Non-radical Species Research Articles

Non-radical oxidation in environmental catalysis: Recognition, identification, and perspectives

• Non-radical species in heterogenous advanced oxidation processes (AOPs) are overviewed. • Principles and limitations for the identifying of non-radical species are discussed. • Driving forces triggering the activating process are summarized. • Critical thinking and further prospects of non-radical based AOPs are proposed. Non-radical oxidation in heterogenous advanced oxidation processes (NR-AOPs) show the superiority for organic contaminants removal in high selectivity, good pH stability and strong anti-interference ability. Thus, it is a hot topic in the recent decade. NR-AOPs are primarily dominated by interfacial catalytic activation. The mechanisms are complicated due to different non-radical species, various authentication methods, and still need a deeper understanding. Therefore, this review summarized latest developments in NR-AOPs, focusing on the recognition and identification of non-radical species (including the 1 O 2 , direct electron transfer, surface active complex and high-valent metal species), as well as the driving forces and conversion of activating paths. In addition, a discussion on the current deficiencies, challenges and future outlook of NR-AOPs were also provided. This critical review aims provide a comprehensive overview and trigger in-depth thinking about NR-AOPs to guide its further development.

Redox signaling at the crossroads of human health anddisease.

Redox biology is at the core of life sciences, accompanied by the close correlation of redox processes with biological activities. Redox homeostasis is a prerequisite for human health, in which the physiological levels of nonradical reactive oxygen species (ROS) function as the primary second messengers to modulate physiological redox signaling by orchestrating multiple redox sensors. However, excessive ROS accumulation, termed oxidative stress (OS), leads to biomolecule damage and subsequent occurrence of various diseases such as type 2 diabetes, atherosclerosis, and cancer. Herein, starting with the evolution of redox biology, we reveal the roles of ROS as multifaceted physiological modulators to mediate redox signaling and sustain redox homeostasis. In addition, we also emphasize the detailed OS mechanisms involved in the initiation and development of several important diseases. ROS as a double‐edged sword in disease progression suggest two different therapeutic strategies to treat redox‐relevant diseases, in which targeting ROS sources and redox‐related effectors to manipulate redox homeostasis will largely promote precision medicine. Therefore, a comprehensive understanding of the redox signaling networks under physiological and pathological conditions will facilitate the development of redox medicine and benefit patients with redox‐relevant diseases.

Activation of Peroxymonosulfate by Phosphate and Carbonate for the Abatement of Atrazine: Roles of Radical and Nonradical Species

Activation of Peroxymonosulfate by Phosphate and Carbonate for the Abatement of Atrazine: Roles of Radical and Nonradical Species

CuO with (0 0 1)-plane exposure efficiently induces peroxymonosulfate to form ≡Cu-OOSO3-intermediates directly oxidizing organic contaminants in water

Copper (Cu)/peroxymonosulfate (PMS) is a complex coupling system due to its multiple activation pathways with the formation of diverse radical and nonradical species. However, the effects of CuO with different plane exposures on the properties of the coupling system are not clear. In this research, Cu atom-terminated (001) plane-exposed CuO (CuO-10) is synthesized by a facile hydrothermal method using NH3·H2O as the structure directing agent for the first time. CuO-10 has the excellent property of inducing PMS to degrade bisphenol A (BPA) in water, and its reaction rate constant (k) reaches 14 times higher than that of commercial CuO with exposed (010) plane terminated by O atoms (CuO-C). Meanwhile, CuO-10 exhibits a wide pHinitial adaptability, and its BPA degradation exceeds 87% in the pH range of 3–9. Furthermore, compared with CuO-C/PMS, less radical and 1O2 are found in CuO-10/PMS oxidation system. Compared to the UV/PMS system, organic contaminants in CuO/PMS systems are easier to oxidize via an oxygen-atom-transfer mechanism. Therefore, the ≡Cu(II)-OOSO3- metastable intermediate is speculated to play an important role in the CuO/PMS activation process, which oxidizes organic contaminants directly through oxygen-atom-transfer and single-electron-transfer pathways. Furthermore, the CuO-10/PMS system is more likely to degrade organic pollutants through the oxygen-atom-transfer pathway than the CuO-C/PMS system. This study not only explores the influence of CuO crystal planes in efficiently inducing PMS activation but also provides new insights into the PMS activation process in the CuO/PMS oxidation system.

New insights into N, S doped carbon from conjugated polymers for efficient persulfate activation: Role of hydrogel beads in enhancement of stability

One-pot design of heteroatoms doped carbocatalysts for remediation of wastewater via persulfate (PS) activation is strongly desirable. Herein, a novel nitrogen and sulfur doped and co-doped carbons with controllable N, S doping is rationally prepared using pyrolysis strategy from polypyrrole-polythiophene polymers and copolymer. The N, S co-doped carbon (NS-C) show highly catalytic oxidation compared by N doped carbon (N-C) and S doped carbon (S-C) due to the synergistic effect between N and S dopants. It’s supposed that N and S doping can effectively create highly and main active sites to the electron transfer via PS activation, which could generate reactive oxygen species (ROS). Structure-dependent activity during activation of PS was confirmed by quenching experiments and electron paramagnetic resonance (EPR) analysis, prove that the non-radical species (1O2) is the main ROS generated. To improve the carbocatalyst separation and stability, the hydrogel beads-based alginate NS-C@Alginate were easily prepared. The catalytic efficiency rate by using the real water matrix shows that the NS-C/PS synergic system non-radical-led pathway exhibited a high ability to remediation of surrounding inorganic or organic compounds. This approach provides an innovative method for production and proves an efficient and environmentally benign carbocatalyst to PS activation for practical applications.

Efficient degradation of trimethoprim with ball-milled nitrogen-doped biochar catalyst via persulfate activation

This study explored a novel eco-friendly metal-free biochar catalyst for trimethoprim (TMP) degradation in an aqueous solution. The preparation of a ball-milled and N-doped mulberry biochar (BMNMB) for the activation of persulfate to degrade an antibiotic. BMNMB exhibits a large contact surface area and high colloidal stability compared to pristine biochar, ball-milled, and thermally treated biochar (BMMB). Surface analysis studies confirmed the heteroatom doping of the ball-milled biochar materials. The degradation efficiency of TMP in the BMNMB900/PS (>97%) was higher than those of the BMMB900/PS (73%) and pristine MB/PS (24%) systems. The TMP removal treads were further verified by the pseudo-first-order kinetic model (PFOKM). The effective degradation of TMP was obtained under neutral pH conditions. The heterogeneous catalytic reaction performance was examined using the Langmuir–Hinshelwood (L–H) kinetic model. The anions had a negative impact on the catalytic activation of BMNMB900 with PS. The chemical scavenger analysis was confirmed via both radical (HO• and SO4•−) and non-radical (1O2) reactive oxygen species (ROS) formed in the BMNMB900/PS system. Further, substantial evidence of 1O2 formation in the BMNMB900/PS system was observed in the electron spin resonance (ESR) analysis in the presence of D2O. Moreover, the linear sweep voltammogram also clearly demonstrated the electron transfer process in the BMNMB900/PS system. The TMP degradation mechanisms were proposed via the intermediate analysis using ultra-high-performance liquid chromatography with mass spectroscopy (UHPLC-MS/MS). The BMNMB900 catalyst with PS system successfully demonstrated the reusability of a catalyst in TMP degradation.

MOFs-derived defect carbon encapsulated magnetic metallic Co nanoparticles capable of efficiently activating PMS to rapidly degrade dyes

In this work, a new defect carbon encapsulated magnetic metallic Co nanoparticles (denoted as Co@DC) was prepared via pyrolyzing Co-BTC (BTC: 1,3,5-trimesic acid) MOFs precursor at 900 °C, and characterized by various technologies to prove that the Co@DC contains Co0, Co2+ and Co3+. It was used to activate peroxymonosulfate (PMS) to degrade Rhodamine B (RhB) dye efficiently. Over 99% of 10 mg/L RhB with initial pH of 5.5 was degraded by 100 mg/L PMS activated by 10 mg/L Co@DC within 5 min. The RhB degradation rate constant in the Co@DC/PMS system was 1.1805 min−1, which was approximately 17 times that of DC/PMS system (0.0695 min−1). The Co@DC displayed a good magnetism, stability, and PMS activation ability in a wide pH range of 3 to 10. After four cycles, the RhB removal rate can still maintain over 90% after 10 min reaction. The Co@DC/PMS system can also rapidly degrade the other dyes (acid fuchsin, methylene blueandmethyl orange), showing excellent universality. The free radical quenching experiments and EPR trials suggest that both the radicals (sulfate radical, hydroxyl radical, and O2•−) and non-radical (singlet oxygen) species are involved in the RhB degradation, while the latter plays a major role. In addition to the cobalt ions, the metallic Co0 also took part in PMS activation and reacted with O2 to generate Co2+, ensuring the sufficient Co2+ to activate the PMS to produce Co3+. The Co3+ ions withdraw electrons from HSO5− or Co0 in the Co@DC catalyst, driving a Co2+/Co3+ cycle to maintain a high performance of the Co@DC/PMS system for RhB removal. The effects of common inorganic anions on RhB removal, the mineralization degree and possible degradation pathway of RhB were studied. Relative to the previous catalysts for PMS activation to degrade RhB, the Co@DC shows lower activation energy of 23.78 KJ/mol. Altogether, this work provides a simple strategy to develop an efficiently magnetic heterogeneous catalyst to activate PMS for the elimination of hardly degradable dyes.

Remediation of phenol contaminated soil using persulfate activated by ball-milled colloidal activated carbon

The degradation of phenolic compounds through persulfate (PS) activation is a valuable approach for soil/groundwater remediation. Several reports have been made related to PS activation and contaminant degradation using carbo-catalysts; however, there is no detailed study on soil remediation by colloidal activated carbon. This study demonstrates the phenol (PhOH) degradation efficiency in spiked and field-contaminated soils by a novel and low-cost ball-milled colloidal activated carbon (CACBM) catalyst. The CACBM/PS system exhibited outstanding degradation performance for PhOH in both spiked and field-contaminated soils. Optimum condition for degradation of 5.63 mmol PhOH kg soil−1 was achieved at 2.5 mg CACBM g soil−1, 5 mM PS, and a solid-liquid ratio of 1:5 at 25 °C in the wide pH range of 3–11. Radical scavenger experiments and electron spin resonance (ESR) spectroscopy revealed that both radical (•OH and SO4•–) and non-radical (1O2) species were involved in the CACBM/PS system. PhOH degradation in soil phase followed several degradation pathways, resulting in various intermediate byproducts such as acetic acid, maleic acid, p-benzoquinone, fumaric acid, and ferulic acid as analyzed by ultra-high-performance liquid chromatography with mass spectroscopy (UPLC−MS). The CACBM/PS system showed a promising potential in the remediation of organic-contaminated soil.

Development of emphatic catalysts for waste water remediation via synchronized free radical and non-free radical routes with composites of strontium hexaferrite, graphene and multi-walled carbon nanotubes

Magnetic nanoparticles have shown exceptional potential in catalysis, however, their tendency to agglomerate has confined their use. The present work encompasses synthesis of eco-friendly and magnetic retrievable catalysts with different fractions of reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNT) as support for strontium hexaferrite (SrFe12O19) for the oxidative degradation of organic pollutants. The morphological, structural and magnetic properties of composites were estimated via PXRD, FT-IR, VSM, FE-SEM, HR-TEM, XPS and BET. The crystallite size decreased from 41.46 nm for SrFe12O19 to 35.85 nm and 33 nm for composites with 20% rGO and MWCNTs, respectively while the surface area increased substantially from 88.1 m2/g for SrFe12O19 to 118.4 and 131.3 m2/g. Further, the composites were employed as catalysts for the oxidative degradation of selected antibiotics and colourant via stimulation of two different oxidants, potassium peroxymonosulphate (PMS) and hydrogen peroxide (H2O2). The degradation followed pseudo first order kinetics with rate constant values increasing with rGO and MWCNT content. The increase in catalyst effectiveness can be ascribed to the synergistic interactions between rGO or MWCNT and SrFe12O19, which provided larger specific surface areas for adsorption and augmented number of catalytically active sites. Systematic chemical quenching studies unveiled a combined role of radical and non-radical species in oxidative degradation of pollutants. Moreover, the synthesized composites exhibited excellent recyclability upto four cycles forming the basis for their utilization as industrial catalysts.

One-Pot Thermal Synthesis of g-C3N4/ZnO Composites for the Degradation of 5-Fluoruracil Cytostatic Drug under UV-LED Irradiation.

Graphitic carbon nitride (g-C3N4) was used to enhance the photocatalytic activity of ZnO nanoparticles for the degradation of 5-fluorouracil (5-FU) cytostatic drug under UV-LED irradiation. CN/ZnO composites were synthetized by an easy one-pot thermal method, varying the g-C3N4 loading, i.e., from 10 to 67 wt% and a post-thermal exfoliation in air. The physicochemical and optical properties of the materials were analyzed by several techniques. CN/ZnO composites showed a coral-like structure of spherical ZnO wurtzite particles on the g-C3N4 structure. In general, the synergism and heterojunction interface between both phases allowed the enhancement of the mesoporosity, light absorption ability, and the aromaticity of the corresponding composites. Moreover, the photocatalytic activity of the CN/ZnO composites was increased with the addition of g-C3N4 in comparison with pristine ZnO. The highest activity was found for the composite containing 25 wt% of g-C3N4 (i.e., CN25/ZnO), reaching the total degradation of 5-FU and a mineralization of 48% at 180 min, as well as a good photostability during four reuse cycles. Experiments with different pH solutions and scavengers allowed for the assessment of the reactive oxygen species (ROS) involved in the 5-FU degradation pathway, with radicals and non-radical species as the main responsible active species. Furthermore, a tentative photocatalytic mechanism was proposed for CN/ZnO composites.

Construction of Li/K dopants and cyano defects in graphitic carbon nitride for highly efficient peroxymonosulfate activation towards organic contaminants degradation

As an emerging peroxymonosulfate (PMS) activation catalyst, graphitic carbon nitride (g-C3N4) is non-toxic and eco-friendly, while its poor catalytic performance hinders the application of pristine g-C3N4. Herein, a simple LiCl/KCl molten salts-assisted thermal polymerization method was adopted to promote the photocatalytic performance of g-C3N4. With the insertion of Li/K dopants and the introduction of surface cyano defects, the modified catalyst exhibited greatly enhanced ability on PMS activation towards acetaminophen removal, observing a 13 times higher rate constant than pristine g-C3N4 (k = 0.0435 min−1 vs. 0.0033 min−1). The main reactive oxygen species for pollutant degradation were identified as sulfate radicals and singlet oxygen. The wavefunction analysis at excited states based on density functional theory suggests that the introduction of cyano defects greatly promotes the separation of photo-generated electron-hole pairs, thereby achieving higher photocatalytic efficiency. In addition, the doping of Li/K significantly enhances the interaction between PMS and the catalyst surface, and orients the electron transfer from PMS to catalyst to generate non-radical species singlet oxygen, which improves the catalyst resistance to anions-containing water matrices.

Waste preserved wood derived biochar catalyst for promoted peroxymonosulfate activation towards bisphenol A degradation with low metal ion release: The insight into the mechanisms

The rational disposal of waste preserved wood is of great significance since its embedded metals (Cu, As, and Cr) pose potential threat to environment and human health. In this study, a biochar catalyst derived from waste preserved wood (PWB) was prepared for the degradation of bisphenol A (BPA) via peroxymonosulfate (PMS) activation. The PWB exhibited prominent catalytic degradation capability towards BPA compared with common wood derived biochar (CWB). Further tests and analysis elucidated that both radical species (OH) and non-radical species (1O2) were generated by the PWB/PMS system, whereas only 1O2 was detected in CWB/PMS system. Specifically, the metal compounds, especially metallic Cu in the PWB activated PMS via radical pathway, and the CO groups in the biochar generated the non-radical pathway, the coexistence of which resulted in higher BPA degradation rate in PWB/PMS system. It was also demonstrated that the heavy metal ion leaching (As and Cr) in PWB/PMS system was negligible. Furthermore, the biochar could effectively inhibit the leakage of oxidized Cu ions. This study provides a novel approach to prepare high-efficient carbocatalysts for organic pollutant degradation in water, which also enables the waste preserved wood with an environmental nondestructive mode of dispatch.

Biomass-derived carbon aerogel for peroxymonosulfate activation to remove tetracycline: Carbonization temperature, oxygen-containing functional group content, and defect degree

A biomass-derived carbon aerogel (CA) was prepared and employed as an efficient metal-free and green carbon-based catalyst for peroxymonosulfate (PMS) activation to degrade tetracycline (TC). The surface functional groups, morphology, and other properties of the CA were characterized using various methods. Different carbonization temperatures were used to produce CA samples to control the oxygen-containing functional group content and defect degree, both of which play important roles in PMS activation. The carbonization temperature showed a clear negative correlation with the oxygen-containing functional group content on the CA surface, while exhibiting a positive correlation with the degree of defects in the CA. The optimal temperature for producing the CA was 300 ℃ owing to the high oxygen-containing functional group content and low loss rate. Neutral and weakly alkaline conditions were conducive to TC removal. Under optimal conditions, 93% removal of TC could be achieved within 90 min. The results of reactive oxygen species (ROS) quenching experiments and electron paramagnetic resonance (EPR) spectroscopy indicated that both non-radical species (1O2 and electrons) and radical species (•OH and SO4•−) resulted in the removal of TC. 1O2 was identified as the main activated ROS. This study deepens our understanding of the preparation of biomass-derived carbon aerogels and control of the oxygen-containing functional group content and defect degree for improving the pollutant removal efficiency.

Removal of antibiotics sulfadiazine by a biochar based material activated persulfate oxidation system: Performance, products and mechanism

Nowadays, the harm of antibiotics residues in environments to human health and ecological safety has been causing more and more attention. In this paper, a biochar based iron material (MBC) was used to activate persulfate (PS) for the removal of sulfadiazine (SDZ) from aqueous solution. Experiment results indicate that the degradation and mineralization of SDZ by MBC/PS system reached 91.79% and 60% within 60 min under the optimal reaction conditions, respectively. MBC/PS system exhibited a better performance on SDZ removal compared with MBC/H2O2 system. The addition of Cu2+ ion could enhance the degradation of SDZ by MBC/PS system. PO43-, Cl- and SO42- had a certain degree of inhibitory effect on the SDZ degradation. Both radicals and non-radical species such as SO4•-, •OH and 1O2 participated in the degradation reaction of SDZ by MBC/PS system, but •OH was the main radical species responsible for SDZ degradation. The liquid chromatograph-mass spectrometer (LC-MS) technique was used to identify the intermediate products of SDZ, and it was proposed that the degradation of SDZ might be achieved through hydrolyzation, hydroxylation, deamination and amino-oxidization processes. A possible reaction mechanism involving a synergistic effect between PS homogeneous and heterogeneous activation processes as well as both radicals and non-radicals reactions was finally proposed.

Pyrite-embedded porous carbon nanocatalysts assembled in polyvinylidene difluoride membrane for organic pollutant oxidation

FeS2-embedded in porous carbon (FeS2/C) was prepared by simultaneous sulfidation and carbonization of an iron-based metal–organic framework precursor, and subsequently immobilized in polyvinylidene fluoride membranes (FeS2/C@PVDF) for organics removal via peroxymonosulfate (PMS) activation. The composition, structure, and morphology of the FeS2/C@PVDF membrane were extensively characterized. Scanning electron microscopy images manifest that the FeS2/C nanoparticles with an average diameter of 40 nm are assembled on the external and internal membrane surface. The as-prepared FeS2/C@PVDF membrane exhibits excellent performances over a wide pH range of 1.53–9.50, exceeding carbon-free syn-FeS2@PVDF. The effective degradation could be improved by inner pyrite FeS2 cores and thus enhanced the electron transfer between carbon shell and PMS. Electron paramagnetic resonance and quenching experiments elucidated that radical (HO∙, SO4∙-) and nonradical (1O2) species were the predominant reactive oxidants. In addition, FeS2/C@PVDF exhibited high stability with low Fe leaching (0.377 mg/L) owing to the effective protection of the outer carbon skeleton. Plentiful porosity of PVDF membranes not only affords a controlled size and confined uniform distribution of the immobilized FeS2/C nanoparticles, but also enables a persistent exposure of active sites and enhanced mass transfer efficiency. Our findings demonstrate a promise for utilizing the novel FeS2/C@PVDF membrane as an efficient catalyst for the environmental cleanup.

Radical versus Nonradical States of Azobis(benzothiazole) as a Function of Ancillary Ligands on Selective Ruthenium Platforms.

The paper deals with the electronic impact of ancillary ligands on the varying redox features of azobis(benzothiazole) (abbt) in the newly introduced mononuclear ruthenium complexes [Ru(pap)2(abbt)]n (1n) and [Ru(bpy)2(abbt)]n (2n), where pap = 2-phenylazopyridine and bpy = 2,2'-bipyridine. In this regard, the complexes [RuII(pap)2(abbt•-)]ClO4 ([1]ClO4), [RuII(pap)2(abbt0)](ClO4)2 ([1](ClO4)2), [RuII(bpy)2(abbt0)](ClO4)2 ([2](ClO4)2), and [RuII(bpy)2(abbt•-)]ClO4 ([2]ClO4) were structurally and spectroscopically characterized. Unambiguous assignments of the aforestated radical and nonradical forms of abbt in 1+/2+ and 12+/22+, respectively, were made primarily based on their redox-sensitive azo (N═N) bond distances as well as by their characteristic electron paramagnetic resonance (EPR)/NMR signatures. Although the radical form of abbt•- was isolated as an exclusive product in the case of strongly π-acidic pap-derived 1+, the corresponding moderately π-acidic bpy ancillary ligand primarily delivered an oxidized form of abbt0 in 22+, along with the radical form in 2+ as a minor (<10%) component. The oxidized abbt0-derived [1](ClO4)2 was, however, obtained via the chemical oxidation of [1]ClO4. Both 1+ and 22+ displayed multiple closed by reversible redox processes (one oxidation O1 and four successive reductions R1-R4) within the potential window of ±2.0 V versus saturated calomel electrode. The involvement of metal-, ligand-, or metal/ligand-based frontier molecular orbitals along the redox chain was assigned based on the combined experimental (structure, EPR, and spectroelectrochemisry) and theoretical [density functional theory (DFT): molecular orbitals, Mulliken spin densities/time-dependent DFT] investigations. It revealed primarily ligand (abbt/pap or bpy)-based redox activities, keeping the metal ion as a simple spectator. Moreover, frontier molecular orbital analysis corroborated the initial isolation of the radical and nonradical species for the pap-derived 1+ and bpy-derived 22+ as well as facile reduction of pap and abbt in 1+ and 2+, respectively.

Activation of peroxymonosulfate by bimetallic CoMn oxides loaded on coal fly ash-derived SBA-15 for efficient degradation of Rhodamine B

• Mesoporous SBA-15 is successfully synthesized with coal fly ash as the silicon source. • CoMn/SBA-15 exhibits excellent performance for RhB degradation by activating PMS. • Synergistic effects of Co and Mn species are inferred. • Non-radical ( 1 O 2 ) rather than radicals (SO 4 − and OH) contributes most to the degradation. • Mechanisms of PMS activation and the degradation pathways of RhB are proposed. In this study, we successfully synthesized SBA-15 mesoporous molecular sieve with coal fly ash (CFA) as the silicon source, fabricated bimetallic CoMn catalysts with the obtained SBA-15 as the support, and evaluated their performance for activating peroxymonosulfate (PMS) to degrade the Rhodamine B (RhB) in an aqueous solution. The characterization results signified that MnCo 2 O 4 spinel was formed and uniformly dispersed on SBA-15 for the as-prepared CoMn/SBA-15. The CoMn/SBA-15/PMS system exhibited markedly higher RhB removal efficiency compared with Co/SBA-15/PMS and Mn/SBA-15/PMS under the same reaction conditions. Moreover, bimetallic CoMn/SBA-15 presented much lighter metal leaching than the monometallic catalysts. Chemical quenching tests and electron paramagnetic resonance experiments ascertained the generation of free radicals (SO 4 − and OH) and non-radical (singlet oxygen, 1 O 2 ) reactive oxygen species by PMS activation and the dominant role 1 O 2 in RhB degradation. The formed intermediate products by RhB degradation were identified with LC-MS analyses. We have also performed LC-MS analyses to determine the formed intermediate products during RhB degradation. The present results demonstrate the pronounced potential of CFA as a silicon source of molecular sieve support for preparing various heterogeneous catalysts for the PMS-based oxidation of organic pollutants in wastewater.

The Reactive Oxygen Species Singlet Oxygen, Hydroxy Radicals, and the Superoxide Radical Anion—Examples of Their Roles in Biology and Medicine

Reactive oxygen species comprise oxygen-based free radicals and non-radical species such as peroxynitrite and electronically excited (singlet) oxygen. These reactive species often have short lifetimes, and much of our understanding of their formation and reactivity in biological and especially medical environments has come from complimentary fast reaction methods involving pulsed lasers and high-energy radiation techniques. These and related methods, such as EPR, are discussed with particular reference to singlet oxygen, hydroxy radicals, the superoxide radical anion, and their roles in medical aspects, such as cancer, vision and skin disorders, and especially pro- and anti-oxidative processes.

Hierarchical microsphere encapsulated in graphene oxide composite for durable synergetic membrane separation and Fenton-like degradation

As a typical advanced oxidation process, persulfate-based heterogeneous Fenton-like reaction has gained widespread attention in removing persistent harmful organic pollutants via the generation of reactive radicals. Nevertheless, persulfate having an inefficient decomposition of the target contaminants and common powdery counterparts causing secondary pollution. Herein, we first design and fabricate a novel metal-organic frameworks (MOFs) derived cobalt-carbon based heterogeneous Fenton-like catalyst (Co@NCNT-MS) with hierarchical structure, the systematic characterization demonstrated that powder catalysts were successfully prepared and the catalyst possessed a favorable degradation capacity of tetracycline (TC), which could be contributed by its particular hierarchical urchin-like structure with abundant active sites and that both radical (·SO4−, ·OH, and ·O2−) and nonradical (1O2) species have been involved in the process. Then, this hierarchical heterogeneous catalyst was encapsulated in Graphene oxide (GO) by facile vacuum filtration to form a robust composite membrane. And the obtained membrane shows good application prospects as it exhibits excellent separation and catalytic degradation properties in removal of anionic dye, cationic dye, and persistent refractory tetracycline. It is speculated that these excellent results could be primarily attributed to the domain effect of micro-nano channels in the membrane on low-life active components, pollutions, and PMS. More than that, the as-prepared membrane displayed excellent stability with continuous removal of TC with high efficiency above 90% and a steady flux around 40 L·m−2·h−1 under 24 h sequential filtration mode. It is promising that this membrane could potentially be used for effectually treating complex wastewater systems with persistent organic contaminants in environmental pollution cleaning up.

Efficient photocatalytic degradation of ciprofloxacin using novel dual Z-scheme gCN/CuFe2O4/MoS2 mediated peroxymonosulphate activation

Modulation in the constituent composition of heterojunction composite materials can efficiently separate photogenerated charge carriers and promote significant improvement towards visible light aided photocatalytic degradation of recalcitrant pollutants. Herein, a novel ternary heterojunction composite g-CN/CuFe2O4/MoS2 (CNCuMo) has been fabricated by improvising g-C3N4 as a fuel and the supporting matrix. The stable dual Z-scheme heterojunction manifested superior visible light driven catalytic activity through efficient electron/hole (e-/h+) separation and generation of reactive species through peroxymonosulphate (PMS) activation. Various surface bound redox cycles play prominent roles in transport of photogenerated charge carriers, activation of adsorbed PMS species and generation of reactive radicals. Benefiting from their synergistic effects, visible light aided photocatalytic degradation of refractory antibiotic Ciprofloxacin (CIP) was studied. 98% CIP was degraded (with 74.8% mineralization) using 0.1 g/l of ternary composite with 10 wt% MoS2 (CNCuMo(10)) and 0.5 g/l of PMS, within 60 min of visible light irradiation. Scavenging experiments confirmed the simultaneous activity of both radical and non-radical species towards degradation. The system also exhibited satisfactory CIP degradation efficiency in various surface water matrixes. LCMS/MS analysis of the identified intermediates interpreted the probable degradation pathways of CIP molecules. Magnetic retrievability, recyclability for five cycles, good structural stability and low metal ion leaching tendency of the synthesized photocatalyst elucidate its potential application for degradation of emerging pollutants for water decontamination.