Observed Rate Constants Research Articles

Photosensitization of TiO2 microspheres by novel Quinazoline-derivative as visible-light-harvesting antenna for enhanced Rhodamine B photodegradation

Water pollution is one of the global threats severely affecting our planet and human health. Organic textile dyes are one of the common organic water pollutants that are presentient to degradation by traditional physical methods. Semiconductor-assisted photocatalysis is considered a green, efficient, and sustainable technology for wastewater treatment. To maximize the efficient utilization of solar radiation, it is of pivotal significance to explore novel organic molecules to be employed as efficient dye sensitizers for wide-bandgap semiconductors to extend their performance to the Visible-light region. Hence, in this work, we are proposing the design and synthesis of novel structures of QAD molecule as a dye photosensitizer with extended visible light absorptivity due to the extended π–π/n–π conjugations, to promote the performance of TiO2 nanoparticles to the visible-light region and enhance the charge separation. The physicochemical characterizations confirmed the successful synthesis of QAD, TiO2, and QAD/TiO2 samples with the proposed structures. The anchoring of QAD molecules on the surface of TiO2 caused a substantial improvement in the optical characteristics of TiO2 as well as overcoming its common drawbacks by decreasing its bandgap energy to 2.6 eV, a remarkable reduction of PL intensity indicating reducing the e–h recombination and enhancing the charge separation, and creation of efficient visible light-harvesting antenna in the range of 400–600 nm. Besides, the QAD/TiO2 sample achieved a 3-fold enhancement in the observed rate constant of the photodegradation of Rhodamine B dye compared to the bare TiO2. The parameters affecting the photodegradation process were optimized and the sample displayed outstanding stability after 4 consecutive cycles. Finally, the effect of the scavengers was investigated and {mathrm{O}}_{2}^{cdot -} was proposed to be the most reactive species and the mechanism of the enhancement was suggested based on the electron injection from the QAD’s HOMO level to the TiO2’s CB. Finally, this work opens the door for various studies for the investigation of the proposed structures or similar structures in various photocatalytic/biomedical applications.

Cobalt doped nitrogen-vacancies-rich C3N5 with optimizing local electron distribution boosts peroxymonsulfate activation for tetracycline degradation: Multiple electron transfer mechanisms

Heterogeneous photocatalysis coupled with peroxymonosulfate (PMS) activation is considered as an advanced water purification technology for emerging contaminates degradation. In this study, Cobalt (Co) doped nitrogen-vacancies-rich C3N5 photocatalysts (Co/Nv-C3N5) were designed to activate PMS for tetracycline removal. The photo-chemical oxidation system displayed superior advantage, in which the observed rate constant of tetracycline degradation (0.1488 min−1) was 10.86 and 1.82 times higher than that of photo-oxidation and chemical-oxidation systems. Density functional theory calculation results verified the reconstruction of local charge distribution during PMS activation, indicating Co doping and nitrogen-vacancy engineering not only promoted photoelectrons capture, but also boosted electron transfer from the C–N framework to PMS and the generation of active species. Furthermore, several unique multiple electron transfer mechanisms were found in nonradicals (h+, 1O2 and Co(IV)) pathways. Additionally, three possible tetracycline degradation pathways were proposed and the toxicity of the intermediates was evaluated. Overall, the findings from this study provided a novel strategy for developing high-efficient photocatalyst for the rapid degradation of organic pollutants.

Silver-poly(N-isopropylacrylamide-co-2-hydroxyethylmethacrylate) hybrid microgels with excellent catalytic potential

Silver nanoparticles have been loaded in poly(N-isopropylacrylamide-co-2-hydroxyethylmethacrylate) [P(NIPA-HEMA)] microgels through in situ reduction method. Presence of silver nanoparticles in micro-hosts was confirmed by different characterization techniques like UV–Visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), Dynamic light scattering (DLS) and Transmission electron microscopy (TEM). Morphologies of micro-hosts and composite microparticles were clearly shown by microscopic analysis to be core–shell types. Nanoparticles were mainly found in the shell region of micro-hosts due to which high catalytic activity was observed towards reduction of p-nitrophenol (p-NP). Value of observed rate constant of the reaction was evaluated by changing different variables such as concentration of p-NP, NaBH4, catalyst and temperature of the reaction medium. Dependence of catalytic activity upon temperature was observed as tunable and switchable under variation of temperature of the medium. Value of observed rate constant (kob) was found to increase from 0.127 per min to 0.232 per min as the temperature (T) increased from 21 °C to 30 °C. Then further rise in temperature dropped the rate constant value to 0.153 per min because of volume phase transition in polymeric network. Further increase in kob with T rise was according to Arrhenius behavior. The positive activation enthalpy (ΔH* = +49641.23 Jmol−1) and positive activation entropy (ΔS* = +70.43 Jmol−1 K−1) indicate that formation of activated complex is an entropy driven endothermic process. P(NIPA-HEMA)-Ag has potential to be used as an efficient catalytic system for degradation of toxic chemicals.

Studies on the Effect of Lipofectamine and Cell-Penetrating Peptide on the Properties of 10-23 DNAzyme.

Cationic polymeric materials and cell-penetrating peptides (CPPs) were often used as the delivery vectors in the evaluation of nucleic acid therapeutics. 10-23 DNAzyme is a kind of potential antisense therapeutics by catalytic cleavage of the disease-related RNAs. Here, lipofectamine 2000 and Tat peptide were evaluated for their effect on the catalytic activity of 10-23 DNAzyme, with the observed rate constant, thermal stability, CD spectra, and PAGE analysis, with a duplex DNA mimicking DNAzyme-substrate as a control. It was shown that the cationic carriers had a negative effect on the catalytic performance of the 10-23 DNAzyme. Significantly, the destabilizing effect of the cationic carriers on the duplex formation was noteworthy, as a duplex formation is an essential prerequisite in the silencing mechanisms of antisense and RNAi.

How Pendant Groups Dictate Energy and Electron Transfer in Perovskite–Rhodamine Light Harvesting Assemblies

Energy and electron transfer processes allow for efficient manipulation of excited states within light harvesting assemblies for photocatalytic and optoelectronic applications. We have now successfully probed the influence of acceptor pendant group functionalization on the energy and electron transfer between CsPbBr3 perovskite nanocrystals and three rhodamine-based acceptor molecules. The three acceptors─rhodamine B (RhB), rhodamine isothiocyanate (RhB-NCS), and rose Bengal (RoseB)─contain an increasing degree of pendant group functionalization that affects their native excited state properties. When interacting with CsPbBr3 as an energy donor, photoluminescence excitation spectroscopy reveals that singlet energy transfer occurs with all three acceptors. However, the acceptor functionalization directly influences several key parameters that dictate the excited state interactions. For example, RoseB binds to the nanocrystal surface with an apparent association constant (Kapp = 9.4 × 106 M-1) 200 times greater than RhB (Kapp = 0.05 × 106 M-1), thus influencing the rate of energy transfer. Femtosecond transient absorption reveals the observed rate constant of singlet energy transfer (kEnT) is an order-of-magnitude greater for RoseB (kEnT = 1 × 1011 s-1) than for RhB and RhB-NCS. In addition to energy transfer, each acceptor had a subpopulation of molecules (∼30%) that underwent electron transfer as a competing pathway. Thus, the structural influence of acceptor moieties must be considered for both excited state energy and electron transfer in nanocrystal-molecular hybrids. The competition between electron and energy transfer further highlights the complexity of excited state interactions in nanocrystal-molecular complexes and the need for careful spectroscopic analysis to elucidate competitive pathways.

New insight into the enhanced ozonation of malodorous compounds by Cu(II): Inhibiting the formation of free radicals to promote ozone utilization.

Metal-enhanced ozonation can greatly improve the decay of organic matter; however, whether this method benefits the decay of malodorous compounds or not and the possible mechanism are not well understood. In this study, nine typical malodorous compounds were selected to reveal that Cu(II)-enhanced ozonation can greatly promote the decay of fatty amines because of the direct ozone oxidation, which was enhanced to promote ozone utilization. Moreover, trace Cu(II) can amplify the observed rate constants of dimethylamine and trimethylamine for 48.9% and 155.7%, respectively, and Cu(II) dosage was the determining factor using response surface methodology to investigate the interactions between initial pH, Cu(II) dosage and ozone dosage. These results demonstrated that the formation of •OH and O2•- was inhibited rather than promoted, which was quite different from some previously reported Cu(II)-enhanced ozonation counterparts. Moreover, the enhanced effect of trace Cu(II) was exhibited in both single and complex malodorous compounds. The conversion pathway of nitrogen and sulfur elements was clarified, with the targeted mineralization of nitrogen of nitrogen-containing malodorous compounds into NO3-N and the odor characteristics of sulfur-containing malodorous compounds disappeared. These findings provided new insight for utilizing metal ions to enhance the direct ozone oxidation capacity of malodorous compounds.

Kinetic studies of copper-catalyzed homocoupling reactions of arylboronic acids in aqueous micellar media

The kinetic studies for copper-catalyzed homocoupling phenylboronic acids (1a-d) have been successfully carried out in an aqueous micellar medium under environmentally benign conditions (water as a solvent, micelle to help solubilize hydrophobic adducts) in this study cetyl trimethyl ammonium bromide (CTAB ) is used as surfactant to produce micelle. Using different copper salts and copper complexes as catalysts under benign to mild conditions at a temperature range (40-65˚C, under air) without the addition of any additives (base, oxidant, and ligands). The reactions were followed using a UV-Vis spectrophotometer and the absorbances were measured at maximum wavelengths for the biphenyl production of each five selected (1a-d). The observed rate constants (kobs) were calculated using a pseudo-first-order equation and unsubstituted 1a was selected for optimization processes. The experimental results showed good to excellent curve fit (R2=0.9967-0.9998) to the pseudo-first-order equation and origin software was used for this purpose. Among all copper catalysts, the observed rate constant (kobs) for cupric acetate (Cu(OAc)2)is much higher than others, (kobs=0.1605 min-1), while CuCl2.2H2O has a minimum observed rate constant, kobs=0.0216min-1. The two copper complexes [Cu(4-mba)2(tmeda)], and [Cu(3-mba)2(H2O)2(tmeda)] require a mild condition (85˚C) which is higher than other copper catalysts when 1a is used as reactant the value of kobs is (0.0176, 0.0343 min-1) respectively, while using p-tolylboronic acid (1b) as reactant the value of kobs is (0.0173, 0.0147 min-1) respectively.

Remarkable Enhancement of Catalytic Activity of Cu-Complexes in the Electrochemical Hydrogen Evolution Reaction by Using Triply Fused Porphyrin.

A bimetallic triply fused copper(II) porphyrin complex (1) was prepared, comprising two monomeric porphyrin units linked through β-β, meso-meso, β'-β' triple covalent linkages and exhibiting remarkable catalytic activity for the electrochemical hydrogen evolution reaction in comparison to the analogous monomeric copper(II) porphyrin complex (2). Electrochemical investigations in the presence of a proton source (trifluoroacetic acid) confirmed that the catalytic activity of the fused metalloporphyrin occurred at a significantly lower overpotential (≈320 mV) compared to the non-fused monomer. Controlled potential electrolysis combined with kinetic analysis of catalysts 1 and 2 confirmed production of hydrogen, with 96 and 71 % faradaic efficiencies and turnover numbers of 102 and 18, respectively, with an observed rate constant of around 107 s-1 for the dicopper complex. The results thus firmly establish triply fused porphyrin ligands as outstanding candidates for generating highly stable and efficient molecular electrocatalysts in combination with earth-abundant 3d transition metals.

Bioleached laterite nano iron catalyst (BLaNFeCs)-based Fenton's degradation of selective dyes in water

Abstract Iron nanocatalyst for its potential application as Fenton's catalyst for the degradation of methylene blue dye was synthesized with the fruit extract of Citrus maxima using bioleached laterite iron as a precursor. Synthesized iron particles were characterized suitably and their catalytic role in the degradation of methylene blue and rhodamine B by Fenton's oxidation was evaluated. The synthesized nanocatalyst exhibits heterogeneous catalytic properties in the degradation of methylene blue and rhodamine B with a degradation efficiency of 93.6 and 91.3%, respectively. Observed rate constants are consistent with the increase in catalyst dosage as it speeds up the reaction. The degradation of methylene blue and rhodamine B follows a pseudo-first-order reaction with a linear fit. Reusability studies confirm the reduction in the catalytic efficiency of the synthesized iron nanoparticles after five consecutive cycles.

Synthesis, Characterization, and Solar Photo-Activation of Chitosan-Modified Nickel Magnetite Bio-Composite for Degradation of Recalcitrant Organic Pollutants in Water

Photocatalysis is a promising process for decomposing harmful organic pollutants in water. In this study, solar/photocatalytic degradation of two model azo dyes, i.e., methylene blue (MB) and methyl red (MR), in water usinga nanostructured chitosan-modified nickel magnetite (CS-NM) bio-composite was investigated. The CS-NM bio-composite was synthesized through a co-precipitation method and characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry (TGA), and UV-Vis spectroscopy. FTIR analysis showed the uniform incorporation and conjugation of nickel magnetite (NM) into the chitosan (CS) polymer matrix. SEM showed that the average particle size was 0.5 μm. The TGA results revealed the good thermal stability of the prepared bio-composite at 300 °C. The point of zero charge was calculated as 7.5. The effect of water quality and process parameters, such as concentration of dyes, catalyst dose, solution pH, and temperatures, was investigated, for application purposes. The solar/CS-NM photocatalysis resulted in 99 and 96% degradation of individual MB and MR (C0 = 50 ppm), respectively, in 90 min. The degradation of MB and MR by solar/CS-NM photocatalysis followed pseudo-first-order kinetics, with observed rate constants (k) of 0.077 and 0.072 min−1, respectively. The CS-NM photocatalyst showed high recyclability, represented by only a 4–6% loss in the photocatalytic efficiency, after four cycles. The results showed that solar/CS-NM photocatalysis is an efficient technique for degrading recalcitrant organic pollutants, such as azo dyes, in water environments.

Stabilization of nano zero-valent iron by electrospun composite mat with good catalysis and recyclability

Nano zero-valent iron (Fe0, nZVI) has been extensively utilized in the treatment of dyed wastewater. However, the dispersibility, stability and reusability of nZVI need to be improved for both efficiency and environmental safety. One nZVI modified nanofiber composite membrane was successfully fabricated by electrospinning, and the performances in different catalytic systems were evaluated. The synthesized composite mat was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The loaded nZVI was verified by the change of fiber diameters and the distribution of iron element with/without loading. The composite membrane possessed good recyclability and dispersion property of nZVI with a mean diameter of 114.46 nm. Three Fenton-like oxidation systems (H2O2, Na2S2O8, and NaClO2) were selected and investigated for the degradation of Rhodamine B (RhB) in water using the as-prepared composite as a catalyzer. The degradability relationship of the oxidation systems was NaClO2>Na2S2O8>H2O2 with observed rate constants (Kobs) of 0.3155, 0.0547, and 0.014, respectively. 50 mg L−1 RhB was completely degraded by 1.5 mM NaClO2 in 15min, which is the best compared with the other two systems. The major free radical species (·OH, SO4·- and ClO2·) in the three oxidation systems were identified by electron paramagnetic resonance (EPR) and quenching studies. The degradation capacity could be maintained after five recycles and the leached nZVI from the composite was negligible (<0.55%). For the degradation process, the contribution of dark adsorption (Kads = 1.5489 × 10−3) was much smaller than that of natural-light-derived photocatalysis (Kphoto = 1.5489 × 10−3) with the adsorption capacity of 4.32 mg g−1 and oxidative degradation amounts of 9.46 mg g−1, 10.90 mg g−1 and 12.32 mg g−1 in H2O2, Na2S2O8 and NaClO2 systems, respectively. Our results demonstrated that the synthesized composite membrane demonstrated good catalytic properties with good recyclability and stability, and NaClO2 was the most efficacious system for RhB degradation in water.

Investigation of g-C3N4 ratio on CaFe2O4 to remove toxic pollutants from wastewater

Pristine and g-C3N4–CaFe2O4 was produced employing hydrothermal method. g-C3N4 is produced via solid state technique. The obtained nanoparticles were studied employing standard characterization techniques. The crystallite size and phase were identified from XRD pattern. The bandgap of the samples were calculated from the UV spectra. The g-C3N4, CaFe2O4, g-C3N4-CaFe2O4 (1:1), g-C3N4-CaFe2O4 (2:1) morphology was analyzed by SEM. The g-C3N4 explored nanosheets are stacked together. The CaFe2O4 sample has shown nanoplates and nanorods like morphology. The g-C3N4–CaFe2O4 composite samples exhibited both nanosheets and nanoparticles. The heterojunction layers formed by the composite contributed to the better photocatalytic activity. The Janus Green B (JG) dyes were used as model pollutant. The observed rate constant was 0.0043, 0.0045, 0.0048, 0.011 and 0.016 min−1 for pure JG, g-C3N4 – JG, CaFe2O4-JG, g-C3N4-CaFe2O4 (1:1) – JG and g-C3N4- CaFe2O4 (2:1) – JG respectively. The increase in g-C3N4 ratio has paved a positive way for CaFe2O4 to reduce the pollutant and this material will be the promising candidate for water remediation.

Local dipole enhancement of space-charge piezophototronic catalysts of core-shell polytetrafluoroethylene@TiO2 nanospheres

This study demonstrates the hydrothermal treatment of core-shell polytetrafluoroethylene (PTFE) nanoparticles decorated with TiO2 (h-PTFE@TiO2); this material exhibits strain-induced local dipole enhancement of the space-charge piezopotential that improves the photocatalytic effect. Under acoustic cavitation, dielectric barrier discharge and electric dipole formation are initiated in voids within the PTFE nanoparticles and at the TiO2–PTFE interface. The h-PTFE@TiO2 nanoparticles (NPs) have exceptionally high catalytic activity in organic dye degradation because of the local dipole enhancement of photoinduced charge separation with a carrier lifetime of 3.14 ns. The observed rate constant of the h-PTFE@TiO2 NPs in the piezophototronic reaction reaches 0.1388 min−1, which is 17 times that of the photocatalytic reaction (0.0084 min−1) and 66 times that of the piezocatalytic reaction (0.0021 min−1). Computational simulation reveals that large strain-induced space charge piezoelectric polarization induces an internal electric field between the unsaturated PTFE (fluorine vacancies) and TiO2 surface. The piezopotential has a critical role in band bending at PTFE-TiO2 interfaces to enhance the electron-hole separation when PTFE is constrained in TiO2 shells. Results of piezoresponse force microscopy reveal that the piezoelectric coefficient d33 of PTFE is approximately 79.77 pCN−1. The findings provide insights into catalytic activity for environmental remediation.

Extraordinary behavior of 5-(3,4-dihydroxyphenyl)-10,15,20-tris(N-methylpyridinium-3-yl)porphyrin triiodide in titration with bases and in albumin oxidation

The observed rate constants of the photoinduced oxidation of albumin increased by a factor of 1.5–2 upon deprotonation of the peripheral hydroxyl groups of 5-(3,4-dihydroxyphenyl)-10,15,20-tris(N-methylpyridinium-3-yl)porphyrin triiodide compared to its phenolic form.

Concerted and Stepwise Proton-Coupled Electron Transfer for Tryptophan-Derivative Oxidation with Water as the Primary Proton Acceptor: Clarifying a Controversy

Concerted electron-proton transfer (CEPT) reactions avoid charged intermediates and may be energetically favorable for redox and radical-transfer reactions in natural and synthetic systems. Tryptophan (W) often partakes in radical-transfer chains in nature but has been proposed to only undergo sequential electron transfer followed by proton transfer when water is the primary proton acceptor. Nevertheless, our group has shown that oxidation of freely solvated tyrosine and W often exhibit weakly pH-dependent proton-coupled electron transfer (PCET) rate constants with moderate kinetic isotope effects (KIE ≈ 2–5), which could be associated with a CEPT mechanism. These results and conclusions have been questioned. Here, we present PCET rate constants for W derivatives with oxidized Ru- and Zn-porphyrin photosensitizers, extracted from laser flash-quench studies. Alternative quenching/photo-oxidation methods were used to avoid complications of previous studies, and both the amine and carboxylic acid groups of W were protected to make the indole the only deprotonable group. With a suitably tuned oxidant strength, we found an ET-limited reaction at pH < 4 and weakly pH-dependent rates at pH > ∼5 that are intrinsic to the PCET of the indole group with water (H2O) as the proton acceptor. The observed rate constants are up to more than 100 times higher than those measured for initial electron transfer, excluding the electron-first mechanism. Instead, the reaction can be attributed to CEPT. These conclusions are important for our view of CEPT in water and of PCET-mediated radical reactions with solvent-exposed tryptophan in natural systems.

ВЛИЯНИЕ СОСТАВА РАСТВОРИТЕЛЯ НА КИНЕТИКУ ГИДРОГЕНИЗАЦИИ 4-НИТРО-2'-ГИДРОКСИ-5'-МЕТИЛАЗОБЕНЗОЛА НА СКЕЛЕТНОМ НИКЕЛЕ В ВОДНЫХ РАСТВОРАХ 2-ПРОПАНОЛА

The article is devoted to the analysis of the kinetics of hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel in aqueous solutions of 2-propanol without additives and with additions of acetic acid and hydroxide. Elucidation of the effect of the solvent composition on the kinetics of transformations of compounds containing several reactive groups is a theoretical and practically significant problem. According to the data obtained, during the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel, the introduction of an acid or base into an aqueous solution of 2-propanol of azeotropic composition leads to a change in the ratio of directions in the parallel-sequential scheme of transformations of the starting compound. With the introduction of acetic acid, the contribution of the direction due to the transformation of the azo group noticeably increases, while the introduction of sodium hydroxide completely suppresses this process and the addition of hydrogen in the first phase of the reaction is carried out exclusively at the nitro group in the starting 4-nitro-2'-hydroxy -5'-methylazobenzene. The change in the contributions of the directions associated with the transformation of the azo or nitro group in 4-nitro-2′-hydroxy-5′-methylazobenzene cannot be caused by a change in the excess adsorption values of the hydrogenated compound. When the adsorption values of 4-nitro-2'-hydroxy-5'-methylazobenzene change within 30%, the rate constants of hydrogenation of the starting compound under the influence of the solvent change more than 8 times. One of the reasons for such a change in the observed rate constants for the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene may be a change in the ratio of forms of hydrogen adsorbed on the catalyst surface under the influence of a solvent.

Biodegradation of tetramethylammonium chloride wastewater and inorganic nitrogen removal by a mixed culture

The disposal of wastewater containing tetramethylammonium chloride (TMAC) generated from the semiconductor and photoelectric industries is a challenging problem due to the limited information is available regarding its treatability. This study aims to investigate the feasibility of using biological processes to treat TMAC. An activated sludge collected from a lake near the Southern Taiwan Science Park was used. Various operational parameters, including operating temperature, pH conditions and TMAC dosages were evaluated for the optimal condition. Results showed that the activated sludge could successfully degrade TMAC, and subsequently achieve simultaneous nitrification and denitrification (SND) of the nitrogen-containing intermediates under mild conditions (pH at a range of 3–7 and temperature at a range of 20–40 °C). Besides, more than 60% of the nitrogen-containing intermediates were converted into gaseous nitrogen (N2). TMAC biodegradation was found to follow first-order kinetics. The observed rate constant of TMAC biodegradation increased from 0.64 ╳ 10−4 to 9.57 ╳ 10−4 1/min as the concentration of TMAC decreased. In addition, TMAC demethylation was identified as the rate-limiting step of the entire reaction. Major functional organisms of the activated sludge were identified as Mycobacterium, Ochrobactrum and Arthrobacter species which are aerobic and acidophilic strains. This study can be an important reference for future researches attempting to treatment TMAC wastewater by biological processes.

Highly efficient debromination of 4,4'-dibrominated diphenyl ether by organic palygorskite-supported Pd/Fe nanoparticles.

Organic palygorskite (OP)-supported Pd/Fe nanoparticles composite (OP-Pd/Fe) was prepared by stepwise reduction method. The removal capacity of 4,4'-dibrominated diphenyl ether (BDE15) by OP-Pd/Fe was compared with other various materials. For better understanding the possible mechanism, the synthesized and reacted OP-Pd/Fe materials were characterized by TEM, SEM, XRD, and XPS, respectively. The effects of major influencing parameters on the degradation of BDE15 were also studied. Benefit from the synergistic effect of the carrier and bimetallic nanoparticles, BDE15 could be completely debrominated into diphenyl ether (DE) under suitable conditions. A two-stage adsorption/debromination removal mechanism was proposed. The degradation of BDE15 with OP-Pd/Fe was mainly stepwise debromination reaction, and hydrogen transfer mode was assumed as the dominated debromination mechanism. The removal process fitted well to the pseudo first-order kinetic equation. The observed rate constants increased with increasing Pd loading and OP-Pd/Fe dosage while decreased with increasing initial BDE15 concentration, the tetrahydrofuran/water ratio, and the initial pH of the solution. The work provides a new approach for the treatment of PBDEs pollution.

Peroxydisulfate bridged photocatalysis of covalent triazine framework for carbamazepine degradation

Covalent triazine frameworks (CTFs) are appealing photocatalysts for environmental remediation. However, high recombination rate of photogenerated electrons and holes is the key limitation for its application. Notably, peroxydisulfate (PDS) can potentially act as electron withdrawing center to efficiently prevent the recombination. Herein, the photocatalysis of CTF under visible light (VL) coupled with PDS shows great potential for pollutants removal, taking carbamazepine (CBZ) as a case, in which the observed rate constant of CBZ degradation in VL/CTF/PDS process is 9.0 and 4.5 times to that in CTF/PDS and VL/CTF processes, respectively. PDS can construct a bridge to enhance the charge separation and transfer efficiency of CTF to prevent the recombination of electrons and holes, thus significantly improving the oxidation ability of the VL/CTF/PDS process. Moreover, the accepted electrons can initiate the PDS activation to generate more reactive species, thus contributing to higher oxidation capacity of the VL/CTF/PDS process. Furthermore, the VL/CTF/PDS process tends to attack the 1 N and 12C–15C atoms of CBZ to induce the cleavage of N-C bond and oxidation of CC bond, thus decomposing CBZ into lower molecules and finally being mineralized. This study will promote the development on applying photocatalysis of CTF materials and PDS activation in practical environmental remediation.

Modeling Chemical Reactivity at the Interfaces of Emulsions: Effects of Partitioning and Temperature.

Bulk phase chemistry is hardly ever a reasonable approximation to interpret chemical reactivity in compartmentalized systems, because multiphasic systems may alter the course of chemical reactions by modifying the local concentrations and orientations of reactants and by modifying their physical properties (acid-base equilibria, redox potentials, etc.), making them—or inducing them—to react in a selective manner. Exploiting multiphasic systems as beneficial reaction media requires an understanding of their effects on chemical reactivity. Chemical reactions in multiphasic systems follow the same laws as in bulk solution, and the measured or observed rate constant of bimolecular reactions can be expressed, under dynamic equilibrium conditions, in terms of the product of the rate constant and of the concentrations of reactants. In emulsions, reactants distribute between the oil, water, and interfacial regions according to their polarity. However, determining the distributions of reactive components in intact emulsions is arduous because it is physically impossible to separate the interfacial region from the oil and aqueous ones without disrupting the existing equilibria and, therefore, need to be determined in the intact emulsions. The challenge is, thus, to develop models to correctly interpret chemical reactivity. Here, we will review the application of the pseudophase kinetic model to emulsions, which allows us to model chemical reactivity under a variety of experimental conditions and, by carrying out an appropriate kinetic analysis, will provide important kineticparameters.