ULTRASOUND-ASSISTED N-ALKYLATION OF PHTHALIMIDE UNDER PHASE-TRANSFER CATALYSIS CONDITIONS AND ITS KINETICS

In this work, N-butylation of potassium phthalimide was carried out under ultrasonic-assisted phase-transfer catalysis condition using n-bromobutane as an alkylating agent. The mechanism of the solid-liquid reaction of alkyl halide and potassium salt of phthalimide in an organic solvent was verified in this work. The kinetics of the reaction depends on the amount of catalyst, agitation speed, type of quaternary ammonium salts, volume of water, type of organic solvent, volume of organic solvents, temperature, and the frequency of the ultrasound. Five different onium salts were examined for the reaction and tetrahexylammonium bromide showed maximum catalytical activity. An improvement of the reaction outcome (yield and reaction time) was achieved through the immersion of the reactor into an ultrasound bath. The rate of the reaction is two times faster under ultrasonic condition (k_app = 10.7 × 10^?3 min^?1) than silent condition (k_app = 5.5 × 10^?3 min^?1) and is five times faster when the reaction is carried out in acetonitrile medium than in cyclohexane medium. The reaction is very fast under anhydrous condition. Based on the experimental data, a rational mechanism for the reaction is proposed.     

Photo-fenton and UV photo degradation of naphthalene with zero- and two-valent iron in the presence of persulfate

An initial set of 12 kinetic experiments was carried out to remove naphthalene from an aqueous effluent by photo-Fenton involving Fe⁰ and Fe²⁺ at two different concentrations of H₂O₂ (150 and 300?mg?L^?1) and three different pHs (3, 5, and 7) (2²×3¹ experiments). The rate constants (k) for the reaction of naphthalene degradation by involving Fe²⁺ as reactant were in general higher than those with Fe⁰, but the use of Fe²⁺ increased the concentration of naphthalene at equilibrium (C_e) when compared with the same response obtained with Fe⁰ at analogous conditions. A second set of twelve kinetic experiments of photo-Fenton degradation was also performed with persulfate as additive at the conditions already reported, but at a constant concentration of H₂O₂ of 150?mg?L^?1 (2¹×3¹ experiments with NaCl +2¹×3¹ experiments without NaCl). In almost all the runs in which only the source of iron was varied, k from the kinetic data involving Fe²⁺ was higher than that involving Fe⁰, but no difference was observed in terms of C_e that was always zero. The addition of persulfate to treat the effluent either containing or not containing salt enhanced the chemical kinetics, and shifted the equilibrium toward the full removal of naphthalene. A final set of nine experiments of UV photo degradation of naphthalene by involving persulfate without iron, with Fe⁰ and Fe²⁺ in the pH range from 3 to 7 (3² experiments) mainly showed that the use of H₂O₂ may be avoided to remove rapidly and completely naphthalene from wastewater.     

Degradation of Carbamazepine by Photo-assisted Ozonation: Influence of Wavelength and Intensity of Radiation

This article presents the results of an investigation into the function of UV in a photo-assisted ozonation process for treatment of carbamazepine (CBZ) in treated domestic wastewaters. Experiments were conducted on synthetic spiked water and secondary treated municipal wastewater. Degradation of CBZ was studied for various combination of O₃ dosage ranging from 4.8 to 14.4 mg/h and UV intensities with varying intensity and wavelength (UVC: λ = 254 nm and UVA: 352 nm). In synthetic spiked water, CBZ was degraded to below detectable limits within 0.5 min for ozone dose of 14.4 mg/h. The rate of degradation of CBZ increased exponentially with increase in ozone dose following a zero-order rate at each dose level. The degradation rate of CBZ in wastewater was slower compared to deionized water (DI) water by 40–75% for various doses of ozone, presumably due to the presence of organic matter remaining in treated wastewater. Optimal UV intensities for UVA and UVC were obtained as 0.62 and 0.82 mW/cm² for all doses of ozone in synthetic spiked water samples and UV intensities beyond this resulted in lower rates of degradation of CBZ. For photo-assisted ozonation with ozone doses of 9.6 and 14.4 mg/L, rate constants were two times higher for UVA irradiations as compared to UVC irradiation. Contrary to observations in DI water, experiments in wastewater showed increase in rate of degradation with higher UV intensities. Overall, photo-assisted ozonation was found to be appropriate for both water and wastewater treatment by exploiting the benefit of direct attack of ozone and of produced ^?OH radicals to yield a greater extent of mineralization of CBZ.     

Synthesis and Characterization of pH-Responsive Organic–Inorganic Hybrid Material with Excellent Catalytic Activity

Poly(N-isopropylmethacrylamide-co-methacrylic acid) [p(NipAam-Mac)] microgels were synthesized and used as microreactors to fabricate silver nanoparticles. Pure and hybrid microgels were characterized using Ultraviolet–Visible (UV/Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy and transmission electron microscopy (TEM). Catalytic activity of hybrid microgels and mechanism of catalysis by this system was explored using different reaction conditions. At the same temperature, apparent rate constant (k_app) was found to be varied from 0.0414 to 0.7852 min^?1 by increasing the concentration of NaBH₄ from 2.49 to 22.41 mM at constant concentration of substrate and catalyst. However upon extra increase in concentration of NaBH₄ from 22.41 to 37.35 mM reduced the value of k_app to 0.2178 min^?1. Likewise, the value of k_app was found to be increased from 0.1242 to 0.5495 min^?1 with increasing the concentration of 4-nitrophenol [Para-nitrophenol (p-Np)] from 0.063 to 0.079 mM keeping other parameters constant. Further increase in concentration of p-Np caused decline in the value of k_app. Kinetic data reveals that catalytic reduction of p-Np obeys Langmuir–Hinshelwood mechanism and p-Np is converted to p-Ap on the surface of the silver nanoparticles passing through various reaction intermediates.     

Efficiency and Mechanism of Ciprofloxacin Hydrochloride Degradation in Wastewater by Fe3o4/Na2S2O8

ABSTRACT

The nanosized Fe₃O₄ catalyst was synthesized via a modified reverse coprecipitation method and characterized by means of a scanning electron microscope (SEM) and an X-ray diffraction (XRD) analysis instrument. The degradation efficiency and reaction rate of Fe₃O₄ in activating sodium persulfate used to degrade ciprofloxacin were determined from the catalyst dosage, oxidant concentration, and initial pH. The results showed that under the optimum conditions of a catalyst dosage of 2.0 g·L^?1, a sodium persulfate concentration of 1.0 g·L^?1, and an initial pH of 7, the degradation rate of ciprofloxacin was 93.73%, the removal rate of total organic carbon was 78%, and the first-order reaction constant was 0.06907 min^?1 within 40 min. It was also demonstrated that the reactive oxygen species in the Fe₃O₄/sodium persulfate catalytic system were mainly composed of SO₄^– and supplemented by OH· and HO₂· using probe compounds such as ethanol, tertiary butanol, and benzoquinone.     

Sorption of Silver Cations by Natural and Na-Exchanged Mordenite

Sorption of Ag⁺ by natural mordenite and its Na-exchanged form was investigated by the batch method. Maximum Ag⁺ uptake was observed at initial pH > 3.0 and contact time 90 min. The kinetic data fitted very well to the pseudo-second-order rate model with values of k ₂ from 37.31 to 0.487 and 48.32 to 0.491 g/meq min for the natural and Na-exchanged mordenite, respectively. The Langmuir model is in good correlation with the isotherm data up to initial concentration of 500 mg Ag⁺/L (q _m = 57.41 (natural sample) and 87.72 mg/g (Na-exchanged sample). The obtained data are promising for clean-up of polluted water.     

Chemometric study of thermal treatment effect on the P25 photoactivity for degradation of tartrazine yellow dye

In the present work, a chemometric study was carried out using a central composite rotatable design (CCRD) to evaluate the effect of thermal treatment on the P25 photoactivity for degradation of tartrazine dye. The factors investigated for thermal treatment were: temperature, heating rate and heating time, and the experimental design response was the photodegradation constant (k_app). The response surface methodology (RSM) was employed to obtain the material with higher k_app value for tartrazine photodegradation, under UV radiation, and investigate the interactions between factors of thermal treatment. The P25 used as precursor, as well as the obtained material from the optimized conditions (TTP_op), and the material with worst photocatalytic activity (TTP-17) were characterized from the N₂ physiosorption, FT-IR, SEM, XRD, DSC/TGA and PAS. The TTP_op was obtained under conditions of temperature of 298?°C, heating rate of 10?°C?min^?1 and heating time of 177?min. TTP_op showed k_app value of 25.7, while P25 and TTP-17 presented k_app values of 20.2 and 10.0, respectively.     

Impact of aluminum oxide nanopowder on thermal,optical and surface properties of polysiloxane-aluminum oxide composites as elastomeric thermal pad for light emitting diode application

ABSTRACT

Virgin polysiloxane and aluminum oxide nanopowder (10%–50%) reinforced polysiloxane composite films were prepared and its thermal, optical, surface properties were investigated. Polysiloxane/aluminum oxide (Al₂O₃) (50%–50%) composite film sample exhibit high thermal conductivity (k – 0.26 W/mK) and UV absorption, decreased junction temperature (ΔT_J = 25.69°C at 700 mA) and thermal resistance (?R_th-tot = 12.41 K/W at 700 mA) compared to virgin polysiloxane film. Overall, the prepared composites can be used as an alternate elastomer thermal pad for efficient thermal management as well as UV blocking encapsulant for future UV-free LED application development.     

Complete mineralization of the antibiotic amoxicillin by electro-Fenton with a BDD anode

On April 30, 2014, the World Health Organization’s first global report on the presence of antibiotics in waters focused on their negative consequences, which may include the growth of microorganisms with antimicrobial resistance. The β-lactam antibiotic amoxicillin (AMX) is widely used in human and veterinary medicine, and it has been recently detected in sewage treatment plants and effluents. In this paper, the degradation of acidic aqueous solutions of AMX by electro-Fenton process has been studied at constant current. Experiments have been performed in an undivided cell equipped with a carbon-felt cathode and a Pt or boron-doped diamond (BDD) anode. In such systems, the organic molecules are mainly oxidized by hydroxyl radical (^?OH) simultaneously formed on the anode surface from water oxidation as well as in the bulk from Fenton’s reaction between Fe²⁺ catalyst and electrogenerated H₂O₂. The decay and mineralization of AMX was monitored by means of high performance liquid chromatography (HPLC) and TOC measurements. The evolution of the concentration of the final aliphatic carboxylic acids and inorganic ions like ammonium, nitrate and sulfate was assessed by HPLC and ion chromatography, respectively. The effect of the anode material, initial AMX concentration and current density was thoroughly studied. The AMX decay always followed a pseudo-first-order kinetics using either Pt or BDD, and the apparent rate constant increased with applied current. A quicker mineralization was reached with BDD because of the larger production of active ^?OH. The absolute rate constant between hydroxyl radical and AMX determined by the competition kinetics method using p-hydroxybenzoic acid as the reference compound was found to be (2.02 ± 0.01) × 10⁹ M^?1 s^?1.     

Active Species of Nonheme Iron and Manganese-Catalyzed Oxidations

The intense catalytic and spectroscopic studies of the last decade provided important insights into the mechanisms of some nonheme iron-catalyzed oxidations with hydrogen peroxide. For manganese-based analogs, direct spectroscopic data on the structure of the reactive intermediates are scarce; mechanistic proposals are mainly based on catalytic studies and on analogy with iron systems. Herein, these data are summarized and contemporary mechanistic landscape is presented. We have mainly focused on iron and manganese complexes with N ₄-donor aminopyridine ligands, which are one of the most successful catalysts for chemo-, regio- and enantioselective transformations of organic substrates with H₂O₂ and H₂O₂/CH₃COOH as oxidants. The low-spin Fe^III–OOH, Fe^IV = O and Fe^V = O species can be spectroscopically trapped in the catalyst systems studied, low-spin Fe^V = O intermediate being the most likely key oxidizing agent.     

Effect of Pulsed Electric Field and Osmotic Dehydration Pretreatment on the Convective Drying of Carrot Tissue

The influence of pulsed electric field (PEF) and subsequent centrifugal osmotic dehydration (OD) on the convective drying behavior of carrot is investigated. The PEF was carried out at an intensity of E = 0.60 kV/cm and a treatment duration of t _PEF  = 50 ms. The following centrifugal OD was performed in a sucrose solution of 65% (w/w) at 40°C for 0, 1, 2, or 4 h under 2400 × g. The drying was performed after the centrifugal OD for temperatures 40–60°C and at constant air rate (6 m³/h).

With the increase of OD duration the air drying time is reduced spectacularly. The dimensionless moisture ratio Xr = 0.1 is reached for PEF-untreated carrots after 370 min of air drying at 60°C in absence of centrifugal OD against 90 min of air drying after the 240 min of centrifugal OD. The PEF treatment reduces additionally the air drying time. The total time of dehydration operations can be shortened when OD time is optimized. For instance, the minimal time required to dehydrate untreated carrots until Xr = 0.1 is 260 min (120 min of OD at 40°C and 140 min of drying at 60°C). It is reduced to 230 min with PEF-treated carrots.

The moisture effective diffusivity D _eff is calculated for the convective air drying based on Fick's law. The centrifugal OD pretreatment increases drastically the value of D _eff . For instance, 4 h of centrifugal OD permitted increasing the value of D _eff from 0.93 · 10^?9 to 3.85 · 10^?9 m²/s for untreated carrots and from 1.17 · 10^?9 to 5.10 · 10^?9 m²/s for PEF-treated carrots.     

Single step modification of micrometer-sized polystyrene particles by electromagnetic polyaniline and sorption of chromium(VI) metal ions from water

This article describes a single-step reproducible approach for the surface modification of micrometer-sized polystyrene (PS) core particles to prepare electromagnetic PS/polyaniline–Fe₃O₄ (PS/PANi–Fe₃O₄) composite particles. The electromagnetic PANi–Fe₃O₄ shell was formed by simultaneous seeded chemical oxidative polymerization of aniline and precipitation of Fe₃O₄ nanoparticles. The weight ratio of PS to aniline was optimized to produce core–shell structure. PS/PANi–Fe₃O₄ composite particles were used as adsorbent for the removal of Cr(VI) via anion-exchange mechanism. The composite particles possessed enough magnetic property for magnetic separation. The adsorption was highly pH dependent. Adsorption efficiency reached 100% at pH 2 in 120 min when 0.05 g of composite particles was mixed with 30 mL 5 mg L⁻¹ Cr(VI) solution. The adsorption isotherm fitted best with Freundlich model and maximum adsorption capacity approached 20.289 mg g⁻¹ at 323 K. The prepared composite was found to be an useful adsorbent for the removal of soluble Cr(VI) ions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47524.     

Degradation of amoxicillin in aqueous solution using nanolepidocrocite chips/H2O2/UV: Optimization and kinetics studies

Degradation of amoxicillin (AMX) by nanolepidocrocite chips/H₂O₂/UV method as a new photo-Fenton like process was investigated and optimized by response surface methodology (RSM). The optimal conditions were initial AMX concentration of 10 mg l⁻¹ and initial H₂O₂ concentration of 60 mg l⁻¹ at pH of 2 under UV radiation for 120 min. The general photo-Fenton process mechanism was applied to propose a new kinetic model for AMX degradation. According to this model, the reaction constant between AMX and OH was obtained 4.55 × 10⁵ M⁻¹ s⁻¹. Also, nanolepidocrocite showed good catalytic activity even after four successive degradation cycles.     

Chemical Properties of 2‐Bromodecanoic Acid

Abstract

Some chemical equilibrium constants for 2‐bromodecanoic acid were investigated. The dimerization constant of 2‐bromodecanoic acid, k₂ =278 M^?1, in tert‐butylbenzene was first derived from IR spectroscopy measurements. Secondly, the distribution coefficient, k _d =799, was found by combining the value of k₂ with distribution data obtained from solvent extraction experiments evaluated with the aid of neutron activation analysis. Finally the dissociation constant, k _a =3.18 ?10^?3 M, was estimated from two‐phase titrations. A theoretical calculation was made based on the obtained constants and this calculation was validated by a second solvent extraction experiment that gave a good correspondence between calculated and experimental values.     

Electrical Properties of Triethylene Glycol Stabilized MnxCo1-xFe2O4 Nanoparticles

We reported on the synthesis and analysis of the composition, micro-structure, ac–dc conductivity performance and dielectric permittivity of triethylene glycol (TEG) stabilized Mn_xCo_1-xFe₂O₄ nanoparticles obtained by polyol method. Crystallite size from XRD and particle size from TEM micrographs are consistent with each other. Conductivity measurements were performed to investigate the influence of the coating with TEG on the conduction characteristics of Mn_xCo_1-xFe₂O₄ NP’s. The frequency-dependency of the ac conductivity shows electrode polarization effect. The dc conductivity is strongly temperature dependent and shows maximum conductivity of about 5 × 10^?5 S cm^?1 for x = 1.0 at 120 °C. Analysis of dielectric permittivity functions suggests that ionic and polymer segmental motions are strongly coupled.     

Structural modification of aminoclay for catalytic applications

Abstract

An eco-friendly catalyst system was synthesized using three step reaction. The Cu nanoparticles bridged aminoclay catalyst was analyzed using various analytical techniques. The structure of the catalyst was confirmed by FTIR and XRD. The synthesized catalyst system was used for the reduction of p-nitrophenol (NP), Cr(VI), and fluorescein (Flur) dye individually, as well as in their mixture forms. The k_app value was computed to access the efficiency of the catalyst. The results indicated that the k_app value of the individual system is higher than that of the mixture systems due to the absence of the complex formation reaction. The catalytic performance of the catalyst was also tested for the Schiff base (SB) formation between poly(ethyleneglycol) (PEG) and aniline (ANI) in an oxygen atmosphere. The ¹H-NMR spectroscopy result indicates that the present catalyst system produced 86% yield.     

Comparison of two synthesis methods on the preparation of Fe,N-Co-doped TiO2 materials for degradation of pharmaceutical compounds under visible light

In this work, we report the synthesis, characterization and photocatalytic evaluation of visible light active iron-nitrogen co-doped titanium dioxide (Fe³⁺-TiO_2−xN_x) nanostructured catalyst. Fe³⁺-TiO_2−xN_x was synthesized using two different chemical approaches: sol-gel (SG) and microwave (MW) methods. The materials were fully characterized using several techniques (SEM, UV–Vis diffuse reflectance DRS, X-ray diffraction XRD, and X-ray photoelectron spectroscopy XPS). The photocatalytic activity of the nanostructured materials synthesized by both methods was evaluated for the degradation of amoxicillin (AMX), streptomycin (STR) and diclofenac (DCF) in aqueous solution. Higher degradation efficiencies were encountered for the materials synthesized by the SG method, for instance, degradation efficiencies values of 58.61% (SG) and 46.12% (MW) were observed for AMX after 240 min of photocatalytic treatment under visible light at pH 3.5. With STR the following results removal efficiencies were obtained: 49.67% (SG) and 39.90% (MW) at pH 8. It was observed the increasing of degradation efficiencies values at longer treatment periods, i.e., after 300 min of photocatalytic treatment under visible light, AMX had a degradation efficiency value of 69.15% (MW) at pH 3.5, DCF 72.3% (MW) at pH 5, and STR 58.49% (MW) at pH 8.     

Enhanced insulating and piezoelectric properties of BiFeO3-BaTiO3-Bi0.5Na0.5TiO3 ceramics with high Curie temperature

BiFeO₃-BaTiO₃ ceramics are promising lead-free piezoelectric ceramics due to their high piezoelectric properties and high Curie temperature, but their high leakage current density makes the poling difficult. In this study, a decreased leakage current density by three orders of magnitude was obtained in Bi_0.5Na_0.5TiO₃ (BNT) added 0.67BiFeO₃-0.33BaTiO₃ (BF-BT) ceramics. It was found that the largely improved insulating properties benefit from the reduced oxygen vacancies and weak reduction of Fe³⁺ to Fe²⁺ as confirmed by photoluminescence and X-ray photoelectron spectroscopy measurements, thereby contributing to high-temperature and high-field poling. In addition, the introduction of BNT leaded to increased grain size. Due to the grown grains as well as reduced oxygen vacancies and Fe²⁺, enhanced insulating and optimal piezoelectric properties with P_r = 24.2 µC/cm², d₃₃ = 183 pC/N, k_p = 0.28, and T_C = 467°C were achieved in BF-BT-0.05BNT ceramics.     

Degradation study of some pharmaceuticals in commercial formulation by electro-Fenton process using a dimensionally stable anode cathode: Analytical technique,optimization conditions,and energy consumption

The aim of this work was to degrade pharmaceuticals such as amoxicillin (AMX), ceftriaxone (CTX), and Telebrix (TLX) by electro-Fenton (EF) process using a dimensionally stable anode (DSA) cathode, Pt-RuO₂-IrO₂ (PRI). For this purpose, the optimal conditions of degradation, the pseudo-first-order kinetics, the current efficiency, the electrochemical energy consumption (EEC), and the energy cost have been investigated. A spectrophotometric analysis technique has been developed. It is a simple, fast, linear, reliable, and selective technique with LOD = 0.013 g/L and LOQ = 0.04 g/L. The optimum working conditions determined are: Fe²⁺ = 0.2 mM, pH = 3, j = 20 mA/cm², and (Pt, PRI) as electrode pair. Under these conditions, the EF process leads to a conversion of the parent compound. In addition, the degradation of compounds by EF follows pseudo-first-order kinetics. The EEC for the degradation of 1 kg COD of an organic compound is 99.48, 66.86, and 50.32 kWh kg COD⁻¹ for AMX, CTX, and TLX respectively. The energy cost for processing these compounds is $4.92 (AMX), $10.03 (CTX), and $7.55 (TLX) with current efficiencies between 26% and 51%. Ultimately, the EF process using PRI at the cathode can be used for the treatment of real wastewater from health centres under optimal conditions.     

Thermal decomposition of potassium persulfate in aqueous solution at 50°C in an inert atmosphere of nitrogen in the presence of acrylonitrile monomer

The rate of thermal decomposition of persulfate in aqueous solution in the presence of acrylonitrile (AN) monomer (M) and of nitrogen, may be written as: in the concentration range of persulfate (1.8 to 18.0) ×10^-3, and of monomer (M), 0.30 to 1.20, mol dm^-3. It was observed that the pH of the solution containing persulfate and monomer did not alter during polymerization if the monomer concentrations were close to its solubility under the experimental conditions. Conductance of the aqueous solutions of persulfate and monomer was found to decrease during the reactions. In an unbuffered aqueous solution containing only persulfate, however, the pH was found to decrease continuously at 50°C with time, while the conductance of the solution was found to increase. The monomer (AN) had no effect on the glass electrodes of the pH meter in aqueous solutions, and also on the electrodes of the conductivity cell. It has been suggested that the secondary or induced decompositions of persulfate were due to the following elementary reactions: where (M_j^· radicals (j = 1 to 10) are water-soluble oligomeric or polymeric free radicals. k_x and k_y at 50°C have been estimated as 1.70 X 10^-5 and 5.08 × 10³ dm³ mol^-1 s^-1, respectively. By measuring pH of freshly prepared persulfate solutions at 25°C, it is suggested that 0.05–0.30% of persulfate reacts molecularly with water (i.e., hydrolysis), as soon as it (10^-3 to 10^-2 mol dm^-3) is added to distilled water (pH 7.0). This hydrolysis was found to be stopped in dilute sulfuric acid solution (pH 3–4).