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[Display omitted] • A simple heat treatment method was proposed to simultaneously introduce Sv and P doping. • The k obs value obtained by CuFe-NC-SP-2 was nearly 33 higher than that of CuFe-PBA. • CuFe-NC-SP-2/PMS system dominated by the electron transfer process (ETP) achieved 100 % removal of SDZ. • Synergistic effect of Sv (improved the adsorption energy of PMS) and P doping (accelerated the electron transport) enhanced the ETP. In this work, Prussian blue analogues (CuFe-PBA) derived copper-iron sulfides/N-doped porous carbon composite (CuFe-NC-SP- x) was prepared as an effective peroxymonosulfate (PMS) activator to degrade sulfadiazine (SDZ). A strategy that kills two birds with one stone was proposed to construct CuFe-NC-SP- x , i.e., S-etched CuFe-PBA (CuFe-PBA-S) was annealed with NaH 2 PO 2 in N 2 atmosphere to simultaneously introduce sulfur vacancy (Sv) and phosphorus doping. 40 μM SDZ was completely removed by CuFe-NC-SP-2/PMS in 20 min (0.2 g/L catalyst and 0.5 mM PMS). The k obs value obtained by CuFe-NC-SP-2 (0.48 min−1) was nearly 33 and 17 times higher than that of CuFe-PBA (0.014 min−1) and CuFe-PBA-S (0.028 min−1), respectively. Quenching tests, electron paramagnetic resonance (EPR) analysis indicated that PMS activation in the system involved radical pathway (26.1 % OH and 22.7 % SO 4 –) and non-radical pathway (17.8 % 1O 2 and 33.4 % electron transfer process). OH, SO 4 – and 1O 2 were mainly produced by S enhanced metal sites for PMS activation. The synergistic effect of Sv and P doping enabled the powerful electron transfer mechanism. Electrochemical tests and DFT calculations demonstrated that Sv existing in CuFe-NC-SP- x improved the electron donor ability and increased the adsorption energy toward PMS, and phosphorus doping accelerated the electron transport from SDZ to PMS. This work not only provides a novel strategy to synthesize a high effective PMS activator by introducing Sv and phosphorous doing in one step, but also manages to comprehensively understand the electron transfer activation mechanisms of PMS facilitated by Sv and phosphorous doping. [ABSTRACT FROM AUTHOR]

Fe VI O 4 2− (Fe VI ) is a promising oxidant/disinfectant and coagulant in treating water. Fe V O 4 3− (Fe V ) and Fe IV O 4 4− (Fe IV ) are intermediates in oxidations performed by Fe VI and are highly effective in degrading recalcitrant contaminants. The performance of each ferrate requires a comprehensive understanding of the mechanism. This paper presents the use of density functional theory (DFT) to understand the oxidation of cyanide by Fe VI , Fe V , and Fe IV . The sequence of steps in the oxidation process is the same for all three species. The electrostatic attraction of the positive H and C on HCN for two of the negative oxygen atoms on the ferrate is followed by the formation of a C-O bond with cleavage of an Fe-O bond. Subsequently, the formation of an H-O bond occurs with cleavage of the H-C bond, resulting in the formation of an NCO – ferrate complex. However, the energetics are different, with C-O bond formation being the rate determining step for Fe VI while for Fe V and Fe IV it is the transfer of the H from C to O. Energy calculations describe the order of reactivity of ferrates with HCN as Fe V > Fe IV > Fe VI , which agrees well with experimental results. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synergistic effect between biochar and mineral for PMS activation was explored. • The mechanism of mineral-biochar composites in PMS activation was explored. • A new insight into the electron transfer regime was provided. Biochar possesses attractive structural (highly porous) and chemical (abundant functional groups) properties, exhibiting promising future in diverse applications such as soil amendment and environmental remediation. However, the interaction between biochar and soil active minerals, especially the synergistic effect on peroxymonosulfate (PMS) activation is largely unknown. In this study, we focused on the origin of the observed synergistic effect between biochar and two typical soil active minerals, i.e., goethite (α-FeOOH) and birnessite (δ-MnO 2) on the activation of PMS by preparing four mineral-biochar composites, i.e., GBC 350 , BBC 350 , GBC 700 , and BBC 700. Interestingly, BBC 350 , BBC 700 , and GBC 700 exhibited distinct synergistic effects for BPA removal, whilst no obvious synergistic effect was observed for GBC 350. The theoretical calculations based on density functional theory (DFT) further confirmed the improved PMS adsorption affinity, ascribing to the delocalization of O electrons (in PMS) to the π bond in C-layer. Furthermore, non-radical regime was elucidated to dominate the BPA oxidation. Mineral species could establish an electron channel between oxidant and catalyst, thus accelerating the electron transfer process. The high-valent Mn species (Mn(V)) also contributed to BPA removal in BBC 350 /PMS process. Overall, this study uncovered the origin of synergistic effect between BC 700 and Fe/Mn minerals by exploring the electron transfer regime, which might provide new insights into PMS activation in practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biochar (BC) was effective in periodate (PI) activation for BPA degradation. • BC 350 and BC 800 exhibited better activation efficiency to PI than other oxidants. • Unique C O O IO 3 complexes were confirmed as main ROS in BC 350 catalyzed processes. • Metastable BC 800 -PI* complexes led to efficient removal of BPA in BC 800 /PI systems. Periodate based advanced oxidation processes (PI-AOPs) exhibited promising future for the abatement of emerging contaminants, yet the underlying mechanism of carbon materials for PI activation was still unclear. In this study, a metal-free biochar (BC x , x represents the pyrolysis temperature) catalyzed PI-AOPs system was established and explored for the degradation of bisphenol A (BPA), one of the endocrine disrupting compounds (EDCs) that was ubiquitously detected in natural ecosystems. Biochar catalysts clearly boosted BPA degradation, suggesting a distinct synergistic effect between PI and biochar. Interestingly, BC 350 and BC 800 exhibited distinct behaviors for PI activation. Specifically, BC 350 performed moderate PI activation, which was believed to be a surface hydroxyl group (OH)-induced nonradical pathway. A unique C O O IO 3 complex was formed and served as the reactive oxidant responsible for the BPA oxidation. On the other hand, BC 800 showed a significant PI activation ability, which was preferentially proved to be a carbon-mediated electron-transfer mechanism. A high potential metastable carbon activated PI complexes (C-PI*) was elucidated to be the dominant oxidative species through electrochemical characterizations and galvanic oxidation process (GOP) experiments. The electron-transfer between adsorbed BPA (electron donor) and C-PI* (electron acceptor) was a crucial step in this pathway. Density functional theory (DFT) calculations confirmed that the interaction between PI and carbon surface was probably caused by the van der Waals force and a part of strong attraction between the interface of PI and BC OH. These findings provide new insights into nonradical pathways in biochar catalyzed PI-AOPs and promote the development and application of PI-AOPs in environmental remediation. [ABSTRACT FROM AUTHOR]

• Co-N-C SACs with Co-N x sites was successfully synthesized by facile method. • SA Co-N-C(30) exhibited an excellent catalytic performance for PMS activation. • Experiments and DFT calculations demonstrated Co-N 3 was optimum active site. • The electron-transfer was regarded as the dominated reactive pathway for CQP degradation. Chloroquine phosphate (CQP) has played a role in the remission of COVID-19, but its large use will undoubtedly pollute the water. Herein, we have designed biomass carbon-based catalysts with anchoring sites for single cobalt atoms in a defined Co-N 3 coordination structure (SA Co-N-C(30)). A peroxymonosulfate (PMS) activation system employing the SA Co-N-C(30) as a high-efficiency catalyst was demonstrated, which can efficiently degrade CQP in a wide pH range (3–11). The electron-transfer was proposed as the dominant non-radical pathway for CQP degradation in SA Co-N-C(30)/PMS system by electrochemical studies and quenching experiments, and the generated singlet oxygen (1O 2) played a negligible role. The density functional theory (DFT) calculations and experimental results showed that Co-N 3 site served as the main active site for PMS activation. In addition, SA Co-N-C(30)/PMS system had excellent efficiencies in oxidative degradation of various organic pollutants. This work opens up a new avenue to efficient degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bifunctional NHGBC-800 can adsorb TC and activate PDS with itself as the activator. • NHBC-800 could maintain above 77.18% adsorption capacity after the 6th cycles. • Non-radical electron-transfer and 1O 2 pathways dominated the regeneration process. • PDS oxidation can regenerated carbon material saturated by organic pollutants well. Carbonaceous material is not only the excellent adsorbent for organic contaminants removal, but also the effective activator for peroxydisulfate (PDS) activation. In this study, a nitrogen-doped hierarchical porous carbon material (NHGBC-800) presented the attractive bifunctional properties was developed for the removal of model organic contaminant antibiotic tetracycline (TC). On the one aspect, the NHGBC-800 had a large specific surface area (1178.0 m2/g) and achieved good TC removal with a maximal adsorption capacity (Q m) of 629.76 mg/g at 303 K. On the other aspect, TC-saturated NHGBC-800 could effectively activate PDS with itself as the activator, by which the mineralization of desorbed TC and in-situ regeneration of exhausted adsorbent were achieved simultaneously. The Q m of NHGBC-800 recovered 90.61% after first regeneration and still retained 77.18% even after the 6th adsorption-regeneration cycles. Moreover, the as-prepared material maintained good adsorption and regeneration performance under a wide range of pH conditions (3.02–9.83) and in the presence of inorganic anions such as Cl−, SO 4 2−, NO 3 −, H 2 PO 4 −, HCO 3 −. The electro spin resonance (ESR), reactive oxygen species (ROS) quenching studies and electrochemical measurement revealed that the electron-transfer and single oxygen mediated the non-radical pathways dominated the TC degradation during the regeneration process. Compared with the conventional thermal and electrochemical regenerations, the in-situ regeneration of bifunctional carbon materials induced by PDS activation is more effective, sustainable and environmental-friendly. [ABSTRACT FROM AUTHOR]

• Acid oxidation of MWCNTs generates oxidized polyaromatic fragments called debris. • The debris affects the surface properties of the oxidized MWCNTs. • The presence of debris has impact on the adsorption capacity of the MWCNTs. • The effects of debris on the thermodynamics and adsorption kinetics were evaluated. • The debris limits electron transfer of redox species at the interface of MWCNTs. The functionalization of carbon nanotubes has become a common approach to modify the surface properties of these materials for different applications such as in the formulation of polymeric composites, as electrodes of electrochemical devices and, mainly, in the removal of organic contaminants. On the other hand, these functionalization procedures generates oxidized polyaromatic fragments known as debris , which impacts the material properties. Unfortunately, most papers published in the literature disregard these effects or do not cite experimental procedures for debris removal, which are strongly adsorbed onto the surface of nanotubes. In this study, we evaluated the effects of debris – generated on multiwalled carbon nanotubes (MWCNT) subjected to acid oxidation – on the capacities, kinetics and adsorption mechanism. For this, three different MWCNTs were employed: a pristine unmodified MWCNT; an oxidized MWCNT (obtained by common procedure and without the removal of debris); and an oxidized MWCNT without debris (obtained after reflux in alkaline medium). In addition, methylene blue (MB) has been used as model adsorbate in these experiments. As a second goal, the effects of debris on MB faradic electron transfer at the MWCNT interface were also investigated using cyclic voltammetry and cyclic chronopotenciometry techniques. Finally, we have shown that debris impacts the adsorption capacity, kinetics and limits the performance of MWCNTs as electrodes. [ABSTRACT FROM AUTHOR]