H2O2 System Research Articles

An autocatalytic Fe(III)/H2O2 Fenton-like process triggered by tetracycline: The overlooked effect of quinone intermediates

The conventional Fe(III)/H2O2 system is of low efficiency on the removal of most organic pollutants. However, we discovered that the Fe(III)/H2O2 system was robust on remediating tetracycline (TC) in water (0.109 min−1 for the pseudo-first kinetic constant), and the reaction was even slightly faster than that in the conventional Fe(II)/H2O2 system (0.105 min−1). The addition of TC could also initiate the degradation of other refractory pollutants in the Fe(III)/H2O2 system. Complexation between Fe(III) and TC with the stoichiometric ratio of 1:1 was observed. Electron transfer from TC to Fe(III) gave rise to the slight production of Fe(II), which served as the initiator of the following Fenton reaction. •OH was ascertained as the main reactive species through quenching experiments, EPR tests and the probe method, while O2•−/HO2• was also a subsidiary contributor. Hydroquinone intermediates were proved to be generated through the hydroxylation of the benzene ring of the TC molecule by •OH and thus facilitate the reductive transformation of Fe(III) to Fe(II). This study analyzes the relationship between molecular structural features of TC and the catalytic efficiency of ferric Fenton-like reactions. We expect to shed light on new mechanistic insights on autocatalysis in the Fenton-like catalytic processes.

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.

Peroxymonocarbonate activation via Co nanoparticles confined in metal-organic frameworks for efficient antibiotic degradation in different actual water matrices.

Traditional advanced oxidation processes suffer from low availability of ultrashort lifetime radicals and declining stability of catalysts. Co nanoparticles in hollow bimetallic metal-organic frameworks (Co@MOFs) were synthesized via a solvothermal method. Nanoconfinement and peroxymonocarbonate (PMC) degradation system endows Co@MOFs with high catalytic activity and stability even in the actual water matrices. The nanocomposites exhibited 100-200nm polyhedron structure with irregular nanocavity between the 20nm shell and multicores. Co nanoparticles were completely encapsulated by the FeIII-MOF-5 shell according to the X-ray diffraction and photoelectron spectra. Both 0.8nm micropores and 3.6nm mesopores were proven to be present. The yolk-shell Co@MOFs exhibited higher catalytic performance than that of Co nanoparticles, hollow FeIII-MOF-5 and its core-shell counterpart toward PMC activation during sulfamethoxazole degradation. The catalytic activities of Co@MOFs for the activation of unsymmetrical peroxides (PMC and peroxymonosulfate) were much higher than those for the symmetrical peroxides (H2O2 and persulfate) and the heterogeneous catalysis was dominant in the Co@MOFs activated H2O2 and PMC systems. The MOF stability was the highest and metal leakages were the least in the activated PMC system among the four peroxides because of mild reaction conditions and the alkalescent solution (pH=8.3-8.4). Furthermore, the high removal efficiencies (>94%) and degradation rates could be maintained in the different actual water matrices due to the confinement effects. The contributions of carbonate and hydroxyl radicals were primary for sulfamethoxazole degradation, and superoxide anion and singlet oxygen also played essential roles according to scavenging experiments and time-series spin-trapping electron spin resonance spectra. Six degradation pathways were proposed according to 26 intermediate identification and the pharmacophores of more than 80% intermediates were destroyed, which would benefit subsequent biological treatment. Successful combination of nanoconfinement and PMC might provide a new effective solution for pollution remediation.

Insight into reactive oxygen species and synergistic mechanism in Fenton-like system using Cu(0) and Fe(III) as the activator

Zero-valent copper (Cu(0))-triggered hydrogen peroxide (Cu(0)/H2O2) process was used to eliminate and mineralize contamination, while its oxidation efficacy was limited by the reaction of Cu(I) with O2. In this study, ferric ion (Fe(III)) was spiked into the Cu(0)/H2O2 (Fe(III)/Cu(0)/H2O2) system, and the degradation rate of paracetamol decreased from 24.9% to 95.4%. In the Fe(III)/Cu(0)/H2O2 system, the reaction of Cu(0) and Cu(I) with Fe(III) expedited the conversion from Fe(III) to Fe(II). The reaction of Cu(I) with O2 was weakened by the competition reaction between Cu(I) and Fe(III), promoting the generation of reactive oxygen species and increasing the utilization of Cu(0). The main reactive oxygen species for pH 4.0 was •OH and Fe(IV) with the contribution rate of •OH and Fe(IV) being 92.3% and 7.7%, but the dominant reactive oxygen species at pH 3.0 was only •OH in the Fe(III)/Cu(0)/H2O2 process. Especially, the contribution of Fe(IV) rose and the contribution of •OH decreased, when the concentrations of 20–80 μmol/L Fe(III), 0.05–0.3 g/L Cu(0) and 50–300 μmol/L H2O2 incremented. In the Fe(III)/Cu(0)/H2O2 process.After we increased the pH of end solution to 7.0/7.5/8.0 and leaching, the total copper in reaction solution was under 6.4/3.3/1.5 μmol/L. In addition, Ni(II) (57.7%), Fe(II) (100%) and Mn(II) (72.4%) obviously enhanced the degradation of paracetamol in the Cu(0)/H2O2 process.

A nonradical oxidation process initiated by Ti-peroxo complex showed high specificity toward the degradation of tetracycline antibiotics

Nonradical oxidation has received wide attention in advanced oxidation processes for environmental remediation. Understanding the relationship between material characteristics and their ability to initiate nonradical oxidation processes is the key to better material design and performance. Herein, a novel titanium-based metal-organic framework MIL-125-Ti/H2O2 system was established to show a highly selective degradation efficacy toward tetracycline antibiotics. MIL-125-Ti with the abundance of TiO6 octahedra units was found to effectively activate H2O2 under dark conditions by forming an oxidative Ti-peroxo complex. The presence of the Ti-peroxo complex, confirmed by UV-visible spectrophotometer, fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterizations, showed superior degradation (>95% removal rate) of oxytetracycline hydrochloride (OTC), doxycycline hydrochloride, chlortetracycline hydrochloride, and tetracycline. Density functional theory calculations were performed to assist the elucidation on the mechanism of H2O2 activation and antibiotics degradation. The MIL-125-Ti/H2O2 system was highly resistant to halogens and background organics, and could well maintain its original catalytic activity in actual water matrices. It retained the ability to degrade 75% of OTC within ten test cycles. This study provides new insight into the nonradical oxidation process initiated by the unique Ti-peroxo complex of Ti-based MOF.

Molybdenum Disulfide-Integrated Iron Organic Framework Hybrid Nanozyme-Based Aptasensor for Colorimetric Detection of Exosomes.

Tumor-derived exosomes are considered as a potential marker in liquid biopsy for malignant tumor screening. The development of a sensitive, specific, rapid, and cost-effective detection strategy for tumor-derived exosomes is still a challenge. Herein, a visualized and easy detection method for exosomes was established based on a molybdenum disulfide nanoflower decorated iron organic framework (MoS2-MIL-101(Fe)) hybrid nanozyme-based CD63 aptamer sensor. The CD63 aptamer, which can specifically recognize and capture tumor-derived exosomes, enhanced the peroxidase activity of the hybrid nanozyme and helped to catalyze the 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 system to generate a stronger colorimetric signal, with its surface modification on the hybrid nanozyme. With the existence of exosomes, CD63 aptamer recognized and adsorbed them on the surface of the nanozyme, which rescued the enhanced peroxidase activity of the aptamer-modified nanozyme, resulting in a deep-to-moderate color change in the TMB-H2O2 system where the change is visible and can be monitored with ultraviolet-visible spectroscopy. In the context of optimal circumstances, the linear range of this exosome detection method is measured to be 1.6 × 104 to 1.6 × 106 particles/μL with a limit of detection as 3.37 × 103 particles/μL. Generally, a simple and accessible approach to exosome detection is constructed, and a nanozyme-based colorimetric aptamer sensor is proposed, which sheds light on novel oncological biomarker measurements in the field of biosensors.

Simultaneous degradation of sulfamethazine and reduction of Cr(VI) by flexible self-supporting Fe-Cu-Al2O3 nanofibrous membranes as heterogeneous catalysts: Insights into synergistic effects and mechanisms

The co-existence of sulfamethazine (SMT) and heavy metal Cr(VI) may alter their migration and conversion laws and even their biological toxicity owing to their different physicochemical properties, greatly aggravating their environmental risks and elevating the difficulty of remediation. Herein, a novel flexible self-supporting Fe-Cu-Al2O3 nanofibrous membrane (1Fe-2Cu-Al2O3-800) was synthesized via a sol–gel method with the combination of electrospinning serving as a heterogeneous catalyst for simultaneous SMT degradation and Cr(VI) removal. Copper and iron elements were highly dispersed in the alumina nanofibrous matrix in the form of Fe(III), Cu(I), and Cu(II) species. There exists a wide applicable range of environmental pH for the 1Fe-2Cu-Al2O3-800/H2O2 system, exhibiting excellent catalytic selectivity and recycling performance. The surfaced-bound hydroxyl radicals activated by reductive Cu(I) species were the main active species of SMT degradation. Meanwhile, anionic Cr(VI) was rapidly adsorbed on 1Fe-2Cu-Al2O3-800 through electrostatic interaction, and then directly reduced to Cr(III) by adjacent reductive ≡Cu(I) species and subsequently incorporated into iron oxide to constitute a stable Fe-Cr(III) complex. Moreover, the degradation kinetics results showed that Fe(II)/Fe(III) cycle in the 1Fe-2Cu-Al2O3-800/H2O2 system could mediate Cr(III)/Cr(VI) cycle to prominently accelerate the SMT degradation through Haber-Weiss-type reaction, thereby having a synergistic effect. Overall, this work would provide new insights and a feasible strategy for the remediation of organic–inorganic composite pollutions, including SMT and Cr(VI).

Electrochemical biotool for the dual determination of epithelial mucins associated to prognosis and minimal residual disease in colorectal cancer

This work reports a dual immunoplatform for the simultaneous detection of two epithelial glycoproteins of the mucin family, mucin 1 (MUC1) and mucin 16 (MUC16), whose expression is related to adverse prognosis and minimal residual disease (MRD) in colorectal cancer (CRC). The developed immunoplatform involves functionalised magnetic microparticles (MBs), a set of specific antibody pairs (a capture antibody, cAb, and a biotinylated detector antibody b-dAb labelled with a streptavidin-horseradish peroxidase, Strep-HRP, polymer) for each target protein and amperometric detection at dual screen-printed carbon electrodes (SPdCEs) using the hydroquinone (HQ)/horseradish peroxidase (HRP)/H2O2 system. This dual immunoplatform allows, under the optimised experimental conditions, to achieve LOD values of 50 and 1.81 pg mL−1 (or mU mL−1) for MUC1 and MUC16, respectively, and adequate selectivity for the determination of the two targets in the clinic. The developed immunoplatform was employed to analyse CRC cell protein extracts (1.0 μg/determination) with different metastatic potential providing results in agreement with those obtained by blotting technologies but using affordable and applicable point-of-care instruments. This new biotool also emerges competitive in state-of-the-art electrochemical immunoplatforms seeking a compromise among simplicity, reduction of test time and analytical characteristics.

In‐situ synthesis of reduced graphene oxide templated MIL‐53(Fe) nanorods for photo‐catalytic degradation of organic dyes under sunlight

AbstractDue to outstanding chemical and physical characteristics, metal‐organic‐frameworks (MOFs) are frequently apprenticed for environmental clean‐up. Within this article, we present a thorough and straightforward hydrothermal method towards the production of reduced graphene oxide templated MIL‐53(Fe) hybrids RGO@MIL‐53(Fe). The structural characteristics of created hybrids were identified by using BET, FESEM, powder X‐ray diffraction, and FTIR techniques. Methylene blue (MB) dye (a model water pollutant) was used to evaluate H2O2‐assisted photo‐catalytic efficiency of RGO@MIL‐53(Fe). In contrast to pristine MIL‐53(Fe)‐H2O2, the RGO@MIL‐53(Fe)‐H2O2 system demonstrated improved photodegradation efficiency (>99%) for the elimination of MB over 60 minutes of solar irradiation. Furthermore, another dye rhodamine B (RhB) was almost 100% degraded in similar conditions within 80 minutes of sunlight. The RGO@MIL‐53(Fe) hetero‐structure, which promotes quick electron transport and reduces the rate at which photo‐induced charge carriers recombine, is credited as the main cause of the improvement in photo‐catalytic efficiency.

Natural substance-mediated synthesis for biochar-supported nanoscale zero-valent iron enhanced the performance of the catalytic process

Nanoscale zero-valent iron (nZVI) has gained increasing attention as a heterogeneous catalyst. However, problems such as aggregation, oxidation, or iron leaching limit its application. An appropriate dispersant and carrier may help solve the problems. Natural substances and their waste have been investigated as potential dispersants and carriers. Chinese herbal medicine residue is a promising raw material for this purpose. Here, black bean peel, a natural substance, was used as a dispersant and stabilizer, and biochar from chaga mushroom residue was used as a support for the first time to synthesize a zero-valent iron composite (B-nZVI-BC). X-ray diffraction (XRD) and electron spin resonance (ESR) studies confirm that the natural extracts prevented the agglomeration and oxidation of nZVI and promoted hydroxyl radical (·OH) generation. The experimental results showed that the B-nZVI-BC (2:1) + H2O2 system reduced Fe leaching to 0.66 mg/L. The synergistic effects of natural extracts, biochar (BC), and nZVI activated H2O2 for tetracycline (TC) removal and increased the removal from 67.56% to 90.07%. New insights were provided into the green synthesis and regeneration of nZVI, offering a promising solution for its practical application.

High-loaded single-atom Cu-N3 sites catalyze hydrogen peroxide decomposition to selectively induce singlet oxygen production for wastewater purification

Single-atom catalysts (SACs) have been widely used in Fenton-like water treatment, but studies on the selective induction of H2O2 to produce singlet oxygen (1O2) are rare. Herein, a carbon nitride supported high-loaded single-atom Cu-N3 catalyst (Cu-CN, Cu load is 15.46 wt%) is prepared to activate H2O2 to selectively form 1O2. Experimental and DFT calculation results reveal that the key factor for 1O2 production is the Cu-N3 coordination structure. Specifically, Cu-N3 coordination structure is conducive to decomposing H2O2 into·OOH/·O2-. Besides, the density of Cu-N3 sites is another key factor, high Cu-N3 site density is conducive to the rapid conversion of·OOH/·O2- to 1O2. Benefitting from the dominant role of 1O2, the Fenton-like degradation performance of Cu-CN/ H2O2 system is not disturbed under high salinity conditions, and the performance is significantly enhanced at high pH. This work represents an important reference in understanding SACs for activated H2O2 to generate 1O2.

Waste leather derived porous carbon boosted Fenton oxidation towards removal of diethyl phthalate: Mechanism and long-lasting performance

The acceleration of Fe(III)/Fe(II) conversion in Fenton systems is the critical route to achieve the long-lasting generation of reactive oxygen species towards the oxidation of refractory contaminants. Here, we found that waste leather derived porous carbon materials (LPC), as a simple and readily available metal-free biochar material, can promote the Fe(III)/H2O2 system to generate hydroxyl radicals (•OH) for oxidizing a broad spectrum of contaminants. Results of characterizations, theoretical calculations, and electrochemical tests show that the surface carbonyl groups of LPC can provide electron for direct Fe(III) reduction. More importantly, the graphitic-N on surface of LPC can enhance the reactivity of Fe(III) for accelerating H2O2 induced Fe(III) reduction. The presence of LPC accelerates the Fe(III)/Fe(II) redox cycle in the Fe(III)/H2O2 system, sustainable Fenton chain reactions is thus initiated for long-lasting generation of hydroxyl radicals without adding Fe(II). The continuous flow mode that couples in-situ Fenton-like oxidation and LPC with excellent adsorption catalytic properties, anti-coexisting substances interference and reusability performance enables efficient, green and sustainable degradation of trace organic pollutants. Therefore, the application of metal-free carbon materials in Fenton-like system can solve its rate-limiting problem, reduce the production of iron sludge, achieve green Fenton chemistry, and facilitate the actual engineering application of economic and ecological methods to efficiently remove trace organic contaminants from actual water sources.

Efficient heterogeneous Fenton-like degradation of methylene blue using green synthesized yeast supported iron nanoparticles

To reduce the consumption of oxidant and catalyst in Fenton-like reaction and to realize the reuse of catalyst, yeast supported iron nanoparticles (nZVI@SCM) was synthesized by tobacco leaf extract and applied in the heterogeneous Fenton-like degradation of aqueous methylene blue (MB) at ambient conditions. The performance of the composite was exploited in terms of catalytic activity and factors influencing MB degradation. The surface changes of nZVI@SCM before and after reaction were characterized by XPS, SEM, FT-IR and XRD. Iron leaching, primary reactive oxidizing species, and the storage stability and reusability of catalyst were also investigated. Typically, 99.7% removal of 50 mg/L MB, with a TOC removal of 97.2%, could be achieved within 10 h by 0.1 g/L nZVI@SCM coupled with 1.0 mM H2O2. The MB degradation is in good agreement with the pseudo-first-order model, and hydroxyl radicals in the bulk solution is the main reactive oxidizing species responsible for MB degradation. Based on the identified intermediates by liquid chromatography/mass spectrometry, the possible MB degradation mechanism in the nZVI@SCM/H2O2 system is discussed. The developed high-performance nZVI@SCM catalyst strategy can provide a new route in enhancing the Fenton-like degradation of organic contaminants with less consumption of catalyst and oxidant.

Solar Photocatalytic Degradation of Diuron in Aqueous Solution by TiO2

The solar photocatalytic degradation of diuron, which is one of the herbicides, has been studied by a solar pilot plant in heterogeneous solar photocatalysis with titanium dioxide. The pilot plant was made up of compound parabolic collectors specially designed for solar photocatalytic applications. The influence of different variables such as, H2O2 initial concentration, TiO2 initial concentration, and diuron initial concentration with their relationship to the degradation efficiency were studied. Hydrogen peroxide (H2O2) found to increase the rate of diuron degradation. The best removal efficiency of heterogeneous solar photocatalytic TiO2 system was found to be 46.65 % and for heterogeneous solar photocatalytic TiO2/ H2O2 system was found to be 80.65 %. Based on these results, the solar photocatalytic degradation by TiO2/ H2O2 system could be a useful technology for the treatment of effluents containing diuron.

Sequential electrocatalysis by single molybdenum atoms/clusters doped on carbon nanotubes for removing organic contaminants from wastewater

Oxygen reduction reaction (ORR) can realize the goal of in-situ H2O2 generation. A suitable catalyst ensures a proper binding strength between the electrocatalyst and the intermediate (i.e., *OOH), thereby avoiding the 4-electron ORR process and H2O production. Herein, we demonstrate that single molybdenum (Mo) atoms/clusters doped on carbon nanotubes can effectively alter the ORR pathway to generate H2O2; meanwhile, the established sequential ORR system for H2O2 production can tandemly remove ibuprofen (IBU) and other organic contaminants from water and wastewater. The results reveal that single atomic Mo clusters preferentially acted as the active sites that are merely required to overcome 0.11 eV downhill to form *OOH. Surprisingly, this tandemly constructed ORR with in-situ generated H2O2 performed better than the in-vitro H2O2 system. These findings offer a promising solution to reduce the costs related to the production and transportation of H2O2 for various applications, including the oxidation and removal of emerging organic contaminants from water and wastewater.

Target Recognition Initiated Self-Assembly-Based Signal Amplification Strategy for Sensitive and Colorimetric Staphylococcus aureus Detection and Diagnosis of Skin Infection.

Staphylococcus aureus (S. aureus), as a Gram-positive bacterium, is commonly encountered in various infectious diseases, such as acute skin and soft tissue infections. Despite that many efforts have been made, sensitive and reliable quantitative determination of S. aureus remains a huge challenge. Here, we depict a novel colorimetric approach for sensitive and accurate detection by combining allosteric probe-based target recognition and chain extension-based dual signal recycling. The single-strand DNA (ssDNA) products generated by the chain extension process lead to the liberation of G-quadruplex sequences, which can fold into active DNAzyme under the assistance of hemin. The active DNAzyme can work as peroxidase mimics to catalyze the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS2-)-H2O2 system, causing the color change of the system. Eventually, the method exhibits a wide detection range from 103cfu/mL to 106cfu/mL. The limit of detection of the approach was determined 232cfu/mL. Considering the robust capability of the approach in S. aureus detection, we believe that it will be a potential alternative tool for biomedical research and clinical molecular diagnostics.

Unexpected role of singlet oxygen generated in urea-modulated LaFeO3 perovskite heterogeneous Fenton system in denitrification: Mechanism and theoretical calculations

This study appears an unprecedented phenomenon that 1O2, generated in urea-modulated LaFeO3 (U-LaFeO3) perovskite heterogeneous Fenton system, is superior to OH• and O2•- in NO removal. The 2.5 U-LaFeO3/H2O2 system can remove 82.9% of NO, with a low H2O2/NO molar ratio (4.7) and high GHSV (30,800 h−1), along with good environmental adaptability and reusability. Urea modulation induced the formations of abundant La defects, O vacancies and Fe(IV), also improved the pore structure and surface area. The contribution order of different free radicals to NO removal is 1O2 > xO2•- > •OH. Characterization combined with theoretical calculation clarify that (i) H2O2 is inclined to derive HO2• on Fe sites; (ii) 1O2 is mainly generated from O2•- reaction with Fe(IV)/Fe(III); (iii) •OH is mainly produced by splitting of H2O2 on Fe site and decomposition of HO2• on OV site. The main denitrification paths are NO+1O2→NO2, NO2 + •OH→NO3- and NO+ •OH→NO2-.

In-situ synthesis of well-dispersed Cu/Cu2O nanoparticles supported on petaloid SiO2 for efficient degradation of high concentration tetracycline hydrochloride

Low-valent transition metal catalysts have shown great application potential in boosting the Fenton-like catalytic performance. The dispersity and particle size are closely related to catalytic performance. However, it is still a challenge to develop a simple and effective strategy to synthesize well-dispersed low-valent transition metal catalysts with small particle size. Herein, Cu/Cu2O nanoparticles with the size of about 42 nm are successfully in-situ synthesized during the carbonization process of surfactants, and evenly dispersed on petaloid SiO2 (x-CS catalysts). The ratio of Cu/Cu2O can be easily adjusted by changing the adding amount of Cu(NO3)2. 6-CS catalyst exhibits the optimal catalytic performance for the degradation of high concentration tetracycline hydrochloride (TC, 100 mg/L). About 89.4 % of TC is degraded within 40 min of reaction. The excellent catalytic ability is mainly attributed to the plenty of exposed highly reactive metal sites, accelerating the activation of H2O2. The experimental results show that Cu species are the catalytic active centers, in which low-valent Cu(0)/Cu(Ⅰ) plays the critical role in boosting the catalytic performance. Interestingly, the leaching concentration of Cu ions in solution is reduced to some extent, which is attributed to the adsorption by functional groups on SiO2. ∙OH, 1O2 and ∙O2– are confirmed to contribute to the degradation of TC. In addition, a catalytic mechanism is proposed in the Cu/Cu2O/SiO2/H2O2 system.

Enhanced organic pollutant removal in saline wastewater by a tripolyphosphate-Fe0/H2O2 system: Key role of tripolyphosphate and reactive oxygen species generation

The effects of tripolyphosphate (TPP) on organic pollutant degradation in saline wastewater using Fe0/H2O2 were systematically investigated to elucidate its mechanism and the main reactive oxygen species (ROS). Organic pollutant degradation was dependent on the Fe0 and H2O2 concentration, Fe0/TPP molar ratio, and pH value. The apparent rate constant (kobs) of TPP-Fe0/H2O2 was 5.35 times higher than that of Fe0/H2O2 when orange II (OGII) and NaCl were used as the target pollutant and model salt, respectively. The electron paramagnetic resonance (EPR) and quenching test results showed that •OH, O2•−, and 1O2 participated in OGII removal, and the dominant ROS were influenced by the Fe0/TPP molar ratio. The presence of TPP accelerates Fe3+/Fe2+ recycling and forms Fe-TPP complexes, which ensures sufficient soluble Fe for H2O2 activation, prevents excessive Fe0 corrosion, and thereby inhibits Fe sludge formation. Additionally, TPP-Fe0/H2O2/NaCl maintained a performance similar to those of other saline systems and effectively removed various organic pollutants. The OGII degradation intermediates were identified using high-performance liquid chromatography–mass spectrometry (HPLC–MS) and density functional theory (DFT), and possible degradation pathways for OGII were proposed. These findings provide a facile and cost-effective Fe-based AOP method for removing organic pollutants from saline wastewater.

Novel Application of MnO2–H2O2 System for Highly Efficient Arsenic Adsorption and Oxidation

A novel manganese dioxide–hydrogen peroxide (MnO2–H2O2) system was developed for effective Arsenic (As) removal. Under the specified conditions of no external mechanical stirring, a trace H2O2 concentration of 0.015 wt%, and a MnO2 concentration of 25 mg/L, high removal efficiency (88%) of As (100 µg/L) was achieved by the MnO2–H2O2 system within 30 min, which differs from conventional adsorption processes that require external mechanical stirring and conventional arsenite (As (III)) oxidation–adsorption processes that require high quantities of oxidants (such as ozone) and specially synthesized adsorbents/catalysts. The high removal efficiency of As (III) by the MnO2–H2O2 system was attributed to the turbulent conditions precipitated by the extensively generated oxygen (O2) from the catalytic decomposition of H2O2, the efficient adsorption of As on the surface of MnO2, and the effective generation of reactive radicals including hydroxyl and superoxide radicals (•OH and •O2−). Moreover, the MnO2 adsorbents before and after As removal were characterized systematically, and the generated radicals were verified using electron spin resonance (ESR). The results showed that the formation of inner-sphere surface complexes by the surface hydroxyl groups of MnO2 particles and As was responsible for the effective As adsorption process, and the oxidation of As (III) to arsenate (As (V)) was achieved via the generated radicals. The influences of representative environmental factors on As removal performance and the application of the MnO2–H2O2 system in river water and ground water were further studied and tested. In conclusion, the MnO2–H2O2 system offers several advantages, including low cost, ease of operation, and strong environmental adaptability, making it highly promising for practical water treatment applications.