Rate Constant Increases Research Articles

Study on the effect of particles in oilfield produced water on the deposition process of CaCO3

In crude oil production, scale deposition significantly reduces production output and elevates operational costs, posing a severe threat to production safety. While chemical methods have been extensively explored for the scaling and inhibition of inorganic salts, the inorganic scaling triggered by solid particle scaling in complex oilfield water has largely been overlooked. This study involves the introduction of particles into a supersaturated CaCO3 solution, utilizing static scale inhibition and conductivity techniques to examine their influence on the scaling process and crystallization rate. It is evident that solid particles expedite the deposition process of CaCO3. Moreover, the deposition rate of CaCO3 is influenced by factors such as the solid particle content, particle size, and stirring speed. It is noteworthy that the presence of solid particles solely impacts the formation rate of CaCO3 crystals, without altering the total deposition. Specifically, under conditions of 70°C, 250/min stirring speed, and 0.08% SiO2 addition, the deposition rate of CaCO3 is enhanced by 13.5%. The nucleus growth rate constant increases from 11.10 × 10-3min-1 to 14.52 × 10-3min-1 and the crystal growth rate constant increases from 3.02 × 10-3min-1 to 3.36 × 10-3min-1 at most. Observations made through scanning electron microscopy (SEM) and polarized light microscopy reveal that scaling occurs predominantly on the added solid particles in later stages, indicating that solid particles in supersaturated solutions serve as crystal nuclei, inducing the growth of CaCO3 crystals and thus accelerating scaling. This research provides valuable insights for the study of scaling in complex water environments.

Removal of aqueous oxytetracycline using copper-loaded biochar-activated peroxodisulfate: Synergistic mechanism of adsorption and nonradical 1O2

Antibiotic contamination from livestock and poultry farming wastewater has caused substantial adverse effects on the environment and humans. Therefore, in this study, bifunctional adsorption and synergistic degradation of Cu and N codoped biochar (Cu-N/BC) were utilized to efficiently promote the activation of peroxodisulfate (PDS) for removing oxytetracycline (OTC). Cu-N/BC exhibited a high adsorption affinity toward OTC. The adsorption of OTC (50 mg/L) by 0.4 g/L catalyst could reach 36.2 mg/g in 30 min, and the removal of OTC reached 97.24 % in 90 min after adding 0.5 mM PDS. Preadsorption experiments demonstrated that the OTC enriched on the Cu-N/BC surface facilitated the subsequent degradation reaction，its reaction rate constant increases from 0.026 to 0.037. Low-valent copper (Cu0/Cu+), pyridine N, and oxygen-containing functional groups (CO) were the main active sites of Cu-N/BC, and the main contribution toward OTC degradation was from the nonradical pathway of singlet oxygen. Furthermore, potential degradation pathways were revealed, and the intermediates in the OTC degradation process were identified. Cu-N/BC exhibited stable performance, a wide pH application range, and great potential for practical application. This study offers a new concept for designing a bifunctional carbon-based material to remove antibiotics from wastewater.

Giant Photodegradation Rate Enabled by Vertically Grown 1T/2H MoS2 Catalyst on Top of Silver Nanoparticles

The exaltation of the photodegradation performance of dichalcogenide MoS2 grown on top of silver nanoparticles (Ag‐NPs) is reported on. The fabricated MoS2 nanosheets nucleate vertically from Ag‐NPs seeds, enabling the growth of both metallic and semiconductor phases 1T/2H‐MoS2. Findings reveal remarkable enhancement of the Raman scattering and an exceptional broadband optical absorption attributed to plasmonic effects induced by the presence of both metallic 1T‐MoS2 and Ag‐NPS at 2H‐MoS2 interfaces. To leverage this effect, photodegradation tests are conducted to remove methyl orange pollutant. Notably, results reveal a significant increase in photodegradation efficiency and rate constant, reaching up to 120% and 550% over pristine 2H‐MoS2, respectively. This finding underscores the role of Ag‐NPs and 1T‐MoS2 tandem to unlock the superior photodegradation properties of vertically aligned 2H‐MoS2 toward methyl orange, paving the way for the development of dichalcogenide‐based hybrid photocatalyst for wastewater treatment and environmental remediation.

Theoretical evidence for a pH-dependent effect of carbonate on the degradation of sulfonamide antibiotics

Carbonate (CO32−/HCO3−) have a significant impact on advanced oxidation processes (AOPs) by consuming reactive free radicals such as HO• to generate CO3•-. However, research on the mechanisms and kinetics of CO3•- remains limited. This study investigates the degradation mechanism and kinetics of sulfonamide antibiotics (SAs) by CO3•- through theoretical calculations. The calculation results revealed that the effect of CO3•- on SAs degradation is pH-dependent due to the dissociable sulfonamide group (-SO2NH-) of SAs in the common water treatment pH range (3–8). The main reaction type of CO3•- with both neutral and anionic molecules of SAs is single electron transfer reaction. Frontier molecular orbital theory (FMO) illustrated that deprotonation of the sulfonamide group of SAs decreases the charge density on the heterocyclic ring, facilitating the electrophilic addition of CO3•-. The second-order rate constants of the neutral and anionic molecules of SAs with CO3•- were calculated as 7.57 × 101∼1.84 × 108 and 1.81 × 107∼7.94 × 109 M−1 s−1, respectively, resulting in an increase in the apparent reaction rate constants with pH. Stepwise multiple linear regression was employed to predict reactivity with anionic sulfonamide antibiotics (SAs−). Two models with outstanding prediction and stability were developed with coefficients of determination R2 of 0.660 and 0.681, respectively. The degradation kinetics simulation indicated that in the UV/H2O2 process in the presence of carbonate, the degradation rate of SAs increased with pH. Furthermore, the contribution of CO3•- to SMX degradation increased while that of HO• decreased. This study highlights the contribution of carbonates to the micropollutant degradation in the UV/H2O2 process as the model, providing theoretical insights into the development of carbonate-based AOPs.

Effect of the EMIM Cation on the CO2 Reduction Reaction on Gold

The electrochemical CO2 reduction reaction (CO2RR) is emerging as a promising method to produce carbon neutral chemical feedstocks. Additives or co-catalysts in the electrolyte can lower the activation barrier for CO2RR, yielding faster conversion rates at lower voltages. Recently, electrocatalytic CO2 reduction mediated by ionic liquids (IL) has been reported but with conflicting accounts to whether the ILs benefit CO2RR or adversely, the competing hydrogen evolution reaction (HER).We report the effect of added IL EMIM-Cl, specifically EMIM+, in aqueous solutions on the electrochemical CO2RR and competing HER on gold. We show the CO2 reduction current increases by ~1.5x with the highest amount of added EMIM+ relative to the pure electrolyte. Differential pulse voltammetry reveals an additional large change in the reduction current that only appears with both CO2 and EMIM+ present. Lastly, we use advanced electrochemical analysis methods to determine the reaction kinetics and preliminary evidence shows that the standard heterogeneous rate constant increases for the reaction at large overpotentials while the HER is suppressed at low overpotentials with EMIM+ present.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Full solar-spectrum available Z-scheme MOF-on-MOF heterostructure for highly efficient photocatalytic VSCs removal

The construction of efficient photocatalysts with strong response to sunlight is crucial for clean and sustainable pollutant degradation and environmental remediation. Herein, a novel MOF-on-MOF structural photocatalyst named HKU@MIL with Z-scheme heterojunction was successfully designed. The light response of the composites effectively extends to the whole solar spectrum through a simple activation process, addressing the issue of the low utilization of sunlight by photocatalysts. The photocatalytic degradation rate of methyl mercaptan by activated HKU@MIL is 2.2, 3.2, and 1.8 times higher than that of NH2-MIL-125, HKUST-1, and HKU/MIL-5 (physical mixtures), respectively. Under simulated sunlight irradiation, the rate constant increases to 0.507 min−1, which is 1.4 times higher than that under visible light. Additionally, the composites exhibit good photocatalytic performance when irradiated with near-infrared light alone. The heterojunction type of the photocatalyst was investigated according to in-depth analysis of X-ray photoelectron spectroscopy. Additionally, the interfacial charge transmission mode of the composites and the probable pathways for methyl mercaptan degradation were explored through band structure analysis, radical quenching tests and electron spin resonance analysis. The improved photocatalytic performance of activated HKU@MIL can be attributed to the full solar spectral response and the successful creation of the Z-scheme electron migration channel, which serves to reinforces the electron pump effect. It achieves this by improving the transmission of photogenerated carriers and ensuring the strongest redox potential. This work presents a new perspective on enhancing the utilization of sunlight by photocatalysts and improving the photocatalytic performance of heterojunction photocatalysts used in environmental remediation.

Plasmon-enhanced fluorescence for biophotonics and bio-analytical applications.

Fluorescence spectroscopy serves as an ultrasensitive sophisticated tool where background noises which serve as a major impediment to the detection of the desired signals can be safely avoided for detections down to the single-molecule levels. One such way of bypassing background noise is plasmon-enhanced fluorescence (PEF), where the interactions of fluorophores at the surface of metals or plasmonic nanoparticles are probed. The underlying condition is a significant spectral overlap between the localized surface plasmon resonance (LSPR) of the nanoparticle and the absorption or emission spectra of the fluorophore. The rationale being the coupling of the excited state of the fluorophore with the localized surface plasmon leads to an augmented emission, owing to local field enhancement. It is manifested in enhanced quantum yields concurrent with a decrease in fluorescence lifetimes, owing to an increase in radiative rate constants. This improvement in detection provided by PEF allows a significant scope of expansion in the domain of weakly emitting fluorophores which otherwise would have remained unperceivable. The concept of coupling of weak emitters with plasmons can bypass the problems of photobleaching, opening up avenues of imaging with significantly higher sensitivity and improved resolution. Furthermore, amplification of the emission signal by the coupling of free electrons of the metal nanoparticles with the electrons of the fluorophore provides ample opportunities for achieving lower detection limits that are involved in biological imaging and molecular sensing. One avenue that has attracted significant attraction in the last few years is the fast, label-free detection of bio-analytes under physiological conditions using plasmonic nanoparticles for point-of-care analysis. This review focusses on the applications of plasmonic nanomaterials in the field of biosensing, imaging with a brief introduction on the different aspects of LSPR and fabrication techniques.

Hydrolysis rate constants of ATP up to 120 °C and 1.6 GPa: Implications for life at extreme conditions

Extreme environments are habitats for a diverse array of microorganisms, namely extremophiles, that have evolved unique biochemical adaptations to their geological setting. Some examples of extremophiles can be found in the subseafloor or near hydrothermal vents on the ocean floor. Cultivated strains of extremophiles have demonstrated the ability to tolerate temperatures (T) up to 122 °C and pressures (P) up to 125 MPa. Organisms depend on the stability of key metabolites, such as adenosine triphosphate (ATP), to survive and reproduce under these conditions. In order to maintain their intracellular ATP levels, living cells must compensate for the abiotic hydrolysis of ATP, which occurs at a particularly rapid rate at high temperatures. The role of high pressures and high temperatures in abiotic hydrolysis of ATP has been rarely investigated despite the potential for this phenomenon to contribute to limit the adaptation of microorganisms to simultaneous extreme temperatures and pressures. This study presents new data on the effect of pressure on the abiotic hydrolysis of ATP to adenosine diphosphate (ADP) at elevated temperatures. In situ Raman spectra were measured at high pressure and high temperature of the hydrolysis of aqueous disodium ATP solutions in two experimental systems: a hydrothermal diamond anvil cell (HDAC) and a gas-pressurized autoclave. These two systems permitted the determination of hydrolysis rate constants of ATP into ADP up to 1670 MPa at 80 °C, 100 °C, and 120 °C. The data exhibited Arrhenian behavior with a slight decrease in activation energy from 0.5 MPa to 140 MPa. The effect of pressure on ATP hydrolysis rate constants was found to be vanishingly low in the so far known vital range up to 125 MPa. Abiotic hydrolysis rates of ATP showed a pronounced increase at higher pressures. For example, at 100 °C, a rise in pressure from 365 MPa to approximately 1670 MPa results in a nearly tenfold increase in the ATP hydrolysis rate constant. When compared with the typical ATP turnover times reported in living cells, the abiotic ATP hydrolysis rates determined in this study provide insights into the pressure and temperature conditions that could be consistent with living microorganisms.

Pharmacokinetic-Pharmacodynamic Analysis of pH-Responsive Doxorubicin-Releasing Micelles with Anticancer Activity.

This study aimed to investigate the effect of in vivo pH-responsive doxorubicin (DOX) release and the targetability of pilot molecules in folic acid (FA)-modified micelles using a pharmacokinetic-pharmacodynamic (PK-PD) model. The time profiles of intratumoral DOX concentrations in Walker256 tumor-bearing rats were monitored using a microdialysis probe, followed by compartmental analysis, to evaluate intratumoral tissue pharmacokinetics. Maximal DOX was released from micelles 350 min after the administration of pH-responsive DOX-releasing micelles. However, FA modification of the micelles shortened the time to peak drug concentration to 150 min. Additionally, FA modification resulted in a 27-fold increase in the tumor inflow rate constant. Walker256 tumor-bearing rats were subsequently treated with DOX, pH-responsive DOX-releasing micelles, and pH-responsive DOX-releasing FA-modified micelles to monitor the tumor growth-time profiles. An intratumoral threshold concentration of DOX (55-64 ng/g tumor) was introduced into the drug efficacy compartment to construct a PD model, followed by PK-PD analysis of the tumor growth-time profiles. Similar results of threshold concentration and drug potency of DOX were obtained across all three formulations. Cell proliferation was delayed as the drug delivery ability of DOX was improved. The PK model, which was developed using the microdialysis method, revealed the intratumoral pH-responsive DOX distribution profiles. This facilitated the estimation of intratumoral PK parameters. The PD model with threshold concentrations contributed to the estimation of PD parameters in the three formulations, with consistent mechanisms observed. We believe that our PK-PD model can objectively assess the contributions of pH-responsive release ability and pilot molecule targetability to pharmacological effects.

On the high temperature oxidation of MoSi2 particles with boron addition

Boron doped MoSi2 particles have been envisioned as sacrificial particles for self-healing thermal barrier coatings (TBCs) but their oxidation behaviour is yet not well understood. In this work, oxidation of MoSi2 based particle is studied in the temperature range of 1050–1200 °C. The oxidation proceeds from a transient to a steady-state oxidation stage. The kinetics during steady-state oxidation is captured with a thermal diffusion-based model. As compared to the oxidation of pure MoSi2 particles, the addition of boron strongly enhances the silica formation. Also, a finer dispersion of MoBx in the MoSi2 matrix accelerates the formation of silica. The oxide growth rate constant increases proportional with the boron content of the MoSi2 particles. This enhanced oxidation is related to the microstructure of the oxide scale. Upon oxidation, boron yields B2O3, which promptly merge with SiO2 to form amorphous borosilicate, hindering the formation of crystalline SiO2. Consequently, the migration of oxygen in the borosilicate oxide scale is faster than in the silica oxide scale on pure MoSi2 particles.

Quantitative investigation on microwave-accelerated fructose conversion via fluorescent thermometry

The use of microwave (MW) is promising for resolving energy-intensive problems that occur in carbohydrate bioconversion. To quantitatively investigate the mechanism of MW-accelerated reactions, the present study designs three carbon-based catalysts with distinct dielectric loss values (namely, SCS-SO3H, SCS-800-SO3H, MHCS-800-SO3H) for fructose hydrolysis. A fluorescence thermometer (Eu/Tb metal organic complex) was loaded on catalysts for in situ measurement of their localized temperature during MW heating. The combination of fluorescence experiments and theoretical modelling predicts that the temperature gradient between SCS-800-SO3H particles and bulk solvents reaches 26.10°C, which causes an 8.13-fold increase in reaction rate constants. Surprisingly, this speedup value is increased to 28.57 because of the thermal gradient up to 62.10°C when using MHCS-800-SO3H. In contrast, the MW-transparent SCS-SO3H exhibits no significant increase in the reaction rate. The quantitative elucidation of dominant roles of hot spots is promising for guiding the development of high-efficiency catalysts for MW-assisted heterogeneous reactions.

Effect of Impurities on Solubility and Metastable Zone Width of Manganese Sulfate Monohydrate

AbstractRecovering manganese from waste batteries is an important issue to promote the development of new energy. Herein, nickel sulfate and cobalt sulfate, representative impurities in waste battery leachate, are selected to examine their influence on the crystallization thermodynamics and crystal nucleation of manganese sulfate monohydrate. This work assessed alterations in solubility and metastable zone width (MSZW) due to the presence of impurities. The results showed a decrease in manganese sulfate monohydrate solubility in water with increasing impurity concentrations of either nickel sulfate or cobalt sulfate. The effects of initial concentration, heating rate, and impurity concentration on MSZW demonstrated a consistent increase in MSZW as these factors increased. The MSZW data are fitted using the self‐consistent Nývlt‐like model and the classical 3D nucleation theory model. The results revealed a general increase in the nucleation rate constant, K, with increasing saturation temperature or decreasing nickel sulfate concentration. Conversely, the solid‐liquid interface energy, γ, generally decreases with increasing saturation temperature or decreasing nickel sulfate concentration. Based on the influence observed on the interface energy, a possible mechanism is proposed that suggests that impurities inhibit crystal nucleation through adsorption.

Addressing challenges of BiVO4 light-harvesting ability through vanadium precursor engineering and sub-nanoclusters deposition for peroxymonosulfate-assisted photocatalytic pharmaceuticals removal

In this study, we present a complex approach for increasing light utilisation and peroxymonosulfate (PMS) activation in BiVO4-based photocatalyst. This involves two key considerations: the design of the precursor for BiVO4 synthesis and interface engineering through CuOx sub-nanoclusters deposition. The designed precursor of ammonium methavanadate (NH4VO3, NHV) leads to reduction in particle size, better dispersion and improved light harvesting ability, confirmed by the calculations of the local volume rate of photon absorption (LVRPA) using the Six-Flux Radiation Absorption-Scattering model. The morphological changes result in a significant improvement in photocatalytic activity under visible light for the degradation of pharmaceuticals (naproxen and ofloxacin) compared to the commercial NH4VO3. Additionally, CuOx sub-nanoclusters were deposited on designed BiVO4 and characterised using X-ray absorption near edge structure (XANES). The presence of sub-nanoclusters enhanced charge carriers separation, resulting in an increase in the apparent rate constants of 1.60 and 3.32-times for photocatalytic NPX and OFL removal, respectively. The application of obtained Vis light active photocatalysts in the presence of 0.1 mM PMS resulted in remarkably more efficient degradation of NPX (100 % within 60 min) and OFL (98.2 % within 120 min). PMS/Vis420/CuOx/BiVO4 system exhibited high stability and reusability in the subsequent cycles of photodegradation. However, high PMS dosage induced Bi leaching which may cause the instability of the photocatalyst. Finally, to address the environmental implications of pharmaceutical removal and adhere to the Guidelines for drinking-water quality, toxicity assessments using Vibrio fischeri bacteria were performed and compared to a quantitative structure–activity relationship (QSAR) model.

Synergistic reduction of nitrophenols by Au-CDs nanoconjugates with NaBH4

Developing sustainable and innovative approaches for the efficient reduction of nitrophenols is crucial for environmental remediation, for managing health concerns posed by their widespread presence as hazardous pollutants in industrial effluents and contaminated water. We report the use of 12.9 ± 1 nm (TEM data) sized gold carbon dot nanoconjugates (Au@CDs) for catalytic conversion of o, m, p-nitrophenols to aminophenols by sodium borohydride. A simple approach was followed to synthesize ultra-small and highly stable Au@CDs, using citric acid and PEG as reducing and stabilizing agents. X-ray diffraction analysis verified the formation of nano-crystalline nanoconjugates. These nanoconjugates showed a remarkable catalytic activity in the range of 0.22–0.33 s−1 (varying with nanoconjugate concentration) which was much higher compared to conventional chemical methods of reduction. All the catalytic reaction experiments were performed at room temperature (27 ± 2 °C). Furthermore, an increase in rate constant was observed with increasing concentration of nanoconjugates. The catalytic activity of Au@CDs nanoconjugates was observed to be in order of m-nitrophenol > o-nitrophenol > p-nitrophenol with apparent rate constant (k aap) values of 0.068, 0.043 and 0.031, respectively. Comparative analysis with GNPs, CDs and Au@CDs nanoconjugates stated that the nanoconjugates had superior catalytic activity. The research can have significant implications in the development of new strategies for environmental remediation and biomedical applications.

Study on the kinetics of formation process of emulsion of heavy oil and its functional group components

Enhanced oil recovery (EOR) by in situ formation of oil-in-water emulsion in heavy oil cold production technology has received growing interest from the petroleum industry. We present an experimental study of emulsification of model oils prepared by heavy oil and its functional group compositions dissolved into toluene brought into contact with a surfactant solution. The effects of functional group composition, emulsifier concentration, temperature, pH and stirring speed on the emulsification rate of heavy oil was investigated. A second-order kinetic model characterizing the temporal variation of conductivity during the emulsification has been established. The results show that acidic and amphoteric fractions exhibit higher interfacial activity, larger emulsification rate constant and faster emulsification rate. With the increase of emulsifier concentration, the emulsification rate constant increase to the maximum value at a concentration of 0.05 mol/L before decreasing. Temperature increase benefits the emulsification rate and the activation energy of the emulsification process is 40.28 kJ/mol. Higher pH and stirring speed indicate faster emulsification rate. The heterogeneity of emulsions limits the accuracy of dynamic characterization of the emulsification process and the determination method of emulsification rate has always been controversial. The conductivity method we proposed can effectively evaluates the emulsification kinetics. This paper provides theoretical guidance for an in-depth understanding of the mechanism and application of cold recovery technology for heavy oil.

Silica polymerization and nanocolloid nucleation and growth kinetics in aqueous solutions

Amorphous silica precipitation from aqueous solutions at low temperatures (<100 °C) involves the initial nucleation and growth of silica polymers followed by aggregation, cementation and recrystallization to form opaline silica. In this study, silica polymerization was studied at temperature 23–80 °C, pH 2.48–9.65, and ionic strength 0.01–0.53 mol kg−1. Measured changes in the concentration of monomeric silica (SiO2(mono)) were fit assuming the polymerization reaction is fourth-order with respect to the difference between the concentration of silicic acid (Si(OH)4(aq)) and its concentration at equilibrium (Si(OH)4(aq)eq) with respect to amorphous silica:r=-k4AsmSi(OH)4(aq)-mSi(OH)4(aq)eq4where r is the overall rate of the reaction, As is the specific surface area of the formed polymers, calculated assuming particle-size-dependent solubility and a spherical polymer geometry, and k4 is the rate constant. The rate constant at zero ionic strength is given by:k0=Aexp-Ea/RTaOH-nwhere A is a pre-exponential constant (0.3822 mmol−3 cm−2 s−1), Ea is the activation energy (29.87 kJ mol−1), and n is equal to −0.80. The overall rate constant as a function of ionic strength (I) is given by:k4=k0Imwhere m is equal to 0.65. The rate constant increases by approximately six orders of magnitude from pH of 2 to 10 and one order of magnitude between temperature ∼20 and 80 °C. However, hydrolysis of silicic acid (Si(OH)4(aq)) at pH above ∼8 decreases the relative abundance of Si(OH)4(aq) while increasing the solubility of amorphous silica, thereby decreasing the rate of silica polymerization. The inferred reaction order is consistent with a reaction mechanism rate-limited by the formation of the cyclic tetramer across a wide range of pH. The time-dependence of the specific surface area during polymerization reflects the formation of critical nuclei towards the beginning of the polymerization process and Ostwald ripening of larger polymers towards the end of the polymerization process. The developed rate equation can predict rates of silica polymerization across a wide range of aqueous solution compositions.

Electrochemical Study of OH− in Molten MgCl2-NaCl-KCl Salts

The present study determines the equilibrium concentration of OH- in molten MgCl2-NaCl-KCl salts and measures the kinetic properties data of OH- (diffusion coefficient, exchange current density, charge transfer coefficient, limiting current density, and standard rate constant) accordingly at different temperatures. The equilibrium concentration of OH- descends as the temperature increases, which ranges from 4.11 to 2.84 × 10−6 mol cm−3 in the temperature range of 600 °C–800 °C. The diffusion coefficient follows Arrhenius law with a value between 2.46 and 4.48 × 10−4 cm2 s−1. The exchange and limit current densities, and standard rate constant increase with temperature. The calculated standard rate constant k0 follows Arrhenius law, which is in the range from 1.23 to 2.50 × 10−4 cm s−1. The measured charge transfer coefficient is independent of temperature, which validates the present measurements.

Activation of peroxydisulfate via BiCoFe-layered double hydroxide for effective degradation of aniline.

The sulfate radical-based advanced oxidation processes (SR-AOPs) is a promising method for the degradation of pollutants, with the development of highly efficient catalysts for persulfate activation has been widely concerned. The novel BiCoFe-LDH (BCF-x) was synthesized successfully by coprecipitation method, which can activate peroxydisulfate (PDS) efficiently to degrade aniline. Comparative analysis with pure CoFe-LDH revealed a remarkable increase in reaction rate constant by approximately 14.66 times; the degradation rate of aniline (10mg/L) was 100% in 60min with the condition of 0.5g/L BCF-1.5 and 0.5g/L PDS, due to BCF-1.5 which was characterized as a complex of CoFe-LDH and Bi2O2CO3, promoting electron transport to improve the efficiency of activated PDS. In the reaction system, SO4•-, ·OH, and 1O2 were responsible for the aniline degradation and ·OH was the primary one. Furthermore, this work proposes a reaction electron transfer catalytic mechanism, which provided a new insight and good application prospect for efficient activation of PDS for pollutant degradation.

Role of tea polyphenols in enhancing the performance, sustainability, and catalytic cleaning capability of membrane separation for water-soluble pollutant removal

Tea polyphenols (TPs), like green tea polyphenol (GTP) and black tea polyphenol (BTP), with phenolic hydroxyl structures, form coordination and hydrogen bonds, making them effective for bridging inorganic catalysts and membranes. Here, TPs were employed as interface agents for the preparation of TPs-modified needle-clustered NiCo-layered double hydroxide/graphene oxide membranes (NiCo-LDH-TPs/GO). The incorporation of porous guest material, NiCo-LDH-TPs, facilitated water channel expansion, enhancing membrane permeability and resulting in the development of high-performance, sustainable catalytic cleaning membranes. The introduction of TPs through coordination weakened the surface electronegativity of NiCo-LDH, promoting a uniform mixed dispersion with GO and facilitating membrane self-assembly. NiCo-LDH-GTP/GO-5 and NiCo-LDH-BTP/GO-5 membranes demonstrated permeances of 85.98 and 90.76 L m−2 h−1 bar−1, respectively, with rejections of 98.73% and 99.54% for methylene blue (MB). Notably, the NiCo-LDH-BTP/GO-5 membrane maintained a high rejection of 97.11% even after 18 cycles in the catalytic cleaning process. Furthermore, the modification of GTP and BTP enhanced MB degradation through PMS activation, resulting in a 0.33% and 0.35% increase in the reaction rate constants of NiCo-LDH, respectively, while reducing metal ion spillover. These findings highlighted the potential of TPs in enhancing the efficiency and sustainability of catalytic cleaning GO membranes for water purification and separation processes.

Experimental study of the evaporation characteristics of unsymmetrical dimethylhydrazine in a sub-supercritical environment

In this study, the temperature–pressure separation technique was used to successfully obtain the process of the unsymmetrical dimethylhydrazine droplet diameter variation with time during evaporation in subcritical, supercritical, and far-supercritical environments at temperatures and pressures of 473–773 K and 1–9 MPa, respectively. The results show that unsymmetrical dimethylhydrazine droplet evaporation has two characteristic stages, transient heating and steady-state evaporation, under low-pressure and low-temperature environments; the steady-state evaporation stage influences droplet evaporation life more than the transient heating stage. Under high-pressure and high-temperature environments, droplet evaporation shows only a single feature of steady-state evaporation, and the droplet expansion process in the transient heating stage disappears. The normalized droplet lifetime decreased exponentially with temperature and decreased linearly and monotonically with pressure. The evaporation rate constant increases linearly and monotonically with temperature and exponentially with pressure.