on Mt through the conversion of FeOOH to Fe3O4 and the organic precursors to graphite carbon. According to the investigation of catalytic performances, the sample after pyrolysis of montmorillonite modified by FeOOH, CPC and TC (Fe/CPC/TC-Mt-p) was determined as the optimum catalyst to activate peroxymonosulfate (PMS), and reaching the degradation efficiency of 96.2% in this oxidation system to treat target pollutants (ofloxacin, OFL). The increase of catalyst dosage and PMS concentration promoted the degradation effect of OFL, while initial pH and anionic species in the solution had little effect. Meanwhile, the synergistic effect of metal and carbon catalytic sites enables this system to have high oxidation activity. Here, Fe/CPC/TC-Mt-p/PMS system was developed with accelerating the generation of 1O2, making 1O2 the major reactive oxygen species for OFL degradation. In addition, Fe/CPC/TC-Mt-p catalyst has good stability, and could reach the initial degradation level of OFL after being regenerated by high temperature pyrolysis. This study provides a novel routine to applications of waste mineral materials and improving treatment efficiency of antibiotic wastewater through PMS activation.

Efficient Reduction of Cr (VI) to Cr (III) over a TiO2-Supported Palladium Catalyst Using Formic Acid as a Reductant

Cr (VI) has been considered to be a harmful environmental pollutant due to its toxicity, mobility and strong oxidation. It has become challenging to remove Cr (VI) from wastewater. In this work, a series of supported palladium-based catalysts were synthesized via a facile wet chemical reduction method. Among all the as-synthesized catalysts, Pd/TiO2 (P25) showed the optimized catalytic activity for the reduction of Cr (VI) to Cr (III) using formic acid (HCOOH) as the reductant. More than 99% of K2Cr2O7 (50 mg/L) was reduced completely within 30 min at 25 °C. The structural properties of the Pd/TiO2 catalyst (such as particle size, hydrophilicity and stability) and the synergistic effect of metal and support played significant roles in the reduction of Cr (VI) to Cr (III). Meanwhile, several pivotal parameters such as Cr (VI) concentration, catalyst loading, HCOOH concentration and temperature were investigated in detail. Furthermore, this catalyst was also active for the reduction of nitro compounds with HCOOH as the reductant at room temperature. Finally, the reasonable reaction mechanism of the Pd/TiO2/HCOOH system for the reduction of Cr (VI) to Cr (III) was put forward.

Enhanced Electrochemical Behavior of Peanut-Shell Activated Carbon/Molybdenum Oxide/Molybdenum Carbide Ternary Composites.

Biomass-waste activated carbon/molybdenum oxide/molybdenum carbide ternary composites are prepared using a facile in-situ pyrolysis process in argon ambient with varying mass ratios of ammonium molybdate tetrahydrate to porous peanut shell activated carbon (PAC). The formation of MoO2 and Mo2C nanostructures embedded in the porous carbon framework is confirmed by extensive structural characterization and elemental mapping analysis. The best composite when used as electrodes in a symmetric supercapacitor (PAC/MoO2/Mo2C-1//PAC/MoO2/Mo2C-1) exhibited a good cell capacitance of 115 F g−1 with an associated high specific energy of 51.8 W h kg−1, as well as a specific power of 0.9 kW kg−1 at a cell voltage of 1.8 V at 1 A g−1. Increasing the specific current to 20 A g−1 still showcased a device capable of delivering up to 30 W h kg−1 specific energy and 18 kW kg−1 of specific power. Additionally, with a great cycling stability, a 99.8% coulombic efficiency and capacitance retention of ~83% were recorded for over 25,000 galvanostatic charge-discharge cycles at 10 A g−1. The voltage holding test after a 160 h floating time resulted in increase of the specific capacitance from 74.7 to 90 F g−1 at 10 A g−1 for this storage device. The remarkable electrochemical performance is based on the synergistic effect of metal oxide/metal carbide (MoO2/Mo2C) with the interconnected porous carbon. The PAC/MoO2/Mo2C ternary composites highlight promising Mo-based electrode materials suitable for high-performance energy storage. Explicitly, this work also demonstrates a simple and sustainable approach to enhance the electrochemical performance of porous carbon materials.

Mild depolymerization of the sinocalamus oldhami alkali lignin to phenolic monomer with base and activated carbon supported nickel-tungsten carbide catalyst composite system

In this study, the sinocalamus oldhami alkali lignin was depolymerized into phenolic products in a combined system by using the composite alkali and Ni-W2C/activated carbon (AC) as catalysts. FT-IR, GPC, TG, 2D-HSQC and GC–MS were used to analyze the composition, structure and distribution of degradation products, and the synergistic effect of metal and alkali catalysts on the depolymerization of lignin was also studied. The results showed that Ni-W2C/AC and composite alkali could effectively improve the catalytic degradation efficiency of lignin under mild conditions, 94.4% of lignin was converted and 17.18% of phenolic monomers were obtained under 260 °C for 5 h. In this composite system, the synergism of the basic sites, the metal active sites and the Lewis acid sites could promote the cleavage of C–O bonds in the lignin molecule and lower the char formation during the base-catalyzed solvolysis. Phenolic monomers were mainly composed of phenol, 2-methyl-phenol and p-cresol etc.

Role of oxygen vacancies in dendritic fibrous M/KCC-1 (M = Ru, Pd, Rh) catalysts for methane partial oxidation to H2-rich syngas production

The fibrous M/KCC-1 (M = Ru, Pd, Rh) catalysts prepared by microwave-assisted hydrothermal approach were investigated for methane partial oxidation (MPO) reaction at stoichiometric CH4/O2 feed ratio and temperature of 500–800 °C. A drop in BET surface area with metal oxide addition suggesting the successful embedment of metal oxides on KCC-1. Low-angle XRD, FTIR and TEM analyses confirmed the formation of bicontinuous concentric lamellar morphologic structure, typical fingerprint of fibrous KCC-1. The H2-TPR and ESR studies revealed that oxygen vacancy (OV) of KCC-1 not only beneficial for the metal-support interactions of catalysts but also strongly and dissociately bind with O2, CO2 and H2O promoting the syngas formation rate. The post-reaction Raman spectroscopy measurement corroborated the M/KCC-1 catalysts hindered the graphitic carbon formation during reaction. The Rh/KCC-1 appeared to be the optimum catalyst as it exhibited the TOF of both CH4 consumption and H2 formation about 2-fold higher to other catalysts meanwhile achieving H2/CO ratio about 2.16 that applicable for industrial applications. Based on the experimental MPO evaluation, post-reaction Raman spectroscopy and the in-situ ESR studies, the synergistic effects of metals and OV from fibrous KCC-1, where metal dissociates CH bonds in CH4 molecules whilst OV generates activated O2− species from oxidants at the OV sites, are determined as the key factors for the enhancement in MPO activity.

Nonstoichiometric Cu0.6Ni0.4Co2O4 Nanowires as an Anode Material for High Performance Lithium Storage.

Transition metal oxide is one of the most promising anode materials for lithium-ion batteries. Generally, the electrochemical property of transition metal oxides can be improved by optimizing their element components and controlling their nano-architecture. Herein, we designed nonstoichiometric Cu0.6Ni0.4Co2O4 nanowires for high performance lithium-ion storage. It is found that the specific capacity of Cu0.6Ni0.4Co2O4 nanowires remain 880 mAh g−1 after 50 cycles, exhibiting much better electrochemical performance than CuCo2O4 and NiCo2O4. After experiencing a large current charge and discharge state, the discharge capacity of Cu0.6Ni0.4Co2O4 nanowires recovers to 780 mAh g−1 at 50 mA g−1, which is ca. 88% of the initial capacity. The high electrochemical performance of Cu0.6Ni0.4Co2O4 nanowires is related to their better electronic conductivity and synergistic effect of metals. This work may provide a new strategy for the design of multicomponent transition metal oxides as anode materials for lithium-ion batteries.

Recent advances in the hydrogenolysis of furfural and its derivatives to 1,5-pentanediol

Biomass is an abundant and renewable organic carbon resource on earth. The conversion biomass to chemicals and fuels is of great significances in terms of reducing the consumption and dependences of fossil resource. Furfural is one of the most important biomass platform molecules and can be converted to various of useful chemicals, such as furfural alcohol, tetrahydrofurfuryl alcohol, 2-methylfuran, 1,5-pentanediol, 1,2-pentanediol, and so on. Recent studies have shown that 1,5-pentanediol based polymer materials was found have better safety in the field of children’s products. Due to the high cost and complex process of synthesizing 1,5-pentanediol from traditional petrochemical routes, it is more promising to synthesize it from biomass. Catalytic conversion of biomass substrates (furfural and its derivatives) to 1,5-pentanediol has attracted much attention in the past decade. Some noble metal and none-noble catalysts had been screened (such as Ir, Rh, Pt, Ni based catalysts), and several reaction mechanisms were proposed. However, there remain open questions on the reaction pathways and catalytic mechanisms. In addition, the use of non-precious metal catalysts to catalyze the hydrogenolysis of furfural and its derivatives to achieve high yields of 1,5-pentanediol remains a significant challenge. In this paper, we reviewed the recent research progress of the selective hydrogenation of tetrahydrofurfuryl alcohol, furfural and furfuryl alcohol to 1,5-pentanediol. This review consists of two parts, which concerned on the hydrogenolysis of tetrahydrofurfuryl alcohol, and the hydrogenolysis of furfural and furfuryl alcohol, respectively. To the hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol, metal-oxide (A-BO x ) type catalysts showed excellent catalytic performances. In the first part of this review, we compared the catalytic performances of the A-BO x type catalysts in the references. We also describe the synergistic effects of metals and oxides in representative catalysts, the critical role of oxide acidity, and the effect of solvents on selectivity, and introduce several widely accepted catalytic mechanisms. The atomic ratio between A and B is critical for hydrogenolysis activity. This atomic ratio determines the dispersion of BO x on metal A, which results in different reaction rates. The acidity of BO x component was also important for the adsorption of the substrates and the ring-opening reaction. As the most used solvent, water played key roles in the hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol. The existence of water was helpful for the transfer of hydride, for stabilizing the carbonium and decreasing the energy barrier of ring opening, and for the form of Bronsted acid and hydrogen bonds, etc. We also review the attempts of hydrogenolysis of furfural and furfural alcohol to 1,5-pentanediol. The 1,5-pentanediol could be obtained by the tandem reaction of hydrogenation of furfural to tetrahydrofurfuryl alcohol and the hydrogelolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol; or by directly ring-opening of furfural/furfural alcohol and followed by hydrogenation. However, the yield of 1,5-PDO is not satisfactory enough due to the complex secondary reactions. Currently, the most study in this field concerned on the noble metal catalysts with surface oxides modifications. It is expected that non-noble metal catalysts can obtain desired catalytic performances once the synergistic of adsorption of tetrahydrofurfuryl alcohol, the activation of C−O bond, the formation of hydrides is well understood and controlled.

Behavioural and biochemical responses to metals tested alone or in mixture (Cd-Cu-Ni-Pb-Zn) in Gammarus fossarum: From a multi-biomarker approach to modelling metal mixture toxicity

Metals are usually present as mixtures at low concentrations in aquatic ecosystems. However, the toxicity and sub-lethal effects of metal mixtures on organisms are still poorly addressed in environmental risk assessment. Here we investigated the biochemical and behavioural responses of Gammarus fossarum to Cu, Cd, Ni, Pb and Zn tested individually or in mixture (M2X) at concentrations twice the levels of environmental quality standards (EQSs) from the European Water Framework Directive. The same metal mixture was also tested with concentrations equivalent to EQSs (M1X), thus in a regulatory context, as EQSs are proposed to protect aquatic biota. For each exposure condition, mortality, locomotion, respiration and enzymatic activities involved in digestive metabolism and moult were monitored over a 120h exposure period. Multi-metric variations were summarized by the integrated biomarker response index (IBR). Mono-metallic exposures shed light on biological alterations occurring at environmental exposure levels in gammarids and depending on the considered metal and gender. As regards mixtures, biomarkers were altered for both M2X and M1X. However, no additive or synergistic effect of metals was observed comparing to mono-metallic exposures. Indeed, bioaccumulation data highlighted competitive interactions between metals in M2X, decreasing subsequently their internalisation and toxicity. IBR values indicated that the health of gammarids was more impacted by M1X than M2X, because of reduced competitions and enhanced uptakes of metals for the mixture at lower, EQS-like concentrations. Models using bioconcentration data obtained from mono-metallic exposures generated successful predictions of global toxicity both for M1X and M2X. We conclude that sub-lethal effects of mixtures identified by the multi-biomarker approach can lead to disturbances in population dynamics of gammarids. Although IBR-based models offer promising lines of enquiry to predict metal mixture toxicity, further studies are needed to confirm their predictive quality on larger ranges of metallic combinations before their use in field conditions.

Corrigendum: Synergistic Effects of Metals in a Promising RuII−PtII Assembly for a Combined Anticancer Approach: Theoretical Exploration of the Photophysical Properties

The authors have noticed an error in the structures of compounds 1 and 2 in Scheme 1 and Scheme 2 of their paper. The schemes erroneously report the dpq substituent instead of the correct dpp one. The corrected versions of both schemes are presented below. The authors apologize for these errors and for any inconvenience caused. Ru-complex 1 and RuII-PtII assembly 2. Investigated hydrolysis process for RuII-PtIIconjugate 2. RuII-polyazine ligands are omitted for clarity.

Inside Cover: Synergistic Effects of Metals in a Promising RuII−PtII Assembly for a Combined Anticancer Approach: Theoretical Exploration of the Photophysical Properties (Chem. Eur. J. 27/2016)

Inside Cover: Synergistic Effects of Metals in a Promising Ru^II−Pt^II Assembly for a Combined Anticancer Approach: Theoretical Exploration of the Photophysical Properties (Chem. Eur. J. 27/2016)

Synergistic effects of metals and oxidants in the curing of marine mussel adhesive

Marine mussels produce an impressive adhesive material for affixing themselves to rocks in the turbulent marine environment. This glue is generated by application of proteins to the surface followed by extensive cross-linking to yield the final matrix. Prior studies have shown that simple oxidation or reactivity brought about by metal ions may be key to this protein cross-linking process. Here we have explored protein cross-linking reactivity in which combinations of metals and oxidants may display synergistic effects with respect to adhesive curing. Extracted adhesive proteins were mixed with a series of metals, oxidants, and combinations thereof. In some cases, synergistic curing was observed. For example, we found that iron(II) ions with hydrogen peroxide brought about a greater degree of protein cross-linking than the sum of the individual components. These studies were performed as part of our efforts to provide perspectives on the connections between biology, chemistry, and functional materials.

The effect of heavy metals on nitrogen and oxygen demand removal in constructed wetlands

The objective of this study is to investigate the respective effects of Zn, Pb and Cd as well as the combined effect of Zn, Pb, Cd and Cu on the removal of nitrogen and oxygen demand in constructed wetlands. Four laboratory-scale gravel-filled subsurface-flow constructed wetland units planted with cattails ( Typha latifolia) were operated outdoors and fed with primary-treated domestic wastewater at a constant flow rate of 25 ml/min. After 6 months, three of the wetland units were fed with the same type of wastewater spiked with Zn(II), Pb(II) and Cd(II), respectively, at 20, 5 and 1 mg/l for a further 9 months. The remaining unit was fed with the same type of wastewater spiked with a combination of Zn(II), Pb(II), Cd(II) and Cu(II) at concentrations of 10, 2.5, 0.5 and 5 mg/l, respectively, over the same period. The chemical oxygen demand (COD) and ammoniacal nitrogen (AN) concentrations were monitored at the inlet, outlet and three additional locations along the length of the wetland units to assess the performance of the wetland units at various metal loadings. At the end of the study, all cattail plants were harvested for the determination of total Kjeldahl nitrogen and metal concentrations. The results showed that the COD removal efficiency was practically independent of increasing metal loading or a combination of metal loadings during the duration of the study. In contrast, the AN removal efficiency deteriorated progressively with increasing metal loading. The relative effect of the heavy metals was found to increase in the order: Zn<Pb<Cd and the synergistic effect of metals was not observed. The metals seem to exhibit some inhibitory effect on nitrogen uptake by cattail plants as indicated by lower nitrogen uptake rates in comparison to rates recorded in wetland systems treating domestic wastewater only.

The absorption of metal ions byEichhornia crassipes

AbstractUptake of metals by whole Eichhornia crassipes plants and excised roots was studied using a bioassay system. Results indicate that in time-series bioassay at concentration of 10 mg L−1 of either Zn or Cu, rapid uptake by whole plants occurred during the first 4 h, but subsequently levelled off after 48 h. A greater proportion of metals absorbed remain in the root system rather than being translocated to other parts of plant. When treated with different combinations of both Cu and Zn, some synergistic effect of metals appeared to have occurred as indicated by enhanced uptake when bioassays involved combination of metals. Absorption kinetics of monovalent K+ by excised Eichhornia roots after a 24-h treatment, indicated an initial linear trend over the range of 1–10 mg K L−1, but subsequently levelled off at 15 mg K L−1 concentration with Vmax of 7.5 × 10–6 M K g−1 dry tissue h−1 and Km of 1.1 × 10−3 M K. Potentiometric titrations revealed existence of pH-dependent charge densities on root system whi...