Degradation of antibiotics by modified vacuum-UV based processes: Mechanistic consequences of H2O2 and K2S2O8 in the presence of halide ions

Vacuum UV-based processes for water and wastewater purification: From unitary to multicomponent systems

Vacuum ultraviolet (VUV) is profitable to strengthen the efficiencies of UV and reduce chemicals use, attracting more attention to water and wastewater purification. Herein, VUV-based water treatment processes from unitary VUV to multicomponent systems were reviewed for the first time to promote VUV applications. The rate of pollutant removal by unitary VUV was 1.3-57 times that of UV, in which hydroxyl radical oxidation was dominant. And the reducibility of hydrated electron and hydrogen atom radical in unitary VUV dehalogenated organics and reduced metal ions. Besides, VUV-based binary systems mainly included processes of VUV/H2O2, VUV/persulfate, VUV/ozone, VUV/chlorine, VUV/sulfite, VUV/iron ion, and VUV-based heterogeneous oxidation. VUV-based ternary systems basically contained three types: VUV-based Fenton-like, VUV coupling dual oxidants, and VUV combined with other technologies activating oxidants. Performance, characteristics, reactive species, and mechanisms of VUV-based binary and ternary systems were summarized. Moreover, the characterization, contribution, and role of reactive species in VUV-based processes were analyzed, and the combination of multiple methods was conducive to accurately identifying the mechanism of reactive species. Furthermore, the combination of VUV and other technologies expanded the application potential of VUV. Compared to UV-based processes, VUV-based processes significantly reduced energy consumption and were more promising in removing contaminants in actual waters. Finally, hot spots and directions (develop new techniques, reduce by-products, combine simulation and experiment, broaden removal objects, enhance pilot studies) of VUV-based water treatment technologies in future were prospected. Overall, VUV-based advanced oxidation processes are expected to be used in water treatment to improve process efficiency.

VUV coupled with low-dose H2O2 as pretreatment prior to UF: Performance, mechanisms, DBPs formation and toxicity evaluation

Ultrafiltration (UF) is widely used in drinking water plants; however, membrane fouling is unavoidable. Natural organic matter (NOM) is commonly considered as an important pollutant that causes membrane fouling. Herein, we proposed VUV/H2O2 as a UF pretreatment and used UV/H2O2 for comparison. Compared to UV/H2O2, the VUV/H2O2 system presented superior NOM removal. In the VUV/H2O2 system, the steady-state concentration of HO• was approximately twice that in the UV/H2O2 system, which was ascribed to the promoting effect of the 185 nm photons. Specifically, 185 nm photons promoted HO• generation by decomposing mainly H2O at a low H2O2 dose or by decomposing mainly H2O2 at a high H2O2 dose. The VUV/H2O2 pretreatment also demonstrated better membrane fouling mitigation performance than did UV/H2O2. An increase in the H2O2 dose promoted HO• generation, thereby enhancing the performance of NOM degradation and membrane fouling alleviation and shifting the major membrane fouling mechanism from cake filtration to standard blocking. The VUV/H2O2 (0.60 mM) pretreatment effectively reduced disinfection byproducts (DBPs) formation during chlorine disinfection. Additionally, the oxidant H2O2 affected the membrane surface morphology and performance but had no evident effect on the mechanical properties. In actual water treatment, the VUV/H2O2 pretreatment exhibited better performance than the UV/H2O2 pretreatment in easing membrane fouling, ameliorating water quality, and reducing DBPs formation and acute toxicity.

Unique effect of bromide ion on intensification of advanced oxidation processes for pollutants removal: A systematic review

Advanced oxidation processes (AOPs) have been developed to decompose toxic pollutants to protect the aquatic environment. AOP has been considered an alternative treatment method for wastewater treatment. Bromine is present in natural waters posing toxic effects on human health and hence, its removal from drinking water sources is necessary. Of the many techniques advanced oxidation is covered in this review. This review systematically examines literature published from 1997 to April 2024, sourced from Scopus, PubMed, Science Direct, and Web of Science databases, focusing on the efficacy of AOPs for pollutant removal from aqueous solutions containing bromide ions to investigate the impact of bromide ions on AOPs. Data and information extracted from each article eligible for inclusion in the review include the type of AOP, type of pollutants, and removal efficiency of AOP under the presence and absence of bromide ion. Of the 1784 documents screened, 90 studies met inclusion criteria, providing insights into various AOPs, including UV/chlorine, UV/PS, UV/H2O2, UV/catalyst, and visible light/catalyst processes. The observed impact of bromide ion presence on the efficacy of AOP processes, alongside the AOP method under scrutiny, is contingent upon various factors such as the nature of the target pollutant, catalyst type, and bromide ion concentration. These considerations are crucial in selecting the best method for removing specific pollutants under defined conditions. Challenges were encountered during result analysis included variations in experimental setups, disparities in pollutant types and concentrations, and inconsistencies in reporting AOP performance metrics. Addressing these parameters in research reports will enhance the coherence and utility of subsequent systematic reviews.

Vacuum-ultraviolet based advanced oxidation and reduction processes for water treatment

The use of vacuum-ultraviolet (VUV) photolysis in water treatment has been gaining significant interest due to its efficacy in degrading refractory organic contaminants and eliminating oxyanions. In recent years, the reactive species driving pollutant decomposition in VUV-based advanced oxidation and reduction processes (VUV-AOPs and VUV-ARPs) have been identified. This review aims to provide a concise overview of VUV photolysis and its advancements in water treatment. We begin with an introduction to VUV irradiation, followed by a summary of the primary reactive species in both VUV-AOPs and VUV-ARPs. We then explore the factors influencing VUV-photolysis in water treatment, including VUV irradiation dose, catalysts or activators, dissolved gases, water matrix components (e.g., DOM and inorganic anions), and solution pH. In VUV-AOPs, the predominant reactive species are hydroxyl radicals (˙OH), hydrogen peroxide (H2O2), and ozone (O3). Conversely, in VUV-ARPs, the main reactive species are the hydrated electron (eaq-) and hydrogen atom (˙H). It is worth noting that VUV-based advanced oxidation/reduction processes (VUV-AORPs) can transit between VUV-AOPs and VUV-ARPs based on the externally added chemicals and dissolved gases in the solution. Increase of the VUV irradiation dose and the concentration of catalysts/activators enhances the degradation of contaminants, whereas DOM and inorganic anions inhibit the reaction. The pH influences the redox potential of ˙OH, the speciation of contaminants and activators, and thus the overall performance of the VUV-AOPs. Conversely, an alkaline pH is favored in VUV-ARPs because eaq- predominates at higher pH.

Sustainable removal of caffeine and acetaminophen from water using biomass waste-derived activated carbon: Synthesis, characterization, and modelling

The removal of caffeine (CFN) and acetaminophen (ACT) from water using low-cost activated carbons prepared from artichoke leaves (AAC) and pomegranate peels (PAC) was reported in this paper. These activated carbons were characterized using various analytical techniques. The results showed that AAC and PAC had surface areas of 1203 and 1095 m2 g-1, respectively. The prepared adsorbents were tested for the adsorption of these pharmaceuticals in single and binary solutions. These experiments were performed under different operating conditions to evaluate the adsorption properties of these adsorbents to remove CFN and ACT. AAC and PAC showed maximum adsorption capacities of 290.86 and 258.98 mg g-1 for CFN removal, 281.18 and 154.99 mg g-1 for the ACT removal over a wide pH range. The experimental equilibrium adsorption data fitted to the Langmuir model and the kinetic data were correlated with the pseudo-second order model. AAC showed the best adsorption capacities for the removal of these pharmaceuticals in single systems and, consequently, it was tested for the simultaneous removal of these pollutants in binary solutions. The simultaneous adsorption of these compounds on AAC was improved using the central composite design and response surface methodology. The results indicated an antagonistic effect of CFN on the ACT adsorption. AAC regeneration was also analyzed and discussed. A statistical physics model was applied to describe the adsorption orientation of the tested pollutants on both activated carbon samples. It was concluded that AAC is a promising adsorbent for the removal of emerging pollutants due to its low cost and reusability properties.

A combined approach of electrodialysis pretreatment and vacuum UV for removing micropollutants from natural waters

Advanced oxidation processes (AOPs) augment traditional water treatment methods, enhancing the removal of persistent contaminants. Efficiency of AOPs that utilize UV radiation for oxidants generation (e.g., ·OH) is reduced in water matrices that contain substants that may act as inner UV filters and/or scavengers for the generated radicals. Among such interfering compounds are major inorganic ions and dissolved organic matter that are naturally present in realistic waters. Thus, to improve AOPs efficiency it is desirable to separate the target pollutants from these natural species before treatment. Here the potential of electrodialysis as such pretreatment was investigated. The impact of this pretreatment on photo-oxidation of the pharmaceutical carbamazepine (CBZ) under VUV (λ<200 nm) irradiation, which yields ·OH generation via water homolysis, was tested in different water matrices. The obtained results indicate that in all tested solutions: Deionized water, groundwater, surface water, and treated wastewater, the addition of electrodialysis pretreatment successfully separated the target micropollutant CBZ from the major natural ions and to some extend the NOM, resulting faster degradation rates of CBZ and its transformation products in the following VUV-based AOP. Energy cost calculations indicated that addition of this pretreatment step reduces the overall energy demand of the system (i.e., energy consumption for the electrodialysis step was smaller than the energy gained by reducing the required VUV irradiation dose).

Occurrence and removal of antibiotics from aquaculture wastewater by solar-driven Fe(VI)/oxone process

In this study, the occurrence and removal of ten selected antibiotics from aquaculture wastewater by the process solar + Fe(VI)+oxone were investigated. The detection levels of the antibiotics in the aquaculture wastewater samples were at ng/L. The degradation of the selected antibiotics under the process solar + Fe(VI)+oxone followed pseudo-first-order kinetics. As the most abundant antibiotic in the studied aquaculture wastewater, norfloxacin (NFX) was used as the model compound to study the reaction mechanism and detoxification ability of the treatment system, as well as the effects of reaction parameters and environmental factors. The active species including O2•-, O21, and Fe(V)/Fe(IV) contributed to NFX degradation in the process solar + Fe(VI)+oxone. Decarboxylation, the piprazine ring opening, defluorination of the benzene ring, oxygen addition and the cleavage of the quinolone/benzene ring were main degradation pathways of NFX. Around 20% mineralization was reached and the inhibition rate of the bacteria (Escherichia Coli) growth was reduced from 95.5% to 47.1% after the NFX degradation for 60 min. Despite the suppression of NFX degradation by NO2-, PO43- and humic acid, the NFX degradation in three aquaculture wastewater samples was faster than that in ultrapure water due to the positive effect of Br-and other factors. The above results demonstrate the treatment process solar-driven Fe(VI)/oxone has a good potential in antibiotics removal from the aquaculture wastewater.

The synergistic effect of radical and non-radical processes on the dephosphorization of dimethoate by vacuum ultraviolet: The overlooked roles of singlet oxygen atom and high-energy excited state

Organophosphorus pesticides are extensively utilized worldwide, but their incomplete dephosphorization poses significant environmental risks. This study investigates the dephosphorization of dimethoate (DMT), a representative organophosphorus pesticide, using a vacuum ultraviolet system. Surprisingly, in addition to hydroxyl radicals (•OH), non-radical processes such as photoexcitation and singlet oxygen atoms (O(1D)) exert more significant effects on DMT dephosphorization. The degradation kinetics of DMT demonstrate a perfect linear correlation with the radical yield in both UV-based and VUV-based advanced oxidation processes (AOPs), with greater efficacy of radical attack observed in the VUV system. This heightened efficiency is attributed to the excitation of DMT to a high-energy excited state induced by UV185 radiation. Additionally, •OH alone is inadequate for achieving complete dephosphorization of DMT. The Fukui index and singly occupied orbital (SOMO) analysis reveal that the O(1D) generated by UV185-induced photolysis of O2 exhibits exceptional selectivity towards P=S bonds, thereby playing an indispensable role in the dephosphorization process of DMT. This study highlights the significant contribution of non-radical pathways in DMT dephosphorization by VUV, which holds great implications for the advancement of photochemical-based AOPs.

In situ formation of red/black phosphorus-modified SiO2@g-C3N4 multi-heterojunction for the enhanced photocatalytic degradation of organic contaminants

A new heterojunction material BP/RP-g-C₃N₄/SiO₂ was obtained by a one-step ball milling method, and its photocatalytic capacity was researched by the degradation of Rhodamine B (RhB) and ofloxacin (OFL) in simulated sunlight. The construction of an in situ BP/RP heterojunction can achieve perfect interface contact between different semiconductors and effectively promote the separation of photogenerated carriers. The composite material was well characterized, which proved that the multi-heterogeneous structure was prepared. Furthermore, the type II heterojunction was formed between the g-C₃N₄ and BP/RP interface, playing an important role in the degradation and promoting electron transfer. The degradation effect of BP/RP-g-C₃N₄/SiO₂ on RhB reached 90% after 26 min of simulated solar irradiation, which was 1.8 times that of g-C₃N₄/SiO₂. The degradation of OFL by BP/RP-g-C₃N₄/SiO₂ reached 85.3% after illumination for 50 min, while the degradation of g-C₃N₄/SiO₂ was only 35.4%. The mechanisms were further discussed, and ˙O₂ ^- and h⁺ were found to be the main active substances to degrade RhB. The catalyst also revealed distinguished stability of catalyst and recyclability, and the degradation effect of RhB can still realize 85% after 4 runs of experiment. Thus, this study provided a novel method for the design and preparation of multi-heterojunction catalysts in the removal of organic pollutants from wastewater.

Mechanism of downward migration of quinolone antibiotics in antibiotics polluted natural soil replenishment water and its effect on soil microorganisms

Reclaimed water is widely concerned as an effective recharge of groundwater and surface water, but trace organic pollutants produced by traditional wastewater treatment plants (WWTPs) would cause environmental pollution (water and soil) during infiltration. Therefore, the effects of reclaimed water containing ofloxacin (OFL) and ciprofloxacin (CIP) in antibiotics polluted natural soil (APNS) were investigated by simulating soil aquifer treatment systems (SATs). The experiment results showed that OFL and CIP in water were adsorbed and microbially degraded mainly at 30 cm, and the concentration of OFL and CIP in soil increased with depth, which were mainly due to the desorption from APNS. Concurrently, the change in replenishment water concentration also significantly affected OFL and CIP in pore water and soil. Although OFL and CIP inhibited the diversity of soil microbial community, they also promoted the growth of some microorganisms. As the dominant bacteria, Proteobacteria and Acidobacteriota can effectively participate in the degradation of OFL and CIP. The degradation effects of soil microorganisms on OFL and CIP were 45.48% and 42.39%, respectively, indicating that soil microorganisms selectively degraded pollutants. This experiment was carried out on APNS, which provided a reference for future studies on the migration of trace organic pollutants under natural conditions.

Dye mineralization under UV/H2O2 promoted by chloride ion at high concentration and the generation of chlorinated byproducts

Chloride ion (Cl^-) may promote or inhibit the oxidation of specific organic compounds treated by hydroxyl radical based advanced oxidation processes (HR-AOPs) depending on the reactivity of chlorine radicals towards the organics. However, the effects of high contents of Cl^- on the removal of total organic compounds (TOC) in high salinity organic wastewater treated by HR-AOPs were unclear. The removal and mineralization of azo dye Orange II (OrgII) by UV/H₂O₂ process with Cl^- at high contents under various pH conditions were investigated. As the pH conditions increased higher than pH 5, TOC removal rates increased slightly possibly related to the increase of O₂^- production and the reduce of futile decomposition of H₂O₂ into O₂. Cl^- at relative high concentration (1000 and 2000 mM) significantly promoted the mineralization of dyes with TOC removal increasing by 10 %-40 % under both acid and alkaline conditions. The proposed mechanism is that the reaction of Cl^- with OH would decline the decomposition of H₂O₂ into O₂ by inhibiting the reaction between OH and H₂O₂, and the generated chlorine species (Cl and Cl₂^-) could further promote the oxidation of dye molecules into intermediates and be helpful for the subsequent mineralization process. In addition, H₂O₂ and Cl^- can slowly react to give HClO and ClO^-, which may partly contribute to the decolorization and mineralization of OrgII. Meanwhile, an appropriate relative proportion between Cl₂^- and OH depending on Cl^- contents and pH conditions is important to enhance the TOC removal. However, the formation of various chlorinated byproducts especially under alkaline condition may increase the risk of environmental pollution accidents. The results demonstrate the promotion of TOC removal by UV/H₂O₂ under certain high contents of Cl^- and provide new insight into the application of HR-AOPs to the pretreatment of high salinity organic wastewater.

Vinasse-based biochar magnetic composites: adsorptive removal of tetracycline in aqueous solutions

Highly efficient and cost-effective adsorbents for antibiotic removal are the key to mitigate pollution by industrial wastewaters. Pyrolyzing low-cost winemaking waste into biochar is a promising means for waste biomass utilization. This study assembled vinasse-derived biochar with manganese ferrite into vinasse-manganese ferrite biochar-magnetic composites (V-MFB-MCs) through simultaneous pyrolysis of waste biomass and metal (Mn and Fe) hydroxide precipitates. Batch experiments were conducted to evaluate the kinetics and isotherms of tetracycline (TC) adsorption as well as the influence of pH value, humic acid, and ionic strength. Morphological characterization showed that crystalline MnFe₂O₄ nanoparticles were impregnated within the framework of fabricated V-MFB-MCs. Superior TC adsorption capacity and fast pseudo-second-order kinetics could be achieved by the V-MFB-MCs-800 at pH 3.0. The TC adsorption onto V-MFB-MCs-800 was highly pH-dependent and controlled by the positive influence of ionic strength and humic acid. V-MFB-MCs-800 showed excellent adsorption performance in different natural water. Multiple interaction mechanisms including pore filling effect, π-π stacking interaction, and hydrogen bonding contribute to TC removal by V-MFB-MCs-800, which can be an innovative biowaste-derived material for industrial wastewater treatment.

A novel approach to interpret quasi-collimated beam results to support design and scale-up of vacuum UV based AOPs

UV-C at 254 nm and vacuum UV (VUV) at 185 nm are the two major emission lines of a low-pressure mercury lamp. Upon absorption of VUV photons, water molecules and selected inorganic anions generate hydroxyl (HO^.) and other redox radicals, both capable of degrading organic micropollutants (OMPs), thereby offering the opportunity to reduce H₂O₂ and energy consumption in UV-based advanced oxidation process (AOP). To be successfully scaled-up, the dual-wavelength VUV+UV/H₂O₂ AOP requires laboratory-scale experiments to establish design criteria. The figures of merit typically used for reporting and interpreting quasi-collimated beam results for UV-based AOPs (time, dose, absorbed energy and E_EO) are insufficient and inaccurate when employed for dual-wavelength AOP such as the VUV+UV/H₂O₂ AOP, and do not support system scale-up. In this study, we introduce a novel figure of merit, useful absorbed energy (uAE), defined as fraction of absorbed energy that results in the generation of oxidative radicals. Here, results of quasi-collimated beam VUV+UV/H₂O₂ AOP experiments on four different water matrices are used to introduce 2D plots that employ both uAE_UV and uAE_VUV as a novel method to represent laboratory-scale experiments of VUV+UV/H₂O₂ AOP and demonstrate how the 2D plots sufficiently support scale-up of the AOP.

Activating peroxymonosulfate using carbon from cyanobacteria as support for zero-valent iron

In the present study, the cyanobacterial char (ACC) prepared from Chaohu cyanobacteria was used as a nanoscale carrier for zero-valent iron (NZVI) to synthesize a highly efficient activation material designated as cyanobacterial char-supported nanoscale zero-valent iron (NZVI@ACC), which was subsequently used for activating peroxymonosulfate (PMS) to degrade the orange II (OII) dye. The XRD and XPS results revealed that NZVI was anchored onto the ACC through coordination bonding, forming a stable structure. The SEM and TEM observations revealed that the NZVI was embedded in the sheet structure of the ACC. The NZVI@ACC had a larger specific surface area (42.249 m²/g) and also magnetism, due to which its components could be separated through an externally applied magnetic field. Using this NZVI@ACC/PMS system, the rate of degradation of OII (100 mg/L) reached 98.32% within 14 min. The OII degradation reaction using the NZVI@ACC/PMS system followed first-order kinetics. The activation energy of this degradation reaction was 17.34 kJ/(mol·K). Quenching and EPR experiments revealed that various free radicals (SO₄·^-, ·OH) were produced, with SO₄·^- playing the major role in the reaction. The theoretical calculations revealed that SO₄·^- attacked the 12 (N) of OII, thereby destroying and degrading both azo and hydrogenated azo structures of OII. The presence of halogen ions in the actual dye-containing wastewater samples inhibited the OII degradation by the NZVI@ACC system to different degrees, and the inhibition effect followed the order I^-  > Br^-  > Cl^-.

Enhanced thermal activation of persulfate by coupling hydrogen peroxide for efficient degradation of pyrene

In this study, H₂O₂ was introduced into thermally activated persulfate oxidation system (T-HPS), and the oxidation of pyrene (PYR) was investigated by the combined T-HPS technology. The results showed that H₂O₂ could significantly improve the reactivity of the thermally activated persulfate system (T-PS), with 240-min PYR degradation ratio increasing from 79.3% to 97.2% at 70 °C. In the T-HPS system, as persulfate initial concentration increased from 5 to 100 μM, the kinetic rate constant (k_obs) of PYR degradation increased from 4.70 × 10^-3 to 3.01 × 10^-2 min^-1, but the k_obs did not show a positive association with H₂O₂ concentration with the same range, and the highest k_obs was obtained at the H₂O₂ initial concentration of 20 μM. The optimal ratio of PS and H₂O₂ was set at 1:1 with the initial concentrations of the two oxidants both being 20 μM. Furthermore, PYR could be removed efficiently in a wide range of pH, and the best PYR degradation performance was obtained under neutral pH. Scavenging experiments demonstrated that OH played a more important role in PYR degradation in the T-HPS system than in the T-PS system. As suggested by the Arrhenius equation, the activation energy decreased from 124.5 to 107.4 kJ mol^-1 after adding H₂O₂ to the T-PS system. This study provides a new oxidation approach that could prompt the T-PS activity by adding a suitable dosage of H₂O₂.

Enhancing hydrogen peroxide activation of CuCo layered double hydroxide by compositing with biochar: Performance and mechanism

In this study, CuCo layered double hydroxide/biochar composite (CuCo LDH/BC) was prepared and employed for activating H₂O₂ to degrade ciprofloxacin (CIP), a common fluroquinolone antibiotic detected in water environment. The as-synthesized catalysts were also comprehensively characterized to study the physiochemical properties. For the catalytic activity, the degradation rate of CuCo LDH/BC to CIP was approximately 1.5 times higher than that of CuCo LDH. The improved catalytic activity can be ascribed to the synergistic effect between CuCo LDH and BC, such as more functional groups, accelerated electron transfer, and varied charge distribution. Meanwhile, CuCo LDH/BC/H₂O₂ could degrade CIP efficiently in a wider pH range comparing with CuCo LDH/H₂O₂, and the efficiency was approximately 84.7% at neutral pH within 90 min. The generation of OH, O₂^- and ¹O₂ in CuCo LDH/BC/H₂O₂ system were then verified by electron spin resonance (ESR) technology. The quenching experiments indicated that both non-radical pathway (¹O₂) and radical pathway (OH, O₂^-) led to CIP degradation, in which O₂^- and ¹O₂ made major contribution. Then, the intermediate products of CIP during catalytic reaction were monitored by high-performance liquid chromatography-mass spectrometry (HPLC-MS), and the environmental risk of these degradation intermediates was tested through seed germination experiments. This study tends to provide valuable information for LDH/BC application in heterogeneous Fenton-like reaction.

Promotive effects of vacuum-UV/UV (185/254 nm) light on elimination of recalcitrant trace organic contaminants by UV-AOPs during wastewater treatment and reclamation: A review

The use of vacuum-UV/UV (185/254 nm) for trace organic contaminants (TOrCs) elimination during wastewater treatments has attracted much attention. Advanced oxidation processes which combine VUV/UV and additional oxidants (vacuum-UV/UV-based advanced oxidation processes, VUV/UV-AOPs) provide a promising method for eliminating recalcitrant and toxic TOrCs for wastewater reclamation. Researches in this area are increasing but the promoting effects, mechanisms, and influencing factors have not been well summarized. A comprehensive discussion of the limitations of this technique and future research directions is needed. VUV/UV-AOPs have considerable synergistic effects by increasing usage of VUV/UV photons and the oxidant, which increases radical generation. In terms of elimination kinetics, VUV/UV-AOPs outperform conventional UV-AOPs and VUV/UV processes in most cases; a 1.2-87.7-fold increase of the fluence-based kinetic constant is achieved. In terms of energy efficiency per order (EE/O) of TOrCs elimination, the EE/O of VUV/UV-AOPs only accounts for 4% of UV-AOPs and 63% of VUV/UV. However, VUV/UV-AOPs still need to be further investigated. Firstly, although VUV and UV processes have similar radical formation pathways, limited information is available on the quantum yields of photolysis and radical formation of oxidants under VUV irradiation. Secondly, optimization of VUV/UV-AOPs operating conditions, especially oxidant dosage and water-flow patterns, is needed. Thirdly, VUV/UV-AOPs are significantly inhibited by organic and inorganic matters, but the mechanisms of inhibition on VUV/UV scattering, radical quenching, and radical conversion are not well understood. Such inhibition suggests that the use of VUV/UV-AOPs would be limited to relatively clear water treatment, e.g., reverse osmosis effluent for potable water reuse and ultrapure water production. Related research is needed to establish a clearer scheme for VUV/UV-AOPs in terms of the spatial distribution of radical species in the VUV/UV irradiation system and the relevant optimization method for promoting oxidation performance.

Nonlinear Autoregressive Neural Network for Antimicrobial Waste Water Treatment

Antibiotics become an emerging contaminant and receive more interests due to its ecotoxicological and strong stability in water ecosystems. Antibiotic adsorption onto carbon materials are biochars among the wastewater mechanisms. This research used machine learning (ML) techniques to generate general adsorption forecasting model for sulfamethoxazole (SMX) and tetracycline (TC) on CBM. Dirichlet design parameters and a combined combination of Neumann and Dirichlet boundary situation are applied to the system of differential equations. In addition, the proposed method use the learning under supervision technique of a nonlinear autoregressive for estimating the CO2 concentration and flows in units of rate of a reaction characteristics, an exogenous (NARX) neural network model with two activation functions was used (Log-sigmoid and hyperbolic tangent) and for both the findings of a TC and SMX absorption simulations showed the random forest performed support vector tree and nonlinear autoregressive exogenous neural networks and machine learning methods. Their relevance and complete dependency graph evaluation lead reasonable CBM uses for antimicrobial wastewater treatment. Also, machine learning forecasting model with good generalization capability is useful for building effective CBMs with few empirical screens. It evaluates the accuracy, precision, recall, false positive rate (FPR), and false negative rate (FNR) and also reduces the experimental screening.

Removal efficiency for emerging contaminants in a WWTP from Madrid (Spain) after secondary and tertiary treatment and environmental impact on the Manzanares River

The effluents from wastewater treatment plants (WWTPs) can be an important contamination source for receiving waters. In this work, a comprehensive study on the impact of a WWTP from Madrid on the aquatic environment has been performed, including a wide number of pharmaceuticals and pesticides, among them those included in the European Watch List. 24-h composite samples of influent (IWW) and effluent wastewater after secondary (EWW2) and after secondary + tertiary treatment (EWW3) were monitored along two campaigns. Average weekly concentrations in IWW and EWW2 and EWW3 allowed estimating the removal efficiency of the WWTP for pharmaceutical active substances (PhACs). In addition, the impact of EWW3 on the water quality of the Manzanares River was assessed, in terms of PhAC and pesticide concentrations, through analysis of the river water collected upstream and downstream of the discharge point. After a preliminary risk assessment, a detailed evaluation of the impact on the aquatic environment, including a toxicological study and screening of pharmaceutical metabolites, was made for the seven most relevant PhACs: sulfamethoxazole, azithromycin and clarithromycin (antibiotics), metoprolol (antihypertensive), diclofenac (anti-inflammatory/analgesic), irbesartan (antihypertensive), and the antidepressant venlafaxine. Among selected PhACs, irbesartan, clarithromycin and venlafaxine presented moderate or high risk in the river water downstream of the discharge. Albeit no acute toxicity was detected, more detailed studies should be carried out for these substances, including additional toxicological studies, to set up potential sublethal and chronic effects on aquatic organisms.

Degradation of tris(2-chloroethyl) phosphate (TCEP) by thermally activated persulfate: Combination of experimental and theoretical study

Organophosphorus esters (OPEs), one kind of the emerging contaminants with high frequency of detection, is rather refractory in natural environment, thus posing great threat to human health. This study investigated the feasibility and mechanism of tris(2-chloroethyl) phosphate (TCEP) degradation in thermally activated persulfate (TAP) system. Influence of impact factors, such as PDS dosage, temperature, initial pH, and presence of natural water matrix (Cl^-, NO₃^-, H₂PO₄^-, NH₄⁺, humic acid), were evaluated. Results showed that 100% degradation of TCEP can be achieved in TAP system in 40 min at 60 °C. SO₄^·- as the dominant oxidant for TCEP degradation was proved by quenching experiment and verified by EPR analysis. Alkaline condition exerted great inhibitory effect by affecting the constituents of oxidative radicals. It is suggested that Cl^- and H₂PO₄^- at lower dosages promoted the degradation by stimulating ·OH production and forming oxidative radicals with better selectivity. Intermediates identified by high resolution mass spectrometer was suggested less toxic than TCEP by ECOSAR program. Meanwhile, the illustrated oxidation mechanism mainly involved radical attack at CCl bond and cleavage of CO bond, as further confirmed by frontier electron density calculation and wavefunction analysis. Moreover, cyclic degradation of TCEP indicated the constant release of SO₄^·- in 450 min, suggesting high efficiency and stability of PDS in TAP system. Four selected OPEs achieved complete removal in TAP system and their degradation discrepancy was further discussed based on the distinctive structures. Altogether, TAP technology can be used as an efficient method in TCEP removal with great potential for application.

Direct 3D printing of zero valent iron@polylactic acid catalyst for tetracycline degradation with magnetically inducing active persulfate

Catalyst stability has become a challenging issue for advanced oxidation processes (AOPs). Herein, we report an alternative method based on 3D printing technology to obtain zero-valent iron polylactic acid prototypes (ZVI@PLA) in a single step and without post etching treatment. ZVI@PLA was used to activate persulfate (PS) for the removal of Tetracycline (TC) in recirculating mode under two different heating methodologies, thermal bath and contactless heating promoted by magnetic induction (MIH). The effect of both heating methodologies was systematically analysed by comparing the kinetic constant of the degradation processes. It was demonstrated that the non-contact heating of ZVI by MIH reactivates the surface of the catalyst, renewing the surface iron content exposed to the pollutant solution, which makes the ZVI@PLA catalyst reusable up to 10 cycles with no efficiency reduction. In contrast, by using a conventional thermal bath, the kinetic constant gradually decreases over the 10 cycles, because of the superficial iron consumption, being the kinetic constant 5 times lower in the 10th run compared to MIH experiment. X-ray diffraction and Mössbauer spectroscopy confirmed the presence of metallic iron embedded in the ZVI@PLA prototype, whose crystalline structure remained unchanged for 10th cycles of MIH. Moreover, it was proven that with no contact heating technology at low magnetic fields (12.2 mT), the solution temperature does not increase, but only the surface of the catalyst does. Under these superficial heated conditions, kinetic rate is increased up to 0.016 min^-1 compared to the value of 0.0086 min^-1 obtained for conventional heating at 20 °C. This increase is explained not only by PS activation by iron leaching but also by the contribution of ZVI in the heterogeneous activation of persulfate.

Gaussian Process Regression and Machine Learning Methods for Carbon-Based Material Adsorption

Antibiotics have received a lot of attention as promising contaminants because of their ecotoxicological and long-term chemical stability in the atmosphere. Antibiotic adsorption on carbon-based materials (CBMs) such as charcoal and activated carbon has been identified as mainly effective for treating the wastewater strategies. Machine learning (ML) approaches were used to create generalized computation methods for tetracycline (TC) and sulfamethoxazole (SMX) adsorption in CBMs in this investigation. In the existing system, random forest and ANN methods were used for TC and SMX for predicting the quantities of antibiotics in the CBMs. For reducing the antibiotics from the industrial wastewater, the broadcast efforts of the experiments are a little complicated. In the proposed method, Gaussian process regression (GPR), active learning (AL), and ANN are used for predicting the antibiotic levels in the industrial wastewater. Below a variety of environmental parameters (e.g., warmth, solution pH) and adsorbent varieties, the created Ml algorithms outperformed classic isotherm models in conditions of generalisation. To evaluate TC and SMX adsorption on CBMs, we used comparative significance investigation and partial trust plots based on ML models. The proposed GPR reduces the antibiotics in wastewater; minimal experimental screening and the comparative significance and partial trust plot help in the treatment of wastewater.

Selective production of singlet oxygen from zinc-etching hierarchically porous biochar for sulfamethoxazole degradation

Porous carbons are appealing low-cost and metal-free catalysts in persulfate-based advanced oxidation processes. In this study, a family of porous biochar catalysts (ZnBC) with different porous structures and surface functionalities are synthesized using a chemical activation agent (ZnCl₂). The functional biochars are used to activate persulfate for sulfamethoxazole (SMX) degradation. ZnBC-3 with the highest content of ketonic group (CO, 1.25 at%) exhibits the best oxidation efficiency, attaining a rate constant (k_obs) of 0.025 min^-1. The correlation coefficient of the density of CO to k_obs (R² = 0.992) is much higher than the linearity of the organic adsorption capacity to k_obs (R² = 0.694), implying that CO is the intrinsic active site for persulfate activation. Moreover, the volume of mesopore (R² = 0.987), and Zeta potential (R² = 0.976) are also positive factors in PS adsorption and catalysis. In the mechanistic study, we identified that singlet oxygen is the primary reactive oxygen species. It can attack the -NH₂ group aligned to the benzene ring to form dimer products which could be adsorbed on the biochar surface to reach complete removal of the SMX. The optimal pH range is 4-6 which will minimize the electrostatic repulsion between ZnBCs and the reactants. The SMX degradation in ZnBC/PS system was immune to inorganic anions but would compete with organic impurities in the real wastewater. Finally, the biochar catalysts are filled in hydrogel beads and packed in a flow-through packed-bed column. The continuous system yields a high removal efficiency of over 86% for 8 h without decline, this work provided a simple biochar-based persulfate catalyst for complete antibiotics removal in salty conditions.

Degradation of micropolluants in flow-through VUV/UV/H2O2 reactors: Effects of H2O2 dosage and reactor internal diameter

The degradation of atrazine (ATZ), sulfamethoxazole (SMX) and metoprolol (MET) in flow-through VUV/UV/H₂O₂ reactors was investigated with a focus on the effects of H₂O₂ dosage and reactor internal diameter (ID). Results showed that the micropollutants were degraded efficiently in the flow-through VUV/UV/H₂O₂ reactors following the pseudo first-order kinetics (R² > 0.92). However, the steady-state assumption (SSA) kinetic model being vital in batch reactors was found invalid in flow-through reactors where fluid mixing was less sufficient. With the increase of H₂O₂ dosage, the ATZ removal efficiency remained almost constant while the SMX and MET removal was enhanced to different extents, which could be explained by the different reactivities of the pollutants towards HO^•. A larger reactor ID resulted in lower degradation rate constants for all the three pollutants on account of the lower average fluence rate, but the change in energy efficiency was much more complicated. In reality, the electrical energy per order (E_EO) of the investigated VUV/UV/H₂O₂ treatments ranged between 0.14-0.20, 0.07-0.14 and 0.09-0.26 kWh/m³/order for ATZ, SMX and MET, respectively, with the lowest E_EO for each pollutant obtained under varied H₂O₂ dosages and reactor IDs. This study has demonstrated the efficiency of VUV/UV/H₂O₂ process for micropollutant removal and the inadequacy of the SSA model in flow-through reactors, and elaborated the influential mechanisms of H₂O₂ dosage and reactor ID on the reactor performances.

Rapid degradation of norfloxacin by VUV/Fe2+/H2O2 over a wide initial pH: Process parameters, synergistic mechanism, and influencing factors

Vacuum UV (VUV) technology has attracted much attention because it effectively splits water to generate reactive oxygen species (ROS) in situ and has the advantages of UV. So far, the synergistic mechanisms, formation pathways and contributions of ROS in VUV/Fe²⁺/H₂O₂ process have not been extensively studied. Herein, complete removal (at 4 min) and 63.3% mineralization (at 8 min) of 45 μM norfloxacin (NOR) were achieved at neutral pH by VUV/Fe²⁺/H₂O₂ (90 μM Fe²⁺ and 3 mM H₂O₂). Compared with its subsystems, VUV/Fe²⁺/H₂O₂ can not only increase the pseudo-first-order reaction rate constant of NOR removal by 2.3-14.9 times and increase the mineralization by 20.4-59.4%, but also reduce the residual ratio of H₂O₂ by 19.9-70.1% and reduce total cost by 20.0-68.0%. The synergy factor of VUV/Fe²⁺/H₂O₂ was 3.97, which was attributed to the VUV irradiation promoting iron redox cycle and H₂O₂ decomposition. Moreover, hydroxyl radical and superoxide radical, which were identified as the main ROS, contributed 79.07% and 18.47% to NOR removal, respectively. Degradation pathways of NOR were proposed. Furthermore, effects of coexisting ions and dissolved organic matter were investigated. As an energy-saving and efficient process, the satisfactory results of VUV/Fe²⁺/H₂O₂ applied in real waters also highlight its application potential.

Visible-Light-Driven Bio-Templated Magnetic Copper Oxide Composite for Heterogeneous Photo-Fenton Degradation of Tetracycline

The development of a visible-light-driven, reusable, and long-lasting catalyst for the heterogeneous photo-Fenton process is critical for practical application in the treatment of contaminated water. This study focuses on synthesizing a visible-light-driven heterogenous bio-templated magnetic copper oxide composite (Fe3O4/CuO/C) by a two-step process of bio-templating and hydrothermal processes. The prepared composite was characterized by field emission-scanning electron microscope (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), electrical impedance spectroscopy (EIS), and vibrating sample magnetometer (VSM). The results reveal that the prepared composite retains the template’s (corn stalk’s) original porous morphology, and a substantial amount of CuO and Fe3O4 particles are loaded onto the surface of the template. The prepared Fe3O4/CuO/C composite was employed as a catalyst for heterogeneous photo-Fenton degradation of tetracycline (TC) irradiated by visible light. The prepared Fe3O4/CuO/C catalyst has high efficiency towards TC degradation within 60 min across a wide pH range irradiated by visible light, which is attributed to its readily available interfacial boundaries, which significantly improves the movement of photoexcited electrons across various components of the prepared composite. The influence of other parameters such as initial H2O2 concentration, initial concentration of TC, and catalyst dosages was also studied. In addition to high efficiency, the prepared catalyst’s performance was sustained after five cycles, and its recovery is aided by the use of an external magnetic field. This research paper highlights the development of a heterogeneous catalyst for the elimination of refractory organic compounds in wastewater.

Stable Fe3O4 submicrospheres with SiO2 coating for heterogeneous Fenton-like reaction at alkaline condition

In the traditional Fenton process, the efficient generation of hydroxyl radical (HO) strongly relies on an acidic circumstance and the iron ions would precipitate and form large amounts of hazardous iron-containing sludge at alkaline pH. To realize stable heterogeneous Fenton-like catalytic degradation at alkaline condition, Fe₃O₄ submicrospheres with SiO₂ coating were successfully synthesized by using water glass as the silica sources via a facile ultrasound assisted method. The as-obtained Fe₃O₄@SiO₂ spheres were further used as catalysts for the Fenton-like degradation of tetracycline hydrochloride (TC). The Fe₃O₄@SiO₂ submicrospheres exhibited superior catalytic activity in higher pH environment (pH value = 11), and the degradation efficiency toward TC was ca. 80% after ten successive runs. The kinetics for the catalytic degradation of TC were agreed well with the second-order kinetic model. The reaction rate constant (k) over the Fe₃O₄@SiO₂ submicrospheres at a pH value of 11 was 7.69 times greater than that at a pH value of 3. Reactive species scavenging experiments revealed that HO and superoxide radical (O₂^- / HO₂^-) played a dominant role during the Fenton-like degradation of TC at pH 3 and pH 11, respectively. Possible Fenton-like degradation pathways of TC were proposed through the identification of intermediates using the high performance liquid chromatography coupled with mass spectrometry (HPLC-MS), which involved cleavage of methyl groups, N-dimethyl group, and hydroxy groups, ring-opening reaction, etc. The degradation efficiency of TC was close to 91.5% and total organic carbon (TOC) in solution was eliminated by about 41.4% at the optimized conditions. In a word, with the unique acidic surface properties and abundant Si-OH bonds, the Fe₃O₄@SiO₂ submicrospheres exhibited well dispersion, good catalytic activity, strong alkali resistance and excellent recyclability in an ultrasonic-Fenton-like system.

Visible-LED-light-driven photocatalytic degradation of ofloxacin and ciprofloxacin by magnetic biochar modified flower-like Bi2WO6: The synergistic effects, mechanism insights and degradation pathways

Bi₂WO₆ possesses good stability but poor photocatalytic activity under visible light. Herein, the coupling of Bi₂WO₆, Fe₃O₄ and biochar (Bi₂WO₆/Fe₃O₄/BC) was investigated to enhance the photocatalytic performance of Bi₂WO₆ through facile hydrothermal method, which almost completely degraded ofloxacin (OFL) and ciprofloxacin (CIP) within 30 min under energy-saving visible LED irradiation. The superior photocatalytic activity of Bi₂WO₆/Fe₃O₄/BC was ascribed to the stronger visible light adsorption capacity and the lower recombination of electron-hole pairs. O₂^- played a major role during the photocatalytic reaction. The characterization results suggested that the introduction of biochar avoided the agglomeration of Bi₂WO₆ microspheres and Fe₃O₄ nanoparticles, at the same time, the biochar participated in OFL and CIP photodegradation by consuming different oxygen-containing functional groups. In order to further evaluate the application potential of Bi₂WO₆/Fe₃O₄/BC, the effects of environment factors and the application in different actual water were carefully investigated. Various transformation products and the possible degradation pathways of OFL and CIP were analyzed based on high resolution mass spectrometry (HRMS) results, moreover, the toxicity evaluation results of Escherichia coli indicated these intermediates products were less toxic compared OFL and CIP. Overall, Bi₂WO₆/Fe₃O₄/BC can provide a potential way for the application of photocatalytic technology in ambient wastewater purification.

Degradation of ciprofloxacin using UV-based advanced removal processes: Comparison of persulfate-based advanced oxidation and sulfite-based advanced reduction processes

In this study, the degradation of ciprofloxacin (CIP) in wastewater was investigated using UV-based sulfate radical advanced oxidation processes (SR-AOP) and UV-based advanced reduction processes (ARP). More specifically, a comparison of the UV-based persulfate advanced oxidation process (the UV/PS process) and the UV-based sulfite advanced reduction process (the UV/sulfite process) was made. Considering the UV-based SR-AOPs, the UV/PS process was much more efficient than the UV-based peroxymonosulfate advanced oxidation process (the UV/PMS process), with pseudo first order reaction rate constants (k_obs) of 0.752 and 0.145 min^-1, respectively. For the UV-based ARPs, the UV/sulfite process was the most efficient, compared to the UV/sulfide and the UV/dithionite process (k_obs of 0.269, 0.0157 and 0.0329 min^-1, respectively). The optimal process parameters for both the UV/PS and the UV/sulfite process were determined and the contribution of the produced reactive species were identified. For the UV/PS process, maximal CIP degradation was found at pH 8, and both OH and SO₄^- were responsible for CIP degradation. For the UV/sulfite process, H and e_aq^- were responsible for CIP degradation, with e_aq^- being the predominant radical at pH 8.5. Although CIP degradation was much faster for the UV/PS process, the UV/sulfite process was determined to be much more efficient in the defluorination of CIP.

Cobalt ferrite nanoparticle-loaded nitrogen-doped carbon sponge as a magnetic 3D heterogeneous catalyst for monopersulfate-based oxidation of salicylic acid

As salicylic acid (SAL) is increasingly consumed as a pharmaceutical product, release of SAL into the environment poses threats to ecology because of its low bio-degradability. Thus, SO₄^•--based chemical oxidation processes have been proposed for degrading SAL. Since monopersulfate (MPS) represents a primary reagent for generating SO₄^•-, and Co is the most capable metal for activating MPS to generate SO₄^•-, C₃O₄ NPs are frequently proposed for activating MPS but they are difficult to recover from water. Thus CoFe₂O₄ is considered as a magnetic alternative to Co₃O₄, and loading of CoFe₂O₄ NPs on substrates could further improve dispersion and avoid aggregation of NPs. Therefore, this study proposes a 3-Dimensional (3D) hierarchical catalyst which is fabricated by loading CoFe₂O₄ NPs on nitrogen-doped carbon sponge (NCS). The NCS is not only adopted as a support for CoFe₂O₄ NPs but also provides additional catalytic sites and enhances catalytic activities of CoFe₂O₄ NPs for MPS activation. As a result, CoFe₂O₄ NPs loaded on NCS (CFNCS) exhibits substantially higher catalytic activities than CoFe₂O₄ NPs and NCS individually with 100% of SAL could be afforded within 30 min. E_a of SAL degradation of 47.4 kJ/mol by CFNCS-activated MPS is also lower than those by other reported catalysts, whereas the RSE was 11.1%, which was also much higher than most of reported values. These features demonstrate that CFNCS is a promising 3D catalyst for enhancing MPS activation to degrade SAL. The findings obtained here are also insightful to develop efficient MPS-activating catalysts for eliminating contaminants.

A Fenton-like system of biochar loading Fe-Al layered double hydroxides (FeAl-LDH@BC) / H2O2 for phenol removal

FeAl-layered double hydroxide (FeAl-LDH) supported by char was synthesized using the hydrothermal method in order to activate hydrogen peroxide (H₂O₂) to degrade phenol. The effects of char type, char synthesis amount, and several important parameters on the degradation were investigated. In addition, the physicochemical properties of FeAl-LDH@BC were revealed by instruments including the transmission electron microscope (TEM), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR). The results showed that the degradation efficiency of phenol (80 mg/L) by FeAl-LDH@BC_0.25 was 85.28% at a pH of 3 and H₂O₂ concentration of 400 mg/L, and exhibited good reusability with a small amount of iron leaching. Electron paramagnetic resonance (EPR) and radical quenching results indicated that ·OH radicals were the main participant during the degradation process, and XRD and FTIR spectra showed that FeAl-LDH was dissolved and rebuilt during the degradation process, and a small amount of iron was leached out resulting in the homogeneous catalysis. Hence, both homogeneous and heterogeneous processes occurred in the phenol oxidation process. Further soil remediation experiments showed that FeAl-LDH@BC_0.25 could also effectively degrade phenol in soil, although the efficiency was lower than that in solution.

Use of biochar/persulfate for accelerating the stabilization process and improving nitrogen stability of animal waste digestate

In China, the growing amount of digestate from anaerobic digestion produced by animal husbandry is an emerging challenge. A common treatment used to eliminate this digestate is long-term stabilization ponds. However, this process can lead to a shortage of digestate storage space and loss of nitrogen nutrients within the digestate. To alleviate those shortcomings, this study developed an efficient stabilization pond using biochar and persulfate (BC/PS treatment). Using this treatment, the germination index (GI) of the digestate increased from 56% to 85% and the stabilization efficiency increased nearly 2.7 times. In addition, the dehydrogenase activity (DHA) in the BC/PS treatment remained between 0.47 and 0.91 μg/(g·h) across the 40 days, which indicated that BC/PS had a positive effect on microbial inactivation. In the traditional stabilization process (CK treatment), dissolved organic nitrogen (DON) decreased from 47.77 mg/L to 0.81 mg/L and ammonium nitrogen almost disappeared. The BC/PS treatment led to the promotion of nitrogen nutrient composition. Particulate total nitrogen (21.49% of total nitrogen) decomposed into dissolved total nitrogen and the DON increased from 47.77 to 58.89 mg/L. The BC/PS treatment showed a faster stabilization time, good microbial inactivation, lower toxicity, and stable nitrogen nutrient composition of the digestate compared to traditional methods.

Application of Fourier transform ion cyclotron resonance mass spectrometry in deciphering molecular composition of soil organic matter: A review

Swiftly deciphering soil organic matter (SOM) composition is critical for research on soil degradation and restoration. Recent advances in analytical techniques (e.g., optical methods and mass spectrometry) have expanded our understanding of the composition, origin, and evolution of SOM. In particular, the use of Fourier transform ion cyclotron resonance mass spectrometers (FTICR-MS) makes it possible to interpret SOM compositions at the molecular level. In this review, we discuss extraction, enrichment, and purification methods for SOM using FTICR-MS analysis; summarize ionization techniques, FTICR-MS mechanisms, data analysis methods, and molecular compositions of SOM in different environments (providing new insights into its origin and evolution); and discuss factors affecting its molecular diversity. Our results show that digenesis, combustion, pyrolysis, and biological metabolisms jointly contribute to the molecular diversity of SOM molecules. The SOM thus formed can further undergo photodegradation during transportation from land to fresh water (and subsequently oceans), resulting in the formation of dissolved organic matter (DOM). Better understanding the molecular features of DOM therefore accelerates our understanding of SOM evolution. In addition, we assess the degradation potential of SOM in different environments to better inform soil remediation methods. Finally, we discuss the merits and drawbacks of applying FTICR-MS on the analysis of SOM molecules, along with existing gaps in knowledge, challenges, and new opportunities for research in FTICR-MS applications and SOM identification.

Biochar cathode: Reinforcing electro-Fenton pathway against four-electron reduction by controlled carbonization and surface chemistry

Porous biochars have attracted tremendous interests in electrochemical applications. In this study, a family of biochars were prepared from cellulose subject to different carbonization temperatures ranging from 400 to 700 °C, and the biochars were in-situ activated by a molten salt (ZnCl₂) to construct a hierarchically porous architecture. The activated porous biochars (ZnBC) were used as a carbocatalyst for electro-Fenton (EF) oxidation of organic contaminants. Results showed that high-temperature carbonization improved the activity of biochar for four-electron oxygen reduction reaction (ORR) due to the rich carbon defects, while the mild-temperature treatment regulated the species and distribution of oxygen functional groups to increase the production of hydrogen peroxide (H₂O₂) via a selective two-electron ORR pathway. ZnBC-550 was the best cathode material with a high ORR activity without compromise in H₂O₂ selectivity; a high production rate of H₂O₂ (796.1 mg/g/h) was attained at -0.25 V vs RHE at pH of 1. Furthermore, Fe(II) addition induced an electro-Fenton system to attain fast decomposition of various organic pollutants at -0.25 V vs RHE (reversible hydrogen electrode) and pH of 3 with a satisfactory mineralization efficiency toward phenolic pollutants. The EF system maintains its excellent stability for 10 cycles. Hydroxyl radicals were identified as the dominant reactive oxygen species based on in situ electron paramagnetic resonance (EPR) analysis and radical quenching tests. This study gains new insights into electrocatalytic H₂O₂ production over porous biochars and provides a low-cost, robust and high-performance electro-Fenton cathode for wastewater purification.

Magnetic Photocatalyst for Wastewater Tertiary Treatment at Pilot Plant Scale: Disinfection and Enrofloxacin Abatement

In this work, we have tested a photocatalytic material consisting of a core of SiO2/Fe3O4 coated with TiO2 (Magnox) for plausible tertiary wastewater treatment. For this, a pilot plant of 45 L equipped with an Ultraviolet light (UVC) lamp was employed to study the degradation of a model contaminant, enrofloxacin (ENR), as well as water disinfection (elimination of Escherichia coli and Clostridium perfringens). The influence of different operational conditions was explored by means of dye (rhodamine-B) decolorization rates, analyzing the effects of photocatalyst quantity, pH and recirculation flow rates. The magnox/UVC process was also compared with other four Advanced Oxidation Processes (AOPs): (i) UVC irradiation alone, (ii) hydrogen peroxide with UVC (H2O2/UVC), (iii) Fenton, and (iv) photo-Fenton. Although UVC irradiation was efficient enough to produce total water disinfection, only when employing the AOPs, significant degradations of ENR were observed, with photo-Fenton being the most efficient process (total enrofloxacin removal in 5 min and c.a. 80% mineralization in 120 min, at pH0 2.8). However, Magnox/UVC has shown great pollutant abatement effectiveness under neutral conditions, with the additional advantage of no acid or H2O2 addition, as well as its plausible reuse and simple separation due to its magnetic properties.

Enhanced vacuum UV-based process (VUV/H2O2/PMS) for the effective removal of ammonia from water: Engineering configuration and mechanistic considerations

In this work, the VUV, VUV/H₂O₂, VUV/PMS, and VUV/H₂O₂/PMS processes were compared with the corresponding UVC-based AOPs under identical experimental conditions for the ammonia removal. Among the examined AOPs, the VUV/H₂O₂/PMS demonstrated the highest performance in converting NH₄⁺ to N₂. A 82.7 % removal of 100 mg/L NH₄⁺, with N₂ selectivity over 99 % was obtained in the VUV/H₂O₂/PMS process within 60 min, operated under near neutral pH. Under these operation conditions, [NO₃^-] was around 0.5 mg-N/L with [NO₂^-] remaining below detection. The VUV-mediated generation of SO₄^•-and HO^• with NH₄⁺ had a relative contribution of 37.9 and 62.1 %, respectively. The VUV/H₂O₂/PMS process operated under a flow-through mode achieved efficient removal of 100 mg/L NH₄⁺ (80.5 %) in a hydraulic retention time (HRT) of 40 min. The continuous-flow VUV/H₂O₂/PMS process efficiently treated a real ammonia-laden groundwater and the concentration of NH₄⁺ decreased from 30 mg/L to around 1 mg/L within 60 min HRT. In summary, the VUV/H₂O₂/PMS process was effective from the technical and energetical point of view, hence is a viable and promising technique for treating effluent containing high concentrations of ammonia.

Carbothermal synthesis of biochar-supported metallic silver for enhanced photocatalytic removal of methylene blue and antimicrobial efficacy

Pinewood biochar (PBC)-supported metallic silver (Ag^o) was prepared via a one-step carbothermal reduction route (AgH) or a wet-chemistry reduction method (AgW). XRD and SEM confirmed Ag^o was soldered on PBC matrix. Low methylene blue (MB) sorption was observed for unsupported Ag^o nanoparticles (AgNP), AgH and AgW. Under ultraviolet (UV) light irradiation, net MB degradation by AgH (15.88 g kg^-1) was higher than that of AgW (12.50 g kg^-1) and AgNP (10.27 g kg^-1). TOC removal percentages after degradation corresponded largely to reduction of MB concentrations in solution, indicating MB was dominantly mineralized. Electron paramagnetic resonance (EPR) revealed that MB was degraded by reactive oxygen species (ROS) such as hydroxyl radical (OH), superoxide radical (O₂-) and singlet oxygen (¹O₂). The scavenging experiments further suggested that OH scavengers suppressed MB degradation to a greater extent than other quenchers. Compared to AgW, AgH possessed greater abundance of persistent free radicals, which enhance ROS generation. PBC could also improve separation of electron-hole (e^--h⁺) pairs and enhance electron transfer ascribing to favorable carbon structure. Besides, PBC-Ag^o maintained good antimicrobial efficacy over E.coli DH5α. This work presented a facile carbothermal route to prepare Ag^o-based photocatalysts for dye removal and microbial inhibition in industrial wastewater.

UV/ peroxymonosulfate process for degradation of chloral hydrate: Pathway and the role of radicals

In this study, kinetics, influencing factors and potential mechanisms involved in the degradation of chloral hydrate (CH) by UV/peroxymonosulfate (PMS) process were demonstrated. The degradation rate of CH could reach 89.6% by UV₂₅₄/PMS process, significantly exceeding UV₃₀₀/PMS (0.7%), UV₃₅₀/PMS (6.3%), UV₂₅₄ direct photolysis (9.0%) and PMS alone (0.0%) processes. CH degradation in UV₂₅₄/PMS system followed pseudo first-order degradation kinetics with an apparent rate constant of 0.186 min^-1, which was suppressed by Cl^- and HCO₃^-. The optimal pH for CH degradation was around 5.0. Direct mineralization accounted for the CH degradation in UV/PMS system. Interestingly, the addition of PMS at the neutral condition before UV irradiation transferred CH into trichloroacetic acid (TCAA). The transformation efficiency of CH into TCAA at 10 min was enhanced from 2.17%-40.38% with the elevation of initial pH from 7.0-8.0. The subsequent exposure of UV lamps ceased the transformation of CH into TCAA and facilitated the direct mineralization of CH, but it did not work in the refractory TCAA degradation. Finally, it was revealed that HO predominantly participated CH degradation in UV/PMS process, while O₂^- was responsible for the transformation of CH into TCAA by addition of PMS before UV irradiation.

Relationship of the physicochemical properties of novel ZnO/biochar composites to their efficiencies in the degradation of sulfamethoxazole and methyl orange

Three different composites were produced, based on zinc oxide and biochar (ZnO/biochar), varying the type of biomass (Salvinia molesta: SM; exhausted husk of black wattle: EH; and sugarcane bagasse: SB), with pyrolysis under mild conditions at 350 and 450 °C. Evaluation was made of the capacities of the composites for photocatalytic degradation of sulfamethoxazole antibiotic (SMX) and methyl orange dye (MO). The properties of the prepared composites were influenced by the biomass source, with larger crystallite size (SB), lower band gap energy (SM), higher specific surface area (SB), and larger pore size (SM) resulting in higher photocatalytic efficiency. Good degradation results were obtained using these innovative photocatalysts prepared at low temperatures, when compared to ZnO/biochar materials reported in previous studies. The best degradation capacities were obtained for the composites produced at 450 °C from SB and SM, with 99.3 and 97% degradation of SMX after 45 min, and 90.8 and 88.3% degradation of MO after 120 min, respectively.

Comparing the electrochemical degradation of the fluoroquinolone antibiotics norfloxacin and ciprofloxacin using distinct electrolytes and a BDD anode: evolution of main oxidation byproducts and toxicity

The effects of the supporting electrolytes (SEs) Na₂SO₄, NaCl, Na₂CO₃, NaNO₃, and Na₃PO₄ on the anodic oxidation of norfloxacin (NOR) and ciprofloxacin (CIPRO), assessed by the respective degradation kinetics and byproducts and electrolyzed solution antimicrobial activity, are compared. Galvanostatic anodic oxidations were performed in a filter-press flow cell fitted with a boron-doped diamond anode. Removal rates higher than the theoretical one for a process purely controlled by mass transfer were found for all SEs, indicative of contribution by indirect oxidation processes. However, the removal rates for NaCl were about tenfold higher, with the lowest energy consumption per order (EC _O) of targeted pollutant removal rate (ca. 0.7 kW h m^-3 order^-1), a very competitive performance. The TOC removal rates were also affected by the SE, but not as markedly. The antimicrobial activity of the electrolyzed solutions against Escherichia coli showed distinct temporal profiles, depending on the fluoroquinolone and SE. For instance, when Na₃PO₄ was used, the antimicrobial activity was completely removed for NOR, but none for CIPRO; conversely, when NaCl was used, complete removal was attained only for CIPRO. From LC-MS/MS analyses of Na₃PO₄ electrolyzed solutions, rupture of the fluoroquinolone ring leading to byproducts with no toxicity against E. coli occurred only for NOR, whereas exactly the opposite occurred for the NaCl solutions. Clearly, the nature of both the SE and the fluoroquinolone influence the oxidation steps of the respective molecule; this was also evidenced by the distinct short-chain carboxylic acids identified in the degradation of NOR and CIPRO.

Tetracycline Removal by Activating Persulfate with Diatomite Loading of Fe and Ce

Persulfate (PS)-based oxidation technology is efficient in removing refractory organics from water. A novel diatomite (DIA) support Fe and Ce composite (Fe-Ce/DIA) was prepared for activating persulfate to degrade tetracycline in water. The Fe and Ce were uniformly loaded on DIA, and the total pore size of Fe-Ce/DIA was 6.99 × 10⁻² cm³/g, and the average pore size was 12.06 nm. Fe-Ce/DIA presented a good catalytic activity and 80% tetracycline was removed under the persulfate system. The Fe-Ce/DIA also had photocatalytic activity, and the corresponding tetracycline removal efficiency was 86% under UV irradiation. Fe-Ce/DIA exhibited less iron dissolution rate compared with Fe-DIA. The tetracycline degradation rate was enhanced when the temperature increased. The optimal tetracycline removal efficiency was obtained when the conditions were of persulfate 10 mM, Fe-Ce/DIA dosage 0.02 g/L, and tetracycline concentration 50 mg/L. In addition, Fe-Ce/DIA showed a wide pH application and good reusability and stability.

Comparison of UV/H2O2, UV/PMS, and UV/PDS in Destruction of Different Reactivity Compounds and Formation of Bromate and Chlorate

In this study, we compared the decontamination kinetics of various target compounds and the oxidation by-products (bromate and chlorate) of PMS, PDS, and H₂O₂ under UV irradiation (UV/PMS, UV/PDS, UV/H₂O₂). Probes of different reactivity with hydroxyl and sulfate radicals, such as benzoic acid (BA), nitrobenzene (NB), and trichloromethane (TCM), were selected to compare the decontamination efficiency of the three oxidation systems. Experiments were performed under acidic, neutral, and alkaline pH conditions to obtain a full-scale comparison of UV/peroxides. Furthermore, the decontamination efficiency was also compared in the presence of common radical scavengers in water bodies [bicarbonate, carbonate, and natural organic matter (NOM)]. Finally, the formation of oxidation by-products, bromate, and chlorate, was also monitored in comparison in pure water and tap water. Results showed that UV/H₂O₂ showed higher decontamination efficiency than UV/PDS and UV/PMS for BA degradation while UV/H₂O₂ and UV/PMS showed better decontamination performance than UV/PDS for NB degradation under acidic and neutral conditions. UV/PMS was the most efficient among the three processes for BA and NB degradation under alkaline conditions, while UV/PDS was the most efficient for TCM degradation under all pH conditions. In pure water, both bromate and chlorate were formed in UV/PDS, small amounts of bromate and rare chlorate were observed in UV/PMS, and no detectable bromate and chlorate were formed in UV/H₂O_2. In tap water, no bromate and chlorate were detectable for all three systems.