Reaction Constants Research Articles

Bioconvection Flow in the Existence of MHD Casson Nanofluid with Viscous Dissipation and Chemical Reaction

Objective: Casson nanofluids are used to investigate the effects of Magneto hydrodynamics (MHD), viscous dissipation, temperature and concentration on convective heat transfer flow through a stretching/shrinking vertical sheet. Method: The BVP4C method in MATLAB is used to obtain numerical solutions for solving the governing Ordinary Differential Equations (ODEs) by converting them into the governing Partial Differential Equations (PDEs) using similarity transformations. To examine the effects of pertinent variables, including the Magnetic parameter, the Brownian motion parameter, the Cassson fluid parameter, the chemical reaction constant, the Prandtl number, the concentration to thermal Buoyancy ratio, the microorganism to thermal Buoyancy ratio, the Lewis number, the bioconvection Peclet number, the bioconvection Lewis number, the local skin friction, the local Nusselt number, the local Sherwood number and the local density number of the motile microorganisms. Result: Quantitative data are plotted according to the bioconvection flow, temperature, concentration and velocity profiles. Conclusion: It is observed that this study helps to compare the variations in the chemical reactions of the MHD Casson nanofluid by using graphs.

Titanium dioxide/reduced graphene oxide nanocomposites as effective photocatalytic for hazardous 4-nitrophenol

Titanium dioxide/reduced graphene oxide nanocomposite (TiO2/rGO NCs) was prepared using various hydrothermal strategies as a highly efficient photocatalyst. The crystal structure, morphology, elemental distribution, chemical structure, optical properties, and electrical conductivity of TiO2/rGO NCs were studied to investigate the effect of the incorporation of rGO with TiO2NPs on these properties. The TiO2/rGO NCs surface exhibits thin sheets of rGO with TiO2NPs distributed on the sheets. The successful incorporation between rGO and TiO2NPs was confirmed by EDX maps, IR spectrum, and XRD patterns. Compared with TiO2NPs, a tiny reduction in the crystallite size and an increase in the microstrain was found; in addition, the TiO2/rGO NCs exhibit a low direct bandgap energy, a high electrical conductivity, and excellent photoconductivity. On the other hand, different amounts of 4-nitrophenol (4-NP) were used to investigate the photocatalyst degradation efficiency of TiO2NPs and TiO2/rGO NCs under UV irradiation. The higher degradation efficiency after 120 min was for TiO2/rGO NCs with 5 mg/L and 10 mg/L of 4-NP, with 94% and 91% values, respectively. The first-order kinetic constant (k1), the kinetic rate constant of the surface reaction (ks) and the adsorption equilibrium constant (KL) were evaluated. The KL of TiO2NPs and TiO2/rGO NCs is 0.003 and 0.182 (mgL−1)−1, and the ks is 2.53 and 0.21 mgL−1.min−1, respectively.

A Methoxylation-Promoted CPET Reaction.

The manuscript discloses a methoxylation reaction to an aromatic carbonyl function that carries out a CPET reaction oxidizing a transition metal ion. Spontaneous methoxylation of a redox non-innocent fragment coordinated to a high spin cobalt(II) ion, promoted concerted proton electron transfer (CPET) reaction oxidizing cobalt(II) to cobalt(III) in air and subsequent demethoxylation induced reduction of cobalt(III) to cobalt(II) producing H2 O2 are authenticated. The cobalt(III)/cobalt(II) electron transfer (ET) potential of the designed complex in CH2 Cl2 is -0.27 V vs Fc+ /Fc redox couple. However, in presence of MeOH the reduction potential decreases to -1.02 V due to CPET involving MeOH proton. In CH2 Cl2 /CHCl3 spontaneous demethoxylation occurs giving back the original complex and reactive methoxyl radical that reacts with O2 producing H2 O2 . Overall one molecule of MeOH produces one molecule of H2 O2 . To analyze the involvement of the proton, the rate constants of the CPET reactions in CH2 Cl2 -MeOH (2 : 1) and CH2 Cl2 -CD3 OD (2 : 1) and the demethoxylation reaction in CHCl3 at 330 K were determined by time drive UV-Vis spectroscopy.

Solvent extraction and recovery of beryllium from hydrochloric acid solution with naphthenic acid

Beryllium is an essential metal for strategic purposes but remains an under-explored element. The separation of beryllium and aluminium and the purification of beryllium hydroxide from a multi-component solution has always been a challenging task in the beryllium industry and offers great research potential in academic fields. In this research, a solvent extraction method was used to purify and recover beryllium from trace impurities. A systematic investigation of the extraction process revealed that under optimal conditions, 98.66% of the beryllium was extracted in a three-stage countercurrent extraction using naphthenic acid (NA) as the extractant. The aluminium, iron and other trace impurities in the organic phase can be scrubbed with 1 mol/L HCl, then 99.27% of the beryllium was stripped with 5 mol/L NaOH by two-stage stripping. Be(OH)2 with a purity of 99.67% was recovered from the stripped beryllium solution by hydrolysis precipitation method. Furthermore, FT-IR analysis and slope analysis demonstrate the mechanism of beryllium extraction with naphthenic acid accompanied by cation exchange. The influence of temperature on the beryllium extraction was investigated and the thermodynamic parameters and the equilibrium constant of the extraction reaction were calculated. Accordingly, a process flowsheet for the separation of beryllium from multiple impurities using naphthenic acid was developed. This process is believed to offer the advantages of high efficiency, recyclability, and a favorable beryllium-aluminium separation effect; presenting a promising new approach to beryllium recovery.

Electrodeposition of Fe-Ni Alloy Films having Invar Compositions with Fe3+ as the Sole Iron Source

Fe-Ni alloy films with invar alloy compositions were electrodeposited from a stable citrate bath containing trivalent iron ions (Fe3+) as the sole iron source. This bath was prepared based on determining the equilibrium constants for acid dissociation, complex formation and precipitation reactions. Electrodeposition was conducted under galvanostatic conditions at 25 °C without agitation and an investigation was carried out into the effects of pH and current density on the composition and microstructure of the films. The results showed that ferric hydroxide (Fe(OH)3), which is normally poorly soluble, did not precipitate after electrodeposition. Fe-Ni alloy films containing 31‒42 mass% Ni (including Fe-36 mass% Ni) were formed with a current efficiency of approximately 70%. The films were smooth and were made up of grains with sub-micron sizes, although some cracks were observed. Fe and Ni were distributed homogeneously throughout the films and the Fe-Ni solid solutions exhibited both face-centered cubic and body-centered cubic structures.

Kinetic Analysis of Dry Reforming of Methane on Traditional and Membrane Catalysts

The article presents an analysis of the results of a kinetic study of dry reforming of methane (UCM) in reactors with traditional (TC) and membrane catalysts (MC). The kinetic experiment in reactors with MC and TC was performed in the temperature range of 820–900°C and the ratio CH4 : CO2 = 1 : 1. In the experiment, an intensification of the process of the methane cracking reaction was established, the rate constant of which increases by an order of magnitude. Such a difference in the results of the DRM on the studied catalysts are due to the intensification of mass transfer on the MC, which is based on the phenomenon of thermal slip. A mathematical description corresponding to the kinetic scheme of DRM process is proposed, and the rates constants of direct and reverse reactions in both reactors are found. In the DRM process, water gas is formed on the TC, and synthesis gas is formed on the MC. At TC, the DRM process is accompanied by the accumulation of carbon deposits (CD), and at MC this accumulation is absent. The DRM process on both catalysts is characterized by three main reactions (methane cracking, gasification of the CD with carbon dioxide and/or water vapor and the reverse water gas shift), which were assumed to be reversible under experimental conditions. It turned out that on TC the gasification of the CD occurs in the reverse reaction of methane cracking, and on the MC—in the reactions of gasification by water vapor (mainly) and carbon dioxide. The process on the MC is characterized by irreversible reactions of methane cracking, gasification of the CD with water vapor and carbon dioxide. The reverse water gas shift reaction on the MC remains reversible, and its rate constants of the direct and inverse reactions turned out to be an order of magnitude lower than similar constants on the TC.

Preparation of g-C3N4/{001}-AR-TiO2 composite photocatalyst and its degradation of tetracycline hydrochloride in sunlight

In this study, a {001}-AR-TiO2 catalyst (001-ART) was prepared by the sol–gel method, where g-C3N4 (CN) was combined with 001-ART to form g-C3N4{001}-AR-TiO2 (CN/001-ART). The crystal shape, morphology, optical properties, photoelectron-hole recombination, and specific surface area of the prepared materials were studied. Tetracycline hydrochloride (TTCH) was used as the target pollutant to investigate the catalytic properties, and the results showed that the specific surface area, visible light response range, band gap, photo-generated carrier separation ability, and average life span of 001-ART after CN composite integration increased. Furthermore, the degradation rate of TTCH within 120 min was 92.48%, and the reaction constant was 0.0215. After 5 repeated use cycles, the degradation rate of TTCH was 85.21%. We also found that OH and O2− were produced in CN/001-ART after exposure to light, and the electrons of 001-ART were excited to the conduction band and combined with the holes in the valence band of CN, thus, forming a Z-type heterostructure. This resulted in the higher activity of CN/001-ART.

Multiple-well master equation study on the propargyl + indenyl recombination and subsequent reactions

The reaction between propargyl and indenyl radicals is investigated focusing primarily on the reaction pathways leading to the formation of acenaphthylene. The potential energy surfaces for recombination of the two radicals, isomerization and dissociation of the adducts, and some subsequent reactions are explored using the CBS-QB3//ωB97X-D and CASPT2 quantum chemical methods. Several reaction pathways for the formation of tricyclic species, which eventually produce acenaphthylene, are identified. The rate constants for reactions involved in these and some other competing pathways are obtained from solutions to the master equations, which provide the steady-state and phenomenological descriptions on the kinetics of the multiple-well systems. The results indicate that acenaphthylene can be formed via roughly three different routes, depending mainly on temperature. A simplified reaction mechanism describing the kinetics of the major reaction pathways is proposed for use in kinetic modeling.

Kinetics, equilibrium, and computational study on the monomerization reaction of {CH3ReVO(pdt)}2 dimer with monodentate ligands

The monomerization reaction of {MeReO(pdt)}2 dimer (the pdt is 1,3-propanedithiolate) with monodentate ligand has been studied experimentally:{MeReO(pdt)} + 2 L ⇌ 2 MeReO(pdt)L and L is a monodentate ligand presented in Figure 1. No monomerization reaction have been observed with the indazole and diphenyl sulfides, and 2-methylpyridne. For the 2-methylpyridne case, the no reaction was observed because of the steric effect of the methyl group at the ortho position prevent the nitrogen from coordination. But the phosphines and pyridines derivatives monomerize the dimer. The rate law is given by ν = (ka[L] + kb [L]2) {MeReO(pdt)2} for ligands 1 to 4 in Table 1 and the rate law is ν = kb [L]2 {MeReO(pdt)2} for ligands 6 to 8 in Table 1. The equilibrium constant of the same reaction has been also evaluated. The rate constant (k) and the equilibrium constant (Keq) values correlate well with the basicity of the ligand. The reaction constant (ρ) is -4.9 and -1.3 for pyridine and phosphine, respectively, obtained from Hammett correlation with σ. The computational study on I1 and I2 intermediates (Scheme 3) shows that these intermediates are not plausible intermediates as previously proposed1, 2. These results are attributed to the high angle strain on the bridging sulfur that prevent the formation of the I1 and I2 intermediates and the reaction proceed through different intermediates (I3 and Ia Scheme 4). Therefore, the proposed mechanism is modified to accommodate the computational results.

Iron electrocoagulation activated peracetic acid for efficient degradation of sulfamethoxazole

Activation of peracetic acid (PAA) by Fe species is the attractive advanced oxidation processes for the removal of antibiotics. However, achieving optimal performance in many of these processes often requires acidic pH conditions, which impedes practical application. In this study, an iron electrocoagulation (EC) system was devised to for activate PAA and oxidate sulfamethoxazole (SMX). Under optimal conditions, the degradation of SMX by the EC/PAA system reached 96.2% within 15 min, with a pseudo-first order reaction constant of 0.241 min−1, but only consuming 0.044 kW·h/m3. Interestingly, the EC/PAA system showed a high buffering capacity in the initial pH range of 4–8 to maintain the final pH of around 7. The quenching experiments revealed both free radical and non-free radical pathways involved in the oxidation of SMX in the EC/PAA system. Specifically, the active species, including •OH, organic radicals (CH3COO• and CH3COOO•) and 1O2, contribute 86.77%, 5.53% and 7.70%, respectively. These findings suggest that the EC/PAA system has unique advantages and potential for the degradation of antibiotic organics such as SMX in aquatic environments due to its strong oxidative capacity, wide pH range and high buffering capacity.

Eclogite thermobarometry: The consistency between conventional thermobarometry and forward phase‐equilibrium modelling

AbstractEclogite thermobarometry is crucial for constraining the depths and temperatures to which oceanic and continental crust subduct. However, obtaining the pressure and temperature (P–T) conditions of eclogites is complex as they commonly display high‐variance mineral assemblages, and the mineral compositions only vary slightly with P–T. In this contribution, we present a comparison between two independent and commonly used thermobarometric approaches for eclogites: conventional thermobarometry and forward phase‐equilibrium modelling. We assess how consistent the thermobarometric calculations are using the garnet–clinopyroxene–phengite barometer and garnet–clinopyroxene thermometer with predictions from forward modelling (i.e. comparing the relative differences between approaches). Our results show that the overall mismatch in methods is typically ±0.2–0.3 GPa and ±29–42°C although differences as large as 80°C and 0.7 GPa are possible for a few narrow ranges of P–T conditions in the forward models. Such mismatch is interpreted as the relative differences among methods, and not as absolute uncertainties or accuracies for either method. For most of the investigated P–T conditions, the relatively minor differences between methods means that the choice in thermobarometric method itself is less important for geological interpretation than careful sample characterization and petrographic interpretation for deriving P–T from eclogites. Although thermobarometry is known to be sensitive to the assumed XFe3+ of a rock (or mineral), the relative differences between methods are not particularly sensitive to the choice of bulk‐rock XFe3+, except at high temperatures (>650°C, amphibole absent) and for very large differences in assumed XFe3+ (0–0.5). We find that the most important difference between approaches is the activity–composition (a–x) relations, as opposed to the end‐member thermodynamic data or other aspects of experimental calibration. When equivalent a–x relations are used in the conventional barometer, P calculations are nearly identical to phase‐equilibrium models (ΔP < 0.1). To further assess the implications of these results for real rocks, we also evaluate common mathematical optimizations of reaction constants used for obtaining the maximum P–T with conventional thermobarometric approaches (e.g. using the highest aGrs2 × aPrp in garnet and Si content in phengite, and the lowest aDi in clinopyroxene). These approaches should be used with caution, because they may not represent the compositions of equilibrium mineral assemblages at eclogite facies conditions and therefore systematically bias P–T calculations. Assuming method accuracy, geological meaningful Pmax at a typical eclogite facies temperature of ~660°C will be obtained by using the greatest aDi, aCel, and aPrp and lowest aGrs and aMs; garnet and clinopyroxene with the lowest Fe2+/Mg ratios may yield geological meaningful Tmax at a typical eclogite facies pressure of 2.5 GPa.

Efficient Mn(III)-oxalate generation for diclofenac oxidation by electro-reduction of potassium permanganate in the presence of oxalate

Although electrochemical activation of permanganate (E-PM) is a green and efficient method to degrade refractory organics by in-situ generated reactive Mn(III)aq, this process highlights on the presence of promoter and/or stabilizer. Oxalate (OA) is a widespread organic chelate in natural water bodies (with concentrations up to 1 mM), but whose effect on the E-PM process is still unclear. In this study, we found electrolysis and the presence of OA both promote the activation of PM for the degradation of diclofenac (DCF), showing a high synergistic coefficient (3.23) and elevated reaction constant (0.1395 min−1). Nevertheless, this process is highly pH-dependent, behaving decreased reactivity as pH value increasing from 3 to 11. Sufficient concentration of OA (≥0.5 mM in this study) is required for stabilizing Mn(III). UV–vis spectra, visual evidence and quenching experiments identified the presence and dominant role of Mn(III)-OA on the degradation of DCF. Using chronoamperometry, we confirmed Mn(III)-OA was primarily generated from the electro-reduction of PM in the presence of OA at pH 5.

Phase field modeling of lithium deposition in porous lithium metal anodes

Fabricating the structured lithium metal anode is an effective method to improve the cycling performance and severe safety problem of the lithium metal anode for commercial application. In this work, we have employed an electrochemical phase field (PF) model to simulate the non-uniform lithium deposition in porous lithium metal anodes. Four factors have been investigated to facilitate homogeneous lithium deposition and increase the capacity for the inside-pore lithium deposition, including 1) the porosity of the lithium metal anode, 2) the diffusion coefficient of lithium ion, 3) the reaction constant for lithium deposition and 4) structured electrode with a gradient of porosity. We have found that the inside-pore lithium deposition can be improved by increasing the diffusion coefficient lithium ion and designing a lithium metal anode with a gradient of reaction constants and a gradient of porosity. These results provide some new thoughts for the development of high-performance lithium metal anodes.

Synthesis of CuO, ZnO and SnO2 Coupled TiO2 Photocatalyst Particles for Enhanced Photodegradation of Rhodamine B Dye

Environmental pollution is a global problem and dye pollution is one of the major factors. TiO2 shows promising photocatalytic properties that can degrade organic pollutants such as dye under ultraviolet (UV) irradiation. However, TiO2 possesses some disadvantages such as a wide band gap and a high recombination rate of electron-hole pairs. Coupling TiO2 with various metal oxides can enhance photocatalytic properties. In this work, photodepositon (reduction of metal ions on TiO2) followed by the thermal oxidation method were used for the coupling of TiO2 with CuO, ZnO, or SnO2 under various methanol concentrations (25 vol% or 50 vol%) and deposition duration (1 h or 3 h) to observe the effect of these parameters on the photocatalytic degradation activity on Rhodamine B (RhB) dye (up to 90 min). The rate constant of the photodegradation reaction (k) has improved from 0.0141 min−1 (uncoupled TiO2) to 0.0151~0.0368 min−1. Overall, CuO/TiO2 and SnO2/TiO2 samples have shown similar photocatalytic properties (average rate constants of 0.0341 min−1 and 0.0327 min-1, respectively), and both performed better than ZnO/TiO2 in terms of RhB photodegradation (average rate constants of 0.0197 min−1). The difference in photocatalytic performance can be explained by the bandgap of metal oxides and their relative band positions with TiO2. Lastly, CuO/TiO2 (50 vol%, 3 h) and SnO2/TiO2 (50 vol%, 3 h) have shown the best photocatalytic properties respectively due to a longer deposition time and higher concentration methanol, resulting in more deposited materials. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Theoretical Study of Methane Dissociation on Pt(111) Surface Using Density Functional Theory (DFT) Calculations

In this work, methane (CH4) dissociation on Pt(111) surface dissociation was studied based on density functional theory (DFT) calculations to evaluate the nature of adsorption and to calculate the rate constant. The most stable configurations for H and CH3 were tested on the surface of Pt(111), and the results displayed that H tends to be adsorbed at the fcc site while CH3 tends to be adsorbed at the top site. The energy of barrier and rate constant of reaction were calculated and found to be (2.28 eV) and (3.21007E−08 s−1) respectively. In addition, the adsorption energy for the reactant and products to investigate the nature of adsorption of the reactant and products on Pt(111) surface either physisorption or chemisorption. The results showed that the kind of adsorption of CH4 adsorbed on the surface of Pt(111) at top site is physisorption, while CH3 and H species adsorption on the Pt(111) surface is chemisorption. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Surface functionalized multi-wall carbon nanotubes for degradation of organic dyes

Eliminating the hazardous dyes from the wastewater is essential for the sustainable furtherance of eco-friendly-oriented industrial growth. The untreated effluents containing dyes can damage the ecosystem and cause serious health issues to humans, animals, and aquatic species. In the present work, the multi-wall carbon nanotubes (MWCNTs) were functionalized using the combination of sulphuric acid and nitric acid. These functionalized multi-wall carbon nanotubes (F-MWCNTs) were characterized using Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray analysis (EDAX) to confirm the presence of functional groups. The catalytic dye degradation efficiency of pristine multi-wall carbon nanotubes (P-MWCNTs) and F-MWCNTs was tested for methylene blue (MB), and indigo carmine (IC) dyes under dark and ultraviolet (UV) light exposure conditions. F-MWCNTs have exhibited appreciable degradation efficiency (∼90%) under dark and UV light compared to P-MWCNTs. An increment in efficiency was observed for UV-light-aided dye degradation. The impact of pH and temperature on degradation was analyzed in detail. The reaction kinetics was studied to determine the rate constants of the degradation reactions. A substantial quantum efficiency (QE) enhancement was noticed for F-MWCNTs compared to P-MWCNTs for both MB and IC degradation.

Fundamental Determinants of the Accuracy of Equilibrium Constants for Affinity Complexes.

The equilibrium constant of a chemical reaction is arguably the key thermodynamic parameter in chemistry; we naturally expect that equilibrium constants are determined accurately. The majority of equilibrium constants determined today are those of binding reactions that form affinity complexes, such as protein-protein, protein-DNA, and protein-small molecule. There is growing awareness that the determination of equilibrium constants for highly stable affinity complexes may be very inaccurate. However, fundamental (i.e., method-independent) determinants of accuracy are poorly understood. Here, we present a study that explicitly shows what the accuracy of equilibrium constants of affinity complexes depends on. This study reveals the critical importance of the choice of concentration of interacting components and creates a theoretical foundation for improving the accuracy of the equilibrium constants. The predicted influence of concentrations on accuracy was confirmed experimentally. The results of this fundamental study provide instructive guidance for experimentalists independently on the method they use.

Silver decoration of Cr2O3 nanoparticles: Facile preparation of Cr2O3 nanoparticles and Ag–Cr2O3 nanocomposites and characterization of their antibacterial activity and ability to photocatalytically degrade organic wastes under visible light

An eco-friendly, single-step process was adopted for the preparation of Cr2O3 nanoparticles (CR-NPs), and different concentrations of Ag were doped into the CR-NPs through liquid impregnation to synthesize a series of Ag-CRNPs composites. In order to prevent agglomeration, chemical transformation, and weak adhesion of Ag to CR-NPs, a mechanical process of circular-motion grinding and high-temperature treatment in a sealed condition were used. Well-defined heterojunctions were successfully formed between Ag and CR-NPs. In comparison to the CR-NPs, the Ag-doped CR-NP composites exhibited excellent performance in photocatalytic and antibacterial applications. Under visible light (VL), the best-performing composite (2 %-Ag decorated CR-NPs) showed 96 %, 79 %, and 57 % decomposition of methylene blue, Congo red, and tetracycline, respectively, in 100 min, which was attributed to a synergetic effect in the composites. The rate constant of the photocatalytic reaction is 14 times higher than that of the reaction without a photocatalyst. The enhanced efficiency was attributed to a reduced bandgap, prolonged retention of photogenerated electron–hole pairs, an increased amount of active spots, and increased absorption of VL. Similarly, the best-performing composite exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus with zones of inhibition of 15.4 and 15.1 mm, respectively. The 2 %-Ag decorated CR-NPs were the most efficient and exhibited robust recyclability until the fifth cycle (≥90 %). The photocatalytic activity was primarily driven by reactive oxygen species, holes and hydroxyl radicals.

Axisymmetric inertialess model for the capture of airborne microparticles using an electrospray

We theoretically analyze the effectiveness of an electrospray of ultrafine droplets to filter out micron sized particles from a gas stream. To that end, we introduce an axisymmetric configuration where the airborne particles merge with the electrospray. The droplets attach to the particles, charging them, and both droplets and charged particles are eventually driven towards a collector by means of an electric field. The attachment process is described through a set of reaction constants based on calculated collision cross-sections, yielding particles with different charge levels. The problem involves computation of the concentrations of each type of particle, the gas flow, and the electric field due to the applied voltages and the space charge. Preliminary numerical simulations show a filtration efficiency that is above 95% for particles larger than about 2μm and rapidly declines for smaller particles, though this drop of the efficiency can be postponed to smaller particle sizes by decreasing the ratio of particle to electrospray fluxes or the ratio of the inlet velocity of the particle carrying gas to the velocity induced by electric forces inside the device. Pending an exhaustive numerical exploration of the parameter space of the system, these results also show that the gas flow structure, which is strongly affected by the charged particles, is key for high filtration efficiency.

Unveiling the mechanisms of peracetic acid activation by iron-rich sludge biochar for sulfamethoxazole degradation with wide adaptability

Advanced oxidation processes (AOPs) based on peracetic acid (PAA) has been extensively concerned for the degradation of organic pollutants. In this study, metallic iron-modified sludge biochar (Fe-SBC) was employed to activate PAA for the removal of sulfamethoxazole (SMX). The characterization results indicated that FeO and Fe2O3 were successfully loaded on the surface of the sludge biochar (SBC). Fe-SBC/PAA system achieved 92% SMX removal after 30 min. The pseudo-first-order kinetic reaction constant of the Fe-SBC/PAA system was 7.34 × 10−2 min−1, which was 2.4 times higher than the SBC/PAA system. The degradation of SMX was enhanced with increasing the Fe-SBC dosage and PAA concentration. Apart from Cl−, NO3− and SO42− had a negligible influence on the degradation of SMX. Quenching experiments and electron paramagnetic resonance (EPR) techniques identified the existence of reactive species, of which CH3C(O)OO•, 1O2, and O2•- were dominant reactive species in Fe-SBC/PAA system. The effect of different water matrices on the removal of SMX was investigated. The removal of SMX in tap water and lake water were 79% and 69%, respectively. Four possible pathways for the decay of SMX were presented according to the identification of oxidation products. In addition, following the ecological structure-activity relationship model (ECOSAR) procedure and the germination experiments with lettuce seeds to predict the toxicity of the intermediates. The acute and chronic ecotoxicity of SMX solution was dramatically diminished by processing with Fe-SBC/PAA system. In general, this study offered a prospective strategy for the degradation of organic pollutants.