Adsorptive recovery of geniposidic acid from gardenia yellow pigment extraction wastewater by anion exchange: equilibrium,thermodynamics and mechanism modeling and simulation

For many years, the traditional process of gardenia yellow pigment extraction has produced wastewater containing significant quantities of Geniposidic acid (GSA), a substance that could be put to pharmacological uses if it could be effectively recovered. This study aimed to provide an efficient adsorption material, D08, for recycling GSA. Batch experiments showed that adsorption capacity depends on initial concentration and temperature. The maximal adsorption capacity of GSA onto an anionic exchanger reached 310 mg/g. The pK _a value of GSA was determined to be 4.21. Pore diffusion coefficients (D _p) of GSA for 283, 298 and 313 K were 3.274 × 10^?10, 5.069 × 10^?10 and 7.356 × 10^?10 m²/s, respectively. Recovery efficiency of GSA was achieved to 99.81 %. In comparison with pseudo first-order and pseudo second-order equations, the PDM model demonstrated the best fit to the kinetics data of GSA adsorption. Adsorption/desorption experiments proved that D08 offers great adsorption capacity, high adsorption rate and good repeatability. In order to help us to accurately comprehend the mass transfer process, numerical simulation and post-processing to variables c(r, t) and q(r, t) were performed to clarify the adsorption process.     

Facile synthesis of 5A zeolite from attapulgite clay for adsorption of <Emphasis Type="Italic">n</Emphasis>-paraffins

5A zeolites were facilely synthesized from attapulgite clay and sodium aluminate precursors. The optimum synthesis condition for 4A zeolite (Na-form) were H₂O/attapulgite ratio of 40:1 volume/mass, NaOH/attapulgite mass ratio of 2.35:1, the crystallization time was 4 h at 80–85 °C. The 4A zeolite was converted to related 5A zeolite (Ca-form) through ionic exchanges using calcium chloride solution with the Si/Al mole ratio of 1.3. SEM images demonstrated that as-synthesized 5A zeolites are ordered cubic crystals, average crystals length dimension is 1–2 μm. And the zeolites product had a specific surface area of 482 m² g^?1 and total pore volume of 0.274 cm³ g^?1. The static adsorption experiments showed that the equilibrium adsorption capacities of n-decane and n-pentadecane on produced 5A zeolite were 0.253 and 0.510 g g^?1, respectively. And the adsorption equilibrium time of n-decane and n-pentadecane on 5A zeolite were 45 and 60 min, respectively. The experimental adsorption data of n-decane and n-pentadecane on three zeolites could be properly fitted by the Langmuir–Freundlich isotherm model.     

Production of <Emphasis Type="Italic">R</Emphasis>-Mandelic Acid Using Nitrilase from Recombinant <Emphasis Type="Italic">E. coli</Emphasis> Cells Immobilized with Tris(Hydroxymethyl)Phosphine

Recombinant Escherichia coli cells harboring nitrilase from Alcaligenes faecalis were immobilized using tris(hydroxymethyl)phosphine (THP) as the coupling agent. The optimal pH and temperature of the THP-immobilized cells were determined at pH 8.0 and 55 °C. The half-lives of THP-immobilized cells measured at 35, 40, and 50 °C were 1800, 965, and 163 h, respectively. The concentration of R-mandelic acid (R-MA) reached 358 mM after merely 1-h conversion by the immobilized cells with 500 mM R,S-mandelonitrile (R,S-MN), affording the highest productivity of 1307 g L^?1 day^?1 and the space-time productivity of 143.2 mmol L^?1 h^?1 g^?1. The immobilized cells with granular shape were successfully recycled for 60 batches using 100 mM R,S-MN as substrate at 40 °C with 64% of relative activity, suggesting that the immobilized E. coli cells obtained in this study are promising for the production of R-MA.     

Heavy Metal Resistances and Chromium Removal of a Novel Cr(VI)-Reducing Pseudomonad Strain Isolated from Circulating Cooling Water of Iron and Steel Plant

Three bacterial isolates, GT2, GT3, and GT7, were isolated from the sludge and water of a circulating cooling system of iron and steel plant by screening on Cr(VI)-containing plates. Three isolates were characterized as the members of the genus Pseudomonas on the basis of phenotypic characteristics and 16S rRNA sequence analysis. All isolates were capable of resisting multiple antibiotics and heavy metals. GT7 was most resistant to Cr(VI), with a minimum inhibitory concentration (MIC) of 6.5 mmol L^?1. GT7 displayed varied rates of Cr(VI) reduction in M2 broth, which was dependent on pH, initial Cr(VI) concentration, and inoculating dose. Total chromium analysis revealed that GT7 could remove a part of chromium from the media, and the maximum rate of chromium removal was up to 40.8 %. The Cr(VI) reductase activity of GT7 was mainly associated with the soluble fraction of cell-free extracts and reached optimum at pH 6.0～8.0. The reductase activity was apparently enhanced by external electron donors and Cu(II), whereas it was seriously inhibited by Hg(II), Cd(II), and Zn(II). The reductase showed a K _m of 74 μmol L^?1 of Cr(VI) and a V _max of 0.86 μmol of Cr(VI) min^?1 mg^?1 of protein. The results suggested that GT7 could be a promising candidate for in situ bioremediation of Cr(VI).     

Enzymatic Hydrolysis of Black Liquor Xylan by a Novel Xylose-Tolerant,Thermostable β-Xylosidase from a Tropical Strain of <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> CBS 135684

From three cell-associated β-xylosidases produced by Aureobasidium pullulans CBS 135684, the principal enzyme was enriched to apparent homogeneity and found to be active at high temperatures (60–70 °C) over a pH range of 5–9 with a specific activity of 163.3 units (U) mg^?1. The enzyme was thermostable, retaining over 80% of its initial activity after a 12-h incubation at 60 °C, with half-lives of 38, 22, and 10 h at 60, 65, and 70 °C, respectively. Moreover, it was tolerant to xylose inhibition with a K _i value of 18 mM. The K _m and V _max values against p-nitrophenyl-β-d-xylopyranoside were 5.57 ± 0.27 mM and 137.0 ± 4.8 μmol min^?1 mg^?1 protein, respectively. When combining this β-xylosidase with xylanase from the same A. pullulans strain, the rate of black liquor xylan hydrolysis was significantly improved by up to 1.6-fold. The maximum xylose yield (0.812 ± 0.015 g g^?1 dry weight) was obtained from a reaction mixture containing 10% (w/v) black liquor xylan, 6 U g^?1 β-xylosidase and 16 U g^?1 xylanase after incubation for 4 h at 70 °C and pH 6.0.     

Growth Parameters,Photosynthetic Performance,and Biochemical Characterization of Newly Isolated Green Microalgae in Response to Culture Condition Variations

This work aimed to characterize two native microalgal strains newly isolated from South Mediterranean areas and identified as Chlorella sorokiniana ES3 and Neochloris sp. AM2. The growth properties and biochemical composition of these microalgae were evaluated in different culture media (Algal, BG-11, f/2, and Conway). Among the tested media, nitrate- and phosphate-rich Algal medium provided the maximum biomass productivities (85.5 and 111.5 mg l^?1 day^?1 for C. sorokiniana and Neochloris sp., respectively), while the nitrate- and phosphate-deficient f/2 medium resulted in the highest lipid productivities (24.1 and 35.8 mg l^?1 day^?1 for C. sorokiniana and Neochloris sp., respectively). The physiological state of both microalgae was investigated under different light and temperature levels using the pulse amplitude-modulated fluorometry. The better photosynthetic efficiency of C. sorokiniana was obtained at 23 °C with a light saturation of 156 μE m^?2 s^?1, while that of Neochloris sp. was achieved at 15 °C with a light saturation of 151 μE m^?2 s^?1. The analysis of fatty acid profile and biodiesel parameters revealed that C. sorokiniana, cultivated in Algal and f/2 media, can be considered as a suitable candidate for high-quality biodiesel production.     

Development and Validation of Stability-Indicating UPLC Method for 9-Desmethyl-<Emphasis Type="Italic">α</Emphasis>-dihydrotetrabenazine

A stability-indicating UPLC method was developed for quantitative determination of 9-desmethyl-α-dihydrotetrabenazine (9-DM-α-DTBZ), the precursor for preparing a widely used vesicular monoamine transporter 2 imaging agent ¹¹C-α-DTBZ. Compound 9-DM-α-DTBZ was subjected to various stress conditions consisting of acidic, alkaline, oxidative, thermal and photolytic forced degradation. The decomposition of 9-DM-α-DTBZ was observed under oxidative condition, whereas no obvious degradation was shown under the other stress conditions. For chromatographic separation of 9-DM-α-DTBZ and its degradation products, an Acquity UPLC BEH C18 column (2.1 × 100 mm, 1.7 μm) and a mobile phase of 20:80 (v/v) methanol/ammonium acetate buffer (pH 4.5, 10 mM) were used. Quantitative determination of 9-DM-α-DTBZ was performed using a PDA detector at a flow rate of 0.30 mL min^?1. UPLC–MS analysis was further utilized to characterize the two degradation products. The proposed method was fully validated as per USP guidelines with respect to linearity, accuracy, precision, robustness, limit of detection (LOD) and limit of quantification (LOQ). The linear regression analysis showed a good linear relationship (r ²  = 0.9995) in the concentration range of 0.001–1.00 mg mL^?1 (n = 6). The assay method was found to have good precision (1.14–1.35% RSD) and recovery (98.91–101.23%). Additionally, the LOD and LOQ of 9-DM-α-DTBZ were 0.30 and 1.00 μg mL^?1, respectively. These results indicated that the present method could be used to evaluate the quality of regular production samples and also used in stability assays.     

Ro-vibrating energy states of a diatomic molecule in an empirical potential

An approximate analytical solution of the Schrödinger equation is obtained to represent the rotational–vibrational (ro-vibrating) motion of a diatomic molecule. The ro-vibrating energy states arise from a systematical solution of the Schrödinger equation for an empirical potential (EP) V _±(r) = D _e {1 ? (?/δ)[coth (ηr)]^±1/1 ? (?/δ)}² are determined by means of a mathematical method so-called the Nikiforov–Uvarov (NU). The effect of the potential parameters on the ro-vibrating energy states is discussed in several values of the vibrational and rotational quantum numbers. Moreover, the validity of the method is tested with previous models called the semiclassical (SC) procedure and the quantum mechanical (QM) method. The obtained results are applied to the molecules H₂ and Ar₂.     

Experimental investigation of radiocesium sorption on ceramic clay using a batch method

In this study, radiocesium sorption on ceramic clay was investigated as a function of particle size and initial ¹³⁷Cs concentration using a batch method. Ceramic clay samples taken from the Sö?üt(?nisar) clay deposit were composed of kaolinite, dickite and quartz. The equilibrium time and the liquid–solid ratio were determined as 60 min and 250 mL g^?1, respectively. The distribution coefficients (K _d) for variable liquid–solid ratio and the percentage adsorption (P _Ad) were calculated. The values of K _d and P _Ad ranged from 483 to 3165 mL g^?1 and 34–93%, respectively. The K _d and P _Ad values increased with increasing particle size, but decreased with increasing initial concentration. The sorption data were interpreted in terms of a Langmuir isotherm. The results indicated that the Sö?üt(?nhisar) ceramic clay has good sorption capacity for cesium.     

Physicochemical studies on bioactive Cr(III) coordination compounds with esters of hydrazine carboxylic acid as hetero donor ligands

Reaction between hydrazine derivative ligands (HrzE) or (HrzB) and chromium salt in 1:2 (metal:ligand) molar ratio yielded monometallic trivalent coordination compounds with general formula [Cr(HrzE)₂X₂]X and [Cr(HrzB)₂X₂]X, where (HrzE) = hydrazine carboxylic acid ethyl ester, (HrzB) = hydrazine carboxylic acid tert-butyl ester, and X = Cl^?, Br^? or F^?. Elemental analysis, conductivity measurements, magnetic moment measurements, and various spectroscopic techniques, viz. infrared, ultraviolet–visible, and electrospray ionization mass spectrometry, were applied to illustrate the structure and composition of the coordination compounds. Analytic and conductivity results were consistent with 1:1 electrolytic behavior and the proposed formulas of the coordination compounds. Electronic absorption data and magnetic moment parameters indicated octahedral geometry surrounding the metal ion in the coordination compounds. The in vitro antimicrobial behavior of the ligands and coordination compounds was screened using four bacterial strains (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Salmonella typhi) and two fungal strains (Candida parapsilosis and Saccharomyces cerevisiae). The results indicated improved activity of the coordination compounds compared with the free ligands against the studied bacteria and fungi.     

Dye removal using 4A-zeolite/polyvinyl alcohol mixed matrix membrane adsorbents: preparation,characterization, adsorption,kinetics, and thermodynamics

In pursuit of improving performance of the methylene blue adsorption process, the potential of a novel 4A-zeolite/polyvinyl alcohol (PVA) membrane adsorbent was investigated. Adding 4A-zeolite particles to the PVA membrane adsorbent provided an effective structure for the adsorptive membrane in dye removal processes. Effect of zeolite content was also studied via synthesis of different mixed matrix membrane adsorbents (MMMAs) with 5, 10, 15, and 20 wt% 4A-zeolite content. Morphology of MMMAs was analyzed by scanning electron microscope and the intermolecular interactions were determined by Fourier transform infrared spectroscopy. X-ray diffraction was performed to determine the crystal structure of MMMAs. For the sake of finding optimum condition, the adsorption capacity was examined at various operating parameters, such as contact time, temperature, pH, and initial concentration. The maximum value of the adsorption capacity (q _e) of 41.08 mg g^?1 and the highest removal efficiency of 87.41 % were obtained by applying 20 wt% loading of 4A-zeolite. The experimental data were fitted well with the Freundlich adsorption isotherm model (R ² = 0.9917) compared with the Langmuir (R ² = 0.9489) and the Tempkin (R ² = 0.8886) adsorption isotherm models, and the adsorption kinetic data verified the best fitting with the pseudo-second-order model (R ² = 0.9999). The estimated data for Gibb’s free energy (ΔG°) showed that the adsorption process is spontaneous at lower temperature values and non-spontaneous at higher temperature values. Other evaluated thermodynamic parameters such as changing in enthalpy (ΔH°) and entropy (ΔS°) revealed that the adsorption process is exothermic with an increase in orderliness at the solid/solution interface.     

Dissolved air flotation for treating wastewater of the nuclear industry: preliminary results

Preliminary testing of dissolved air flotation (DAF) for wastewater treatment is presented. A combined coagulation-flocculation/DAF column system is used to remove oil and ⁶⁰Co from nuclear industry wastewater. In this work, operational conditions and coagulant/flocculant concentrations are optimized by varying pH. Determinations of air-solids ratio (G/S), retention time (θ), pressure (P), volume of depressurized air–water mixture (V), turbidity and ⁶⁰Co concentrations are reported. The effect of the treatment on the efficiency of separation of oily residues is also discussed. The results establish that the coagulant/flocculant system, formed by a modified polyamine (25 mgL^?1) and a slightly cationic polyacrylamide (1.5 mgL^?1), under specific operational conditions (pH = 7, mixing intensity Im₁ = 300 s^?1 and Im₂ = 30 s^?1), allowed the destabilization of colloidal matter, resulting in resistant flocs. It was concluded that by using G/S = 0.3, θ = 15 min, P = 620 kPa and V = 0.0012 m³, the greatest percentage removals of oil, turbidity, total cobalt and ⁶⁰Co were obtained. These preliminary results then show that dissolved air flotation represents a good alternative for treatment of nuclear industry wastewater contaminated with radionuclides.     

Modeling of fixed-bed column studies for removal of cobalt ions from aqueous solution using <Emphasis Type="Italic">Chrysanthemum indicum</Emphasis>

The present study investigates the adsorption capability of raw and biochar forms of Chrysanthemum indicum flowers biomass to remove cobalt ions from aqueous solution in a fixed-bed column. Column adsorption experiments were conducted by varying the bed height (1.0, 2.0, 3.0 cm), flow rate (1.0, 2.5, 5.0 mL min^?1) and initial cobalt ion concentration (25, 50, 75 mg L^?1) to obtain the experimental breakthrough curves. The adsorption capacity of the raw and biochar forms of C. indicum flowers were found to be 14.84 and 28.34 mg g^?1, respectively, for an initial ion concentration of 50 mg L^?1 at 1.0 cm bed height and 1.0 mL min^?1 flow rate for Co (II) ion adsorption. Adam–Bohart, Thomas and Yoon–Nelson models were applied to the experimental column data to analyze the column performance. The Thomas model was found to best represent the column data with the predicted and experimental uptake capacity values correlating well and with higher R ² values for all the varying process parameters. Desorption studies revealed the suitability of the adsorbents for repeated use up to four adsorption–desorption cycles without significant loss in its efficiency. It can thus be inferred from the fixed-bed column studies that C. indicum flowers can suitably be used as an effective adsorbent for Co (II) ion removal from aqueous solution on a higher scale.     

Saw-sedge <Emphasis Type="Italic">Cladium mariscus</Emphasis> as a functional low-cost adsorbent for effective removal of 2,4-dichlorophenoxyacetic acid from aqueous systems

For the first time in the published literature, a study is described concerning the use of the saw-sedge Cladium mariscus (C. mariscus) for adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous systems. Among the experiments carried out, the elemental composition of C. mariscus was determined (C = 48.0 %, H = 7.1 %, N = 0.95 %, S = 0.4 %), FTIR spectroscopic analysis was performed to confirm the chemical structure of the adsorbent, and porous structure parameters were measured: BET surface area (A _BET  = 0.6 m²/g), total pore volume (V _p  = 0.001 cm³/g) and average pore size (S _p  = 6.6 nm). It was shown that the effectiveness of removal of 2,4-D from aqueous systems using C. mariscus depends on parameters of the process: contact time, system pH, mass of sorbent, and temperature. Maximum adsorption was attained for a solution at pH = 3. Further increase in the alkalinity of the tested systems led to a reduction in the effectiveness of the process. The kinetic of adsorption of 2,4-D by C. mariscus was also determined, and thermodynamic aspects were investigated. The experimental data obtained correspond to a pseudo-second-order kinetic model of type 1. Additionally the negative values obtained for ΔHº indicate that the process is exothermic, and the negative values of ΔGº show it to be spontaneous. As the temperature of the system increases the spontaneity of adsorption is reduced, in accordance with the exothermic nature of the process.     

Ethanol Production from Starch Hydrolyzates using <Emphasis Type="Italic">Zymomonas mobilis</Emphasis> and Glucoamylase Entrapped in Polyvinylalcohol Hydrogel

The glucoamylase from Aspergillus niger, immobilized into poly(vinylalcohol) hydrogel lens-shaped capsules LentiKats®, was used for simultaneous saccharification and fermentation (SSF) with Zymomonas mobilis in free form. This system was stable in both the repeated batch and continuous mode of SSF. The microorganism was found to adsorb on the capsules with immobilized enzyme. This increased the ethanol productivity of the repeated batch system with 5% w/v of immobilized glucoamylase almost 2.1 times (7.2 g l^?1 h^?1) compared to free enzyme–free microorganism system (3.5 g l^?1 h^?1). The continuous SSF with the immobilized glucoamylase (11.5% w/v) tested for 15 days had productivity 10 g l^?1 h^?1, which is comparable to continuous experiments on semi-defined glucose medium (10 g l^?1 h^?1). These two systems were stable in both glucoamylase activity and microorganism productivity.     

Growth of Cyanobacteria: Optimization for Increased Carbohydrate Content

Growths of Lyngbya limnetica and Oscillatoria obscura were investigated at varying pH, light intensity, temperature, and trace element concentration with a view to optimize these parameters for obtaining the maximum carbohydrate content. The maximum growth for both strains was obtained at pH 9.0 and temperature 20 ± 3 °C using a light intensity of 68.0 μmol m^?2 s^?1 with continuous shaking. Growth under the nitrogen starvation condition affected the carbohydrate content more compared to the phosphorus starvation, and maximum concentrations were found as 0.660 and 0.621 g/g of dry biomass for L. limnetica and O. obscura, respectively. Under the optimized nitrogen-rich conditions, the specific growth rates for the two strains were found to be 0.187 and 0.215 day^?1, respectively. The two-stage growth studies under nitrogen-rich (stage I) followed by nitrogen starvation (stage II) conditions were performed, and maximum biomass and carbohydrate productivity were found as 0.088 and 0.423 g L^?1 day^?1 for L. limnetica. This is the first ever attempt to evaluate and optimize various parameters affecting the growth of cyanobacterial biomass of L. limnetica and O. obscura as well as their carbohydrate contents.     

Conducting materials prepared by the oxidation of <Emphasis Type="Italic">p</Emphasis>-phenylenediamine with <Emphasis Type="Italic">p</Emphasis>-benzoquinone

p-Phenylenediamine was oxidized with p-benzoquinone in the aqueous solutions of methanesulfonic acid (MSA). The conductivity of the products increased with increasing concentration of MSA from 1.5?×?10^?12 S cm^?1 in 0.1 M MSA up to 3.4?×?10^?4 S cm^?1 in 5 M MSA. The low-molecular-weight products are basically composed of one p-benzoquinone and two p-phenylenediamine molecules. Their molecular structure is discussed on the basis of mass, Fourier-transform infrared, Raman, NMR and electron paramagnetic resonance (EPR) spectroscopies. The formation of 2,5-di(p-phenylenediamine)-p-benzoquinone protonated with methanesulfonic acid best complies with the information provided by spectroscopic techniques. Its conversion to hydroquinone tautomer explains the formation of unpaired spins observed by EPR and their potential contribution to the conduction.     

Theoretical and experimental study of the catalytic cathodic stripping square-wave voltammetry of chromium species

The electrocatalytic mechanism of Cr(III) reduction in the presence of diethylenetriaminepentaacetic acid (DTPA) and nitrate ions is studied theoretically and experimentally by using stripping square-wave voltammetry (SWV). Experimental curves are in excellent agreement with theoretical profiles corresponding to a catalytic reaction of second kind. This type of mechanism is equivalent to a CE mechanism, where the chemical reaction produces the electroactive species. Accordingly, the reaction of Cr(III)–H₂O–DTPA and \( {\mathrm{NO}}_3^{-} \) would produce the electroactive species Cr(III)–NO₃–DTPA and this last species would release \( {\mathrm{NO}}_2^{-} \) to the solution during the electrochemical step. In this regard, the complex of Cr(III)–DTPA would work as the catalyzer that allows the reduction of \( {\mathrm{NO}}_3^{-} \) to \( {\mathrm{NO}}_2^{-} \). Furthermore, it was found that the electrochemical reaction is quite irreversible, with a constant of k _s?=?9.4?×?10^?5 cm s^?1, while the constant for the chemical step has been estimated to be k _chem?=?1.3?×?10⁴ s^?1. Considering that the equilibrium constant is K?=?0.01, it is possible to estimate the kinetic constants of the chemical reaction as k ₁?=?1?×?10² s^?1 and k _?1?=?1.29?×?10⁴ s^?1. These values of k ₁ and k _?1 indicate that the exchange of water molecules by nitrate is fast and that the equilibrium favors the complex with water. Also, a value for the formal potential E°’?≈??1.1 V was obtained. The model used for simulating experimental curves does not consider the adsorption of reactants yet. Accordingly, weak adsorption of reagents should be expected.     

Fabrication and characterisation of a mixed oxide-covered mesh electrode composed of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> and its capability of generating hydroxyl radicals during the oxygen evolution reaction in electrolyte-free water

A mixed oxide-covered mesh electrode composed of NiCo₂O₄ (MOME-NiCo₂O₄) was prepared on a stainless-steel substrate using thermal decomposition (slow-cooling rate method). Surface, bulk and electrochemical properties of MOME were studied using different techniques, namely scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV) with determination of the electrochemical porosity (?) and morphology factor (φ) parameters, quasi-stationary polarisation curves (PC) and electrochemical impedance spectroscopy (EIS). SEM images revealed a good coverage of the metallic wires by a compact oxide layer (absence of cracks). XRD analysis confirmed the formation of the spinel NiCo₂O₄ with the presence of NiO. The ‘in situ’ surface parameters denoted as ? and φ exhibited values of 0.39 and 0.33, respectively, revealing that the electrochemically active surface area is mainly confined to the ‘outer/external’ surface regions of the oxide layer. The PC was characterised by two Tafel slopes distributed in the low (b ₁ = 46 mV dec^?1) and high (b ₂ = 59 mV dec^?1) overpotential domains. The corresponding apparent exchange current densities were j ₀₍₁₎ = (3.43 ± 0.11) × 10^?6 A cm^?2 and j ₀₍₂₎ = (6.70 ± 0.08) × 10^?6 A cm^?2, respectively. The EIS study accomplished in the low-overpotential domain revealed a Tafel slope (b ₁) of 51 mV dec^?1. According to the spin-trapping reaction using N,N-dimethyl-p-nitrosoaniline (RNO), the MOME-NiCo₂O₄ electrode exhibited good performance for the generation of weakly adsorbed hydroxyl radicals (HO^?) during the OER in electrolyte-free water.     

Synthesis,antifungal and insecticidal activity of novel [1,2,4]triazolo[4,3-<Emphasis Type="Italic">a</Emphasis>]pyridine derivatives containing a sulfide substructure

A series of [1,2,4]triazolo[4,3-a]pyridine derivatives bearing a sulfide substructure was designed, synthesized and characterized via ¹H·NMR, ¹³C·NMR, IR and elemental analyses. Bioassay Results indicated some of the derivatives displayed good fungicidal activity on Rhizoctonia cerealis, moderated insecticidal activity against Plutella xylostella and good insecticidal activity on Helicoverpa armigera. The inhibitory effects of compounds 4g and 4u against Rhizotonia cerealis were 70.9% at 50 μg mL^?1; the IC₅₀ values of compounds 4d and 4s against Plutella xylostella were 43.87 and 50.75 μg mL^?1, respectively. And the IC₅₀ values of compounds 4d, 4q, and 4s on Helicoverpa armigera were 58.3, 77.14 and 65.31 μg mL^?1, respectively, which were better than that of commercial chlorpyrifos (103.77 μg mL^?1).