Showing papers in "Research on Chemical Intermediates in 2018"

Production of activated carbon as catalyst support by microwave pyrolysis of palm kernel shell: a comparative study of chemical versus physical activation

Abstract: Palm kernel shell (PKS), representing an abundantly available oil palm waste in Malaysia, was transformed into activated carbon by microwave vacuum pyrolysis. PKS was first carbonized to produce biochar, followed by an activation process with chemical or water to produce chemically and physically activated carbon, respectively. The activated carbon materials were characterized for their porous characteristics and elemental and proximate composition to examine their suitability as catalyst support. Catalysts were synthesized by supporting nickel on the activated carbon materials and tested for their performance in the methane dry reforming reaction. Microwave vacuum pyrolysis of PKS-derived char resulted in up to 89 wt% yield of activated carbon. The activated carbon was detected to have high Brunauer–Emmett–Teller (BET) surface area associated with a highly porous surface, characteristics of high adsorption capacity corresponding to many sites for adsorption of metal atoms with great potential for use as catalyst support material. Nickel atoms were detected on the surface of the activated carbon catalyst support, indicating successful synthesis of nickel-supported catalyst. The catalysts showed high methane conversion (up to 43 %), producing approximately 22 % gaseous products (CO + H2). These results show that activated carbon produced from microwave pyrolysis of palm kernel shell is a promising catalyst support material. Chemically activated carbon performed better as catalyst support compared with physically activated carbon in terms of CH4 and CO2 conversions.

Enhanced photocatalytic degradation of methyl orange using ZnO/graphene oxide nanocomposites

Abstract: ZnO/graphene oxide (ZnO/GO) nanocomposites were synthesized by hydrothermal method using zinc acetate and graphite as precursors. Properties of synthesized materials were investigated by different physico-chemical techniques and their photocatalytic performance was evaluated with the aid of the photodegradation of methyl orange under UV irradiation. Impacts of reaction conditions such as pH of solutions, catalyst loading and initial concentration on photodegradation rate of synthesized photocatalysts were also investigated. TEM images showed that the average size of the synthesized ZnO was approximately 35 nm, being in good agreement with the obtained XRD results which revealed good dispersion of ZnO particles over the wrinkled GO layers. UV–Vis absorption spectra of these synthesized materials revealed that 5% ZnO/GO exhibited the highest visible light absorption. Photocatalytic experimental results showed that the highest photodegradation rates occurred in a neutral solution with an initial methyl orange (MO) concentration of 10 mg/L. After 2 h of reaction under UV irradiation, more than 95% of MO was degraded at optimal conditions. The photodegradation of MO followed the pseudo-first-order kinetics with apparent reaction rate constants in the range of 0.009–0.030 (min−1). ZnO/GO photocatalyst was relatively stable in neutral aqueous solutions during the photodegradation of MO, with a decrease of 6% in photocatalytic performance observed after four cycles compared with the first cycle.

Perspective on catalyst development for glycerol reduction to C3 chemicals with molecular hydrogen

Abstract: Recent developments in catalytic reduction with H2 of glycerol, which is a by-product of biodiesel manufacture, and the involved chemistry are summarized and reviewed. There are more than ten potential C3 products of glycerol reduction. Among them, 1,2-propanediol can be obtained in very high yield and the production from glycerol is now commercialized. Production of 1,3-propanediol, allyl alcohol and propylene are now possible in > 60%, > 90% and > 80% yield, respectively. Key reaction steps are metal-catalyzed dehydrogenation/hydrogenation, acid-catalyzed dehydration, carbonyl-induced dehydration, metal-catalyzed direct hydrogenolysis and deoxydehydration. The 2-Propanol and small-ring compounds (oxetane, propylene oxide) cannot be produced from glycerol by combinations of these key reaction steps, and no catalytic system is known at present, although the conversion reactions have minus ∆G°.

Enhanced adsorption of methylene blue onto graphene oxide-doped XFe2O4 (X = Co, Mn, Ni) nanocomposites: kinetic, isothermal, thermodynamic and recyclability studies

Abstract: The nanocomposites XFe2O4/GO with various metal sites (X = Co, Mn, and Ni) were successfully synthesized via the polymerized complex method. The XFe2O4/GO family was characterized using X-Ray diffraction analysis, scanning electron microscopy (SEM), and a vibrating sample magnetometer. We also investigated the effect of three fundamental parameters (initial concentration, dosage, and pH) on the removal of methylene blue using the response surface methodology. A high F value, very low P value (< 0.00001), a non-significant lack of fit, and the determination coefficient (R 2 > 0.95) demonstrated a strong correlation between experimental and predicted values of the responses. The predicted optimal conditions for maximum removal efficiency were easily determined to adhere to the following trend for actual test experiments: MnFe2O4/GO (60.1%) < CoFe2O4/GO (80.3%) < NiFe2O4/GO (87.7%). Moreover, the adsorption behavior was well-described by the Langmuir isotherm and a pseudo-second-order kinetic model. The maximum capacity for adsorption of methylene blue onto XFe2O4/GO was found from 42.2 to 80.6 mg/g. Moreover, the XFe2O4/GO could be regenerated for several cycles without a considerable decrease in removal yield, suggesting that this highly promising XFe2O4/GO could be applied as an efficient and novel adsorbent.

Cadmium removal from aqueous solution by biochar obtained by co-pyrolysis of sewage sludge with tea waste

Abstract: Resource utilization is a critical pathway for sustainable solid waste treatment. Biochar was prepared from the co-pyrolysis of sewage sludge and tea waste. Brunauer–Emmett–Teller measurement, scanning electron microscopy and Fourier transform infrared analysis were employed to characterize the biochar. Then, the interface behavior between biochar and Cd from aqueous solution was investigated. The effect of adsorbent dose and pH on Cd adsorption was evaluated. Adsorption kinetics and the adsorption isotherm were studied, and the adsorption mechanism was explored. The results showed that the suitable adsorbent dose was 4 g L−1 and the optimal pH of the Cd solution remained at 6.0. Cadmium sorption on the biochar could be well described by the pseudo-second order kinetic model (R 2 > 0.98). The adsorption process was described using the Langmuir (R 2 > 0.86), Freundlich (R 2 > 0.86), Temkin (R 2 > 0.84) and Dubinin–Radushkevich (R 2 > 0.86) isotherm models. The proportion of organic constituents in biochar was 69.2–72.4%. Minerals that originated in biochar played an important role during the Cd adsorption process, and the contribution of minerals accounted for 27.6–30.8% of the total adsorption. The main mechanism of the Cd adsorption process by biochar involved ion exchange, surface complexation, electrostatic interaction, surface co-precipitation, and other mechanisms. Therefore, biochar created by the co-pyrolysis of sewage sludge and tea waste could be used as an adsorbent for the removal of metal ions from contaminated water.

Biosynthesis, characterization, and antibacterial activity of silver nanoparticles using Rheum turkestanicum shoots extract

Abstract: Silver nanoparticles (Ag-NPs) were synthesized through a facile and “green” method, which uses the aqueous shoots extract of Rheum turkestanicum at room temperature. The formation of Ag-NPs was indicated by observing the change in solution color, turning from light brown to dark brown. The synthesized Ag-NPs were characterized with different instrumental tools such as UV–vis, XRD, FESEM, EDAX, FTIR, and TEM. The formation of Ag-NPs at 1.0 mM concentration of silver nitrate resulted in nanoparticles with spherical shapes and a mean diameter of 26 nm. In addition, the biosynthesized Ag-NPs were found to illustrate stronger antibacterial activities against human pathogenic bacteria. From the results and observations, this method can be applied for large-scale preparations of other noble metals regarding various medical and industrial applications.

Microwave-mediated synthesis of spinel CuAl2O4 nanocomposites for enhanced electrochemical and catalytic performance

Abstract: The present study explores synthesis of spinel copper aluminate nanocomposites (CuAl2O4 NCs) for electrochemical applications and solvent-free synthesis of xanthanedione derivatives. CuAl2O4 NCs were synthesized from copper nitrate and aluminum nitrate with/without use of sodium dodecyl sulfate (SDS) by aqueous precipitation and microwave-assisted (MW) technique. As-synthesized CuAl2O4 NCs were characterized structurally and morphologically using X-ray diffraction (XRD) analysis, Fourier-transform infrared (FT-IR) spectroscopy, diffuse reflectance spectroscopy (DRS), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Formation of cubic spinel structure after calcination at 900 °C was confirmed by XRD analysis, while Raman, XPS, and EDS validated the composition and purity. TEM revealed that the particles had uniform nanosphere shape with average size of 10 nm for microwave-assisted with surfactant (MWS-CuAl2O4), while aqueous precipitation with surfactant (APS-CuAl2O4) NCs exhibited nanograins with particle size of 17 nm. AFM revealed higher surface roughness for MWS-CuAl2O4 NCs than APS-CuAl2O4 NCs. The electrochemical performance of the CuAl2O4 NCs was examined in aqueous Na2SO4 (1 M) as electrolyte using cyclic voltammetry (CV), revealing that the MWS-CuAl2O4 NCs demonstrated high specific capacitance (125 F g−1 at current density of 0.5 mA cm−2). Furthermore, one-pot, facile, eco-friendly MWS-CuAl2O4 NC-catalyzed synthesis of xanthanediones was developed, exhibiting excellent yield and reusability with negligible reduction in efficiency even after four consecutive cycles. MWS-CuAl2O4 NCs showed enhanced electrochemical and catalytic performance.

A facile green synthesis of silver nanoparticle-decorated hydroxyapatite for efficient catalytic activity towards 4-nitrophenol reduction

Abstract: Silver nanoparticles (AgNPs) were gradually grown on a hydroxyapatite surface via a green self-reducing approach. Hydroxyapatite (HAP) was functionalized by dopamine and subsequently self-polymerized onto the HAP surface. Surface-adhered polydopamine acted as a self-reducing agent for the Ag+ ion; thus the process is considered to be green. The nanoparticles were evaluated by UV–visible spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The characterization data revealed that the AgNPs were spherical and crystalline, with an average size of 14.79 nm. The AgNP-decorated HAP was applied as a heterogeneous catalyst for the reduction of 4-nitrophenol (4-NP), which obeyed first-order reduction kinetics. Our reported catalyst can thus be used as an eco-friendly, efficient, cost-effective, and easy-to-fabricate heterogeneous catalyst system with potential use in industrial applications.

Methylene blue removal from aqueous solution by magnetic clinoptilolite/chitosan/EDTA nanocomposite

Abstract: In this study, clinoptilolite as a natural zeolite which was magnetized using precipitation of maghemite nanoparticles was coated by chitosan and then modified by thylenediamine tetra-acetic acid to add functional groups and its performance in the removal of toxic methylene blue from aqueous solution was investigated. Synthesized magnetic nanocomposite was characterized by VSM, XRD, SEM, and FTIR analyses. The saturation magnetization of the final nanocomposite was obtained as 22.2 emu/g. In addition, the factors affecting adsorption process and its optimization were investigated using response surface methodology and central composite design. Data obtained by different isotherm, adsorption kinetic and thermodynamic models were also studied. The results showed good agreement of these data with the Freundlich isotherm model (R 2 = 0.99), and it was found that adsorption follows the second-order kinetics model (R 2 = 1). Negative values of ΔG and positive values of ΔH obtained from this adsorption thermodynamic study revealed that the methylene blue adsorption process is exothermic and spontaneous. The optimum conditions to ensure maximum adsorption efficiency were determined, and included pH = 5.54, adsorbent amount of 0.03 g, temperature of 31.18 °C, and initial solution concentration of 16.21 mg/l which resulted in a removal efficiency of 99.44%. The results indicated that this nanocomposite can be used as a proper adsorbent for adsorbing methylene blue and other dye contaminants.

Solar light-assisted photocatalytic degradation of methylene blue with Mo/TiO 2 : a comparison with Cr- and Ni-doped TiO 2

Abstract: Highly active Cr-doped, Ni-doped and Mo-doped TiO2 photocatalysts were synthesized by a sol–gel method. The synthesized catalysts were characterized by UV–DRS, BET, XRD, FE-SEM–EDS, TEM and XPS. Metal doping decreased the band gap of TiO2 to 2.83 eV for Mo-doped TiO2 and Ni-doped TiO2. The activity of the synthesized photocatalysts was evaluated by studying the degradation of MB as a model pollutant under both UV and solar irradiation. The Mo/TiO2 catalyst achieved 98% degradation under solar light within 120 min. The activity of the catalysts was in the order Ni-doped TiO2 7 and followed pseudo-first order kinetics. Degradation by-products were analyzed on HR-LCMS and a mechanism is proposed.

Mesoporous activated carbon from Pentace species sawdust via microwave-induced KOH activation: optimization and methylene blue adsorption

Abstract: This work studied the optimization of preparation conditions of Pentace species sawdust activated carbon (PSAC) via microwave-induced KOH activation for the adsorption of methylene blue (MB) dye from aqueous solutions. The produced activated carbon was characterised through Brunauer–Emmett–Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy, and Fourier transform infrared spectroscopy. Response surface methodology technique was used to optimize the radiation power, radiation time and impregnation ratio for MB removal and PSAC yield through central composite design. The optimum preparation conditions for PSAC were obtained at a radiation power of 418 W, radiation time of 6.4 min, and an impregnation ratio of 0.5, which resulted in 27% PSAC yield and 93.74% MB removal. A mesoporous structure of PSAC was formed, with a BET surface area, total pore volume and average pore diameter of 914.15 m2/g, 0.52 cm3/g, and 3.19 nm, respectively. The experimental kinetic data were well described by a pseudo-second-order model and intraparticle diffusion. Adsorption data fitted the Redlich–Peterson equation better than the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and Sips equations. However, the exponential value of Redlich–Peterson approached unity, hence, resulting in the original Langmuir equation, with adsorption capacity of 357.14 mg/g. The adsorption performance was effectively preserved even after four consecutive cycles, demonstrating good regeneration ability.

Recent advances in chitosan-based self-healing materials

Abstract: Over the past few decades, self-healing materials derived from chitosan have attracted a great deal of attention due to their excellent physical and biological properties related to their self-healing ability, biodegradability, biocompatibility and antibacterial activity. This review discusses the most recent progress in the preparation and application of chitosan-based self-healing materials. Various strategies that have been used to prepare chitosan-based self-healing materials are reviewed, including the construction of dynamic covalent and non-covalent bonds. Applications of chitosan-based self-healing hydrogels and coatings in tissue engineering, drug delivery systems and anti-corrosion are also discussed.

Modulated large-pore mesoporous silica as an efficient base catalyst for the Henry reaction

Abstract: In this study, mesoporous silica materials with tuned pores and surface areas were successfully synthesized by adjusting the amount of applied hexane and controlling the hydrothermal temperature. The synthesized silica materials were then functionalized by an amine group to produce solid base catalysts and be applicable as efficient heterogeneous base catalysts for the Henry reaction. The mesoporous silica catalysts possessing large-pores and surface area expose their active catalytic sites and thereby improve contacts with reactants fulfilling the reactions expeditiously in comparison with solid base catalysts possessing small-pores and surface area. The results indicated that the yield of the products is significantly dependent on the structure of the applied solid base catalysts. The modulated large-pore solid base catalysts presented high catalytic activity in Henry reactions and could be reused for five consecutive cycles.

Biosynthesis of gold nanoparticles using Prosopis farcta extract and its in vitro toxicity on colon cancer cells

Abstract: Gold nanoparticles (Au-NPs) were prepared by “green” synthesis through the aqueous extract of Prosopis farcta. The P. farcta is a special herbal, which it can be a suitable candidate in the reduction process of Au3+ to Au0. The structure and morphology of the synthesized Au-NPs were characterized by UV–visible spectrophotometry, powder X-ray diffraction analysis and high-magnification transmission electron microscopy techniques. The Au-NPs were spherically uniform in shape with particle size of about 25 nm. The cytotoxicity effect of Au-NPs was studied on a colon (HT-29) cancerous cell line via the MTT assay, and the IC50 of Au-NPs was calculated to be 419.7 µg/mL. The results indicated that the apoptotic effects were increased on cells when the Au-NPs concentration reached 200 µg/mL. The Au-NPs were synthesized easily and with a very low cost and time by P. farcta extract for the first time.

Sono-chemical synthesis and characterization of Fe 3 O 4 @mTiO 2 -GO nanocarriers for dual-targeted colon drug delivery

Abstract: In this study, a kind of magnetic Fe3O4@mTiO2-GO (where m was shorted mesoporous) hybrids with core–shell nano-structure for controlled dual targeted drug delivery was synthesized using a facile sono-chemical method. The structure and chemical composition of the nanocarrier (NC), and its surface morphology, were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX), vibrating sample magnetometer (VSM) spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Synthesis of Fe3O4@mTiO2-GO was proved by XRD and FT-IR. SEM showed that the particle size of this NC was in the range of ∼ 85–95 nm. EDX confirmed the presence of Ti, Fe, C and O in the nanocarrier. VSM analysis showed the magnetic behavior of the Fe3O4@mTiO2-GO nano-hybrids with saturation magnetization (M S) of 1.57 emu/g at room temperature. Curcumin (CUR) as a hydrophobic and an anti-tumor model drug was loaded on the NC. Drug loading capacity and encapsulation efficiency of this NC were as high as 17.85 and 72.45%, respectively. The drug release behavior was sustained and pH-responsive. MTT results demonstrated no significant cytotoxicity of the NC on Human Foreskin Fibroblast Normal cell line (HFF-2), indicating that this NC can be safe for use as a drug carrier for delivering anticancer drugs to tumor sites. The results of an MTT test on Caco-2 cancerous cells proved that CUR in nano-carriers has retained its anti-cancer properties.

Promotional effect of Ce on the SCR of NO with NH3 at low temperature over MnO x supported by nitric acid-modified activated carbon

Abstract: Different amounts of Mn and Ce oxides were loaded onto nitric acid-modified activated carbon (ACN) by wet impregnation. The series of catalysts were employed for the selective catalytic reduction of NO x by NH3 at temperatures between 100 and 250 °C. Cerium-modified catalysts exhibited higher de-NO x performance than those modified with Mn/ACN, even with the same total loadings. The precursor solution with a molar ratio for Ce/(Mn + Ce) of 0.4 exhibited the highest catalytic activity. Enhanced resistance to SO2 and H2O and better stability were observed for 10%Mn–Ce(0.4)/ACN relative to 10%Mn/ACN. The catalysts were further characterized by N2 physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), and temperature-programmed desorption of ammonia (NH3-TPD). The N2 physisorption and XRD results suggested that co-doping Ce with Mn increased the surface area and promoted the dispersion of Mn–Ce binary metal oxides. H2-TPR the NH3-TPD results demonstrated that the interaction between manganese oxide and cerium oxide species enhanced the redox and surface acidity of 10%Mn–Ce(0.4)/ACN.

Photo-fenton refreshable Fe 3 O 4 @HCS adsorbent for the elimination of tetracycline hydrochloride

Abstract: A yolk–shell-structured sphere composed of a superparamagnetic Fe3O4 core and a carbon shell (Fe3O4@HCS) was etched from Fe3O4@SiO2@carbon by NaOH, which was synthesized through the layer-by-layer coating of Fe3O4. This yolk–shell composite has a shell thickness of ca. 27 nm and a high specific surface area of 213.2 m2 g−1. Its performance for the magnetic removal of tetracycline hydrochloride from water was systematically examined. A high equilibrium adsorption capacity of ca. 49.0 mg g−1 was determined. Moreover, the adsorbent can be regenerated within 10 min through a photo-Fenton reaction. A stable adsorption capacity of 44.3 mg g−1 with a fluctuation <10% is preserved after 5 consecutive adsorption–degradation cycles, demonstrating its promising application potential in the decontamination of sewage water polluted by antibiotics.

Biosynthesis of silver nanoparticles and their role in photocatalytic degradation of methylene blue dye

Abstract: Nowadays, synthesis of nanoparticles, particularly silver nanoparticles (Ag-NPs), has become a research priority due to their wide application in medicine and industry. In this study, Ag-NPs were synthesized utilizing aqueous extract of Prosopis farcta fruit and characterized using ultraviolet–visible (UV–Vis) spectroscopy, powder X-ray diffraction analysis, and transmission electron microscopy. The results showed that the obtained nanoparticles were uniform in size (median 30 nm) with spherical shape. The catalytic activity of the synthesized Ag-NPs was studied using methylene blue (MB) in presence of visible light, showing rapid degradation of MB in the first 30 min. The results revealed color degradation of 70.20% within the same time, indicating that the synthesized nanoparticles can quickly degrade artificial colorants and eliminate some environmental contaminants.

Immobilization of a nickel complex onto functionalized Fe3O4 nanoparticles: a green and recyclable catalyst for synthesis of 5-substituted 1H-tetrazoles and oxidation reactions

Abstract: In the present research, a magnetically recoverable catalyst was easily prepared by anchoring nickel onto the surface of organically modified magnetite nanoparticles. Characterization of the prepared nanostructure was performed by various physico-chemical techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, thermal gravimetric analysis and vibrating sample magnetometer measurements. The catalytic behavior of the prepared nanohybrid as an efficient catalyst was successfully probed in the oxidation of sulfides, oxidative coupling of thiols and synthesis of 5-substituted 1H-tetrazoles. This method was found to have significant advantages, including high yield, green reaction conditions, short reaction time, easy separation and workup, as well as the ability to tolerate a wide variety of substitutions in the reagents.

Synthesis of Fe- or Ag-doped TiO2–MWCNT nanocomposite thin films and their visible-light-induced catalysis of dye degradation and antibacterial activity

Abstract: Thin films of TiO2, TiO2-multiwalled carbon nanotubes (TiO2–MWCNT), Fe-doped TiO2–MWCNT (Fe–TiO2–MWCNT), and Ag-doped TiO2–MWCNT (Ag–TiO2–MWCNT) supported on glass substrates were successfully prepared by sol–gel drop coating method. MWCNTs were treated by H2SO4 and HNO3 to oxidize graphitic carbon. The composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet–visible (UV-Vis) absorption spectroscopy to confirm their structure and optical properties. XRD patterns of all prepared films exhibited (101), (004), (200), (105), (211), (204), (116), (220), (215), and (224) planes of anatase-phase TiO2. A pronounced broad peak at ~3400 cm−1 in the FTIR spectrum of the MWCNT confirmed oxidation of some carbon atoms on the surface of MWCNTs by HNO3 and H2SO4. The photocatalytic and antibacterial activities of the prepared materials were tested under visible-light irradiation based on degradation of methylene blue (MB) dye in aqueous solution and reduction in the viable count of Escherichia coli, respectively. Fe or Ag was doped into the TiO2-MWCNT composites, lowering the bandgap and thereby enabling enhanced photocatalytic activity in the visible-light region. Based on the MB photodegradation results, the photocatalytic efficiency of the Fe–TiO2–MWCNT and Ag–TiO2–MWCNT composites could be due to the following mechanism: (1) adsorption and photoinduced electron absorption by MWCNT, and (2) electron trapping by Fe or Ag within the TiO2 matrix, in addition to the usual photocatalytic activity of TiO2. Moreover, as-synthesized Ag–TiO2–MWCNT composite films showed outstanding antimicrobial activity.

Sodium ascorbate as an expedient catalyst for green synthesis of polysubstituted 5-aminopyrazole-4-carbonitriles and 6-amino-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles

Abstract: Sodium ascorbate (SA) was used as a safe catalyst for the synthesis of 5-aminopyrazole-4-carbonitriles from the one-pot three-component cyclocondensation (3-CC) of aldehydes, phenylhydrazine, and malononitrile at 50 °C. This 3-CC proceeds in a mixture of ethanol–water as a green reaction medium to give the desired densely functionalized pyrazoles in good to high yields. 6-Amino-1,4-dihydropyrano-[2,3-c]pyrazole-5-carbonitriles were also synthesized in the presence of SA via an eco-friendly and simple four-component cyclocondensation (4-CC). This 4-CC performed in refluxing water as a green medium and dihydropyrano-[2,3-c]pyrazole products were obtained in excellent yields and relatively shorter reaction times. These environmentally friendly multicomponent cyclocondensations offer some interesting advantages, including time-saving, easily available starting materials, mild conditions, minimizing the amount of waste, good atom efficiency, avoiding hazardous organic solvents or catalysts, and the ease of the work-up.

One-pot multicomponent synthesis in aqueous medium of 1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile and derivatives using a green and reusable nano-SiO2 catalyst from agricultural waste

Abstract: Nanosilica from wheat straw—an agricultural waste—was utilized as a novel and efficient heterogeneous catalyst for synthesis of bioactive pyrano[2,3-c]pyrazole derivatives via one-pot four-component reaction of various aryl aldehydes, hydrazine hydrate, ethyl acetoacetate, and malononitrile in aqueous medium at 80 °C. The nano-SiO2 extracted from wheat straw was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, particle size analysis, energy-dispersive X-ray (EDX) analysis, and scanning electron microscopy (SEM). All the synthesized pyrano[2,3-c]pyrazoles were characterized by FT-IR spectroscopy, electrospray ionization (ESI) mass spectroscopy (MS), 1H and 13C nuclear magnetic resonance (NMR), and elemental analysis. Additional features of this method include an efficient, rapid, and ecofriendly reaction process, easy workup, high yield, short reaction time, and recyclable green catalyst.

Removal of methylene blue by silver nanoparticles loaded on activated carbon by an ultrasound-assisted device: optimization by experimental design methodology

Abstract: Ultrasonic waves superimposed with Ag nanoparticles festooned on AC was used as a new economical and green methodological adsorbent for the efficient removal of noxious methylene blue (MB) from the solvent phase. The developed adsorbent was characterized using various analytical techniques namely SEM, XRD, and BET. The impact of influential variables such as pH, sonication time, temperature, initial dye concentration, and adsorbent dosage on MB removal and adsorption were well investigated and optimized using central composite design. Additionally, the optimized operating conditions were obtained through the desirability function superimposed with response surface methodology. It was observed that the very low amount of the adsorbent dose (0.015 g) is applicable for successful removal of MB (RE >95 %) in a very short span of time (4.0 min) with maximum adsorption capacity (75.2 mg g−1). The modeling of the adsorption process is carried out using MLR and RF models. The optimal tuning parameters for the RF model were achieved based on n tree = 100, m try = 2. For the testing data set, the MSE values of 0.0013, the correlation coefficient (R 2) values for RF and MLR model, are 0.9783 and 0.7573 respectively. Pictorial presentation of surface, response and absorbance behavior of MB

Bis(p-sulfoanilino)triazine-functionalized silica-coated magnetite nanoparticles as an efficient and magnetically reusable nano-catalyst for Biginelli-type reaction

Abstract: The preparation of bis(p-sulfoanilino)triazine-functionalized silica-coated magnetite nanoparticles and their use as a novel magnetically separable nanocatalyst for the synthesis of various Biginelli adducts are presented. The materials were characterized by various microscopic and spectroscopic techniques such as scanning electron microscopy, vibrating sample magnetometer, X-ray powder diffraction, and FT-IR spectroscopy, etc. A series of 3,4-dihydropyrimidinones or thione products were conveniently prepared by this green protocol from the reactions of aromatic aldehydes with the 1,3-dicarbonyl compounds and urea or thiourea using the catalyst under solvent-free conditions. The present method is operationally simple and offers several advantages such as good to excellent yields, short reaction times, the absence of a solvent, and simple work-up. Moreover, the aforementioned nanocatalyst can be easily recovered from the reaction mixture with the assistance of an external magnetic field and reused several times without any loss of its catalytic activity.

Transition (Mn, Fe) and rare earth (La, Pr) metal doped ceria solid solutions for high performance photocatalysis: Effect of metal doping on catalytic activity

Abstract: In this work, various transition and rare earth metal ions (M3+; M = Mn3+, Fe3+, La3+, and Pr3+) doped CeO2 solid solutions were prepared by a simple sol–gel method for the degradation of an organic dye, Rhodamine B (RhB) as a model pollutant. The as-prepared samples were thoroughly studied by various characterization techniques to understand the surface and optical properties. The XRD results suggested formation of solid solutions, and TEM studies confirmed the nanosized nature of the ceria particles. The Raman and XPS results revealed that the doping of metal ions enhanced the formation of Ce3+ ions associated with the oxygen vacancies. The doping of M3+ ions in the CeO2 lattice strongly influenced the band gap tuning of undoped CeO2 (3.01 eV) from the UV to Visible region (i.e., 2.45–2.90 eV). Photoluminescence studies suggested that doping of M3+ cations suppresses the recombination rate of photogenerated electron–hole pairs. The photocatalytic activity results indicated that the doped CeO2 samples exhibit substantially enhanced photocatalytic performance for the degradation of RhB compared to undoped CeO2. The better catalytic activity of doped CeO2 samples could be attributed to the presence of defects (Ce3+ ions and oxygen vacancies), which play a prominent role as trapping centres for excited electrons and inhibit the recombination process. The scavengers tests confirmed that the generation of highly reactive hydroxyl (·OH) and super oxide (·O2−) radicals are actively involved in the photodegradation process. This work rendered a new concept for rational design and development of doped CeO2-based materials as better photocatalysts.

Hydrogen production by methanol steam reforming on a cordierite monolith reactor coated with Cu–Ni/LaZnAlO 4 and Cu–Ni/γ-Al 2 O 3 catalysts

Abstract: The performance of Cu–Ni/LaZnAlO4 and Cu–Ni/γ-Al2O3 catalysts in the methanol reforming process in a monolith reactor in the temperature range of 200–350 °C, feed flow rate of WHSV = 20.8 h−1 and atmospheric pressure has been investigated. In order to perform a more thorough investigation, surface area, morphology and crystalline structure of the synthetic catalysts have been studied using BET, FE-SEM, TPR, FT-IR, TEM, TGA and XRD analyses. The results have shown that Cu–Ni/LaZnAlO4 catalyst synthesized by combustion reaction method under ultrasound irradiation has a very high efficiency and catalytic activity, low reduction temperature, high mechanical resistance and large pore sizes. The latter causes a higher percentage of active metal impregnation and better distribution on the support, greater resistance against sintering and maintenance of catalyst inertness at temperatures over 1000 °C, in comparison with conventional catalysts such as Cu–Ni/γ-Al2O3. This make its substitution for currently used catalysts affordable.

A novel dicationic ionic liquid as a highly effectual and dual-functional catalyst for the synthesis of 3-methyl-4-arylmethylene-isoxazole-5(4H)-ones

Abstract: A novel dicationic ionic liquid, N,N,N′,N′-tetramethyl-N,N′-bis(sulfo)ethane-1,2-diaminium mesylate [TMBSED][OMs]2), has been produced, and identified by analysis of its 1H NMR, 13C NMR, FT-IR, mass and thermal gravimetric data. Thereafter, it has been utilized as a highly effectual, homogeneous and dual-functional catalyst to promote the multi-component reaction of ethyl acetoacetate, hydroxylamine hydrochloride and arylaldehydes under solvent-free conditions for the synthesis of 3-methyl-4-arylmethylene-isoxazole-5(4H)-ones. Due to the dual-functionality of [TMBSED][OMs]2 (possessing acidic and basic sites), and also having two sites of each, it was a highly effective and general catalyst for the synthesis. Moreover, a plausible and attractive mechanism based on the dual-functionality of the catalyst has been proposed.

Flavonoid dihydromyricetin-mediated silver nanoparticles as potential nanomedicine for biomedical treatment of infections caused by opportunistic fungal pathogens

Abstract: Dihydromyricetin-mediated silver nanoparticles (DMY-AgNPs) were synthesized and their efficacy against fungal pathogens tested in vitro. The shape of DMY-AgNPs appeared to be spherical with size of ~34 nm. Fourier-transform infrared (FT-IR) analysis indicated that –OH and C=O groups were involved in nanoparticle formation. The XRD pattern of DMY-AgNPs showed strong peaks at 38°, 44°, and 64°, corresponding to reflection from (111), (200), and (220) planes. Five opportunistic fungal pathogens, namely Aspergillus fumigatus, Aspergillus niger, Paecilomyces formosus, Candida albicans, and Candida parapsilosis, were isolated from patients suffering from respiratory tract infections. Growth of each fungal strain was inhibited by DMY-AgNPs. The zone of inhibition of DMY-AgNPs against A. fumigatus, A. niger, P. formosus, C. albicans, and C. parapsilosis was 17.6, 19.2, 22.2, 15.8, and 18.5 mm. The minimal inhibitory concentration was found to be 0.83, 0.73, 0.67, 0.95, and 0.89 µg mL−1, respectively. This is the first report on DMY-AgNPs as an effective antifungal agent. DMY-AgNPs are a potential alternative to commercially available antifungal fungicidals.

Binary copper and iron oxides immobilized on silica-layered magnetite as a new reusable heterogeneous nanostructure catalyst for the Knoevenagel condensation in water

Abstract: In this study, a novel heterogeneous and reusable nanostructure catalyst was synthesized through the immobilization of bimetallic Cu–Fe mixed oxides on silica-layered magnetite. The prepared nanomagnetic Fe3O4@SiO2@CuO–Fe2O3 was characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, Brunauer–Emmett–Teller analysis, thermogravimetric analysis, differential thermal gravity, a vibration sample magnetometer, transmission electron microscopy and inductively coupled plasma optical emission spectroscopy. The catalytic activity of this mesoporous nanocomposite was studied in the Knoevenagel condensation of aromatic aldehydes and malononitrile in water to afford benzylidenemalononitriles in high to excellent yields. The nanocatalyst was able to be recycled five times without a significant loss in catalytic activity. This nanostructure catalyst allows for mild reaction conditions and acceptable reaction times, while delivering the desired products in high purity and yield without the use of dangerous organic solvents.

Biosynthesis of TiO 2 nanoparticles using Justicia gendarussa leaves for photocatalytic and toxicity studies

Abstract: Eco-friendly biosynthesis of polycrystalline titanium dioxide (TiO2) nanoparticles (NPs) was synthesised using Justicia gendarussa (J. gendarussa) leaf extract as oxidizing agents. They were compared with TiO2 NPs synthesized using the glacial acetic acid and also studied was the combined effect of synthesis of TiO2 NPs. The crystalline nature and structural formation of TiO2 NPs synthesized by different methods were confirmed by the X-ray diffraction technique, and functional groups of materials were confirmed by FT-IR spectroscopy. The synthesized materials were investigated for photocatalytic activity for methylene blue under UV irradiation and toxicity activity against MCF-7 and MDA-MB-231 cells. The result indicates that TiO2 NPs synthesised by J. gendarussa showed superior and enhanced activity against MCF-7 and MDA-MB-231. Biosynthesized TiO2 NPs showed higher photodegradation of dyes when compared with other TiO2 NPs synthesized by different methods. This is due to the alterations in band gap; structural changes and surface area in nanoparticles that increased the activity. Also, nanosphere/disc like morphology of TiO2 NPs is confirmed using TEM.