Reaction Kinetic Constants Research Articles

Applying Bayesian statistics and MCMC to ozone reaction kinetics: Implications for water treatment models.

Ozonation is an advanced oxidation process widely used for water and wastewater treatment. The pseudo-first-order kinetic model is frequently applied for designing and scaling this treatment, offering insights into oxidation pathways through ozone reaction rate constants (kO3,P and kOH,P) and the exposure ratio term (Rt). This work evaluates the kinetic constants for ozonation reactions involving three pharmaceuticals, caffeine (CAF), atenolol (ATL), and propranolol (PRO), classified as emerging contaminants (ECs), with the aim of guiding future research and industrial applications for various pollutants. Two estimation methods were compared: the conventional indirect linearization method and a novel direct Bayesian approach employing the Monte Carlo Markov Chain (MCMC) method with the Metropolis-Hastings (MH) algorithm. Additionally, measurement uncertainties (σmed - 1, 2 and 5%) were incorporated into the direct method, enabled by Bayesian inference, to assess the impact of noise on the estimation of kinetic constants. This consideration is critical for ensuring safety, efficiency, and reproducibility in industrial applications. Results indicated that the direct Bayesian method was both accurate and promising. It effectively estimated the pollutant concentration curves despite the presence of noise, providing improved parameter adjustments compared to the indirect method. While, σmed influenced the parameter estimation, the Bayesian approach maintained a superior fit to the curves even with measurement noises, showing applicability of the proposed method. The obtained Markov chains exhibited good convergence, particularly for the direct oxidation parameter (kO3,P), suggesting the method's effectiveness and sensitivity to the molecular structure of each compound. Furthermore, the use of direct residual ozone measurement (sensors) in this study was found to influence parameter prediction, leading to variations in rate constants compared to values reported in the literature. Therefore, this study recommends using the direct Bayesian method with the exposure ratio term for more reliable industrial-scale ozonation applications, offering a significant advancement over traditional approaches.

Confined pyrolysis to transfer MXene-like MOF into 2D carbon nanosheet boosting the ozone oxidation of antibiotic: Degradation behavior and intrinsic mechanism

Ozone oxidation as a means of water treatment has received great attention in recent years, but ozone has low solubility and utilization, which hinders their efficient treatment of refractory pollutants. Herein, a dopamine-encapsulated 2D MOF strategy is proposed, where different metal salts including (acetylacetone iron, manganese, copper, etc.) are doped in it as active site precursors. After pyrolysis, 2D hollow porous carbon nanosheet catalysts such as Mn-HCNSs, Fe-HCNSs, Cu-HCNSs and Co-HCNSs are formed due to the rigid interface-induction of dopamine. Mn-doped Mn-HCNSs exhibits the best catalytic degradation performance when the antibiotic tetracycline is used as the target pollutant, and the degradation efficiency reached 90 % within 25 min (k = 0.213 min−1). This excellent catalytic performance can be attributed to several advantages: (i) the hollow porous 2D structure facilitates mass transfer and enhances the reaction kinetic constants; (ii) the confinement effect of dopamine wrapping facilitates the generation of more dispersed active sites and accelerates its ozone decomposition efficiency. This study expands the application of 2D MOF-derived porous carbon materials in ozone oxidation.

Preparation of CoS2/Fe/SA hydrogel spheres with Fe2+ slow-release effect to improve Fenton reaction efficiency

Fenton reaction is a traditional advanced oxidation process that has long been used for wastewater treatment. However, the narrow pH range of 2–4, the inefficient utilization of both H2O2 and Fe2+, and the large amount of iron sludge formation limit its application. Here, we prepared sodium alginate composite hydrogel spheres with both Fe2+ and CoS2 loading (denoted as CoS2/Fe/SA hydrogel spheres) to construct a CoS2/Fe/SA + H2O2 reaction system. The degradation efficiency of carbamazepine (CBZ) in the CoS2/Fe/SA + H2O2 system was significantly enhanced with a first-order kinetic reaction constant of 0.1958 min−1, which is 8.9 times higher than that in Fe2++H2O2 system. When the initial solution pH was in the range of 2–8, the removal rate of CBZ at 90 min reaction time ranged from 96.5 % to 99.9 %. The enhanced degradation efficiency even in a slightly alkaline aqueous solution was due to the sustained slow release of Fe2+ from the CoS2/Fe/SA hydrogel spheres that enhances the utilization of Fe2+ and the promotion of Fe3+/Fe2+ cycling via CoS2. Moreover, the release amount of Fe2+ in CoS2/Fe/SA hydrogel spheres could be controlled by tuning the Fe2+ loading amount during preparation, which in turn determines its number of cycling uses.

Ultrafast degradation of Cu(II)-EDTA by peroxymonosulfate activated with polyoxometalate clusters intercalated layered double hydroxides: Simultaneous decomplexation and resourcelization

Technologies used to handle metal pollution are often ineffective for complexed metals, which have refractory biodegradability, high solubility, and strong mobility, posing significant threats to the ecological environment. This work proposed a novel catalytic system for the proper disposal of Cu(II)-EDTA pollution. Polyoxometalate cluster intercalated CaFe layered double hydroxide (LDH-CoPW) prepared through a mild and convenience method was applied to activate peroxymonosulfate (PMS) for the degradation of Cu(II)-EDTA and the simultaneous immobilization of the released Cu(II). Compared to direct waste or complex regeneration of catalysts, the application of used LDH-CoPW in clean energy production was proposed to further reduce carbon emissions. Under the combination of 0.1 g/L of LDH CoPW and 0.1 mM of PMS, nearly 100 % of Cu(II)-EDTA was removed within 3 min of reaction time, and 49.6 % of Cu(II) was adsorbed within 60 min of reaction time. The second-order reaction kinetic constants of Co(IV) = O with various probes were confirmed by competition kinetics method. Based on this, Co(IV) = O was identified as the dominant RSs using a scientific probe-based kinetic model. Furthermore, CaFe-LDH did not directly activate PMS but ensured the reactivity of the catalytic system by promoting the redox cycle of cobalt species. Finally, due to the regulation of Cu on the electronic structure of the catalyst, the electrochemical performance of the used LDH-CoPW surpassed that of fresh LDH-CoPW and CaFe-LDH, showing great potential in clean energy production.

Carpet Grass Polyphenol Reductive Degradation of Aqueous Nitrate-A Conceptual Field Application Study.

Rainwater flowing along the ground, and from hard surface such as pavement and roofs, becomes surface water runoff, which flows to surface waters, and infiltrates into the ground to become groundwater. Surface water runoff can contain elevated levels of nitrates (NO3 -) from various sources including animal wastes and fertilizers. Reducing elevated levels of NO3 - in surface water runoff can minimize and/or prevent groundwater and surface water contamination. Natural polyphenols in carpet grass, due to phenolic hydroxyl groups, can degrade aqueous NO3 -. This study evaluated the potential for carpet grass to purify water by denitrifying NO3 - as surface water flows through grass-covered land. The research investigated nitrate removal efficiency and reaction kinetics under various flow rates and doses of carpet grass, validating the feasibility of using natural polyphenols for water purification. A grass dose of 100 g and a retention time of 24 h, which produced approximately 20-80 mg/L as gallic acid equivalent (GAE) of polyphenol in simulated surface water runoff, were demonstrated to effectively degrade NO3 - in aqueous solution (110 mg/L) and result in the denitrification of NO3 - to nitrite (NO2 -) and eventually N2. The first-order reaction kinetic rate constants for NO3 - degradation, NO2 - formation, and subsequent degradation of NO2 - are k obs(NO3-degradation) = 6.89 × 10-2 h-1, k 1(NO2-formation) = 5.11 × 10-2 h-1, and k 2(NO2-degradation) = 4.63 × 10-2 h-1, respectively, with a conversion rate (α) of NO3 - to NO2 - to be 0.74. Implementing natural vegetation, such as carpet grass, in water management practices offers an environmentally sustainable approach to reducing nitrate contamination in surface water runoff.

Green‐Synthesized SnO2 Derived From Kombucha Tea and Assessment of Its Photocatalytic Activity for the Degradation of Procion Red MX‐5B

AbstractThis study introduces a green synthesis approach for producing tin dioxide (SnO2) nanoparticles (NPs) using Kombucha tea and evaluates their photocatalytic effectiveness in degrading the Procion Red MX‐5B (PR) dye. Characterization techniques, including UV–vis, FTIR, XRD, and TEM, confirmed the successful synthesis of SnO2 NPs with appropriate optical and structural properties. For instance; the absorption peak at 526 cm−1 in FT‐IR diagram is attributed to Sn–O which indicates the successful synthesis of SnO2. Photocatalytic tests under optimized conditions showed a notable degradation efficiency of PR dye, with the highest observed degradation efficiency reaching 97.60% at a catalyst loading of 30 mg, pH 6, in 90 min. A kinetic study was performed and the PR degradation followed first‐order reaction kinetics. For this process, the reaction kinetic rate constants were found to be 0.0589, 0.078, 0.1367, and 0.1389 min−1 for 25, 35, 45, and 55 °C, respectively. Moreover, the activation energy for the degradation process was calculated to be 25.75 kJ/mol, indicating a chemisorption mechanism. The reusability of SnO2 NPs was tested and after five subsequent usages, it still showed high degradation efficiency (95.7%). These results demonstrate the potential of Kombucha‐derived SnO2 nanoparticles as an efficient, low‐cost, reusable, and environmentally friendly photocatalyst for wastewater treatment applications.

Perylene diimide configuration to construct g-C3N4 and iron phthalocyanine composite catalyst as PMS activator for contaminant degradation

The photocatalysis-assisted peroxymonosulfate (PMS) activation process has shown great potential for organic wastewater treatment. Herein, the composite photocatalyst (FeTAPc/PDI/CN) was obtained by grafting graphitic carbon nitride (CN) and amino iron phthalocyanine (FeTAPc) onto both ends of perylene tetracarboxylic anhydride (PTCDA) through an imidization process. Under simulated solar irradiation, the catalyst exhibited a remarkable degradation performance toward the target pollutant by activated PMS over a wide pH range from 3 to 11. The degradation efficiency of SMX reached 100 % in 7 min with the reaction kinetic constant of 0.845 min−1, which was 13 times higher than that of pure CN. In addition, the removal rate of FeTAPc/PDI/CN-4 for SMX was more than 80 % after 9 cycles. The introduction of phthalocyanine and PDI improved the separation efficiency of photogenerated electron-hole pairs. Furthermore, the active species involved in the SMX degradation were identified as •OH, SO4•-, •O2– and 1O2. The possible degradation pathways were proposed based on the identified intermediates, in which the oxidation of the amino group on the benzene ring was the main degradation pathway. This study is anticipated to result in a favorable method for designing CN-based photocatalysts with high stability and excellent catalytic activity for environmental remediation.

Phosphorus heteroatom doped BiOCl as efficient catalyst for photo-piezocatalytic degradation of organic pollutant and unveiling the mechanism: Experiment and DFT calculation

A novel phosphorus heteroatom doped bismuth oxychloride (P-BiOCl) catalyst was synthesized and the photo-piezocatalytic degradation of rhodamine B dye performances were explored under the ultrasound vibration and light illumination. The P-BiOCl exhibited excellent photo-piezocatalytic degradation activity, such as an ultra-high reaction kinetic rate constant of 0.3961 min−1, efficient degradation efficiency (94.7 % within 8 min) and excellent stability compared to solely piezocatalysis and photocatalysis. More impressively, these outstanding performances of P-BiOCl exceeded pure BiOCl and most other catalytic materials systems. The relevant experimental and density functional theory (DFT) calculation results were exhibited to clarify enhanced photo-piezocatalytic mechanism. The introduction of P heteroatom could reduce the bandgap of BiOCl, modulate electronic structure and charge redistribution, provide novel electron channel to promote electron transfer and restrain charge carriers recombination. Additionally, P-doped could also enhance the adsorption of oxygen and water molecules, promote intrinsic catalytic activity, leading to the increased production of active free radicals ·O2– and ·OH, thus significantly boosting the efficiency of organic pollutant degradation. This work provides a comprehensive understanding of heteroatom doping enhancing photo-piezocatalytic activity and presents a potential new strategy for designing highly efficient catalysts for wastewater treatment.

Persistent ultraviolet luminescence and photocatalytic properties of SiO2-Zn2SiO4:Ga,Pb nanoparticles

Persistent phosphors possess unique afterglow optical properties. In this paper, a class of ultra-violet (UV) persistent luminescence nanoparticles were developed for catalytic photodegradation applications. UV persistent luminescence nanoparticles of SiO2-Zn2SiO4:Ga and SiO2-Zn2SiO4:Ga,Pb were successfully synthesized by using a mesoporous template method. The UV persistent luminescence intensity of SiO2-Zn2SiO4:Ga at 405 nm was enhanced up to ca. 3.5 times by co-doping with Pb2+ (396 nm), along with longer persistent luminescence duration. The photodegradation results indicate that it is useful to introduce UV persistent luminescence property into SiO2-Zn2SiO4:Ga,Pb to obtain enhanced catalytic activity of SiO2-Zn2SiO4 with a bigger catalytic oxidation reaction kinetic constant (up to ∼4 times). This kind of UV persistent catalysis strategy may become a potential feasible method for better catalytic photodegradation activity. The UV persistent photocatalyst has potential applications in the photooxidation of organic molecules in high chroma and/or turbidity aqueous systems.

Design of a novel direct Z-scheme BiOIO3/Bi2WO6 heterojunction for enhanced photocatalytic degradation of norfloxacin under visible light

The unique electronic structure, appropriate bandgap energy, and excellent electron transfer capability make bismuth-based semiconductors hotspots in the field of photocatalysis. Novel BiOIO3/Bi2WO6 Z-scheme heterojunctions were fabricated via in-situ hydrothermal synthesis. The BIOBIW-3 heterojunctions (BiOIO3:Bi2WO6=0.25:0.8, mole ratio) exhibited excellent photocatalytic activity for norfloxacin (NOR), with a degradation efficiency of 90.41 % after 90 min of photoreaction and a reaction kinetic constant of 0.02132 min−1, which was 5.02 and 9.35 times higher than that of BIO and BIW, respectively. The superior photocatalytic performance can be attributed to the intimate interface between BiOIO3 and Bi2WO6, as well as the staggered energy band structure that facilitates the formation of a Z-type heterojunction. This not only widens the range of visible light absorption but also enhances the separation and transfer of photogenerated carriers while maintaining a high capacity for redox reactions. The dominant active species in the degradation process were photogenerated holes (h+) and superoxide (∙O2−) radicals, and an in-depth exploration of the possible mechanism was conducted. Furthermore, the effects of various parameters, including solution pH, catalyst dosage, and NOR concentration on the photocatalytic degradation of NOR were also investigated. The prepared BiOIO3/Bi2WO6 heterojunctions exhibited remarkable photocatalytic performance and chemical stability, presenting a novel research direction for employing layered bismuth-based materials in the degradation of fluoroquinolone antibiotic wastewater.

Quantitative Kinetic Insights from Operando-UV/Vis Spectroscopy: An Application to NH3-SCR of NOx on Cu-CHA Catalysts.

We employ UV/Vis Diffuse Reflectance spectroscopy directly coupled with a packed bed flow reactor to extract quantitative kinetic information. We use as a show-case the CuII/CuI redox dynamics during the reduction half cycle of the NH3-Selective Catalytic Reduction (SCR) on Cu-CHA catalysts. Our measurements enable quantification of the fraction of oxidized Cu, reconstructed by Multivariate Curve Resolution (MCR) together with monitoring of the gas-phase evolution during the reaction. These data both on the dynamics of the gas-phase and of the active site oxidation state have been used to assess the reduction half cycle rate equation and estimate the rate constant. Our results in terms of reaction orders and kinetic constant are in line with previous findings in the literature. Overall, our results demonstrate that the combined analysis of the UV spectra and of the gas-phase dynamics provides converging and unparalleled kinetic insight: this approach effectively resolves ambiguities concerning RHC kinetics and mechanism. More in general, this work provides evidence that operando spectroscopy can be used to extract quantitative kinetic information on catalytic cycles.

Quantitative Kinetic Insights from Operando‐UV/Vis Spectroscopy: An Application to NH3−SCR of NOx on Cu‐CHA Catalysts

AbstractWe employ UV/Vis Diffuse Reflectance spectroscopy directly coupled with a packed bed flow reactor to extract quantitative kinetic information. We use as a show‐case the CuII/CuI redox dynamics during the reduction half cycle of the NH3‐Selective Catalytic Reduction (SCR) on Cu‐CHA catalysts. Our measurements enable quantification of the fraction of oxidized Cu, reconstructed by Multivariate Curve Resolution (MCR) together with monitoring of the gas‐phase evolution during the reaction. These data both on the dynamics of the gas‐phase and of the active site oxidation state have been used to assess the reduction half cycle rate equation and estimate the rate constant. Our results in terms of reaction orders and kinetic constant are in line with previous findings in the literature. Overall, our results demonstrate that the combined analysis of the UV spectra and of the gas‐phase dynamics provides converging and unparalleled kinetic insight: this approach effectively resolves ambiguities concerning RHC kinetics and mechanism. More in general, this work provides evidence that operando spectroscopy can be used to extract quantitative kinetic information on catalytic cycles.

MoS2 nanosheets wrapped magnetic foamed recycled glass (NMG) for efficient photo-Fenton degradation of tetracycline: Sustainable mindset of “treating waste with waste”

Every year, tens of millions of tons of waste glass are buried on-site, causing serious resource waste and challenging environmental problems. Therefore, dealing with the problem of waste glass is a technical challenge with important economic significance. We used waste glass as a precursor to obtain foam recycled glass and then used a simple impregnation method to obtain magnetic foamed recycled glass (MG) and MoS2 nanosheets wrapped magnetic foamed recycled glass (NMG). Subsequently, we established an excellent NMG/H2O2 system for the efficient degradation of tetracycline (TC) under low-power light sources. The NMG/H2O2 system has a 92.2% removal rate of TC, accompanied by the apparent reaction kinetic constant is 0.01865 min−1. Meanwhile, the degradation mechanism of ·OH and 1O2 as the main active species was determined. Finally, the theoretical reaction sites of TC in the NMG/H2O2 system were obtained through density functional theory (DFT) calculation. The theoretical reaction sites were consistent with the reaction sites in the possible degradation pathways we obtained through the degradation fragment. In our work, we approach environmental issues with a “treating waste with waste” mindset, which combines economic and environmental considerations and may become the mainstream mindset in future environmental treatment.

Degradation of organic pollutants by the Cl-/PMS process.

The viewpoints on whether high concentrations of chloride ion (Cl-) promote or inhibit the oxidation activity of activated persulfates are still inconclusive. Furthermore, the degradation of organic pollutants by the persulfates in the presence of high Cl- concentrations without any activation medium has not yet been studied. In this work, the efficiency and mechanism of degradation of organic pollutants such as carbamazepine (CBZ), sulfadiazine (SDZ), and phenol (PN) by Cl--activated PMS (denoted as Cl-/PMS) were investigated. Results showed that Cl- could effectively activate PMS for the complete removal of CBZ, SDZ, and PN with reaction kinetic constants of 0.4516min-1, 0.01753min-1, and 0.06805min-1, respectively. Parameters such as PMS dose, Cl- concentration, solution pH, and initial concentrations of organic pollutants that affect the degradation efficiencies of the Cl-/PMS process were optimized. Unlike conventional activated persulfates, it was confirmed that the free chlorine was the main active species in the Cl-/PMS process. Finally, the degradation by-products of CBZ and SDZ as well as their toxicity were detected, and a possible degradation pathway for CBZ and SDZ was proposed. Though higher toxic chlorinated by-products were generated, the Cl-/PMS process was still an efficient oxidation method for the removal of organic pollutants in aqueous solutions which contain high concentrations of Cl-.

Synthesis, Characterization, and Photocatalytic Properties of Sol-Gel Ce-TiO2 Films

In this study, nanostructured cerium-doped TiO2 (Ce-TiO2) films with the addition of different amounts of cerium (0.00, 0.08, 0.40, 0.80, 2.40, and 4.10 wt.%) were deposited on a borosilicate glass substrate by the flow coating sol-gel process. After flow coating, the deposited films were dried at a temperature of 100 °C for 1 h, followed by calcination at a temperature of 450 °C for 2 h. For the characterization of sol-gel TiO2 films, the following analytic techniques were used: X-ray diffraction (XRD), differential thermal analysis (DTA), thermal gravimetry (TG), differential scanning calorimetry (DSC), diffuse reflectance spectroscopy (DRS), and energy dispersive X-ray spectroscopy (EDS). Sol-gel-derived Ce-TiO2 films were used for photocatalytic degradation of ciprofloxacin (CIP). The influence of the amount of Ce in TiO2 films, the duration of the photocatalytic decomposition, and the irradiation type (UV-A and simulated solar light) on the CIP degradation were monitored. Kinetics parameters (reaction kinetics constants and the half-life) of the CIP degradation, as well as photocatalytic degradation efficiency, were determined. The best photocatalytic activity was achieved by the TiO2 film doped with 0.08 wt.% Ce, under both UV-A and solar irradiation. The immobilized catalyst was successfully reused for three cycles under solar light simulator radiation, with changes in photocatalytic efficiency below 3%.

Efficient removal of bisphenol A from water using a novel organic–inorganic hybrid heterojunction

Organic-inorganic hybrid heterojunctions have the ability to efficiently remove trace pollutants from water due to efficient photosensitivity. In this work, an organic–inorganic hybrid S-scheme heterojunction photosensitizer (RCP-BW) was successfully fabricated by growing cross-linked β-CD/riboflavin copolymer on the surface of bismuth tungstate (Bi2WO6). The fabrication of the copolymer retains the photosensitivity of riboflavin and the confinement effect of β-CD and forms an internal electric field with Bi2WO6 to enhance the photoelectron transport ability. Photogenerated electrons are transferred and stacked from Bi2WO6 to β-CD/riboflavin copolymers, which greatly enhances the ability of organic copolymers to reduce oxygen and produce superoxide radicals. We combined electrochemistry, free radical chemistry and DFT to study the photoelectron migration mechanism and photocatalytic performance enhancement mechanism in S-scheme heterojunctions. The pseudo-first-order reaction kinetic constant (kRCP-BW = 0.081 min−1) for BPA degradation was four times that of unmodified BW (kBW = 0.020 min−1). β-CD regulates the band structure of riboflavin to match with Bi2WO6, and utilizes charged contaminants and intermediate degradation products to promote the production of reactive oxygen species through interface electron transfer and excited state transition energy transfer. This work provides theoretical support and technical means for photocatalytic oxidation technology to control endocrine disruptors.

Kinetics of ascorbate and dithiothreitol oxidation by soluble copper, iron, and manganese, and 1,4-naphthoquinone: Influence of the species concentration and the type of fluid

An alternative metric to account for particulate matter (PM) composition-based toxicity is the ability of PM-species to generate reactive oxygen species (ROS) and deplete antioxidants, the so-called oxidative potential (OP). Acellular OP assays are the most used worldwide, mainly those based on ascorbic acid (AA) and dithiothreitol (DTT) depletion; OP values are calculated from AA/DTT concentration over time kinetic curves. Since a great variability in OP-DTT and OP-AA values can be found in the literature, the understanding of those factors affecting the kinetic rate of AA and DTT oxidation in the presence of PM-bound species will improve the interpretation of OP values. In this work, a kinetic study of the oxidation rate of AA and DTT driven by species usually found in PM (transition metals and naphthoquinone (NQ)) was carried out. In particular, the influence of the concentration of Cu(II), Fe(II), Fe(III), Mn(II), Mn(III), and 1,4-NQ, and the type of fluid used in the assay (phosphate buffer (PB), phosphate buffer saline (PBS) and artificial lysosomal fluid (ALF)) is analysed and discussed. The reaction orders with respect to the AA/DTT and the active compound, and the kinetic rate constants were also determined. The results show great variability in OP values among the studied species depending on the fluid used; the OP values were mostly higher in PB0.05 M, followed by PBS1x and ALF. Moreover, different species concentration-responses for OP-DTT/OP-AA were obtained. These differences were explained by the different reaction orders and kinetic rate constants obtained for each active compound in each fluid.

Confinement effect of FeMOFs glass enhances the proton coupled electron transfer reaction for the organic pollutants polymerization toward sustainable water purification

Polymerization-driven removal of pollutants in advanced oxidation processes (AOPs) offers a sustainable way for the simultaneous achievement of contamination abatement and resource recovery, supporting a low-carbon water purification approach. In this work, metal–organic frameworks (MOFs) glass complexes (g-ZIF-62@8) were used as a platform to enhance proton transfer through the confinement effect of nanopores, modulating proton coupled electron transfer (PCET) reaction to promote organic pollutant polymerization. The results show that the confinement effect of nanopores in ZIF-62 glass can significantly improve the proton and electron transfer behavior, the proton diffusion coefficient is increased by 4.9 times (2.91*10−3 to 1.43*10−2), the energy barrier of the PCET reaction can be reduced by 1.9 eV, and the reaction kinetic rate constant is increased from 0.0198 min−1 to 0.20118 min−1. Photogenerated holes and Fe(IV = O), as the main reactive oxygen species (ROS), undergo PCET reaction with Bisphenol A (BPA) to convert them into phenoxy radicals, which are then polymerized into macromolecular organic compounds. PCET with proton-electron synergy was identified as a key driver of pollutant polymerization. This enables low-carbon purification and organic carbon recovery in wastewater. Our work provides new insights into the application of confinement effects to enhance proton and electron behavior to regulate pollutant polymerization toward sustainable water purification.

Simultaneous degradation of pharmaceutical contaminants and sterilization in real hospital wastewater by a highly efficient electrocatalytic ozonation process: Performance, mechanism and application

Herein, this work investigated an electrocatalytic ozonation (ECO) strategy using stainless steel-graphite plates as cathode–anode for the degradation of the pharmaceutical pollutant dexamethasone (DXMS) and the treatment of real hospital wastewater. The reaction kinetic constant of the ECO degradation of DXMS (0.387 min−1) was 4 times higher than that of single ozone (0.087 min−1). The established efficient ECO system successfully degraded pharmaceutical contaminants and had excellent bactericidal effects against pathogenic microorganisms (Escherichia coli). The results of scavenging experiments, chemical probe experiments, and electron paramagnetic resonance (EPR) analysis indicated that the newly generated 1O2 in the ECO system achieved the synergistic effect of the combined EC-ozonation process. More to the point, the ECO system has a high removal rate of chemical oxygen demand (COD) and total organic carbon (TOC) for real hospital wastewater treatment. After 60 min treatment of the ECO system, the COD removal of hospital wastewater ranged from 70 % to 88.91 %, and the TOC removal ranged from 52.05 % to 71.81 %. The ECO system developed in this work has the capacity for simultaneous degradation of pharmaceutical contaminants and sterilization of pathogenic microorganism for hospital wastewater treatment.

Catalytic dechlorination and deep hydrogenation of 4-chlorophenol in a hydrogen-based internal circulation reactor for efficient wastewater detoxification

Catalytic dechlorination is an attractive technique for chlorophenol degradation but was restricted to the low reaction kinetics and high toxicity of the intermediate products. This work aimed to develop a hydrogen-based internal circulation reactor (H2-ICR) for the efficient detoxification of 4-chlorophenol (4-CP). The structure and catalytic performance of commercial Pt/C, Pd/C, and Ru/C catalysts were systematically investigated. Compared to Pd and Ru, Pt-based catalysts exhibited better performance for the detoxification of chlorophenols. Over 99 % 4-CP was removed within 6 min by employing Pt/C as the catalyst for an initial 4-CP concentration of 2 mM (equivalent to 257 mg L−1). The reaction kinetic constant reaches 0.68 min−1, with the performance almost unchanged at different solution pH (3–11). Mechanistic analysis indicates that phenol hydrogenation is the rate-limiting step on Pt/C. The main product of Pt/C is cyclohexanol, suggesting the simultaneous occurrence of dechlorination and hydrosaturation reactions. In contrast, traditional Pd/C catalysts can hardly catalyze the hydrosaturation reaction, leaving toxic phenol as the main product. Biotoxicity assessment both in silico and by experiment demonstrates that the Pt catalyst can realize efficient detoxification of 4-CP wastewater. Both electron spin resonance (ESR) and radical quenching experiments confirmed the pivotal role of atomic hydrogen (H*). This study provides useful guidance for the design of hydrogenation catalysts and reactors with high safety, which may lead to a paradigm shift for chlorophenol wastewater remediation.