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Single‐atom catalysts (SACs) are widely investigated in Fenton‐like reactions for environmental remediation, wherein their catalytic performance can be further improved by coordination structure modulation, but the relevant report is rare. Herein, a series of atomically dispersed cobalt catalysts with diverse coordination numbers (denoted as CoNx, x represents nitrogen coordination number) are synthesized and their peroxymonosulfate (PMS) conversion performance is explored. The catalytic specific activity of CoNx is found to be dependent on coordination number of single atomic Co sites, where the lowest‐coordinated CoN2 catalyst exhibits the highest specific activity in PMS activation, followed by under‐coordinated CoN3 and normal CoN4. Experimental and theoretical results reveal that reducing coordination number can increase the electron density of single Co atom in CoNx, which governs the Fenton‐like performance of CoNx catalysts. Specifically, the entire Co–pyridinic NC motif serves as active centers for PMS conversion, where the single Co atom, and pyridinic N‐bonded C atoms along with nitrogen vacancy neighboring the unsaturated Co–pyridinic N2 moiety account for PMS reduction and oxidation toward radical and singlet oxygen (1O2) generation, respectively. These findings provide a useful avenue to coordination number regulation of SACs for environmental applications. [ABSTRACT FROM AUTHOR]

• The Fenton-like Cu-PAN 3 catalysts is first synthesized by co-precipitation and carbon thermal reduction method. • Dual reaction centers are constructed around graphene-like carbon and Cu species. • The pollutants as electron donors inhibit the ineffective decomposition of H 2 O 2 at the electron-poor centers. • The pollutant removal mainly relies on the surface cleavage at the electron-poor centers. High energy consumption has seriously hindered the development of Fenton-like reactions for the removal of refractory organic pollutants in water. To solve this problem, we designed a novel Fenton-like catalyst (Cu-PAN 3) by coprecipitation and carbon thermal reduction. The catalyst exhibits excellent Fenton-like catalytic activity and stability for the degradation of various pollutants with low H 2 O 2 consumption. The experimental results indicate that the dual reaction centers (DRCs) are composed of Cu-N-C and Cu-O-C bridges between copper and graphene-like carbon, which form electron-poor/rich centers on the catalyst surface. H 2 O 2 is mainly reduced at electron-rich Cu centers to free radicals for pollutant degradation. Meanwhile, pollutants can be oxidized by donating electrons to the electron-poor C centers of the catalyst, which inhibits the ineffective decomposition of H 2 O 2 at the electron-poor centers. This therefore significantly reduces the consumption of H 2 O 2 and reduces energy consumption. [Display omitted] [ABSTRACT FROM AUTHOR]

Cu-doped LaAlO 3 perovskite (LaAl 1−x Cu x O 3 ) was synthesized via a Pechini-type sol–gel process for the oxidative degradation of persistent organic compounds. The characterization results show that Cu was incorporated into the structure of sphere-like LaAlO 3 and formed the bond of La/Al O Cu. LaAl 0.95 Cu 0.05 O 3 performed excellent activity and stability for the degradation and mineralization of various organic pollutants through heterogeneous Fenton-like reactions. In the practical reaction process, at the organic pollutant initial concentration of 25 mg L −1 , 1.0 mol H 2 O 2 produces 1.8 mol HO radicals within 60 min and 1.0 mol H 2 O 2 still produces 1.3 mol HO radicals after reaction time of 240 min. The results of ESR and active species trapping experiments indicated that HO radicals acted the dominant role during the degradation of pollutants in LaAl 0.95 Cu 0.05 O 3 /H 2 O 2 system. Combining with in-situ Raman analysis and the XPS results of LaAl 0.95 Cu 0.05 O 3 before and after reaction, H 2 O 2 was predominantly reduced to HO on the electron-rich Cu center, and H 2 O 2 /H 2 O can be dissociated on oxygen vacancies (OVs) to enhance formation of HO on the surface of LaAl 0.95 Cu 0.05 O 3 , resulting in the high catalytic activity of LaAl 0.95 Cu 0.05 O 3 . This efficient material can potentially be used as a promising catalyst for the efficient degradation of organic pollutants in environmental pollution cleanup. [ABSTRACT FROM AUTHOR]

Excessive consumption of energy and resources is a major challenge in wastewater treatment. Here, a novel heterogeneous Fenton-like catalyst consisting of Cu-doped graphene-like catalysts (Cu-GCD NSs) was first synthesized by an enhanced carbothermal reduction of β-cyclodextrin (β-CD). The catalyst exhibits excellent Fenton-like catalytic activity for the degradation of various pollutants under neutral conditions, accompanied by low H 2 O 2 consumption. The results of structural characterization and theoretical calculations confirmed that the dual reaction centers (DRCs) were constructed on Cu-GCD NSs surface through C-O-Cu bonds supported on zero-valent copper species, which play a significant role in the high-performance Fenton-like reaction. The pollutants that served as electron donors were decomposed in the electron-poor carbon centers, whereas H 2 O 2 and dissolved oxygen obtained these electrons in the electron-rich Cu centers through C-O-Cu bonds, thereby producing more active species. This study demonstrates that the electrons of pollutants can be efficiently utilized in Fenton-like reactions by DRCs on the catalyst surface, which provides an effective strategy to improve Fenton-like reactivity and reduce H 2 O 2 consumption. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] The heterogeneous Fenton process suffers from low efficiency because of the low electron transfer cycle rate of Fe3+/Fe2+, which often consumes enormous amounts of hydrogen peroxide (H 2 O 2) or other energy. Herein, we report a novel Co-based Fenton-like catalyst (in-situ -Co-g-C 3 N 4) synthesized via the surface complexation method, in which Co species were modified in situ into the framework of the graphitic carbon nitride (g-C 3 N 4) substrate through C–O–Co chemical bonding. The catalyst exhibited higher Fenton-like catalytic activity than pure g-C 3 N 4 in the degradation of various pollutants under neutral conditions, as evidenced by the approximately 150-fold higher Fenton-like reaction rate constant of in-situ -Co-g-C 3 N 4 than that of g-C 3 N 4. Density functional theory (DFT) calculations and a series of experimental and characterization analyses revealed the interfacial reaction mechanism between H 2 O 2 , pollutants and in-situ -Co-g-C 3 N 4. During the Fenton-like reaction, the electron-poor C center on the aromatic ring of g-C 3 N 4 could capture the electrons deprived from pollutants, and subsequently deliver them to around the electron-rich Co center to efficiently reduce H 2 O 2 to hydroxyl radicals (•OH), enabling H 2 O 2 to be used efficiently for the degradation of pollutants. This study provides a strategy for improving Fenton-like degradation efficiency by effectively utilizing the energy of organic pollutants. [ABSTRACT FROM AUTHOR]

• Mesoporous reduction state cobalt species-doped silica nanospheres are first prepared. • Excellent activity is realized in mp -RSCo-SiO 2 NSs/H 2 O 2 system. • Efficient dual-pathway degradation of pollutant is achieved in Fenton-like process. • Pollutants replace H 2 O 2 as electron donors for the mp -RSCo-SiO 2 NSs system. • A new interfacial Fenton-like reaction mechanism involving pollutants is proposed. A novel heterogeneous Co-containing Fenton-like catalyst consisting of mesoporous reduction state cobalt (RSCo)-doped silica (SiO 2) nanospheres (mp -RSCo-SiO 2 NSs) was prepared by an enhanced hydrothermal process. The catalyst exhibited very high activity and stability for a series of refractory pollutant degradation in a very wide pH range of 3.1–10.9. The Fenton-like reaction rate constant of this Co-containing catalyst was approximately 290 times higher than that of Co 3 O 4 for pollutant degradation under the neutral and mild conditions. Based on the characterization, the catalyst possessed a porous nanosphere morphology, and the reduction state cobalt species, including nano-zero-valent cobalt (nZVCo) and Co2+, were found to be generated in the SiO 2 framework through forming Co O Si bonds. During the Fenton-like reaction, the electron donation effect of organic pollutants was successfully realized through the interaction of "Pollutants → Co2+/0-SiO 2 ". The obtained electrons from pollutants were transferred to the catalyst surface and captured by H 2 O 2 , resulting in the generation of hydroxyl radicals (OH). Therefore, a dual-pathway degradation of the pollutants was realized: (I) oxidation and degradation as the electron donors for the system and (II) attacking and destruction by OH radicals. This work provided a new perspective on the effective utilization of the electrons of pollutants and the improvement of Fenton reaction efficiency. [ABSTRACT FROM AUTHOR]

• Cu-Al/KIT-6 with single electron of Cu species was successfully synthesized. • Cu-Al/KIT-6 showed excellent activity and stability for BPA degradation. • O 2 can be activated to produce reactive oxygen species by Cu(I) on Cu-Al/KIT-6. • O 2 as an electron acceptor triggered the Fenton reaction over Cu-Al/KIT-6. • BPA and its products chelating with Cu(II) further promoted BPA degradation. Framework Cu doped Al 2 O 3 dispersed on KIT-6 (Cu-Al/KIT-6) was synthesized by the ultrasonic impregnation method and characterized by multi-technologies. The catalyst performed superior catalytic performance and stability for bisphenol A (BPA) degradation in heterogeneous Fenton-like catalysis. Especially, the effect of O 2 and N 2 on BPA degradation was detected over Cu-Al/KIT-6 in the presence of hydrogen peroxide (H 2 O 2). DMPO spin-trap electron spin resonance (ESR) experiments indicated that O 2 can be activated to produce reactive oxygen species (ROS) by Cu(I) on the surface of Cu-Al/KIT-6. Meanwhile, O 2 as an electron acceptor can trigger the reaction at the beginning of reaction, which decreased the consumption of H 2 O 2. In addition, BPA and its intermediate products chelate with Cu(II) to form Cu(II)-phenol complex, resulting in a series of reactions to further promote BPA degradation. These findings provide useful insights into the fundamental theories of Fenton catalysts via interface engineering for practical application. [ABSTRACT FROM AUTHOR]

Single-atom Fe catalysis has exhibited remarkable potentials in water treatment applications. However, rational design of single-atom Fe catalysts with controlled catalytic performance is still challenging, due to the lack of the fundamental understanding on the corelated factors of structure, property, and catalytic behavior. Herein, PMS activation performance of the single-atom Fe sites is successfully boosted by molecular-engineering on the polymeric carbon nitride (CN) framework. Benzene-1,4-diamine regulates the polymerization process, and rises the ratio of carbon/nitrogen; the valence of the single-atom Fe is thereby positively shifted, leading to favorable thermal dynamics of the high-valent Fe(IV)=O involved oxidation reaction. The carbon-rich CN supported single-atom Fe catalyst thus exhibits remarkable performance in selective degradation of a series of organic pollutants via high-valent Fe(IV)=O oxidation pathway. The findings in this work implicate the significance of electronic properties of the support as one of the essential descriptors for a robust single-atom catalyst for pollutants abatement. [Display omitted] • Benzene diamine in precursor for synthesis of single-atom Fe catalyst could positively shift the valence of Fe center. • A 5.1 times of performance improvement in bisphenol A degradation reaction was realized. • The single atom Fe catalyst with optimized valence is durable in a fixed-bed reactor. • Theoretical simulation states that positive valence of Fe center lowered the energy barrier of the catalytic reaction. [ABSTRACT FROM AUTHOR]

Nanoscale LaFeO 3 was prepared via sol–gel method and characterized by XRD, FTIR and N 2 adsorption/desorption experiment. The results indicated that, LaFeO 3 had a typical perovskite structure with a BET area of 8.5 m 2 /g. LaFeO 3 exhibited excellent Fenton activity and stability for the degradation of pharmaceuticals and herbicides in water, as demonstrated with sulfamethoxazole, phenazone, phenytoin, acyclovir and 2,4-dichlorophenoxyacetic acid, 2-chlorophenol. Among them, sulfamethoxazole (SMX) could be completely removed in LaFeO 3 –H 2 O 2 system after reaction for 120 min at neutral pH. Based on the ATR–FTIR analysis, the surface complex of LaFeO 3 and H 2 O 2 was formed, which was important and essential for the enhanced Fenton reaction by accelerating the cycle of Fe 3+ /Fe 2+ . Hence, more OH and O 2 − /HO 2 − were then produced in LaFeO 3 –H 2 O 2 system, resulting in more efficient removal of refractory organic compounds. Based on the surface interaction of LaFeO 3 and H 2 O 2 , a heterogeneous Fenton reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

• Heterogeneous Fenton-like reaction was studied using a pilot scale test. • TCM, DCAA and TCAA were the main compositions of DBPs in drinking water. • C1-C5 and F1-F5 of NOM were the main precursors of different DBPs. • This treatment improved removal efficiency of DBPs and NOM without adjusting pH. • This treatment process also controlled the genotoxicity of drinking water. This paper explores the removal of natural organic matter (NOM) and disinfection by-products (DBPs) in drinking water by heterogeneous Fenton-like oxidation and granular activated carbon (GAC) filtration in a pilot scale test without adjusting pH of the water. pH of the used water in this study was from 7.5 to 8.7. Comparing with conventional water treatment processes, heterogeneous Fenton-like reaction and GAC filtration increased the removal rate of dissolved organic carbon (DOC), NOM with different apparent molecular weight (AMW) (F1-F7) and with different compositions (C1-C5) to 75.11%, 88.65% and 58.73%, respectively. Moreover, heterogeneous Fenton-like reaction and GAC filtration increased the removal rate of DBPs to 88.18%. The multivariate statistical analysis indicated that haloacetic acids (HAAs) and haloketones (HKs) mainly came from fulvic-like and humic-like NOM with AMW lower than 1.5 K Da. These substances with AMW between 1.5 K Da and 3.5 K Da were the main precursors of trihalomethanes (THMs). The main precursors of halonitriles (HANs) were soluble microbial byproduct-like (SMP-like), tyrosine-like and tryptophan-like substance with the AMW between 3.5 K Da and 4.5 K Da. Overall, without adjusting pH of water, heterogeneous Fenton-like reaction and GAC filtration improved the removal efficiency of NOM and DBPs, and controlled the genotoxicity of drinking water. [ABSTRACT FROM AUTHOR]

• Nanoscale Fe 2 (MoO 4) 3 is successfully developed as a HPPA catalyst. • Fe 2 (MoO 4) 3 HPPA process can rapidly degrade micropollutants via two pathways. • An interfacial reaction mechanism for inhibiting e−/ h+ recombination is revealed. • Persulfate is responsible for capturing photogenerated electrons to produce SO 4 −. • Pollutants can capture holes and be oxidized through HPPA synergistic process. Photogenerated electron-hole recombination has been a bottleneck problem for photocatalytic reactions for a long time. Herein, we propose an efficient solution strategy through capturing electrons and holes with environmental factors. In this study, nanoscale iron molybdate (Fe 2 (MoO 4) 3) was successfully synthesized, characterized and used in a heterogeneous photo-combined persulfate (PS) activation (HPPA) process for micropollutant removal. The reaction rate in this system was ˜98 and ˜59 times higher for Fenton-like and photocatalytic oxidation alone, respectively, which was attributed to strong synergistic effects of HPPA process. During the HPPA reaction, PS could quickly capture the photogenerated electrons to produce sulfate radicals (SO 4 −), which was further converted to hydroxyl radicals (•OH) in water. Induced by PS, the electron-rich pollutants could actively capture the holes and be oxidized and degraded. This synergistic process not only inhibited the electron-hole recombination but also enabled rapid dual-pathway degradation of pollutants through free radical attack and hole oxidation. [ABSTRACT FROM AUTHOR]