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Metal-free activation of peroxydisulfate (PDS) for degrading organic pollutants in water has received increasing attention because it can prevent secondary pollution. However, most of the catalysts that are efficient are derived from non-renewable fossil resources, are very expensive and have complex preparation processes. Also, the emerging non-radical mechanism is still unclear. Herein, 3D sucrose-derived N-doped carbon xerogels (NCXs) were synthesized by a simple and sustainable hydrothermal process and then employed as novel metal-free PDS activators to degrade organic pollutants. The structure, composition and performance of NCXs were regulated by changing the carbonization temperature. The sample carbonized at 900 °C (NCX900) exhibited the best catalytic performance, completely removing bisphenol A in 60 min. Quenching experiments and linear sweep voltammograms demonstrated that PDS was activated mainly through an electron-transfer non-radical mechanism. It was found that graphitic N played a critical role in activating PDS. With this non-radical mechanism, the NCX900/PDS system could adapt well to the wide pH range (3–11) and high Cl− concentration; it selectively oxidized organic pollutants with low ionization potentials. This work provides a sustainable approach to the low-cost and efficient metal-free catalysts for wastewater treatment.

A reduced-order model (ROM) is developed for proton exchange membrane fuel cells (PEMFCs) considering the non-isothermal two-phase effects, with the goal of enhancing computational efficiency and thus accelerating fuel cell design development. Using analytical order reduction and approximation methods, the fluxes and source terms in conventional 1D conservation equations are reduced to six computing nodes at the interfaces between each cell component. The errors associated with order reduction are minimized by introducing new approximation methods for the potential distribution, the transport properties, and the membrane hydration status. The trade-off between model accuracy and computational efficiency is studied by comparing the simulation results and computational times of the new model with a full 1D model. The new model is nearly two orders of magnitude faster without sacrificing too much accuracy (

High-temperature nitrogen (N) doping boosts the activity of biochars for peroxymonosulfate (PMS) activation, but the N heat loss causes the unsatisfactory catalytic efficiency. Improving the surface area for obtaining the high exposure of N sites is a promising solution. Herein, a soft template-KHCO

In this study, nitrilotriacetic acid (NTA) was used to enhance UV/Fe0/H2O2 process for highly salty wastewater at neutral pH. The addition of Fe0 could not accelerate the UV/H2O2 process for salty wastewater treatment at neutral pH due to the precipitation of Fe ions. While NTA added into UV/Fe0/H2O2 process which could form complex with Fe ion, the tartrazine removal could increase from 45.7% to 84.7% within 60 min. The k-value of the UV/Fe0-NTA/H2O2 system to remove tartrazine is also 2.2 times higher than that in UV/Fe0/H2O2 system. Meanwhile, the UV/Fe0-NTA/H2O2 process could obtain good performance for salt wastewater treatment under a wide salt concentration level of 0–0.2 M. It can also expand the application range of pH to neutral pH. SEM and XPS characterization showed that the corrosion rate of Fe0 in salty system was faster, and the presence of NTA could accelerate the recirculation of Fe3+/Fe2+ on the Fe0 surface. EPR spectroscopic analysis and scavenge experiments showed that •OH was the main reactive radical for the removal of tartrazine in the UV/Fe0-NTA/H2O2 system. In addition, the k-value for removing tartrazine in various types of salt systems in the UV/Fe0-NTA/H2O2 system was 3.2–4.2 times that of the UV/Fe0/H2O2 system. It demonstrated UV/Fe0-NTA/H2O2 processes fits to different types of salt system. Therefore, this study will provide a new method for the treatment of saline wastewater at neutral pH.

Nutrients and heavy metals (HM) in the sediment have an impact on microbial diversity and community structure. In this study, the distribution characteristics of nutrients, HM, and microbial community in the sediments along the Longsha River, a tributary of the Pearl River (or Zhu Jiang), China were investigated by analyzing samples from 11 sites. On the basis of the HM-contamination level, the 11 sampling sites were divided into three groups to explore the changes in microbial communities at different ecological risk levels. Results indicated that nutrient concentrations were higher near farmlands and residential lands, while the ecological risk of HM at the 11 sampling sites was from high to low as S10 S2 S9 S6 S11 S7 S5 S8 S3 S4 S1. Among these HM, Cu, Cr, and Ni had intense ecological risks. In addition, the results of Variance Partitioning Analysis (VPA) revealed a higher contribution of HM (35.93%) to microbial community variation than nutrients (12.08%) and pH (4.08%). Furthermore, the HM-tolerant microbial taxa (Clostridium_sensu_stricto_1, Romboutsia, norank_o__Gaiellales, and etc.) were the dominant genera, and they were more dynamic around industrial lands, while microbes involved in the C, N, and S cycles (e.g., Smithella, Thiobacillus, Dechloromonas, Bacter oidetes_vadinHA17, and Syntrophorhabdus) were inhibited by HM, while their abundance was lower near industrial lands and highway but higher around residential lands. A three-unit monitoring program of land-use types, pollutants, and microbial communities was proposed. These results provide a new perspective on the control of riparian land-use types based on contaminants and microbes, and different microbial community response patterns may provide a reference for contaminant control in sediments with intensive industrial activities.

Sulfamethazine (SMT) is extensively used as growth promoters and antibacterial drugs. In this study, premagnetized Fe0 was used to catalyze H2O2 decomposition (pre-Fe0/H2O2) in the presence of nitrilotriacetic acid (NTA) to remove SMT at neutral pH conditions. In all, 30.3% and 99.8% of SMT were removed by the pre-Fe0/H2O2 process (60 min) and the pre-Fe0-NTA/H2O2 process (30 min), respectively. The removal rate of SMT in the pre-Fe0-NTA/H2O2 process was 2.5 times larger than that in the Fe0-NTA/H2O2 process. Electron paramagnetic resonance signals indicated that more radicals were generated in the pre-Fe0-NTA/H2O2 system. SMT and NTA and their degradation by-products adsorbed on pre-Fe0 reduced the contact angle of the particle and prevented the formation of Fe3O4 on the particle surface, thus accelerating Fe0 corrosion. Tafel scan images confirmed the enhancement of Fe0 corrosion in the presence of NTA and magnetic field. The Fe0 corrosion rate (109) after 20 min of reaction was 6.61 cm/s in pre-Fe0-NTA/H2O2, much higher than that in Fe0/H2O2 (0.73 cm/s), pre-Fe0/H2O2 (1.47 cm/s) and Fe0-NTA/H2O2 (2.94 cm/s). Pre-Fe0-NTA/H2O2 could also keep the fast SMT removal with eight consecutive runs without the addition of pre-Fe0 and NTA and presented high efficiency for SMT removal in real municipal wastewater.

This study presents a novel pre-magnetized Fe0/ethylenediaminetetraacetic acid/air (pre-Fe0/EDTA/air) Fenton-like system to remove sulfamethazine (SMT). SMT removal only reached 10.6% in pre-Fe0/air system (0.2 g L−1, SMT 3 mg L−1, pH 5) while reached 88.5% in pre-Fe0/EDTA/air system within 1 h (0.2 g L−1, SMT 3 mg L−1, EDTA 2 mM, pH 5). EDTA could combine with FeII or FeIII to keep iron soluble in the solution and the fast activation of molecular oxygen by Fe-EDTA complex could induce the fast and more production of H2O2. It was found that much more H2O2 (5.1 mg L−1) and OH radical (26.4 μM) were produced in the pre-Fe0/EDTA/air system than in the pre-Fe0/air system (0.06 mg L−1, 0.6 μM) within 1 h. The degradation rate of SMT (1 0 3) in pre-Fe0/EDTA/air system (38.4 min−1) was also 2.3 times as large as that in the Fe0/EDTA/air system (17.0 min−1), owing to the fast corrosion rate of pre-Fe0. 81.5 mgL−1 total Fe ions could be generated in pre-Fe0/EDTA/air while 53.6 mg L−1 in Fe0/EDTA/air. Fe0 dosage (0.05–0.8 g L−1) and EDTA dosage (0–8 mM) were optimized and the optimal dosage for Fe0 and EDTA was 0.2 g L−1 and 2 mM, respectively. The degradation rate of SMT in pre-Fe0/EDTA/air system were 1.6–2.9 times at different initial pH (3–6) and 2.3–3.1 times in the presence of inorganic ions (SO42−, Cl− and HCO3−) and natural organic matter (NOM) compared with Fe0/EDTA/air system. Decrease of Fe0 contact angle in the presence of magnetization and EDTA enhanced the corrosion rate of Fe0. Accordingly, pre-Fe0/EDTA/air system would be a cost-effective and promising eco-friendly alternative for removal of SMT.

Antibiotics have been frequently detected in the aquatic environment and are of emerging concern due to their adverse effect and potential of inducing antibiotic resistance. In this study, we developed an UV/pre-magnetized Fe0/H2O2 process (UV/pre-Fe0/H2O2) valid for neutral pH conditions, which could remove sulfamethazine (SMT) completely within only 30 min and enhance 1.8 times of SMT removal. Meanwhile, this process demonstrated outstanding mineralization capability with the TOC removal of 92.1%, while for UV/H2O2 and UV/Fe0/H2O2 system it was 53.9% and 72.1%, respectively. Better synergetic effect between UV irradiation and pre-Fe0/H2O2 system was observed, and the value of synergetic factor was 6.3 in the presence of both ions and humic acid, which was much higher than that in deionized water (4.4), humic acid (5.5) and ions (1.5). Moreover, the process could efficiently remove various antibiotics (800 μg L-1 oxytetracycline (OTC); 800 μg L-1 tetracycline (TC); 400 μg L-1 sulfadiazine (SD) and 400 μg L-1 SMT) in the secondary wastewater effluent. After optimization of Fe0 and H2O2 dosage, these antibiotics could be removed within 10 min (kapp (103) = 288.6 min-1) with a very low treatment cost of 0.1 USD m-3, and the EE/O value was only 1.22 kWh m-3. Compared with O3, UV/Fe2+/PDS, VUV/UV/Fe2+ and other US-based processes, the degradation rates by this process could enhance as high as 22.3 folds while the treatment cost or EE/O value could reduce greatly. Therefore, UV/pre-Fe0/H2O2 process is promising and cost-effective for the treatment of antibiotics in secondary wastewater effluents.

Emerging contaminants (ECs) have been frequently detected in the aquatic environment and have adverse effect on the environment. In our present study, four ECs (800 μgL−1 oxytetracycline (OTC) and tetracycline (TC); 400 μgL−1 sulfadiazine (SD) and sulfamethazine (SMT)) spiked into the secondary wastewater effluent (SWE) were treated by novel UV/pre-magnetized Fe0/PS process (UV/pre-Fe0/PS). TC, OTC and SMT could be completely removed within 30 min and 98.4% SD could be removed within 60 min, while less than 10%, 20% and 60% ECs could be removed by Fe0/PS, pre-Fe0/PS and UV process within 60 min. Synergetic factor values (6.1–12.3) in UV/pre-Fe0/PS were much larger than in UV/Fe0/PS (2.3–5.4) to remove various ECs, achieving 0.7–2.2 times enhancement in degradation rate constants and 45%–86% reduction in treatment costs. EPR spectra and scavenging tests by tert-butyl alcohol and methanol confirmed that not only faster and more SO4 − and OH radicals were produced but also their contributions to SMT removal were enhanced. Optimization of dosage of Fe0 (0–0.4 mM) and dosage of PS (0–0.4 mM) indicated that 0.2 mM Fe0 and 0.2 mM PS was the optimal dosage. Meanwhile, this process not only could enhance 0.7–15.8 times degradation rate constant but also could reduce about 14.3–97.9% costs to remove various ECs compared with US/Fe0/PS, ozonation, VUV/UV/Fe3+ and UV/H2O2 process. Moreover, it could enhance 1.4 times of degradation rate constant and reduce about 62% cost to remove SMT in another SWE, indicating the applicability in different wastewaters. Therefore, UV/pre-Fe0/PS process is promising and cost-effective to remove ECs in SWEs.

Nitrobenzene (NB) is toxic and resistant to biodegradation and widespread in surface water and groundwater. The persulfate (PS) system has been employed for the NB degradation and proved to be effective. Zero-valent iron (Fe0) has been used for the activation of PS (Fe0/PS) recently. However, the process exhibits a significant drawback of slow release of Fe2+ from Fe0, resulting in low efficiency of the approach as Fe2+ is the primary species for the PS activation. In this study, a weak magnetic field was utilized to pre-treat Fe0 for PS activation (pre-Fe0/PS) based on the magnetic memory of iron. The efficiency of the pre-Fe0/PS process was tested on the degradation of NB in simulated groundwater under anoxic conditions. The NB removal in the pre-Fe0/PS process was significantly enhanced compared with that in the Fe0/PS process. The effect of Fe0, PS, and NB concentration on the NB degradation was investigated. The influence of single inorganic ions, anion couples and humic acids as ubiquitous species in groundwater on the NB removal in the pre-Fe0/PS and Fe0/PS processes were studied and discussed. A column filled with pre-Fe0 was designed to test the NB removal in the pre-Fe0/PS process in a continuous-flow mode. The experimental results indicated that pre-Fe0/PS is a promising approach for the remediation of groundwater with high NB concentration.

Diclofenac sodium (DCF) is frequently detected as a non-steroidal pharmaceutical in the aquatic environment. In this study, the degradation of DCF in two heterogeneous systems, pre-magnetization Fe0/H2O2 (Pre-Fe0/H2O2) and Fe0/H2O2 system, was comparably studied. Our findings proved that Pre-Fe0 could significantly improve the degradation and dechlorination of DCF due to the change of Fe0 characteristics after pre-magnetization. Compared with Fe0/H2O2 process, Pre-Fe0/H2O2 process has 2.1-7.0 times higher rate constant for DCF degradation at different H2O2 dosages (0.25-2.0 mM), initial pH (3.0-6.0) and Fe0 dosages (0.25-1.5 mM). The characterizations by X-ray Photoelectron Spectroscopy and Electron Paramagnetic Resonance confirmed that the enhancement attributed to the increase of Fe0 corrosion and fast generation of OH. In addition, preliminary degradation mechanism was elucidated by major products identification using UPLC-MS, through which the degradation intermediates, such as 4-hydroxy-diclofenac or 5-hydroxydiclofenac, 2,6-dichloroaniline, phenylacetic acid, 1,3-dichlorobenzene and 2-aminophenylacetic acid were identified. Hydroxylation, decarboxylation, CN bond cleavage and ring-opening involving the attack of OH or other substances, were the main degradation mechanism. Therefore, Pre-Fe0/H2O2 process, which does not need extra energy and costly reagents, is an efficient and environmental-friendly process to degrade DCF.

Sulfamethazine (SMT) is widely used in human and veterinary medicine as growth promoters and antibacterial drugs and it can pose potential threats to human and ecosystem health. In this study, removal of SMT by ultrasound pre-magnetized Fe0/PS process was investigated for the first time. Degradation rate for removing SMT increased 3.3 folds and the synergy factor increased from 1.2 to 2.7 compared with US/Fe0/PS process. Affecting factors such as pH (3–10), Fe0 dosage (0–0.8 mM) and initial SMT concentration (0–10 mg L−1) were studied. Stronger signals of DMPO–OH and DMPO–SO4 adduct also illustrated more and faster SO4 − and OH radicals produced in the system. FeOOH was detected through the mossbauer spectrum which could both enhance the catalysis of H2O2 and activation of PS. The intermediates of the SMT degradation were investigated, and a degradation pathway was proposed. Higher correlation factor (△k and △S) in US/pre-magn-Fe0/PS system illustrated the good synergistic effect between US input power and magnetic field. Moreover, the process could efficiently remove SMT in municipal wastewater and keep pH neutral. So, US/pre-magn-Fe0/PS process is a energy saving and promising approach to remove antibiotics in real wastewater.

The oxygen reduction reaction (ORR) activated by Fe

Sulfide-modified zero-valent iron (S-Fe0) is regarded as a promising method to enhance the catalytic activity of Fe0 for peroxymonosulfate (PMS) activation. However, the roles of sulfidation and the application of the sulfidation treatment method are worth to further investigation. In our study, the effects of the S/Fe ratio, Fe0 dosage, and initial pH on sulfadiazine (SDZ) removal were investigated. The characterization of S-Fe0 with SEM, XPS, contact angle and Tafel analysis confirmed that the formation of sulfur species on the Fe0 surface could enhance the catalytic performance of Fe0. S2− played the major role and SO32- played the minor role in accelerating the conversion of Fe3+ to Fe2+. EPR tests, radical quenching and quantitative determination experiments identified •OH as playing the major role and SO4•− also playing an important role in SDZ removal in S-Fe0/PMS system. Sulfidation produced no notable change in the role of •OH and SO4•−. A possible degradation pathway of SDZ was proposed. Effect of sulfidation on various sizes of Fe0 was also studied which demonstrated that the smaller sizes of Fe0 (

The Fe2+/peroxymonosulfate (PMS) process always faced the major drawbacks of slow Fe2+ regeneration, reagent waste and strict pH requirement. Significant synergy was found by combining the visible light driven g-C3N4 photocatalysis with Fe2+(or Fe3+)/PMS at very low amount of reagent dosages. The synergistic mechanisms were investigated systematically. It was found that visible light played a minor role and the photoelectrons excited from g-C3N4 played the dominant role in the fast regeneration of Fe2+, and iron species should be the dominant activator for PMS compared with g-C3N4 in the combined process. For the complete degradation of 0.01 mM Bisphenol A (BPA), the consumption of PMS and Fe2+ in the combined process accounted for only 1/27 and 1/198 as that consumed in Fe2+/PMS process. The O2•–, 1O2 and Fe(IV) were found to be the dominant reactive species in Fe2+/PMS, while •OH was more preferably and continuously produced in the combined process. Moreover, the combined process showed significant advantages to maintain high efficiency over a wide pH range (3.0 ∼ 8.5) and to degrade pollutants with high concentrations. Stronger mineralization capability was also achieved by the combined process than the inclusive processes. Two degradation pathways of BPA degradation were proposed based on identifying the intermediates.

An efficient heterogeneous catalyst, pre-magnetized Fe 0 (pre-Fe 0 ) could significantly activate persulfate (PS) to remove Rhodamine B (RhB). The effect of pH, Fe 0 and PS dose on the RhB removal in the pre-Fe 0 /PS and Fe 0 /PS processes were investigated, and optimized by response surface methodology (RSM) to analyze the rate constants of the RhB removal in the pre-Fe 0 /PS process and Fe 0 /PS process ( f ). High RhB removal was obtained at low pH and high dose of Fe 0 and PS in both systems. Low Fe 0 and high PS dose and large pH would result in big value of f , and the simulated maximum f of 44.3 was achieved at 2 mM Fe 0 , 16 mM PS and pH 9. The synergetic factor of pre-Fe 0 /PS (45.6) was larger than that of Fe 0 /PS (21.4). The pre-Fe 0 /PS process presented 2.1–37.5 folds enhancement than the Fe 0 /PS process for the degradation of RhB. The RhB removal in the pre-Fe 0 /PS process was 1.5–11.2 folds enhancement than that of the Fe 0 /PS process in the presence of different anions and cations. Scanning Electron Microscope (SEM) results and the larger intensity of DMPO-SO 4 − adduct signal in the Electron Paramagnetic Resonance (EPR) confirmed the primary role of sulfate radicals generated from the reaction of PS with Fe 0 in the contaminant degradation. The pre-Fe 0 /PS process exhibited advantages over other processes to remove RhB in terms of contaminant removal, working pH range and chemical dose. Therefore, the pre-Fe 0 /PS process is a cost-effective approach for degrading RhB.

Nowadays, Fenton (Fe2+/H2O2) process is increasingly applied to wastewater treatment, however, the treatment efficiency would be inhibited largely when treated salty wastewater. To overcome this limitation, pre-magnetization (pre-magn-Fe0)/H2O2 process was investigated to treat salty wastewater, which could enhance the degradation rate of organic pollutants (1.2–171.2 folds enhancement) and reduce reagents dosage (save 75% H2O2) in salty system compared with Fe0/H2O2 process, using Orange G as the target pollutant and Na2SO4 as the model salty system. The characterizations by SEM, XRD and XPS and the intensity of DMPO–OH adduct signals in different processes confirmed this enhancement attributed to the increase of corrosion of Fe0 inducing fast catalysis of H2O2 and generation of hydroxyl radicals. Pre-magn-Fe0/H2O2 process could also have 5.9, 26.4 and 93.7 folds enhancement in NaCl, NaNO3 and Na2HPO4 salty system, respectively. Meanwhile, pre-magn-Fe0/H2O2 process could keep close performance in Na2SO4 and NaCl salty systems and have better performance in NaNO3 and Na2HPO4 salty systems than Fenton process. Pre-magn-Fe0/H2O2 process also had remarkable improvement (1.1–5.3 folds) on the removal of many refractory contaminants in salty system. Furthermore, it could also keep good performance in real reverse osmosis concentrated wastewater and petrochemical wastewater. Therefore, pre-magn-Fe0/H2O2 process is a more cost-effective process to treat salty wastewater, which could have not only improved performance than conventional system and Fe0/H2O2 process, but also good performance as Fenton process.

Sulfide-modified zero-valent iron (S-Fe0) has been regarded as a promising method to enhance the catalytic activity of Fe0. Therefore, peracetic acid (PAA) firstly activated by S-Fe0 was conducted to remove sulfamethazine (SMT) in this study. Only 13.1% SMT could be removed within 60 min in Fe0/PAA system while 86.5% SMT could be removed within 60 min in S-Fe0/PAA system at condition of [PAA] = 100 μΜ, [S-Fe0] = 20 mg/L, [SMT] = 5 mg/L, pH = 4.0. The effect of S/Fe ratio, S-Fe0 dosage, PAA concentration and initial pH on SMT removal were investigated. The characterization of S-Fe0 such as SEM, XPS, contact angle and Tafel confirmed that the formation of sulfur species on Fe0 surface could enhance the catalytic performance of Fe0. S2− played the major role and SO32- played the minor role in accelerating the conversion of Fe3+ to Fe2+. •OH and R-O• exhibited 67.1% and 32.5% contribution for SMT removal in S-Fe0/PAA system, respectively. The possible degradation pathway of SMT was also proposed. Cl− and HCO3– had a negligible adverse effect on SMT removal in S-Fe0/PAA system indicating the good adaptability of inorganic ions. In addition, S-Fe0/PAA system had the good recycle ability of S-Fe0 and showed a better performance in removing SMT in the natural fresh water. Therefore, this study notably showed the potential applicability of S-Fe0/PAA system in degrading SMT in natural fresh water.

Peracetic acid (PAA) was successfully activated by UV and Fe0 to degrade sulfamethazine (SMT) in this study. UV/Fe0/PAA system not only could enhance SMT removal efficiency but also could reduce the energy consumption in comparison with UV, Fe0/PAA and UV/PAA systems. The R O• radical was the main radical for the degradation of SMT in UV/Fe0/PAA system and photolysis, •OH and R-O• exhibited 15.6%, 17.6% and 66.8% contribution for SMT degradation, respectively. Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscope (SEM), and X-ray photoelectron spectroscopy (XPS) were conducted to investigate the characterization of Fe0 after reaction in UV/Fe0/PAA system. The possible SMT degradation pathway was also proposed. Affecting factors such as Fe0 dosage (0–0.2 g L−1), PAA concentration (0–200 μM) and initial pH (3–9) were also studied. Cl−, NO3-, SO42- and HCO3- had a negligible adverse effect on SMT removal in this system indicating the good adaptability to inorganic ions. In addition, UV/Fe0/PAA system had the good recycle ability of Fe0 and showed a good performance in removing antibiotic in the nature fresh water. Therefore, this study notably improved the knowledge of PAA activated by Fe0 and UV and showed the potential applicability of UV/Fe0/PAA system in degrading antibiotics in nature fresh water.

Coupling adsorption and advanced oxidation processes (AOPs), two widely used wastewater treatment technologies, has been an attractive idea pursued by many researchers. Although many studies have demonstrated that adsorption could facilitate AOPs such as persulfate (PS) activation, the inhibitory effect of adsorption on PS activation was ignored. In this work, both as adsorbents and catalysts, sucrose-derived carbon xerogels (CXs) were prepared to investigate the effect of adsorption on PS activation. The results showed that the specific surface areas (SSAs) and N contents of CXs varied with the HCl concentration. Among different CXs, CX-0.5 with the highest SSA and N content exhibited the highest adsorption capacity and catalytic activity for acid orange 7 (AO7) degradation by simultaneously adding CXs and PS, where the promoting effect of adsorption on catalysis was found. Quenching tests demonstrated that degradation of pollutants in the CX-0.5/PS system were mainly by nonradical pathway. However, the catalytic activities of CXs were inhibited after the pre-adsorption of AO7 on CXs. Comparing the molecular structures of several compounds, the sulfonic group on chemicals might play a crucial role in the inhibitory effect. We concluded that if CXs have the same adsorption sites for pollutants and PS, adsorption of pollutants would inhibit the catalytic PS activation. These findings provided a comprehensive understanding of the effect of adsorption on AOPs, which had a significant guidance for future researches and applications.

This study demonstrated a fast and efficient treatment of highly salty wastewater in a hydroxylamine (HA) enhanced Fe0/H2O2 system. The apparent rate constant (k) in Fe0-HA/H2O2 system could achieve 7.9 times higher than that in Fe0/H2O2 system using tartrazine as the target pollutant and Na2SO4 as the model salt. The value of k for removing tartrazine in the salty system by Fe0-HA/H2O2 process even 12.7 times higher than that in the conventional system which was attributed to the faster Fe0 corrosion rate in the salty system. Meanwhile, Fe0-HA/H2O2 process could obtain remarkable performance for highly salty wastewater treatment at wide salt concentration levels (0–0.2 M) and could also widen the application of pH to neutral pH. The characterizations by SEM and XPS, the intensity of DMPO–OH adduct signals and detection of Fe2+ and Fe3+ ions in different systems confirmed the good performance was owing to the faster Fe0 corrosion rate in the salty system and acceleration of Fe3+/Fe2+ recycle owing the addition of HA inducing fast catalysis of H2O2 and generation of hydroxyl radicals. Moreover, the value of k for removing tartrazine in various types of salty system by Fe0-HA/H2O2 process was 2.9–30.8 times larger than Fe0/H2O2 process demonstrating the good suitability of Fe0-HA/H2O2 process at various types of salty system. Therefore, this study will shed lights on the reactivity of the Fe0-HA/H2O2 system and provide an alternative pathway for removal of salty wastewater.

Highly efficient persulfate oxidation process activated with pre-magnetization Fe0 (pre-magnetization Fe0/PS) was employed to degrade Orange anthraquinone dye at different Fe0 dosages (1–8 mmol/L), initial pH levels (3–10) and PS dosages (2–8 mmol/L). Pre-magnetization Fe0/PS possessed 8.4–119.6 folds enhancement in degradation rate and could widen pH range and save 90% Fe0 and PS dosage when compared with conventional Fe0/PS process. And this effect was ascribed to the change of Fe0 characteristics after pre-magnetization. This significant improvement was also observed on the degradation of many refractory contaminants of tartrazine, phenol, 2,4-dichlorophenol (2,4-DCP), p-chlorophenol, chlorobenzene, nitrobenzene, p-nitrophenol and p-nitrchlorobenzene, which were 2.8–11.4 folds of those by Fe0/PS process. Pre-magnetization Fe0/PS is a more promising process since it does not require any change of the present water and wastewater treatment process, and does not need an extra energy source, costly materials, and complex equipment.

Advanced oxidation processes (AOPs) has great potential for wastewater treatment, but still limited in application due to their high cost for extensive reagent and energy demand, and restricted working conditions (e.g. narrow pH range). Here, AOPs based on pre-magnetization Fe0 (Pre-Fe0) were found to be highly efficient at wider pH conditions, partly solved the above problems. After pre-magnetization, Fe0 was supposed to be easier to be corroded, which remarkably improved processes (e.g., Pre-Fe0/H2O2, Pre-Fe0/K2S2O8) efficiency several to >100 folds and valid for many refractory contaminants (e.g. dyes, phenols, organic acids), compared with that conventional processes without pre-magnetization. Moreover, the process efficiency could be sustained by the recovery of magnetism of Pre-Fe0. Thus AOPs based on pre-Fe0 is more promising to take place of conventional Fe0 based AOPs since it is more efficient but does not require any change of the present water and wastewater treatment process, and does not need an extra energy source, costly materials, and complex equipment.

The abatement of chlorophenols is of great environmental importance. Though Fe0 can activate persulfate (PS) to improve performance, our findings proved that pre-magnetized Fe0 (Pre-Fe0) could significantly enhanced the degradation and dechlorination of 2,4-dichlorophenol (2,4-DCP), and this Pre-Fe0/PS process was more efficient than Fe(II)/PS. The Fe0 before and after magnetization was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), suggesting the acceleration of Fe2+ release after magnetization. The effects of some important operating parameters such as Fe0 dosage, PS dosage, pH, and initial 2,4-DCP concentration on the 2,4-DCP degradation and dechlorination by Pre-Fe0/PS were investigated and compared with that of Fe0/PS, observing a 1.9–5.2-fold enhancement in the degradation rate of 2,4-DCP. Although SO4− was the dominant active species responsible for 2,4-DCP degradation in two processes, pre-magnetization could promote more OH generation. Identified by GC–MS and IC, the degradation intermediates such as 4-chlorophenol (4-CP), 2-chlorophenol (2-CP), phenol, and some carboxylic acids were detected, and possible degradation pathway was proposed. This Pre-Fe0/PS process was also efficient for 4-chlorophenol and chlorobenzene degradation, obtaining a 5.2 and 3.2 folds enhancement, respectively. This work demonstrated that such a Pre-Fe0/PS would be very promising and environmental-friendly for organics degradation and dechlorination since pre-magnetization required no extra energy source while the introduction of Pre-Fe0 was rather simple and no need to change the present treatment system.

Due to the high demand for structural reliability, Structural Health Monitoring (SHM) has drawn intensive attention. Fiber Bragg Grating (FBG) sensor with many advantages has become one of the most promising sensing elements in this area. However, the axial sensitivity, as the main parameter of the FBG sensor, has received little attention. This paper tried to explore the influence of the ply stacking of composite on the axial sensitivity of the FBG sensor. The calibration test, the repeatability test, and the influence test had been carried out in this paper. Thereinto, the theoretical axial strain sensitivity of the FBG sensor (1.06312 pm/μe) was obtained by the calibration test. The repeatability test verified that the effect of preparation and operating conditions on the test results could be ignored, while the influence test was used to demonstrate that the three kinds of stacking could affect the axial sensitivities of the FBG sensors. The experimental results showed that: the axial sensitivities of two FBG sensors embedded between 45°/45° layers were equal. But, a difference was observed between the FBG sensors embedded between the layers of 0°/0°, 45°/45°, and 90°/90°. The maximum relative difference was about 2.587%. It indicated that the laying sequence of the FBG sensor influenced the axial sensitivity of the FBG sensor. Subsequently, the ANSYS software was adopted to simulate the deformation distribution of the sensor under a tensile load of 800N. A good agreement was observed between the numerical prediction and experimental results.

2,4-dichlorophenoxyacetic acid (2,4-D)'s removal was studied in the photoelectrocatalysis/photoelectro-Fenton (PEC-PEF) process with Blue-TiO2 nanotube (Blue-TNTs) and modified carbon felt as the anode and cathode, respectively. Polytetrafluoroethylene and carbon black were used to modify the carbon felt to improve the efficiency of H2O2 production. The impact factors of 2,4-D degradation in the PEC-PEF process were investigated, including Fe2+ dose, bias potential, light intensity and the concentration of 2,4-D. It was found that the removal of 2,4-D increased firstly and then decreased with the increase of Fe2+ dose. Bias potential and light intensity played a positive role on 2,4-D removal, while the opposite was right for the impact of 2,4-D initial concentration. Compared with stainless steel, the modified carbon felt was found more efficient for 2,4-D removal as it could generate more H2O2. Reactive species for 2,4-D degradation was studied and it was proved that •OH radical rather than holes was mainly responsible for the removal. Such PEC-PEF process offered a promising alternative for herbicide-containing wastewater treatment.

Molybdenum sulfide (MoS2) was for the first time used as a co-catalyst to enhance the performance of Fe0 based heterogeneous electro-Fenton (Fe0-EF) process for the degradation of sulfamethazine (SMT), which was belonging to the sulfonamide family and extensively used as growth promoters and antibacterial drugs. Compared with Fe0-EF process, MoS2/Fe0-EF process could enhance the rate constant of SMT degradation 2 times under the optimal conditions of current 50 mA, MoS2 dosage 0.02 g L-1, Fe0 dosage 0.224 g L-1, and initial pH 4, in which SMT could be completely degraded within 10 min while 42% TOC could be achieved after 60 min reaction. The role of MoS2 as co-catalyst in MoS2/Fe0-EF process and Fe2+/Fe3+ cycle was supported by iron elemental analysis, transmission election microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) characterizations. Owing to the characteristics of co-catalysis, MoS2 could greatly facilitate the Fe3+/Fe2+ recycle reaction by the exposed Mo4+ active sites, which significantly promoted the decomposition of H2O2 that generated in Fe0-EF system and improved the generation of hydroxyl radical. Besides, a possible degradation pathway of SMT was proposed and the stability of MoS2/Fe0-EF process for SMT removal and TOC mineralization was certified base on five consecutive runs. The real wastewater test and energy consumption and economic analysis confirmed its advantage and cost-effectiveness for application. In all, this study provides a new perspective for improving heterogeneous Fe0-EF process with MoS2 for highly efficient and rapid degradation of antibiotics.

A new modified Fenton-like process (pre-magnetization Fe 0 /H 2 O 2 ) was employed to enhance the degradation of organic pollutants and reduce reagents dosage, using azo dye of tartrazine as the model. Compared with Fe 0 /H 2 O 2 process, pre-magnetization Fe 0 /H 2 O 2 process could have 1.3–11.2 folds enhancement in the degradation rate of tartrazine at different Fe 0 dosages (0.5–4 mmol), initial pH levels (2–6.5) and H 2 O 2 dosages (0.25–2 mmol) owing to the change of Fe 0 characteristics after pre-magnetization. The contact angle of pre-magnetization Fe 0 decreased from 58.4° to 19.8° enhancing the hydrophilicity and BET increased from 0.15 m 2 /g to 1.94 m 2 /g, which improved the corrosion of Fe 0 and accelerated the generation of Fe 2+ . Similar to the case of tartrazine, pre-magnetization Fe 0 /H 2 O 2 process had remarkable improvement on many refractory contaminants. The degradation rate constant of methyl orange, orange, methylene blue, 2,4-dichlorophenol (2,4-DCP), acetylsalicylic acid, phenol and tetracycline by pre-magnetization Fe 0 /H 2 O 2 process was 5.2, 21.3, 9.2, 5.6, 12.3, 9.5 and 3 folds of that by Fe 0 /H 2 O 2 process, respectively. The “magnetic memory” of pre-magnetization Fe 0 could last 24 h which was suitable for off-site application, and the lost some or all “magnetic memory” could be recovered after second pre-magnetization. Pre-magnetization Fe 0 /H 2 O 2 is a more promising and highly efficient Fenton process since it does not require any change of the present water and wastewater treatment process, and does not need an extra energy source and complex equipment but can widen pH range and save more than 75% Fe 0 and H 2 O 2 dosages.

Ethylenediaminetetraacetic acid (EDTA) was used to enhance pre-magnetized Fe0/H2O2 process for sulfamethazine (SMT) removal at neutral pH. Only 19.4% SMT was removed in pre-Fe0/H2O2 within 60 min at neutral pH while 90.6% SMT was removed after addition of 0.1 mM EDTA. Meanwhile, k (103) value for SMT removal in pre-Fe0-EDTA/H2O2 was 1.3 folds larger than in Fe0-EDTA/H2O2. Single-factor experiments and response surface methodology (RSM) were used to optimize the system for SMT removal. Maximum k (103) value was 81.4 min−1 obtainning at conditions of Fe0 0.28 g L−1, EDTA 0.13 mM, and H2O2 36.2 μM. The presence of EDTA and magnetization could inhibit the generation of iron oxides, reduce the contact angle of Fe0, and improve the recovery of surface FeII which induced a faster catalytic decomposition of H2O2. The system could still achieve good performance for removing SMT after six consecutive reaction cycles. These results demonstrated that pre-Fe0-EDTA/H2O2 system has the potential application for wastewater treatment.

In this study, UV irradiated photochemical reactions of oxalate (Ox) with premagnetized-Fe0 (pre- Fe0) as the catalyst was used to degrade sulfamethazine (SMT). Magnetic field promoted the release of iron ion from Fe0 thus enhanced SMT and Ox removal in UV/pre- Fe0/Ox process. X-ray photoelectron spectroscopy demonstrated that the presence of UV and Ox promoted the transformation of Fe3+ to Fe2+ on Fe0, which enhanced the surface bound •OH (•OHsurf) generation. Ox inhibited the formation of iron (hydro)xides and enhanced the hydroxylation of Fe0 surface. •OHsurf was mainly responsible for SMT removal (44%), while UV direct photolysis and •OH in the solution both caused around 28% SMT removal. The process with Ox exhibited much higher efficiency in SMT degradation than that added with H3PO4, citric acid and ethylenediaminetetraacetic acid, which greatly expanded the chelate-modified Fenton processes and their treatment efficiency.

Coronavirus disease (COVID-19), caused by SARS-CoV-2, evolved into a global pandemic in 2020, and the outbreak has taken an enormous toll on individuals, families, communities and societies around the world. One practical and effective strategy is to implement rapid case identification based on a rapid testing to respond to this public health crisis. Currently, the available technologies used for rapid diagnostics include RT-PCR, RT-LAMP, ELISA and NGS. Still, due to their different limitations, they are not well suited for rapid diagnosis in a variety of locations. Paper-based devices are alternative approaches to achieve rapid diagnosis, which are cost-effective, highly selective, sensitive, portable, and easy-to-use. In addition to individual virus screening, wastewater-based epidemiology has been emerged to be an effective way for early warning of outbreak within the population, which tests genomic viral sequence to reflect information on the spread and distribution of the virus because SARS-CoV-2 can be shed into wastewater through the feces and urine from infected population. In this paper, we describe paper-based device as a low-cost and rapid sensor for testing of virus for both diagnosis and early warning of outbreak for wastewater-based epidemiology. Most importantly, the device has great potential for real-time detection in the field, without any advanced facilities and well-trained skilled personnel, and provides early warning or timely intervention of an outbreak of pandemic.

The activation rate of oxygen by zero-valent iron (Fe°) was very low. In this study, ethylenediaminetetraacetic acid (EDTA), oxalate (Ox), and phosphate ions (Na2HPO4) were used to enhance the oxygen activation by Fe° for sulfamethazine (SMT) removal. The addition of these ligands could significantly enhance the SMT degradation. SMT removal was improved from 10.5 % in the Fe° system (360 min) to 70.3 %, 85.2 % and 77.8 % in the Fe°/EDTA (60 min), Fe°/Ox (180 min) and Fe°/phosphate (360 min) systems, respectively. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX), Fourier transform infrared reflection (FTIR), contact angle and X-ray photoelectron spectra (XPS) of Fe° in different systems were recorded. The presence of chelating agents hydroxylated Fe°, inhibited the iron oxide formation on the Fe° surface and promoted iron ion release from the solid. Moreover, the agents improved the recovery of surface Fe2+ which could subsequently enhance the activation of O2 to produce more H2O2 and reactive oxygen radicals for SMT removal. OH radical produced mainly through H2O2 decomposition was primarily responsible for removing SMT in all three systems. The Fe° system added with chelating agents is a new and promising approach for treating wastewaters containing ligands.