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Biosensors and nanoscale analytical tools have shown huge growth in literature in the past 20 years, with a large number of reports on the topic of ‘ultrasensitive’, ‘cost-effective’, and ‘early detection’ tools with a potential of ‘mass-production’ cited on the web of science. Yet none of these tools are commercially available in the market or practically viable for mass production and use in pandemic diseases such as coronavirus disease 2019 (COVID-19). In this context, we review the technological challenges and opportunities of current bio/chemical sensors and analytical tools by critically analyzing the bottlenecks which have hindered the implementation of advanced sensing technologies in pandemic diseases. We also describe in brief COVID-19 by comparing it with other pandemic strains such as that of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) for the identification of features that enable biosensing. Moreover, we discuss visualization and characterization tools that can potentially be used not only for sensing applications but also to assist in speeding up the drug discovery and vaccine development process. Furthermore, we discuss the emerging monitoring mechanism, namely wastewater-based epidemiology, for early warning of the outbreak, focusing on sensors for rapid and on-site analysis of SARS-CoV2 in sewage. To conclude, we provide holistic insights into challenges associated with the quick translation of sensing technologies, policies, ethical issues, technology adoption, and an overall outlook of the role of the sensing technologies in pandemics.

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.

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.

This study presented the efficient removal of tartrazine, a typical biorefractory dye, in a heterogeneous photochemical Fenton-like system adopting Fe0 and oxalate (Ox) (UV/Fe0/Ox). Only 47.4% tartrazine could be removed within 60 min with a UV/Fe0 system. The addition of Ox could significantly enhance the removal of tartrazine to 72.4% within only 20 min with the UV/Fe0/Ox system. The effects of various factors, such as the Fe0 dose (0–0.8 g/L), Ox dose (0–2 mM), initial pH (2–6), and initial tartrazine concentration (2–30 mg/L), on the removal of tartrazine were examined. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and Mossbauer spectroscopy were conducted to explore the mechanism by which oxalate enhances the performance of the UV/Fe0 system. Ox could inhibit the formation of iron (hydro)xides on the Fe0 surface, thus guaranteeing the reactivity of Fe0 during the reaction. Compared with Fe2O3, FeS, and Fe3O4, Fe0 was a good heterogeneous iron catalyst for the photolysis of tartrazine with the Ox system. Compared with H3PO4, nitrilotriacetic acid, and ethylenediaminetetraacetic acid, Ox was also a good photolysis chelating agent. The UV/Fe0/Ox system could also maintain fast tartrazine removal after five consecutive runs without the addition of Fe0, indicating the good stability of Fe0.

Antimicrobial resistance (AMR) in the environment is a global concern for public health and recent studies have shown that various soil pollutants (e.g. heavy metals, petroleum hydrocarbons) can cause the emergence of antibiotic-resistant bacteria and antibiotic-resistance genes in the soil. This emergence of AMR in soil is therefore prompting the research community for the development of rapid and real-time monitoring tools to better understand the source, fate and transfer pathway of AMR in contaminated soils. In this respect, the recent development of rapid sensors-based methods has been critically reviewed. The analytical performance of each sensing technique along with their advantages and limitations is further discussed to inform future development needs for the next generation sensors that would allow rapid and multiplexed detection of AMR in contaminated soils. By doing so, it would assist the decision making during remediation project and provide crucial insights into the risk assessment for contaminated sites.

Public health is attracting increasing attention due to the current global pandemic, and wastewater-based epidemiology (WBE) has emerged as a powerful tool for monitoring of public health by analysis of a variety of biomarkers (e.g., chemicals and pathogens) in wastewater. Rapid development of WBE requires rapid and on-site analytical tools for monitoring of sewage biomarkers to provide immediate decision and intervention. Biosensors have been demonstrated to be highly sensitive and selective tools for the analysis of sewage biomarkers due to their fast response, ease-to-use, low cost and the potential for field-testing. This paper presents biosensors as effective tools for wastewater analysis of potential biomarkers and monitoring of public health via WBE. In particular, we discuss the use of sewage sensors for rapid detection of a range of targets, including rapid monitoring of community-wide illicit drug consumption and pathogens for early warning of infectious diseases outbreaks. Finally, we provide a perspective on the future use of the biosensor technology for WBE to enable rapid on-site monitoring of sewage, which will provide nearly real-time data for public health assessment and effective intervention.

In this study, we report long-term measurements of Polycyclic Aromatic Hydrocarbons (PAHs) collected from the surface waters of seven river basins across China. The spatial distribution, source apportionment, and potential risk assessment of 16 USEPA designated PAHs were reviewed. Water samples were collected from the Songhua River Basin (SRB), Yangtze River Basin (YtRB), Yellow River Basin (YRB), Pearl River Basin (PRB), Huai River Basin (HuRB), Liao River Basin (LRB), and Hai River Basin (HRB). Our results show that the total PAH concentration in the surface waters from primary river basins ranged from 99.60 to 3805.00 ng/L in the dry season with a geometric mean value of 797.96 ng/L, and from 235.84 to 11,812.20 ng/L in the wet season with a geometric mean value of 820.75 ng/L. In the river basins examined, the geometric concentration of Σ16PAHs ranged from 215.50 ng/L to 1969.91 ng/L, with a median value of 837.73 ng/L. In the decreasing order across seven river basins, the geometric mean Σ16PAHs content varied as: SRB (1969.91 ng/L) > LRB (1155.87 ng/L) > YRB (884.06 ng/L) > PRB (837.73 ng/L) > HuRB (559.10 ng/L) > HRB (261.84 ng/L) > YtRB (215.50 ng/L). Moreover, the total PAH concentration was slightly lower in the dry season than in the wet season. The pollution level of PAHs in North China was higher than in South China. No discernible temporal trend was observed in Σ16PAHs observed in China during the past decade. Overall, PAHs designated for priority control measures were Nap, Phe, and Flu; as 2- and 3-ring PAHs were the dominant compounds in the river basins, accounting for 33.7% and 36.9% of the total PAHs, respectively. Source analysis revealed that coal and biomass combustion were the main contributors to PAHs in the river basins, accounting for about 40% of the total. The geometric mean concentrations of individual PAH, including BaP, BaA, BbF, BkF, Ind, and DaA in some water samples exceeded the environmental quality standards of both China and the United States. According to metrics describing eco-toxicity from water contamination, the river basin was at moderate risk in YtRB, YRB, PRB, HuRB, and HRB, but at high risk in SRB and LRB, suggesting that targeted control measures or remedial actions should be undertaken to decrease PAH contamination in China.

The abuse of illicit drugs usually associated with dramatic crimes may cause significant problems for the whole society. Wastewater-based epidemiology (WBE) has been demonstrated to be a novel and cost-effective way to evaluate the abuse of illicit drugs at the community level, and has been used as a routine method for monitoring and played a significant role for combating the crimes in some countries, e.g. China. The method can also provide temporal and spatial variation of drugs of abuse. The detection methods mainly remain on the conventional liquid chromatography coupled with mass spectrometry, which is extremely sensitive and selective, however needs advanced facility and well-trained personals, thus limit it in the lab. As an alternative, sensors have emerged to be a powerful analytical tool for a wide spectrum of analytes, in particular aptamer sensors (aptasensors) have attracted increasing attention and could act as an efficient tool in this field due to the excellent characteristics of selectivity, sensitivity, low cost, miniaturization, easy-to-use, and automation. In this review, we will briefly introduce the context, specific assessment process and applications of WBE and the recent progress of illicit drug aptasensors, in particular focusing on optical and electrochemical sensors. We then highlight several recent aptasensors for illicit drugs in new technology integration and discuss the feasibility of these aptasensor for WBE. We will summarize the challenges and propose our insights and opportunity on aptasensor for WBE to evaluate community-wide drug use trends and public health., Graphical abstract Image 1, Highlights • The concept of wastewater-based drug epidemiology (WBE) was outlined. • The recent advances of nanomaterial-based aptasensors for illicit drugs detection are described, focusing on optical and electrochemical strategies. • The emerging DNA technology are discussed for drug detection as well as engineering of aptasensors for portable assay. • The feasibility of illicit drug aptasensors for WBE are discussed. • The future trends and our insights on aptasensors for illicit drug are provided.

Background Environmental behavior of pesticide in soils is a key current research focus. Studying the adsorption characteristics of pesticides in soils as a parameter for evaluating the risk of groundwater pollution by pesticides is commonly applied in agriculture. Results To provide a theoretical basis for environment risk assessment and pollution remediation, the thermodynamics and kinetics of the equilibrium of atrazine adsorption in the Three-Gorges Reservoir area were assessed and analyzed via batch experiments. Results showed that the sorption of atrazine was an exothermic and spontaneous process at temperatures of 298–318 K. Atrazine was more easily adsorbed by soils at concentrations of 0–30 mg L−1, with low-temperature adsorption being more effective than high-temperature adsorption. The adsorption of atrazine to the two assessed soils was well fitted by the Freundlich and Langmuir models. The adsorption kinetics of atrazine in soils were consistent with the quasi-second-order kinetic model and intraparticle diffusion was found not to be the only control step. The monolayer adsorption occurred with non-uniform energy distribution on the soil surface, indicating that the adsorption of atrazine by the two kinds of soil was controlled by internal diffusion surface adsorption and liquid film diffusion, leading to the complexity of its adsorption kinetics. The values of standard free energy $$\Delta rG_{m}^{0}$$ΔrGm0 $$\Delta {\text{r}}H_{m}^{0}$$ΔrHm0) indicated that the adsorption was exothermic. Conclusions Atrazine exhibited a weak adsorption capacity in both soils, indicating it is highly mobile in the soil–water environment and can easily cause groundwater pollution. Therefore, much attention should be paid to the environmental behavior of pesticide soil moisture fluctuations, potentially leading to the broad transfer and spread of pollution.

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.

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.

Long-term (2004–2018) persistent organic pollutants (POPs) data were collected for urban soils of China. The dataset included concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in soils, comprising a range of different compounds. Understanding the source of OCP and PCB pollution is an important step in controlling and reducing pollution levels in the environment. This study aimed to analyze the spatio-temporal distribution, pollution sources, and potential health risks of OCPs and PCBs in urban soils in different regions of China. It was found that the total OCP concentrations ranged from 7.6 to 37331 μg/kg with a mean value of 2861 μg/kg, and PCBs concentrations ranged from 0.3 to 123467 μg/kg with a mean value of 4984 μg/kg. The highest OCP concentrations were observed in Beijing and Hebei, whereas the highest PCB concentrations were found in the Zhejiang province. The geographical distribution showed that the total mean concentration of POPs of urban soil was much higher in East China than in West China. According to the isomer ratios, about 64% of provinces and cities showed new sources of dichlorodiphenyltrichloroethane (DDT) input and dicofol input was found in 30% of China. Hexachlorocyclohexane (HCH) in urban soils was mainly derived from fresh usage of lindane (γ-HCH) in most regions of China. Lifetime carcinogenic and non-carcinogenic risks of OCPs and PCBs through ingestion, inhalation, and dermal contact indicated that PCBs in urban soils of China often exceeded safe levels. The total lifetime carcinogenic risk values of PCBs were higher than the individual lifetime acceptable risk level (10−4) in 64% of the studied regions and the non-carcinogenic risk values exceeded the target risk level (10−1) in 53% of the regions. The improved knowledge of the distribution and main pollution sources of POPs in urban soil of China as a result of this study can contribute to better decision-making support for soil pollution control and monitoring.

Low pH requirement is one of the biggest limitations of the application of traditional Fenton and electro-Fenton (EF) process because FeII/FeIII would precipitate at high pH. In this study, a flow-through EF system operated in batch recirculation mode was constructed. Nitrilotriacetic acid (NTA) was used as a chelating agent in the EF system (NTA/EF) to keep iron soluble at high pH values, producing OH by reaction of H2O2 generated in situ with FeIINTA that obtained by the reduction of FeIIINTA at the cathode. This flow-through NTA/EF system accelerated the mass transfer of target molecules to the electrode surface and showed high efficiency for phenol removal at pH 5–8 with rate constants (k) at around 0.26 min−1, higher than that of the batch test (k = 0.15 min−1) and EF process without NTA (k = 0.16 min−1). The influences of aeration rate, current, flow rate, Fe dose, the ratio of NTA to Fe, pH, and initial phenol concentration on the phenol removal were investigated. The system could be used for at least 3 times for phenol removal without obvious efficiency decline. The flow-through NTA/EF system is promising for the removal of organic contaminants in a wide pH range.

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.

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.

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.

Understanding the spatial distribution and controlling factors of soil organic carbon (SOC) at different scales is essential for an accurate estimation of soil organic carbon stocks. Furthermore, this understanding is vital for evaluating the impact of soil management on both soil quality and climate change. This study was conducted in a Loess revegetated small watershed and the effects of the topography and vegetation factors on the content and distribution of SOC at different soil depths were evaluated. Soil profiles (0–200 cm; n = 122) were sampled that represent six vegetation types (i.e., natural mixed forests, artificial mixed forests, artificial forests with a single tree species, shrubbery, and grassland) and four topographic factors (i.e., elevation, slope gradient, slope position, and slope aspect). The following results were obtained: (1) The mean SOC of the 200 cm soil profile ranged from 2.34 g kg−1 to 5.70 g kg−1, decreasing with increasing soil depth. (2) The interactions between vegetation type and topography and soil depth significantly impacted SOC (P

Pre-magnetized Fe0 (Pre-Fe0) was for the first time applied as heterogeneous catalyst to enhance the oxidation efficiency of electro-Fenton (EF) for the degradation of p-nitrophenol (PNP). The parameters including current, initial pH and pre-Fe0 dosage of Pre-Fe0/EF process were optimized and compared with other two processes (conventional Fe0/EF and electro-oxidation) to confirm its advantage. The rate constants of PNP removal were 1.40–3.82 folds of those by Fe0/EF process under various experimental conditions. The application of pre-Fe0 as catalyst could extend the working pH range from 3.0 to neutral conditions for PNP removal and reduce the Fe0 dosage from 2 to 0.5 mM corresponding to Fe0/EF, avoiding the second pollution of iron sludge. The superiority of Pre-Fe0/EF process was also verified to improve the degradation and mineralization of other phenols and antibiotics. Furthermore, a possible pathway of PNP degradation was revealed by the identification of intermediates and organic acids, and the possible mechanism of pre-Fe0 efficiently enhanced the EF efficiency was proposed. This work demonstrated that such a novel heterogeneous EF process using pre-Fe0 catalyst was clean and promising for the degradation of refractory organic pollutants.

International audience; The chlorinated phenoxy herbicide of 2,4-dichlorophenoxyacetic acid (2,4-D) was oxidized by thermally activated persulfate (TAP). This herbicide was studied for different persulfate dosages (0.97–7.29 g L−1), for varying initial pH levels (3–12) and temperatures (25–70 °C). Compared with Fe2+/PS, TAP could achieve a higher total organic carbon (TOC) removal under wider pH ranges of 3–12. Increasing the mole ratio of PS to 2,4-D favored for the decay of 2,4-D and the best performance was achieved at the ratio of 50. The 2,4-D degradation rate constant highly depended on the initial pH and temperature, in accordance with the Arrhenius model, with an apparent activation energy of 135.24 kJ mol−1. The study of scavenging radicals and the EPR confirmed the presence of both SO4− and OH. However, SO4− was the predominant oxidation radical for 2,4-D decay. The presence of both Cl− and CO32− inhibited the degradation of 2,4-D, whereas the effect of NO3− could be negligible. Verified by GC/MS, HPLC and ion chromatography, a possible degradation mechanism was proposed

2,4-dichlorophenoxyacetic acid (2,4-D) is one of the most applicable herbicides in the world, its residue in aquatic environment threatens the human health and ecosystems. In this study, for the first time, inexpensive Fe-C after pre-magnetization (Pre-Fe-C) was used as the heterogeneous catalyst to activate persulfate (PS) for 2,4-D degradation, proving that Pre-Fe-C could significantly improve the degradation and dechlorination. The results indicated the stability and reusability of Pre-Fe-C were much better than pre-magnetization Fe0 (Pre-Fe0), while the leaching iron ion was lower, indicating that using Pre-Fe-C not only reduced the post-treatment cost, but also enhanced the removal and dechlorination efficiency of 2,4-D. Several important parameters including initial pH, Fe-C dosage, PS concentration affecting 2,4-D degradation and dechlorination by Pre-Fe-C/PS were investigated and compared with that of Fe-C/PS, observing a 1.2-2.7 fold enhancement in the degradation rate of 2,4-D. The Fe-C and Pre-Fe-C were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and SEM-EDX-mapping, suggesting that the content of Fe and O changed more obviously after magnetization. The degradation intermediates, such as chloroquinol, 2-chlorophenol, were identified by a gas chromatography mass spectrometry (GC/MS) and an ion chromatography (IC), and a possible degradation pathway was proposed.

Efficient anode materials are essential to electrochemical advanced oxidation processes (EAOPs) for organic wastewater treatment. In this regard, blue TiO2 nanotube arrays (Blue-TNA) anode was prepared for the first time in formic acid electrolyte by electrochemical self-doping and applied for electrochemical degradation of contaminants. Characterized by XPS, Raman and Mott-Schottky curves, the formation of Ti3+ on Blue-TNA was confirmed. This anode was more efficient and had a higher hydroxyl radical production activity (1.7 × 10−14 M) than BDD (9.8 × 10-15 M), inducing a higher TOC and COD removal of 100 mg/L phenol with a lower energy consumption of 9.9 kW h/(kg COD) at current density 2.5 mA/cm2, pH 5 in 0.1 M Na2SO4, account for the lower accumulation of degradation intermediates. Both •OH and SO4•- were responsible for the degradation on Blue-TNA anode, while their contributions differed greatly with that of BDD, and could be affected and regulated by the operating parameters like current density, initial pH and Na2SO4 concentration. Blue-TNA anode represented a relative stable performance for 5 cycles degradation of 100 mg/L phenol for each cycle of 300 min, and such an oxidation capacity could be easily regenerated by electrochemical reduction in formic acid. Blue-TNA anode had an excellent performance on the TOC removal and MCE especially at low current density of 2.5 mA/cm2 when compared with other anodes. Therefore, Blue-TNA anode is hopeful a promising and cost-effective anode for electrochemical oxidation.

Hydrogen peroxide (H2O2) is a green oxidant that widely used in environmental remediation and chemical industries, hence the exploration of suitable modified cathode for the cost-effective electrochemical synthesis of H2O2 is of great importance. In this work, tert-butyl-anthraquinone (TBAQ) was attempted to modify four kinds of typical carbon materials (carbon aerogel, carbon nanotube (CNT), carbon black and graphene-doped carbon black) to fabricate gas diffusion electrode (GDE) to improve H2O2 production for potential use in electro-Fenton process. It was found that CNT-GDE containing 2% TBAQ had the highest H2O2 production (150.6 mg/L) with a high current efficiency (95%) and low energy consumption (2.43 kWh/(kg H2O2)) among four carbon materials because of the redox of TBAQ and more active sites (C–C sp3 carbon and oxygen-containing functional groups). The effects of TBAQ addition amount, current and initial pH on H2O2 performance were investigated. The presence of TBAQ could improve oxygen reduction activity, H2O2 selectivity and hydrophobicity to improve H2O2 production. Suitable current (50 mA) and initial pH benefited the enhancement in H2O2 production. The CNT-GDE containing 2% TBAQ showed better H2O2 production performance with good stability when comparing with literature, indicating promising for electro-Fenton application.