Efficiency Of Advanced Oxidation Processes Research Articles

Modulating electronic structure of NiFe layered double hydroxide membrane by interlayer-confinement for enhanced water decontamination

Herein, the role of nanoconfinement on modulating the electronic structure of the catalyst that influences the efficiency of advanced oxidation processes (AOPs) was investigated. Peroxymonosulfate (PMS)-based AOP was conducted within the nanoconfined sub-nanometer interlayer channels of a 2D NiFe layered double hydroxide membrane (NiFeM). The interlayer-confined NiFeM exhibited complete removal of sulfamethoxazole, with a degradation rate constant of 211.67 s−1 that was 2.6–946.2 times higher than previously reported nanoconfined AOPs systems, and also demonstrated broad pH working range and anti-interference ability with excellent catalytic stability in 25 h. Theoretical calculations suggested such interlayer confinement upshifted the catalyst metal d-band center, accounting for strengthened PMS adsorption and electron transfer from catalyst to PMS molecules. This work embodies the interlayer confinement effect on modulating the electronic structure of catalyst and provides insights for designing catalysts with excellent capability for environmental remediation, energy conversion and chemical synthesis.

Adjusting Oxidation Pathways via Fine-tuning Atomic Ratios in Window-opening MO0F Membranes for Efficient Self-cleaning

Peroxymonosulfate (PMS) can be used as a green oxidant to mitigate catalytic membranes fouling and restore filtration performance through advanced oxidation processes (AOP). However, the adjustment of oxidation pathways and the understanding of underlying mechanisms for efficient cleaning without sacrificing the filtration performance need to be studied systematically. We optimized the membranes microenvironment via thermal modification from 25 °C to 400 °C below the catalyst ZIF-8 framework's decomposition temperature. The modified membranes have a doubled pure water flux (158.3 LMH bar−1) and remain rejection rates due to intact ZIF-8 framework structure with “window-opening” effect. The methyl dissociation and self-catalyzed graphitization were regulated by changing temperature, resulting in adjustable nonradical pathway proportion (correlated with the C/Zn atomic ratio at 0.96). The enhanced nonradical pathway targeted attacks on electron-rich regions of organic compounds, resulting in efficient cleaning and almost complete flux recovery (99.3%). The theoretical simulations revealed that methyl groups dissociation and graphitization significantly influence the electron density and adsorption energy at active sites for tunable oxidation pathways and enhanced catalytic performance. Our work offers a rational strategy to improve both filtration and catalytic performance in catalytic membranes. The enhanced understanding of oxidation mechanisms guides the design of designing efficient AOP membrane cleaning systems.

Molecular insights into pilot-scale selective removal of emerging contaminants in hospital wastewater

Advanced oxidation processes (AOPs) are a promising technology for removing emerging organic contaminants (EOCs) from wastewater, while the coexisting dissolved organic matter (DOM) significantly hinders effective oxidative removal of EOCs. Understanding the effects of DOM on EOCs removal in real water matrices is crucial for designing more efficient AOPs. Herein, a pilot-scale integrated in-situ ozonation/ultrafiltration process was conducted to remove EOCs from hospital wastewater. Furthermore, the ozonation reactivity of DOM and EOCs was contrastingly analyzed at the molecular level. Our integrated process selectively removed 85 % of EOCs at a relatively low oxidant dosage of 0.44 mg O3 per mg dissolved organic carbon (DOC). Using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), we reveal that ozone selectivity for EOCs arose from their overall reductive characteristics of being more aromatic and unsaturated in molecular composition compared to DOM. Additionally, specific DOM compounds potentially facilitate EOCs removal. This work provides pilot-scale experience in EOCs removal from hospital wastewater and in-depth understanding of DOM’s role in the integrated process, guiding the development of effective AOPs for selective removal of emerging contaminants.

Modulating Cu2O/CuO on attapulgite for boosting peroxymonosulfate activation

Peroxymonosulfate (PMS) activation is an economically viable and efficient advanced oxidation process used to degrade recalcitrant organic pollutants. In this study, the copper oxide/attapulgite (CuxO/ATP) catalyst was synthesized via the hydrothermal method. The catalytic degradation efficiency was assessed using ciprofloxacin (CIP) as the model pollutant. The influence of catalyst dosage and PMS concentration on CIP degradation was examined. Additionally, the capability of the catalyst to degrade CIP under varying pH conditions, temperatures, and in the presence of diverse inorganic ions was investigated. The findings revealed that CuxO/ATP exhibited superior performance compared to pure CuxO in PMS activation for CIP degradation. Microstructural analysis indicated well-dispersed CuxO nanoflowers on the attapulgite, facilitating a synergistic effect between the two components. The presence of attapulgite enhanced the dispersion of CuxO, leading to an increase in the exposed surface area. In addition, attapulgite facilitated the adsorption of pollutants onto the CuxO interface, while CuxO, in turn, activated PMS to generate active free radicals, thereby enabling the catalytic oxidation of pollutants. Through a series of free radical quenching experiments, sulfate radicals were identified as the predominant species responsible for CIP degradation, playing a pivotal role in the system. Moreover, a plausible catalytic mechanism was discussed. Furthermore, reusability tests demonstrated the catalyst's stability and recyclability. This research not only presents a novel and robust approach for CuxO catalyst synthesis but also offers deeper insights into the mechanism underlying CuxO activation of PMS.

Cu-TNT hollow nanoreactors: Efficient Fenton-like degradation of organic pollutants across a wide pH range

Advanced oxidation processes (AOPs) operating under neutral to alkaline conditions are highly desirable for industrial applications. This study focuses on the use of Cu-doped titanate (Cu-TNT) hollow nanoreactors to effectively degrade organic pollutants in a Fenton-like manner across a broad pH from 3 to 10. The resulting Cu-TNT material possessed a BET surface area of 391.2 m2/g and pores with sizes between 2 and 20 nm. Experimental results from Fenton-like reactions reveal that Cu-TNT exhibited superior catalytic activity and long-term stability in degrading methyl orange compared to Na-titanate, Fe-titanate, copper ions, cuprous chloride, and solid sphere Cu-doped titanate. Notably, Cu-TNT performed optimally at a pH of 9, with singlet oxygen (1O2) and hydroxyl radicals (•OH) being recognized as the main active components. The improved catalytic efficiency was due to the extensive surface area, efficient mass diffusion in limited space, and quick Cu(Ⅰ)/Cu(Ⅱ) transformations. This study provided a feasible pathway to develop Cu-based nanoreactors as heterogeneous catalysts for highly efficient AOPs.

PbO2 /graphite and graphene/carbon fiber as an electrochemical cell for oxidation of organic contaminants in refinery wastewater by electrofenton process; electrodes preparation, characterization and performance

The electro-Fenton oxidation process was used to treat organic pollutants in industrial wastewater as it is one of the most efficient advanced oxidation processes. The novel cell in this process consists of a prepared PbO2 electrode by electrodeposition on graphite substrate and carbon fiber modified with graphene as a cathode. X-ray diffraction, fluorescence, analysis system, atomic force microscopy, and scan electron microscopy were used to characterize the prepared anode and cathode. XRD patterns clearly show the characteristic reflection of the mixture of  - and β phases of PbO2 on graphite and carbon fiber, and AFM results for cathode and anode present that PbO2 on graphite substrate and graphene on carbon fiber surface are on a nanoscale. Contact angle measurement was determined for the carbon fiber cathode before and after modification. The anodic polarization curve showed a higher anodic current when utilizing the PbO2 anode than the graphite anode. Phenol in simulated wastewater was removed by electro-Fenton oxidation at 8 mA/cm2 current density, 0.4 mM of ferrous ion concentration at 35 °C up to 6 h of electrolysis. Chemical oxygen demand for the treated solution was removed by 94.02 % using the cell consisting of modified anode and cathode compared with 81.23% using modified anode and unmodified cathode and 79.87 % when using unmodified anode and modified cathode.

Design of Environmental-Friendly Carbon-Based Catalysts for Efficient Advanced Oxidation Processes.

Advanced oxidation processes (AOPs) represent one of the most promising strategies to generate highly reactive species to deal with organic dye-contaminated water. However, developing green and cost-effective catalysts is still a long-term goal for the wide practical application of AOPs. Herein, we demonstrated doping cobalt in porous carbon to efficiently catalyze the oxidation of the typically persistent organic pollutant rhodamine B, via multiple reactive species through the activation of peroxymonosulfate (PMS). The catalysts were prepared by facile pyrolysis of nanocomposites with a core of cobalt-loaded silica and a shell of phenolic resin (Co-C/SiO2). It showed that the produced 1O2 could effectively attack the electron-rich functional groups in rhodamine B, promoting its molecular chain breakage and accelerating its oxidative degradation reaction with reactive oxygen-containing radicals. The optimized Co-C/SiO2 catalyst exhibits impressive catalytic performance, with a degradation rate of rhodamine B up to 96.7% in 14 min and a reaction rate constant (k) as high as 0.2271 min-1, which suggested promising potential for its practical application.

Bi-ZFO/BMO-Vo Z-scheme heterojunction photocatalysis-PMS bidirectionally enhanced coupling system for environmental remediation

Given the urgency of organic pollutant removal and the low efficiency of advanced oxidation processes (AOPs), a novel Bi-ZFO/BMO-Vo photocatalyst was fabricated via the solvothermal method. A coupling system was constructed to combine photocatalysis with peroxymonosulfate (PMS) oxidation processes, which synergistically degrade organic pollutants. Bi-ZFO/BMO-Vo exhibited excellent photocatalytic performance, which could remove 100 % RhB in 110 min and degrade 100 % MG in 70 min, and 88 % H-TC in 50 min. The excellent catalytic performance of Bi-ZFO/BMO-Vo was not only attributed to the synergistic effect of PMS activation and photocatalysis, but also attributed to the SPR effect of Bi nanoparticles, electron capture of oxygen vacancies, and intense contact of Bi-ZFO/BMO-Vo heterojunctions. The active species capture experiments and EPR tests indicated that 1O2, SO4–·, ·OH, and O2–· worked together for the RhB removal. The degradation intermediates of RhB were identified by LC-MS. Based on the experimental results, the band structure and Z-scheme charge transfer mechanism were proposed. Toxicity evaluation indicated that Bi-ZFO/BMO-Vo-Vis/PMS could significantly reduce RhB toxicity. This efficient and stable catalyst is expected to be used in organic wastewater degradation and practical applications.

Assessing the application of a biochar-supported iron oxide catalyst to the treatment of imidacloprid by photo-Fenton technologies

Emerging contaminants entail a great challenge to conventional treatment systems because they are not able to remove most of these bio-recalcitrant compounds. In particular, the presence of pesticides, such as imidacloprid, in the environment is a great hazard to soil microbiota, pollinating insects, and the aquatic environment. This research aims to enhance the treatment efficiency of advanced oxidation processes applied to the removal of bio-recalcitrant pollutants that are present in stormwater by assessing the application of a newly designed, economical, and efficient treatment alternative. Specifically, solar and LED (365 and 420 nm) heterogeneous photo-Fenton processes were carried out to remove a concentration of 5 mg·L−1 of imidacloprid, which was selected as the model pollutant that has been identified present in stormwater, using a magnetic iron oxides catalyst supported on pinewood waste biochar. The removal kinetics and mineralization of this contaminant were determined under the effect of the natural pH value of the solution and under a circumneutral pH environment, and heterogeneous and homogeneous catalytic contributions to the process were assessed. All these treatments achieved the successful efficient removal of the contaminant whether applying LED (UVA or visible blue) or solar radiation. The heterogeneous photo-Fenton treatment using a magnetic iron oxide catalyst supported on pinewood waste biochar totally removed imidacloprid after 10 minutes of oxidation at the initial natural pH value of the solution using 365 nm UVA LED radiation. Moreover, a 70% TOC removal was addressed after 60 minutes of treatment. The solar version of this heterogeneous photo-Fenton process removed the contaminant after 60 minutes of reaction, together to a TOC removal of the 60–65% after 120 minutes of treatment, including certain photolytic contribution; as well as it showed very efficient results under the effect of a circumneutral pH value. The assessed biochar-supported iron oxide catalyst was displayed as very stable under all the tested reaction conditions and its heterogeneous contribution to the process was confirmed superior to an exclusive homogeneous process.

Simultaneous Degradation, Dehalogenation, and Detoxification of Halogenated Antibiotics by Carbon Dioxide Radical Anions

Despite the extensive application of advanced oxidation processes (AOPs) in water treatment, the efficiency of AOPs in eliminating various emerging contaminants such as halogenated antibiotics is constrained by a number of factors. Halogen moieties exhibit strong resistance to oxidative radicals, affecting the dehalogenation and detoxification efficiencies. To address these limitations of AOPs, advanced reduction processes (ARPs) have been proposed. Herein, a novel nucleophilic reductant—namely, the carbon dioxide radical anion (CO2−)—is introduced for the simultaneous degradation, dehalogenation, and detoxification of florfenicol (FF), a typical halogenated antibiotic. The results demonstrate that FF is completely eliminated by CO2−, with approximately 100% of Cl− and 46% of F− released after 120 min of treatment. Simultaneous detoxification is observed, which exhibits a linear response to the release of free inorganic halogen ions (R2 = 0.97, p < 0.01). The formation of halogen-free products is the primary reason for the superior detoxification performance of this method, in comparison with conventional hydroxyl-radical-based AOPs. Products identification and density functional theory (DFT) calculations reveal the underlying dehalogenation mechanism, in which the chlorine moiety of FF is more susceptible than other moieties to nucleophilic attack by CO2−. Moreover, CO2−-based ARPs exhibit superior dehalogenation efficiencies (> 75%) in degrading a series of halogenated antibiotics, including chloramphenicol (CAP), thiamphenicol (THA), diclofenac (DLF), triclosan (TCS), and ciprofloxacin (CIP). The system shows high tolerance to the pH of the solution and the presence of natural water constituents, and demonstrates an excellent degradation performance in actual groundwater, indicating the strong application potential of CO2−-based ARPs in real life. Overall, this study elucidates the feasibility of CO2− for the simultaneous degradation, dehalogenation, and detoxification of halogenated antibiotics and provides a promising method for their regulation during water or wastewater treatment.

Predictive modeling of Enterococcus sp. removal with limited data from different advanced oxidation processes: A machine learning approach

The removal of contaminants through Advanced Oxidation Processes (AOPs) is a complex task that demands the simultaneous consideration of multiple operating parameters, such as type and concentration of oxidant and catalyst, type and intensity of radiation, composition of aqueous matrix, etc. Designing efficient AOPs often requires expensive and time-consuming laboratory experiments. To improve this process, this study proposes a Machine Learning approach based on a Random Forest (RF) model, to predict Enterococcus sp. concentration in wastewater treated with various AOPs, even when dealing with limited data. To assess our approach under diverse conditions, a data partitioning methodology is used to categorize the different AOPs into three distinct study cases of increasing complexity, from Case I to Case III. The evaluation of the RF model’s performance, combined with the data partitioning methodology, demonstrated its usefulness in predicting missing or additional disinfection values at any instant during the AOPs. Specifically, in Case I, the model excels at generalizing predictions across various AOP treatments, followed by Case II and III, which achieve Root Mean Squared Error (RMSE) values below or comparable to the average RMSE of Case I (0.72) in 8 out of 15 and 2 out of 4 treatments, respectively. Moreover, the effects of imbalanced data on model performance are discussed. This highlights the potential of our approach to assess AOPs performance and facilitate the design of new experiments of the same treatment type without the need for additional laboratory trials, even in challenging conditions.

2D surfaces twisted to enhance electron freedom toward efficient advanced oxidation processes

Two-dimensional (2D)-interface engineering for designing effective electron-rich catalyst center is pivotal in manipulating the catalytic behaviors and activity, but still challenging. Here, we’ve successfully twisted the surfaces of the 2D layered FeOCl, fulfilling the targeted fine-tuning of its Fe sites. The obtained new catalyst can boost peroxymonosulfate activation for reactive species with much lower energy barriers and efficiently oxidized target organic with almost 41 orders of magnitude faster reaction kinetics than pristine FeOCl. The increased degree of freedom of electron around Fe site has been identified as the key driver. The distorted geometry structure around Fe has led to an increased polarization of charge distribution, associating with less symmetric electron valence cloud and higher electron mobility. Thus, the twisted surfaces enable a much enhanced interfacial charge transfer between Fe site and the electron-deficient peroxymonosulfate. This work highlights the concept of twisted surface construction toward efficient advanced oxidation catalyst design.

A Comprehensive Review on Modification of Titanium Dioxide-Based Catalysts in Advanced Oxidation Processes for Water Treatment.

It has become necessary to develop effective strategies to prevent and reduce water pollution as a result of the increase in dangerous pollutants in water reservoirs. Consequently, there is a need to design new catalyst materials to promote the efficiency of advanced oxidation processes (AOPs) in the field of wastewater treatment plant to ensure the mineralization of trace organic contaminants. A notable approach gaining attention involves the coupling of sulfate radicals-based AOPs to photocatalysis or electrocatalysis processes, aiming to achieve the complete removal of refractory contaminants into water and carbon dioxide. Titanium dioxide as metal oxide has received great attention for its catalytic application in water purification. TiO2 catalysts offer a multitude of advantages in AOPs. They are characterized by their high photocatalytic activity under both ultraviolet and visible light, making them environmentally friendly due to the absence of toxic byproducts during oxidation. Their versatility is remarkable, finding utility in various AOPs, from photocatalysis to photo-Fenton processes. TiO2's durability ensures long-lasting catalytic activity, which is crucial for continuous treatment processes, and their cost-effectiveness is particularly advantageous. Furthermore, their chemical stability allows it to withstand varying pH conditions. However, the large band gap energy and low electrical conductivity hinder the catalytic reaction effectiveness. This review aims to examine various approaches to enhance the catalytic performance of titanium dioxide, with the objective of enabling more efficient water purification methods.

Photocatalytic reduction of chromium(VI) using multiwall carbon nanotubes/bismuth oxide nanocomposite under solar irradiation.

Semiconductor photocatalysis is the most efficient advanced oxidation processes for wastewater treatment. A new carbon-based photocatalyst bismuth oxide/multi-walled carbon nanotube (Bi2O3/MWCNT) nanocomposite has a considerable impact on improving photocatalytic performance. Bi2O3/MWCNTs (BMC) nanocomposite was prepared through the hydrothermal processing with 2.5, 5, 7.5 and 10 wt% of MWCNTs. The preparedphotocatalysts have been thoroughly examined by various techniques. The X-ray diffraction confirmed the prepared photocatalyst as α-Bi2O3 with high crystallinity. The band gap of Bi2O3 and BMC 7.5 nanocomposite was found to be 2.41 and 1.94eV. The prepared photocatalyst revealed smooth and porous merged flower-like structure with respect to the addition of MWCNTs. The model pollutant chromium(VI) (Cr(VI)) has been used to check the reduction efficiency of the prepared photocatalyst under solar irradiation. It was found that BMC 7.5 nanocomposite showed enhanced photocatalytic metal ion reduction (87.48%) compared to pristine Bi2O3 (69.29%). The preliminary photocatalytic Cr(VI) ion reduction experiments were carried to determine the photoreduction efficiency of pristine bismuth oxide and bismuth MWCNT nanocomposite. The kinetic study on Cr(VI) ion reduction obeyed pseudo-first-order rate kinetics for both the prepared photocatalysts. The efficiency of the photocatalysts was further analysed by reusing the same up to 3 cycles without loss of the efficacy.

Photogenerated and cocatalytic system cooperate to accelerate Fe3+/Fe2+ cycle in CNFe/FeS2/MoS2 composite with Z-scheme heterojunction constructed by interfacial chemical bond for advanced oxidation processes

Currently, the utilization of Fenton or Fenton-like reactions is prevalent in various domains such as environmental control, biology, and life science. In this study, we drew inspiration from the MoS2 cocatalytic heterogeneous Fenton system and devised CNFe/FeS2/MoS2 heterojunction. This heterojunction is connected through atomic-level Fe-S-Mo and Mo-N interfacial chemical bonds, serving as a catalyst for synergistic photocatalytic effects in conjunction with Fenton reactions. The suitable Mo/Fe molar ratio of 1.5 gives the CNFe/FeS2/MoS2 catalyst higher conductivity and higher carrier separation efficiency. The utilization of dual reduction approaches involving photo-generated electrons and Mo4+ effectively facilitates the stable circulation of Fe3+/Fe2+ with high efficiency in an acidic microenvironment, which is facilitated by the S-SO42- edge of MoS2. Moreover, the CNFe/FeS2/MoS2 heterojunction exhibits enhanced production of ∙O2 and H2O2. This effect not only reduces the quantity of hydrogen peroxide generated but also contributes to cost reduction. This work not only experimentally verifies the coupling effect of heterojunction and cocatalytic heterogeneous Fenton system but also provides a new idea for the design of efficient advanced oxidation processes (AOPs).

Preparation of Co-C/N flower-like single-atom catalysts via TCPP coordination confinement for enhanced activation of peroxymonosulfate

The design and preparation of highly efficient advanced oxidation processes (AOPs) catalysts is a crucial research area in the field of water pollution control. Herein, a single-atom AOP catalyst Co-N/C material (TPM-650) has been synthesized through the pyrolysis of the flower-shaped Co-TCPP MOF precursor, which is designed based on coordination confinement with TCPP. HAADF-STEM image analysis confirms the uniform distribution of single Co atoms throughout the TPM-650 material, which served as the highly efficient catalytic centers and can achieve 99.99% catalytic degradation of MG dyes in 24 min with only trace dosage ([TPM-650] = 1 mg/L, pseudo-first-order kinetic model, Kobs=0.302 min−1) and low leaching of Co ions (0.348 μg/L). Under optimal condition, the degradation of MG exhibits a high turnover number (dTON) of 68.5 mmol h−1 gcat−1 and a significant reduction in total organic carbon (TOC) by 58.7%. Radical quenching experiments and EPR measurements demonstrated that various reactive oxygen species (•SO4−, •OH, 1O2, MIV(O)/MV(O)) contributes to accelerating MG degradation. The enhanced efficiency and stability were attributed to the ultrathin layer supported single-atom Co-N/C structure, high mesopore volume, and synergy between the catalyst and peroxymonsulfate (PMS) with a synergy index of 16.5. This study not only reports a highly efficient and stable advanced oxidation catalyst Co-N/C, but also confirms that the nitrogen-coordinated Co sites are the primary active sites responsible for PMS activation; thus providing valuable insights into designing efficient transition metal-based AOP catalyst via coordination method for environmental remediation.

Monolithic CoMgAl mixed metal oxide nanosheets on Al2O3 granules for the efficient advanced oxidation process

Cobalt-based catalysts are good candidates for the degradation of organic pollutants in wastewater treatment due to their high activity, while powdered catalysts for practical applications face challenges like difficulty in regeneration. To solve the problem, this work designs a monolithic catalyst by in-situ growth of CoMgAl mixed metal oxide (CoMgAl-MMO) nanosheets on the Al2O3 granules. The obtained catalyst possesses a developed mesoporous structure with highly-dispersed Co on the surface. The catalytic activity of CoMgAl-MMO/AG in the dye degradation is dependent on the Co/Mg molar ratio. All monolithic catalysts show high degradation performance, of which the CoMgAl-MMO/AG catalyst with Co/Mg ratio of 0.8/1.2 exhibited the highest degradation rate, achieving 95 % acid orange (AO7) removal in 10 min testing.

The rate constants KOH+S with some antibiotics determination by the competetive inhibitors method

Advanced oxidation processes (AOP) are widely used for the degradation of antibiotics and other micropollutants in surface and waste waters. The degree of degradation of a drug by an AOP can be predicted from the rate constant of the interaction of hydroxyl radicals with the substrate - KOH+S value, as well as from other physicochemical properties accompanying the degradation processes, and therefore these factors are important for the design of technological schemes of treatment of polluted water. Moreover, a substrate withKOH+S value known can be used to evaluate the applicability and efficiency of AOP and elucidate the kinetics and degradation mechanism of the given pollutant. In this work, the rate of the oxidation of N,N-Dimethyl-p-nitrosoaniline (PNDMA) during the photolysis of hydrogen peroxide in distilled water and in the presence of different amounts of polluted water (aqueous solutions containing sulfonamides – acetazolamide (AC) and phthalylsulfathiazole (FL), fluoroquinilones - moxifloxacin (MOX) and ciprofloxacin (CPF) as pollutants) in the UV - H2O2 systems was studied. The concentration of the drugs varied between 2.5 mg/L and 25 mg/L. The ,,ДРТ-1000” high-pressure mercury vapor lamp as the irradiation source was used. Using competitive acceptors method and based on the kinetic curves, the interaction constants of •OH radicals with the mentioned drugs were determined: kOH+AC = 8.5 ×109 L/mol×s; kOH+FL = 8.5×109 L/mol×s; kOH+MOX = 1.42×109 L/mol×s; kOH+CPF = 6.3×109 L/mol×s and the inhibiting capacity of natural waters Σ ki[Si] in the selfpurification process in the model systems used. The calculated values of the respective constants are varies between (5.4-17.7)×106 s-1.

Degradation of dimethyl phthalate by morphology controlled β-MnO2 activated peroxymonosulfate: The overlooked roles of high-valent manganese species

Activated peroxymonosulfate (PMS) processes have emerged as an efficient advanced oxidation process to eliminate refractory organic pollutants in water. This study synthesized a novel spherical manganese oxide catalyst (0.4KBr-β-MnO2) via a simple KBr-guided approach to activate PMS for degrading dimethyl phthalate (DMP). The 0.4KBr-β-MnO2/PMS system enhanced DMP degradation under different water quality conditions, exhibiting an ultrahigh and stable catalytic activity, outperforming equivalent quantities of pristine β-MnO2 by 8.5 times. Mn(V) was the dominant reactive species that was revealed by the generation of methyl phenyl sulfone from methyl phenyl sulfoxide oxidation. The selectivity of Mn(V) was demonstrated by the negligible inhibitory effects of Inorganic anions. Theoretical calculations confirmed that Mn (V) was more prone to attack the CO bond of the side chain of DMP. This study revealed the indispensable roles of high-valent manganese species in DMP degradation by the 0.4KBr-β-MnO2/PMS system. The findings could provide insight into effective PMS activation by Mn-based catalysts to efficiently degrade pollutants in water via the high-valent manganese species.

Performance evaluation of a solar nano-photocatalytic reactor for wastewater treatment applications: Reaction kinetics, CFD, and scale-up perspectives

The solar-driven photocatalytic process, as a clean and efficient advanced oxidation process (AOP), is widely operated in wastewater treatment applications. In the present work, a solar nano photocatalytic reactor is designed, manufactured, and tested under different operating conditions. The irradiation-dependence reaction kinetics is studied in a batch operation process. A comprehensive computational fluid dynamics (CFD) model taking into account realistic solar flux distribution is developed and validated using experimental data. Finally, the reactor scaling-up analysis for higher treatment capacities is performed with the aim of the design of industrial-scale solar photocatalytic reactors. The research results indicate that when the initial dye concentration is increased from 5 to 175 mg/L, the period required to achieve 95% pollutant removal in 20 L solution and 10 mg/L photocatalyst concentration boosts up to 2.2 times. When the photocatalyst concentration in the solution is increased from 5 to 20 mg/L, the time required to achieve 95% total removal is reduced to 35.7%. For the photocatalyst concentration of 75 mg/L compared to 20 mg/L, the time required for 95% degradation increases up to 16.7%. To treat 90% of the total pollutant in a 50 mg/L dye solution with an initial volume of 5 m3 and using 20 mg/L photocatalyst concentration under 11 h operation with an average solar irradiation intensity of 750.46 W/m2, a solar reactor with a surface area of 50.45 m2 is required, while for 10 m3 wastewater sample and the same conditions and 95% pollutant removal, the collector area is obtained to be 121.36 m2. A horizontal solar reactor compared to its optimal tilt angle can reduce the treatment capacity up to 55%.