Hollow Nanoreactors Unlock New Possibilities for Persulfate-Based Advanced Oxidation Processes.

As a novel type of catalytic material, hollow nanoreactors are expected to bring new development opportunities in the field of persulfate-based advanced oxidation processes due to their peculiar void-confinement, spatial compartmentation, and size-sieving effects. For such materials, however, further clarification on basic concepts and construction strategies, as well as a discussion of the inherent correlation between structure and catalytic activity are still required. In this context, this review aims to provide a state-of-the-art overview of hollow nanoreactors for activating persulfate. Initially, hollow nanoreactors are classified according to the constituent components of the shell structure and their dimensionality. Subsequently, the different construction strategies of hollow nanoreactors are described in detail, while common synthesis methods for these construction strategies are outlined. Furthermore, the most representative advantages of hollow nanoreactors are summarized, and their intrinsic connections to the nanoreactor structure are elucidated. Finally, the challenges and future prospects of hollow nanoreactors are presented.

The generation and transformation mechanisms of reactive oxygen species in the environment and their implications for pollution control processes: A review.

Reactive oxygen species (ROS), substances with strong activity generated by oxygen during electron transfer, play a significant role in the decomposition of organic matter in various environmental settings, including soil, water and atmosphere. Although ROS has a short lifespan (ranging from a few nanoseconds to a few days), it continuously generated during the interaction between microorganisms and their environment, especially in environments characterized by strong ultraviolet radiation, fluctuating oxygen concentration or redox conditions, and the abundance of metal minerals. A comprehensive understanding of the fate of ROS in nature can provide new ideas for pollutant degradation and is of great significance for the development of green degradation technologies for organic pollutants. At present, the review of ROS generally revolves around various advanced oxidation processes, but lacks a description and summary of the fate of ROS in nature, this article starts with the definition of reactive oxidants species and reviews the production, migration, and transformation mechanisms of ROS in soil, water and atmospheric environments, focusing on recent developments. In addition, the stimulating effects of ROS on organisms were reviewed. Conclusively, the article summarizes the classic processes, possible improvements, and future directions for ROS-mediated degradation of pollutants. This review offers suggestions for future research directions in this field and provides the possible ROS technology application in pollutants treatment.

Effect of pyrite on the treatment of chlorophenolic compounds with zero-valent iron-Fenton process under uncontrolled pH conditions: reaction mechanism and biodegradability.

This current study explored the effect of pyrite on the treatment of chlorophenolic compounds (CP) by Fenton process with micron-sized zero-valent iron (ZVI) as the catalyst. The experiments were conducted in batch reactors with 100 mg L-1 CP, 0-0.02 M H2O2, and variable pyrite and ZVI doses (0-1 g L-1). Our findings show that while the reactor with 1 g L-1 ZVI as the only catalyst achieved only 10% CP removal efficiency due to rapid ZVI surface passivation and ZVI particle aggregation, the CP removal efficiency increased with increasing pyrite dose and reached 100% within couple of minutes in reactors with 0.8 g L-1 pyrite and 0.2 g L-1 ZVI. The CP removal was mainly driven by the oxidative treatment of CPs with some strong radicals such as hydroxyl radicals (•OH) while the adsorption onto the catalyst surface was only responsible for 10 to 25% of CP removals, depending on the type of CP studied. The positive impact of pyrite on CP removal by the ZVI/H2O2 system could be attributed to the ability of pyrite to (1) create an acidic environment for optimum Fenton process, (2) provide support material for ZVI to minimize ZVI particle agglomeration, and (3) stimulate iron redox cycling for improved surface site generation. Following oxidative Fenton treatment, the degradation intermediate products of CPs, including some aromatic compounds (benzoquinone, hydroquinone, etc.) and organic acids (e.g., acetic acid), became more biodegradable in comparison to their mother compounds. Overall, the treatment systems with a mixture of ZVI and pyrite as catalyst materials could offer a suitable cost-effective technology for the treatment of wastewater containing biologically non- or low-degradable toxic compounds such as chlorophenols.

Reactive Oxygen Species (ROS)-Mediated Antibacterial Oxidative Therapies: Available Methods to Generate ROS and a Novel Option Proposal.

The increasing emergence of multidrug-resistant (MDR) pathogens causes difficult-to-treat infections with long-term hospitalizations and a high incidence of death, thus representing a global public health problem. To manage MDR bacteria bugs, new antimicrobial strategies are necessary, and their introduction in practice is a daily challenge for scientists in the field. An extensively studied approach to treating MDR infections consists of inducing high levels of reactive oxygen species (ROS) by several methods. Although further clinical investigations are mandatory on the possible toxic effects of ROS on mammalian cells, clinical evaluations are extremely promising, and their topical use to treat infected wounds and ulcers, also in presence of biofilm, is already clinically approved. Biochar (BC) is a carbonaceous material obtained by pyrolysis of different vegetable and animal biomass feedstocks at 200-1000 °C in the limited presence of O2. Recently, it has been demonstrated that BC's capability of removing organic and inorganic xenobiotics is mainly due to the presence of persistent free radicals (PFRs), which can activate oxygen, H2O2, or persulfate in the presence or absence of transition metals by electron transfer, thus generating ROS, which in turn degrade pollutants by advanced oxidation processes (AOPs). In this context, the antibacterial effects of BC-containing PFRs have been demonstrated by some authors against Escherichia coli and Staphylococcus aureus, thus giving birth to our idea of the possible use of BC-derived PFRs as a novel method capable of inducing ROS generation for antimicrobial oxidative therapy. Here, the general aspects concerning ROS physiological and pathological production and regulation and the mechanism by which they could exert antimicrobial effects have been reviewed. The methods currently adopted to induce ROS production for antimicrobial oxidative therapy have been discussed. Finally, for the first time, BC-related PFRs have been proposed as a new source of ROS for antimicrobial therapy via AOPs.

Carbon Nanotubes as Controllable Electric-Field-Induced Bipolar Electrodes for Efficient Water Purification.

Advanced oxidation processes (AOPs) are the most efficient water cleaning technologies, but their applications face critical challenges in terms of mass/electron transfer limitations and catalyst loss/deactivation. Bipolar electrochemistry (BPE) is a wireless technique that is promising for energy and environmental applications. However, the synergy between AOPs and BPE has not been explored. In this study, by combining BPE with AOPs, we develop a general approach of using carbon nanotubes (CNTs) as electric-field-induced bipolar electrodes to control electron transfer for efficient water purification. This approach can be used for permanganate and peroxide activation, with superior performances in the degradation of refractory organic pollutants and excellent durability in recycling and scale-up experiments. Theoretical calculations, in situ measurements, and physical experiments showed that an electric field could substantially reduce the energy barrier of electron transfer over CNTs and induce them to produce bipolar electrodes via electrochemical polarization or to form monopolar electrodes through a single particle collision effect with feeding electrodes. This approach can continuously provide activated electrons from one pole of bipolar electrodes and simultaneously achieve "self-cleaning" of catalysts through CNT-mediated direct oxidation from another pole of bipolar electrodes. This study provides a fundamental scientific understanding of BPE, expands its scope in the environmental field, and offers a general methodology for water purification.

Application of Engineered Nanomaterials as Nanocatalysts in Catalytic Ozonation: A Review.

Given the growing scarcity of water and the continuous increase in emerging pollutants detected in water bodies, there is an imperative need to develop new, more effective, and sustainable treatments for wastewater. Advanced oxidation processes (AOPs) are considered a competitive technology for water treatment. Specifically, ozonation has received notable attention as a promising approach for degrading organic pollutants in wastewater. However, different groups of pollutants are hardly degradable via single ozonation. With continuous development, it has been shown that using engineered nanomaterials as nanocatalysts in catalytic ozonation can increase efficiency by turning this process into a low-selective AOP for pollutant degradation. Nanocatalysts promote ozone decomposition and form active free radicals responsible for increasing the degradation and mineralization of pollutants. This work reviews the performances of different nanomaterials as homogeneous and heterogeneous nanocatalysts in catalytic ozonation. This review focuses on applying metal- and carbon-based engineered nanomaterials as nanocatalysts in catalytic ozonation and on identifying the main future directions for using this type of AOP toward wastewater treatment.

Bridge-oxygen bonding modulates Ru single atoms for peroxymonosulfate activation: Importance of high-valent Ru species and 1O2.

The application of single-atom catalysts (SACs) to advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) has attracted considerable attention. However, the catalytic pathways and mechanisms underlying these processes remain unclear. In this study, NiFe-LDH was synthesized and single Ru atoms were stably loaded onto it by forming Ru-O-M (M=Ni or Fe) bonds (Ru@NiFe-LDH). This was demonstrated using high-angle annular dark-field scanning TEM (HAADF-STEM) and X-ray absorption fine structure spectra (XANES). The Ru@NiFe-LDH/PMS system showed a high catalytic reactivity (100 % sulfamethoxazole degradation in only 30 min), high stability (97 % reactivity was maintained after continuous operation for 400 min), and wide pH suitability (working pH range 3-11) for AOPs. The crucial roles of the high-valent species (Ru(V) = O) and 1O2 in this reaction were verified. Density functional theory (DFT) calculations revealed that electron transfer produced a positively charged Ru. This enhances the adsorption of negatively charged PMS anions onto the Ru monoatomic sites, thereby, causing the formation of Ru-PMS* complexes. This study implies that the structure-function relationship between organic compounds and SACs plays a significant role in PMS-based AOPs, and provides a comprehensive mechanism for the role of high-valent species in heterogeneous Fenton-like systems.

FeCo@hydrochar nanocomposites as efficient peroxymonosulfate activator for organic pollutant degradation.

Sulfate radical-based advanced oxidation processes (SR-AOPs) are renowned for their exceptional capacity to degrade refractory organic pollutants due to their wide applicability, cost-effectiveness, and swift mineralization and oxidation rates. The primary sources of radicals in AOPs are persulfate (PS) and peroxymonosulfate (PMS) ions, sparking significant interest in their mechanistic and catalytic aspects. To develop a novel nanocatalyst for SR-AOPs, particularly for PMS activation, we synthesized carbon-coated FeCo nanoparticles (NPs) using solvothermal methods based on the polyol approach. Various synthesis conditions were investigated, and the NPs were thoroughly characterized regarding their structure, morphology, magnetic properties, and catalytic efficiency. The FeCo phase was primarily obtained at [OH-] / [Metal] = 26 and [Fe] / [Co] = 2 ratios. Moreover, as the [Fe]/[Co] ratio increased, the degree of xylose carbonization to form a carbon coating (hydrochar) on the NPs also increased. The NPs exhibited a spherical morphology with agglomerates of varying sizes. Vibrating-sample magnetometer analysis (VSM) indicated that a higher proportion of iron resulted in NPs with higher saturation magnetization (up to 167.8 emu g-1), attributed to a larger proportion of FeCo bcc phase in the nanocomposite. The best catalytic conditions for degrading 100 ppm Rhodamine B (RhB) included 0.05 g L-1 of NPs, 2 mM PMS, pH 7.0, and a 20-min reaction at 25 °C. Notably, singlet oxygen was the predominant specie formed in the experiments in the SR-AOP, followed by sulfate and hydroxyl radicals. The catalyst could be reused for up to five cycles, retaining over 98% RhB degradation, albeit with increased metal leaching. Even in the first use, dissolved Fe and Co concentrations were 0.8 ± 0.3 and 4.0 ± 0.5 mg L-1, respectively. The FeCo catalyst proved to be effective in dye degradation and offers the potential for further refinement to minimize Co2+ leaching.

Revisiting the Electron Transfer Mechanisms in Ru(III)-Mediated Advanced Oxidation Processes with Peroxyacids and Ferrate(VI).

The potential of Ru(III)-mediated advanced oxidation processes has attracted attention due to the recyclable catalysis, high efficiency at circumneutral pHs, and robust resistance against background anions (e.g., phosphate). However, the reactive species in Ru(III)-peracetic acid (PAA) and Ru(III)-ferrate(VI) (FeO42-) systems have not been rigorously examined and were tentatively attributed to organic radicals (CH3C(O)O•/CH3C(O)OO•) and Fe(IV)/Ru(V), representing single electron transfer (SET) and double electron transfer (DET) mechanisms, respectively. Herein, the reaction mechanisms of both systems were investigated by chemical probes, stoichiometry, and electrochemical analysis, revealing different reaction pathways. The negligible contribution of hydroxyl (HO•) and organic (CH3C(O)O•/CH3C(O)OO•) radicals in the Ru(III)-PAA system clearly indicated a DET reaction via oxygen atom transfer (OAT) that produces Ru(V) as the only reactive species. Further, the Ru(III)-performic acid (PFA) system exhibited a similar OAT oxidation mechanism and efficiency. In contrast, the 1:2 stoichiometry and negligible Fe(IV) formation suggested the SET reaction between Ru(III) and ferrate(VI), generating Ru(IV), Ru(V), and Fe(V) as reactive species for micropollutant abatement. Despite the slower oxidation rate constant (kinetically modeled), Ru(V) could contribute comparably as Fe(V) to oxidation due to its higher steady-state concentration. These reaction mechanisms are distinctly different from the previous studies and provide new mechanistic insights into Ru chemistry and Ru(III)-based AOPs.

Enhanced degradation of 2,4-dichlorophenol in groundwater by defective iron-based metal-organic frameworks: Role of SO3- and electron transfer.

The purposeful formation of crystal defects was regarded as an attractive strategy to enhance the catalytic activity of Fe-MOFs. In this study, the pyrolytic hydrochloric acid-modulated MIL-101-NH2 (P250HMN-2) was fabricated for the first time, and the important role of pyrolysis in the formation of crystal defects was confirmed. PDS was introduced as an enhancer for the P250HMN-2/Na2SO3 system. Without pH adjustment, 99.7 % of 2,4-DCP was removed by the P250HMN-2/Na2SO3/PDS system in 180 min. The catalytic performance of P250HMN-2 improved 2.5-fold than that of MIL-101-NH2. It was found that the high density of Fe-CUSs on P250HMN-2 were the major active sites, which could efficiently react with SO32- to generate ROS through electron transfer. The results of quenching experiments, probe tests, and EPR tests indicated that SO3-, SO4-, 1O2, OH, and SO5- were involved in the 2,4-DCP degradation process, with SO3-, SO4-, and 1O2 playing major roles. Moreover, P250HMN-2 could effectively degrade 2,4-DCP for 148 h in a fixed-bed reactor with excellent stability and reusability, indicating a promising catalyst for practical applications.

Comparative study of organic removal by pre-adsorption oxidation and synchronous adsorption oxidation processes: Performance and mechanism.

Both adsorption and oxidation occur and contribute to organics removal in carbonaceous materials based advanced oxidation processes, while the correction of adsorption and oxidation, and the role of adsorption in the veritable removal of organic are not clear. Herein, we investigated the performance of carbamazepine (CBZ) removal by peroxymonosulfate (PMS) activated by magnetic Fe-doped biochar through two models of pre-adsorption oxidation and synchronous adsorption oxidation processes. The adsorption process was better fitted by pseudo-second-order kinetic model and the adsorption mechanism was obtained by comprehensive analysis of equilibrium adsorption capacities, surface functional groups, specific surface area, pore volume, and ID/IG value. It is noted that pre-adsorption highly inhibited the further oxidation of CBZ in 0.5Fe@LSBC700/PMS system due to the occupied catalytic active sites. Total CBZ removal in pre-adsorption oxidation (45 %) was inferior to synchronous adsorption oxidation (∼100 %), as well as the veritable CBZ oxidation removal of 27 % for pre-adsorption oxidation vs ∼100 % in synchronous adsorption oxidation at 30 min. Oxidation degradation of CBZ based on radical oxidation was identified by quenching experiments and electron paramagnetic resonance measurements. This work is conducive to identifying the role of adsorption during the removal of organics in the adsorption-oxidation process, as well as veritable adsorption and oxidation removal of organics.

A critical review of persulfate-based electrochemical advanced oxidation processes for the degradation of emerging contaminants: From mechanisms and electrode materials to applications.

The persulfate-based electrochemical advanced oxidation processes (PS-EAOPs) exhibit distinctive advantages in the degradation of emerging contaminants (ECs) and have garnered significant attention among researchers, leading to a consistent surge in related research publications over the past decade. Regrettably, there is still a lack of a critical review gaining deep into understanding of ECs degradation by PS-EAOPs. To address the knowledge gaps, in this review, the mechanism of electro-activated PS at the interface of the electrodes (anode, cathode and particle electrodes) is elaborated. The correlation between these electrode materials and the activation mechanism of PS is systematically discussed. The strategies for improving the performance of electrode material that determining the efficiency of PS-EAOPs are also summarized. Then, the applications of PS-EAOPs for the degradation of ECs are described. Finally, the challenges and outlook of PS-EAOPs are discussed. In summary, this review offers valuable guidance for the degradation of ECs by PS-EAOPs.

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

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

Mechanisms and Strategies of Advanced Oxidation Processes for Membrane Fouling Control in MBRs: Membrane-Foulant Removal versus Mixed-Liquor Improvement.

Membrane bioreactors (MBRs) are well-established and widely utilized technologies with substantial large-scale plants around the world for municipal and industrial wastewater treatment. Despite their widespread adoption, membrane fouling presents a significant impediment to the broader application of MBRs, necessitating ongoing research and development of effective antifouling strategies. As highly promising, efficient, and environmentally friendly chemical methods for water and wastewater treatment, advanced oxidation processes (AOPs) have demonstrated exceptional competence in the degradation of pollutants and inactivation of bacteria in aqueous environments, exhibiting considerable potential in controlling membrane fouling in MBRs through direct membrane foulant removal (MFR) and indirect mixed-liquor improvement (MLI). Recent proliferation of research on AOPs-based antifouling technologies has catalyzed revolutionary advancements in traditional antifouling methods in MBRs, shedding new light on antifouling mechanisms. To keep pace with the rapid evolution of MBRs, there is an urgent need for a comprehensive summary and discussion of the antifouling advances of AOPs in MBRs, particularly with a focus on understanding the realizing pathways of MFR and MLI. In this critical review, we emphasize the superiority and feasibility of implementing AOPs-based antifouling technologies in MBRs. Moreover, we systematically overview antifouling mechanisms and strategies, such as membrane modification and cleaning for MFR, as well as pretreatment and in-situ treatment for MLI, based on specific AOPs including electrochemical oxidation, photocatalysis, Fenton, and ozonation. Furthermore, we provide recommendations for selecting antifouling strategies (MFR or MLI) in MBRs, along with proposed regulatory measures for specific AOPs-based technologies according to the operational conditions and energy consumption of MBRs. Finally, we highlight future research prospects rooted in the existing application challenges of AOPs in MBRs, including low antifouling efficiency, elevated additional costs, production of metal sludge, and potential damage to polymeric membranes. The fundamental insights presented in this review aim to elevate research interest and ignite innovative thinking regarding the design, improvement, and deployment of AOPs-based antifouling approaches in MBRs, thereby advancing the extensive utilization of membrane-separation technology in the field of wastewater treatment.

Ultraviolet technology application in urban water supply and wastewater treatment in China: Issues, challenges and future directions.

This study thoroughly explores the application of Ultraviolet (UV) water treatment technology in urban wastewater treatment and water supply in China, highlighting its crucial role in enhancing water quality safety. UV technology, with its environmentally friendly and low-carbon characteristics, is deemed more in line with the demands of sustainable development compared to traditional chemical disinfection methods. The widespread application of UV technology in urban wastewater treatment in China, particularly in the context of urban sewage treatment, is examined. However, to better promote and apply UV technology, there is a need to deepen the understanding of this technology and its application among a broad base of users and design units. The importance of gaining in-depth knowledge about the performance of UV water treatment equipment, the design calculation basis, and operational considerations, as well as the ongoing development of relevant standards, is underscored to ensure that the equipment used in projects complies with engineering design and production requirements. Furthermore, the positive trend of UV technology in the field of advanced oxidation, indicating a promising trajectory for engineering applications, is pointed out. Regarding the prospects of industrial development, a thorough analysis is conducted in the article, emphasizing the necessity for all stakeholders to collaborate and adopt a multi-level approach to promote the sustainable development and application of UV water treatment technology. This collaborative effort is crucial for providing effective safeguards for China's environment, ecology, and human health.

Continuous UV-C/H2O2 and UV-C/Chlorine applied to municipal secondary effluent and nanofiltration retentate: Removal of contaminants of emerging concern, ecotoxicity, and reuse potential.

As global effects of water scarcity raise concerns and environmental regulations evolve, contemporary wastewater treatment plants (WWTPs) face the challenge of effectively removing a diverse range of contaminants of emerging concern (CECs) from municipal effluents. This study focuses on the assessment of advanced oxidation processes (AOPs), specifically UV-C/H2O2 and UV-C/Chlorine, for the removal of 14 target CECs in municipal secondary effluent (MSE, spiked with 10 µg L-1 of each CEC) or in the subsequent MSE nanofiltration retentate (NFR, no spiking). Phototreatments were carried out in continuous mode operation, with a hydraulic retention time of 3.4 min, using a tube-in-tube membrane photoreactor. For both wastewater matrices, UV-C photolysis (3.3 kJ L-1) exhibited high efficacy in removing CECs susceptible to photolysis, although lower treatment performance was observed for NFR. In MSE, adding 10 mg L-1 of H2O2 or Cl2 enhanced treatment efficiency, with UV-C/H2O2 outperforming UV-C/Chlorine. Both UV-C/AOPs eliminated the chronic toxicity of MSE toward Chlorella vulgaris. In the NFR, not only was the degradation of target CECs diminished, but chronic toxicity to C. vulgaris persisted after both UV-C/AOPs, with UV-C/Chlorine increasing toxicity due to potential toxic by-products. Nanofiltration permeate (NFP) exhibited low CECs and microbial content. A single chlorine addition effectively controlled Escherichia coli regrowth for 3 days, proving NFP potential for safe reuse in crop irrigation (<1 CFU/100 mL for E. coli; <1 mg L-1 for free chlorine). These findings provide valuable insights into the applications and limitations of UV-C/H2O2 and UV-C/Chlorine for distinct wastewater treatment scenarios.

Potential of metallurgical iron-containing solid waste-based catalysts as activator of persulfate for organic pollutants degradation.

The production of solid wastes in the metallurgical industry has significant implications for land resources and environmental pollution. To address this issue, it is crucial to explore the potential of recycling these solid wastes to reduce land occupation while protecting the environment and promoting resource utilization. Steel slag, red mud, copper slag and steel picking waste liquor are examples of solid wastes generated during the metallurgical process that possess high iron content and Fe species, making them excellent catalysts for persulfate-based advanced oxidation processes (PS-AOPs). This review elucidates the catalytic mechanisms and pathways of Fe2+ and Fe0 in the activation PS. Additionally, it underscores the potential of metallurgical iron-containing solid waste (MISW) as a catalyst for PS activation, offering a viable strategy for its high-value utilization. Lastly, the article provides an outlook towards future challenges and prospects for MISW in PS activation for the degradation of organic pollutants.

In-situ groundwater remediation of contaminant mixture of As(III), Cr(VI), and sulfanilamide via electrochemical degradation/transformation using pyrite.

Electrochemical advanced oxidation processes (EAOPs) are effective in removing persistent contaminants from groundwater. However, their practical applicability depends significantly on various site-specific characteristics. Therefore, the primary objective of this investigation was to study the feasibility of EAOPs and pyrite, which is a sulfide mineral, to effectively remove the mixture of arsenic (As (III)), chromium (Cr (VI)), and sulfanilamide in groundwater. We conducted a comparison of three systems: (1) EAOP alone, (2) pyrite alone, and (3) a combined EAOP and pyrite system. In EAOP alone, sulfanilamide was effectively oxidized (80%), while the electrochemical transformation of As(III)/Cr(VI) into As(V)/Cr(III) was limited. In just the pyrite system, As(III), Cr(VI), and sulfanilamide were adsorbed onto the surface of pyrite (60%, 20%, and 18%). Neither the EAOP nor the pyrite system alone could effectively treat the contaminants mixture. Nonetheless, the combined system completely removed As(III), Cr(VI), and sulfanilamide by the synergistic reaction. This could be attributed to the formation of green rust, a natural adsorbent mineral produced as a reaction of dissolved iron, generated via electrochemical pyrite oxidation, with the groundwater electrolyte (e.g., CO3 or SO4). This system harmonized the combined approach of EAOP and pyrite to effectively eliminate both organic and inorganic contaminants. ENVIRONMENTAL IMPLICATION: A paper proposed electrochemical oxidation (EO) with pyrite to remove both organic and inorganic contaminants from groundwater. The removal performance of the combined system was evaluated, and the synergistic mechanism was revealed. The combination of EO and pyrite with synergistic removal effectively removed the mixture of both contaminants. This could be attributed by the formation of green-rust by electrochemical activation for pyrite. Compared to the single system of EO and pyrite alone, the combined system with EO and pyrite improved removal performance. Results suggested that the combined system could be used for green groundwater remediation.

Recent advances and prospects of neonicotinoid insecticides removal from aquatic environments using biochar: Adsorption and degradation mechanisms.

In recent years, neonicotinoid insecticides (NNIs), representing a new era of pest control, have increasingly replaced traditional classes such as organophosphorus compounds, carbamates, and pyrethroids due to their precise targeting and broad-spectrum efficacy. However, the high water solubility of NNIs has led to their pervasion in aquatic ecosystems, raising concerns about potential risks to non-target organisms and human health. Therefore, there is an urgent need for research on remediating NNI contamination in aquatic environments. This study demonstrates that biochar, characterized by its extensive surface area, intricate pore structure, and high degree of aromaticity holds significant promise for removing NNIs from water. The highest reported adsorption capacity of biochar for NNIs stands at 738.0 mg·g-1 with degradation efficiencies reaching up to 100.0 %. This review unveils that the interaction mechanisms between biochar and NNIs primarily involve π-π interactions, electrostatic interactions, pore filling, and hydrogen bonding. Additionally, biochar facilitates various degradation pathways including Fenton reactions, photocatalytic, persulfate oxidations, and biodegradation predominantly through radical (such as SO4-, OH, and O2-) as well as non-radical (such as 1O2 and electrons transfer) processes. This study emphasizes the dynamics of interaction between biochar surfaces and NNIs during adsorption and degradation aiming to elucidate mechanistic pathways involved as well as assess the overall efficacy of biochar in NNI removal. By comparing the identification of degradation products and degradation pathways, the necessity of advanced oxidation process is confirmed. This review highlights the significance of harnessing biochar's potential for mitigating NNI pollution through future application-oriented research and development endeavors, while simultaneously ensuring environmental integrity and promoting sustainable practices.

The "4 + 1" strategy fabrication of iron single-atom catalysts with selective high-valent iron-oxo species generation.

Single-atom catalysts (SACs) with atomic dispersion active sites have exhibited huge potentials in peroxymonosulfate (PMS)-based Fenton-like chemistry in water purification. However, four-N coordination metal (MN4) moieties often suffer from such problems as low selectivity and narrow workable pH. How to construct SACs in a controllable strategy with optimized electronic structures is of great challenge. Herein, an innovative strategy (i.e., the "4 + 1" fabrication) was devised to precisely modulate the first-shell coordinated microenvironment of FeN4 SAC using an additional N (SA-FeN5). This leads to almost 100% selective formation of high-valent iron-oxo [Fe(IV)═O] (steady-state concentration: 2.00 × 10-8 M) in the SA-FeN5/PMS system. In-depth theoretical calculations unveil that FeN5 configuration optimizes the electron distribution of monatomic Fe sites, which thus fosters PMS adsorption and reduces the energy barrier for Fe(IV)═O generation. SA-FeN5 was then attached to polyvinylidene difluoride membrane for a continuous flow device, showing long-term abatement of the microcontaminant. This work furnishes a general strategy for effective PMS activation and selective high-valent metal-oxo species generation by high N-coordination number regulation in SACs, which would provide guidance in the rational design of superior environmental catalysts for water purification.