State of the art in self-sustaining smoldering for remediation of contaminated soil and disposal of organic waste

Smoldering combustion applications in energy and environmental fields have attracted increasing research attention in recent years. Smoldering has demonstrated considerable green advantages, such as having a low carbon footprint and being sustainable, for remediation of organic-contaminated soil and disposal of high-moisture, low-calorific value, slurry-type organic waste due to its self-sustaining reaction characteristic. This review aims to analyze and summarize studies on smoldering applications to refine the critical components of applied smoldering systems, key reaction characteristics, and corresponding influencing conditions that affect their effectiveness. Furthermore, the common characteristics and influencing factors of different smoldering application scenarios are compared to provide a comprehensive reference for commercial applications. Thus, this paper specifically includes an overview of the impact of inert porous media, combustible material, and oxidants in applied smoldering systems; a review of the research status of the three key reaction characteristics, including peak temperature, smoldering front propagation velocity, and self-sustainability; a summary of typical influencing factors, disposal material characteristics, and control conditions in the two mainstream application directions, which are remediation of contaminated soil and disposal of organic waste; and a comparative analysis of the common modes of applied smoldering beyond the lab scale. As a technically effective and energy-efficient emerging technology, the prospects of smoldering as a robust treatment process in environmental pollution cleanup are presented.

Comparative study by microwave pyrolysis and conventional pyrolysis of pharmaceutical sludge: Resourceful disposal and antibiotic adsorption

Compared with conventional pyrolysis, microwave pyrolysis has superior heat transfer performance and promotes the decomposition of organic matter. The paper focuses on the harmless treatment and resource utilization of pharmaceutical sludge (PS) by microwave heating and conventional heating methods. The experimental results showed that the conventional pyrolysis gas is dominated by CO2, CO and H2. For microwave pyrolysis gas, the "microwave effect" promoted secondary cracking of volatile fractions and increases the content of CH4, CxHy, H2 and CO through condensation, aromatization, and dehydrogenation. Conventional pyrolysis oils contained the highest percentage of oxygenated compounds. However, high-temperature microwave radiation accelerated the cleavage of polar oxygenated molecular bonds and long-chain hydrocarbons, thereby increasing the aromatics content of pyrolysis oils. The solid residues obtained from microwave pyrolysis is highly graphitized and porous, with a surface area of 146.2 m2/g. Furthermore, the solid residue was rich in pyridine-N and pyrrole-N that could be utilized for adsorption and catalysis. The MA-600 removes up to 99% of tetracycline (TC) in 6 h. It was also found that the adsorption process of TC by the two pyrolysis residues was consistent with the proposed secondary and Freundlich models.

Effects of Temperature and DC Electric Fields on Perfluorooctanoic Acid Sorption Kinetics to Activated Carbon

Sorption to activated carbon is a common approach to reducing environmental risks of waterborne perfluorooctanoic acid (PFOA), while effective and flexible approaches to PFOA sorption are needed. Variations in temperature or the use of electrokinetic phenomena (electroosmosis and electromigration) in the presence of external DC electric fields have been shown to alter the contaminant sorption of contaminants. Their role in PFOA sorption, however, remains unclear. Here, we investigated the joint effects of DC electric fields and the temperature on the sorption of PFOA on activated carbon. Temperature-dependent batch and column sorption experiments were performed in the presence and absence of DC fields, and the results were evaluated by using different kinetic sorption models. We found an emerging interplay of DC and temperature on PFOA sorption, which was linked via the liquid viscosity (η) of the electrolyte. For instance, the combined presence of a DC field and low temperature increased the PFOA loading up to 38% in 48 h relative to DC-free controls. We further developed a model that allowed us to predict temperature- and DC field strength-dependent electrokinetic benefits on the drivers of PFOA sorption kinetics (i.e., intraparticle diffusivity and the film mass transfer coefficient). Our insights may give rise to future DC- and temperature-driven applications for PFOA sorption, for instance, in response to fluctuating PFOA concentrations in contaminated water streams.

Characteristics of the pyrolytic products and the pollutant emissions at different operating stages from a pilot waste tire pyrolysis furnace

Pyrolysis is considered a highly practical, cost-effective, and environment-friendly technology for waste tires disposal. In this study, pyrolysis processes of waste tires were conducted in a pilot scale furnace feeding at 30 kg/h. The properties of pyrolytic products and the distribution patterns of pollutants generated in different operating stages (start-up, steady, and shut-down) were investigated. The pyrolytic gas in the steady state had a high caloric value of 10799 kJ/Nm3, valuable as heating source for pyrolysis. The elements of sulfur and zinc were effectively fixed as ZnS in the pyrolytic carbon. The basic properties of pyrolytic oil were in line with commercial diesel oil except for the lower flash point. Heavy metals were mainly concentrated in the pyrolytic carbon, with slightly higher concentrations in the steady state. Moreover, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were mainly concentrated in the pyrolytic oil, with predominated low-ring PAHs and high chlorinated PCDD/Fs. The concentrations of PAHs and PCDD/Fs in the gas phase were higher during the start-up stage due to the memory effect, whereas were effectively reduced during the steady stage. The concentration of PAHs in the solid phase was highest during the furnace start-up and lowest in the shut-down stage. In contrast to PAHs, the PCDD/Fs in the solid phase reached their highest concentration during the shut-down stage, which was mainly affected by temperature. The results provide guidance for the reducing of pollutant emissions and the recycling of pyrolytic products.

Method for Measuring the Three-Dimensional Morphology of Near-Wall Bubbles and Droplets Based on LED Digital Holography

Digital holography, recognized for its noncontact nature and high precision in three-dimensional imaging, is effectively employed to measure the morphology of bubbles and droplets. However, in terms of near-wall bubbles and droplets, such as confined bubbles in microfluidic chips, the measurement of the interface morphology of bubbles near the glass surface has not yet been resolved due to the coherent noise resulting from glass surface reflections in microfluidic chips. Accordingly, an off-axis digital holography system was devised by using Linnik interferometry. Measuring the confined bubble interface near the wall within a microfluidic chip and droplet evaporation on solid surfaces was studied. Partially coherent LED sources and reference light modulation techniques were employed in the optical setup to mitigate the coherent noise. Dual exposure and weighted least-squares unwrapping algorithms were introduced to correct phase distortions, enhancing image quality. Imaging two confined CO2 bubbles was done near the wall in silicon oil within a porous microfluidic chip, and contact angles of 4.7 and 4.5° were measured. Additionally, the measurement of the three-dimensional morphology of vertically evaporating deionized water droplets on a glass surface was done, due to which calculation of contact angles at various orientations was possible. This work offers a feasible new method for measuring the 3D interface morphology of bubbles and droplets, particularly in microfluidic visualization, addressing current measurement gaps.

Synergetic degradation of perfluorooctanoic acid (PFOA) in soil using electrical resistance heating induced persulfate activation

Due to wastes from production of fluorinated materials and use of aqueous fire-fighting foams (AFFF), soils contaminated with perfluorooctanoic acid (PFOA) is of concern. However, current PFOA-contaminated soil disposal techniques have relatively low degradation efficiencies and are not suitable for on-site remediation. In this study, an electrical resistance heating (ERH) device and a box experimental device were used to study whether ERH induced persulfate activation (ERH/PS) could degrade PFOA in the soil. The results indicated that single ERH and single PS addition could not effectively degrade PFOA (with approximately 0.3 % and 3.9 % degradation after 9 h, respectively), while the degradation efficiency of PFOA with coupled ERH/PS could reach 87.3 % after 9 h of reaction. Moreover, effects of PS content, heating temperature, and soil organic matter on the degradation of PFOA were explored. During the ERH/PS process, PFOA was gradually transformed into short chain perfluorinated compounds and finally mineralized to fluoride ions. Finally, using a box experimental device, PS was effectively transported to the target contaminated area through electrokinetic (EK)-assisted delivery. After activating PS through ERH, the degradation rate of PFOA could reach 95.5 %. This is a novel study demonstrating the feasibility of ERH induced PS activation to degrade PFOA in soil, which provides a potential on-site strategy for remediation of PFOA-contaminated soil.

A novel fire smoke removal technology using electric agglomeration: The concept, experimental verification and mechanisms

Electric agglomeration technology is effective in removing particulate matter from the environment and has been widely used in the field of dust removal. For the first time, this technology is applied to the field of fire smoke removal at lab scale. By varying applied electric potential and initial concentration of smoke, the removal characteristics and mechanisms during the electric agglomeration process are systematically studied. The results show that when the applied electric potential is higher than 4 kV, the smoke transmittance increases from 4% to 90% in just 10 s, and the threshold for people safe escape can be reached in only 5 s. Three main mechanisms involved in the process of smoke removal using electric agglomeration are proposed. In addition to the conventional Coulomb agglomeration of charged particles, the turbulence-enhanced agglomeration induced by ionic wind and dipole chainization at the grounded plate are also observed. This study demonstrates the feasibility and potential of electric agglomeration technology to remove fire smoke.

Pre-Drying of Chlorine-Organic-Contaminated Soil in a Rotary Dryer for Energy Efficient Thermal Remediation

In response to the current problem of the high energy consumption of direct thermal desorption systems when treating soils with a high moisture content, we propose using the waste heat of the system to pre-dry soil to reduce its moisture. Taking chlorine-organic-contaminated soil as an object, an experimental study on the drying and pollutant desorption characteristics of soil in an indirect rotary dryer was carried out. The results show that the non-isothermal drying process was divided into warm-up and falling rate periods, and no constant period was observed. The higher the rotation speed, the lower the soil outlet temperature and the higher the drying tail gas temperature. Soil outlet and dry tail gas temperatures were lower for soils with a higher moisture content. Benzene and cis-1,2-dichloroethylene are easily desorbed. Therefore, the disposal of dry tail gas should be determined according to the type and concentration of soil pollutants present. The volumetric heat transfer coefficient was found to be 85-100 W m^-3 °C^-1, which provides a key parameter for the size design of a rotary dryer.

[Efficacy analysis of high-sensitivity troponin I concentration and its changes in the diagnosis of acute myocardial infarction]

Objective: To explore the feasibility and accuracy of 0-1 h high sensitivity cardiac troponin I (hs-cTnI) concentration and its changes in judging non-ST segment elevation myocardial infarction (NSTEMI), and to investigate the feasibility of a simplified process. Methods: Patients with acute chest pain and suspected NSTEMI who were admitted to the emergency department of Fuwai Hospital, the First Affiliated Hospital of Sun Yat-sen University and Nanjing First Hospital from January 2017 to September 2020 were selected. Hs-cTnI test was carried out for the selected patients at the time of visit (0 h) and 1 h after visit. According to the 0-1 h hs-cTnI diagnostic process and threshold standard recommended by European Society of Cardiology (ESC) guidelines in 2015, the laboratory adjudication was determined. Cardiologists who did not participate in the project design and did not know the results of hs-cTnI test performed the clinical judgment according to the routine diagnosis and treatment process of emergency department. Taking clinical judgment as the gold standard, the diagnostic efficacy of 0-1 h hs-cTnI concentration and its change recommended by the guidelines for judging NSTEMI in Chinese population was analyzed. The guide process was simplified. Under the condition of not considering the time of chest pain, the guideline threshold was used for test and judgement, and the diagnostic efficacy of the simplified process was evaluated. Results: A total of 1 534 patients were enrolled in the study, aged (62±12) years and 952 (62.1%) patients were male. Among them, 402 patients (26.2%) were clinically diagnosed as NSTEMI and 1 132 patients (73.8%) were diagnosed as non-NSTEMI. According to the diagnosis and determination process recommended by the guidelines, NSTEMI was excluded in 672 patients (42.8%), and 464 patients (30.2%) were diagnosed as NSTEMI. The consistency rate with clinical determination reached 92.4% (1 050/1 136), the sensitivity of excluding diagnosis was 99.5% (95%CI: 98.0%-99.9%), the negative predictive value was 99.7% (95%CI: 98.8%-99.9%), and the negative likelihood ratio was 0.008 (95%CI: 0.002-0.335). The diagnostic specificity was 92.6% (95%CI: 90.9%-94.0%), the positive predictive value was 81.9% (95%CI: 78.0%-85.2%), and the positive likelihood ratio was 12.739 (95%CI: 10.356-15.670). According to the simplified process, NSTEMI was excluded in 675 patients (44.0%), and 463 patients (30.2%) were diagnosed as NSTEMI. The consistency rate with clinical judgment was 92.4% (1 051/1 138), the sensitivity of exclusion diagnosis was 99.3% (95%CI: 97.6%-99.8%), the negative predictive value was 99.6% (95%CI: 98.6%-99.9%), and the negative likelihood ratio was 0.012 (95%CI: 0.004-0.389). The diagnostic specificity was 92.6% (95%CI: 90.9%-94.0%), the positive predictive value was 81.9% (95%CI: 78.0%-85.2%), and the positive likelihood ratio was 12.705 (95%CI: 10.328-15.630). There was no significant difference in diagnostic efficacy between the simplified process and the recommended process (all P>0.05). Conclusion: The diagnostic process for judging NSTEMI according to the 0-1 h hs-cTnI concentration and its change criteria recommended by the 2015 ESC guidelines is applicable in the Chinese population and remains highly accurate in judging NSTEMI without considering the duration of chest pain at the time of presentation.

Revealing the Mechanism of Dioxin Formation from Municipal Solid Waste Gasification in a Reducing Atmosphere

Gasification is an effective technology for the thermal disposal of municipal solid waste (MSW) with lower dioxin emission compared to the prevailing incineration process. Nevertheless, the mechanism of dioxin formation in the reducing atmosphere during the gasification process was seldomly explored. Herein, the effects of the atmosphere, temperature, and chlorine source were systematically investigated in terms of dioxin distribution. With CO₂ and H₂O as gasification agents, a reducing reaction atmosphere was formed with abundant H₂ which effectively suppressed the generation of C-Cl, contributing to a substantial decrease of dioxin concentration by ∼80% compared to the incineration process. The formation of dioxin was favored at temperatures below 700 °C with its peak concentration achieved at 500 °C. It was unveiled that inorganic chlorine played a dominant role in the reducing atmosphere, with a lower proportion of C-O-C/O-C═O on residual slag compared to an oxidizing atmosphere. Additionally, the generated H₂ reduced the concentration of dioxins by attacking C-Cl and inhibiting the crucial Deacon reaction for dioxin formation, validated by density functional theory calculation. Eventually, the formation route paradigm and the reaction mechanism of dioxin formation from MSW gasification were revealed, facilitating and rationally guiding the control of dioxin emission.

Kill two birds with one stone: Ceramisite production using organic contaminated soil

Disposal of organic-contaminated soil through ceramsite production can not only generate ceramsite with acceptable properties but also completely remediate the organic-contaminated soil owing to high treatment temperature. However, the removal mechanism of organic pollutants and the gas-solid phase distribution of the pollutants remain unclear. In this study, coking contaminated soils with high concentrations of polycyclic aromatic hydrocarbons (PAHs) and petroleum hydrocarbon (PHC) were used to prepare ceramsite at 1160 °C. The quality of ceramsite met the required product standard when the disposal ratio of contaminated soil was up to 60%. The concentration of PAHs and PHC in the soil was 57.7 mg kg^-1 and 255 mg kg^-1. After the experiment, almost no PAHs and PHC were found in the ceramsite. High-ring PAHs were dominant in the flue gas when using model soil spiked with PAHs. Computed tomography scanning indicated that cracks developed in the ceramsite when the temperature was higher than 200 °C. High-temperature in-situ thermal analysis showed that when the temperature was increased to 400 °C, the pollutant from the interior of ceramsite would flow into the flue gas with the released volatile matter. Thermal desorption and degradation of PAHs were the main mechanisms of pollutant removal.

Formation and control of dioxins during thermal desorption remediation of chlorine and non-chlorine organic contaminated soil

Formation and emission of dioxins is a great concern during thermal desorption remediation of organic contaminated soil. The differential formation of dioxins from chlorine organic contaminated soil (COCS) and non-chlorine organic contaminated soil (NCOCS) is still unclear and the control technique for the dioxins generated is an urgent need. In this study, the formation and distribution characteristics of dioxins were investigated in the thermal desorption unit combined with flue gas purification system during COCS and NCOCS treatments. Although organic contaminates were well desorbed, de-novo formation of dioxins was observed for both COCS and NCOCS, as well as synthesis from precursors for NCOCS. The gas-phase dioxin in the flue gas purification system continuously decreased during NCOCS thermal desorption, while the dioxin concentration in the quench tower sharply increased from 0.46 to 2.13 ng/Nm³ through de-novo synthesis during COCS treatment. Furthermore, the emission of dioxins only slightly reduced (for COCS) or even increased (for NCOCS) at 70% operating load. The catalytic adsorption tower within modified activated carbon and V₅-Mo₅-Ti catalyst after bag filter can reduce the emission of dioxins up to 91.4% at the condition of secondary combustion chamber closure, demonstrating that the catalytic adsorption tower can replace the secondary combustion chamber for controlling dioxin emission. More importantly, the highly toxic low-chlorinated polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDD/PCDFs) were selectively removed from flue gas by the catalytic adsorption tower. These results reveal the differential formation characteristics of dioxins during COCS and NCOCS thermal treatments and highlight V₅-Mo₅-Ti/ modified activated carbon as a promising catalytic adsorption material to control the emission of dioxins from the thermal desorption of organic contaminated soil.

Formation behavior of PAHs during pyrolysis of waste tires

Polycyclic aromatic hydrocarbons (PAHs) formation from the pyrolysis of waste tires is inevitable because of the complexity of tire formulations and the addition of certain chemicals. In this study, the formation behavior and distribution of PAHs in three-phases were investigated from waste tires under pyrolysis conditions. The influencing factors including the temperature, heating rate, holding time, particle size, catalyzer, and atmosphere, were systematically evaluated. The results showed that PAHs were mainly concentrated in pyrolysis oil (94.59-99.03%), followed by the gas phase (0.96-5.34%), and their content was very low in the solid phase (0.01-0.99%). A higher temperature and slower heating rate lead to partial PAHs decomposition, thus reducing their emissions. The overall formation of PAHs can be inhibited when pyrolyzing coarse-grained tire powder. Furthermore, the PAHs formation mechanisms in waste tires were determined through reaction molecular dynamics, electron paramagnetic resonance, and intermediate products. Tires were mainly decomposed into benzene series, *C₂H₃, and *CH₃; therefore, it was determined that PAHs were formed by the joint action of the hydrogen abstraction, and vinyl radical addition and methyl addition cyclization mechanisms. Among them, low and middle-ring PAHs were formed more easily, particularly naphthalene. The generation of PAHs can be inhibited by reducing the concentration of hydrocarbons and monocyclic benzene series. Regarding the distribution law and generation pathways of PAHs, our results provide guidance for reducing PAHs formation and emissions.

Emission characteristics of dioxins during iron ore Co-sintering with municipal solid waste incinerator fly ash in a sintering pot

The disposing of municipal solid waste incineration(MSWI) fly ashes containing dioxins is an intractable problems. Co-sintering is one of the most ideal methods to dispose MSWI fly ash, because it not only degrades the dioxins but also makes it possible to re-utilize MSWI fly ashes. In the present study, MSWI fly ash(FA) and water washed MSWI fly ash(WFA) were added into the sinter raw mixture in a lab-scale sintering pot. Different effects of fly ash and water washed fly ash on emission characteristics of dioxins were studied, and possible pathways to form dioxins were discussed in detail. During co-sintering, at least 88.9%, 99.1% of dioxins brought in by FA, WFA was decomposed, respectively, and re-synthesis with a significant distribution characteristic of dioxins originated from sintering process. In the preheating and dry zone, the recombination and condensation reaction of precursors were the main formation pathways of 2,3,7,8-PCDDs in the sintering process and 2,3,7,8-PCDFs were formed by de novo synthesis. In addition, the resynthesis process was affected by chlorine and calcium brought in by fly ash. Sufficient chlorine boosted the chlorination of reactants while calcium increased the residence time, causing the emission concentration of toxic dioxins and the adding ratio were nonlinearly dependent. Therefore, the maximum proportion of water washed MSWI fly ash that can be added into the sintering process was 0.5 wt.%. Besides, the possible pathways to form dioxins were proposed.

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.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

PCDD/Fs characteristics in flue gas and surrounding environment of iron and steel smelting industry

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) concentrations and distributions, emission factors and amounts, and ambient air and soil potential sources were investigated by collecting flue gas, ambient air, and soil samples from ten sintering furnaces and two electric arc furnaces of eight iron and steel smelting industries (ISSI) in China. In flue gas, the concentrations of PCDD/Fs ranged from 0.05 to 2.93 ng I-TEQ Nm^-3 (mass, from 0.38 to 30.67 ng Nm^-3), with an average of 0.42 ng I-TEQ Nm^-3 (mass, 4.99 ng Nm^-3), respectively. In ambient air, the concentrations ranged from 0.05 to 0.35 pg I-TEQ m^-3 (mass, from 0.66 to 5.66 pg m^-3), with an average of 0.20 pg I-TEQ m^-3 (mass, 2.96 pg m^-3), respectively. In surface soil, the concentrations ranged from 1.80 to 21.02 ng I-TEQ kg^-1 (mass, from 34.29 to 836.00 ng kg^-1), with an average of 5.82 ng I-TEQ kg^-1 (mass, 252.10 ng kg^-1), respectively. In deep soil, the concentrations ranged from 1.17 to 12.00 ng I-TEQ kg^-1 (mass, from 56.83 to 1488.00 ng kg^-1), with an average of 7.76 ng I-TEQ kg^-1 (mass, 433.20 ng kg^-1), respectively. Compared with emission limits for PCDD/Fs, the compliance was 78.9% in flue gas, 100% in ambient air, and 77.3% in soil. In congener profiles, the contributions of PCDFs were much higher than those of PCDDs in flue gas and ambient air, but the opposite was observed in soil. In ten sintering furnaces, the emission factors ranged from 22.11 to 901.22 ng I-TEQ t^-1, with an average of 373.80 ng I-TEQ t^-1, respectively. In two electric arc furnaces, the emission factors were 1667.52 and 894.96 ng I-TEQ t^-1, with an average of 1281.24 ng I-TEQ t^-1. According to both principal component analysis and hierarchical cluster analysis, all ambient air samples were affected by the emissions of PCDD/Fs from ISSIs, but to different degrees. However, the concentrations of PCDD/Fs in most soil samples were not influenced by the ISSI emissions.

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.

Formation of DF, PCDD/Fs and EPFRs from 1,2,3-trichlorobenzene over metal oxide/silica surface

The formation of dibenzofuran (DF), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and environmentally persistent free radicals (EPFRs) from 1,2,3-trichlorobenzene (1,2,3-TrCBz) over metal oxide / silica surface were investigated using a tubular furnace. PCDD/Fs increased exponentially from 250 to 550 °C over copper oxide / silica surface and PCDD/Fs had the maximum growth from 400 to 450 °C. The ratio of PCDD / PCDF was much less than 1, especially when the temperature raised from 450 to 550 °C. Pentachlorianated dibenzo-p-furan (PeCDF) dominated among the homologues, which contributed 45-61% to the total PCDD/Fs. Two peaks of the yield of DF occurred at 400 °C and 500 °C respectively. Furthermore, the oxygen contents have different effects for PCDD and PCDF formation, and low oxygen could promote PCDD production, especially for tetrachlorinated dibenzo-p-dioxin (TCDD). More PCDF were formed on the oxygen rich condition, indicating that the oxygen promoted the chlorination of DF. Iron oxides are better than copper oxides to catalyze the formation of PCDD/Fs from 1,2,3-TrCBzs at 350 °C, especially for PCDF. The major EPFRs on the catalysts were formed with g values in the range of 2.0040 to 2.0049, which were phenoxy radicals and semiquinone occurred with higher g value of 2.0075 when the temperature increased to 550 °C, and more EPFRs were produced with the temperature increasing. The addition of iron oxides reduced the spins concentrations of oxygen-centered radicals but increase the spins concentrations of signals with lower g values. The different possible formation pathways of PCDD and PCDF from 1,2,3-TrCBz over metal oxide surface were also proposed.

Laser picoscopy of valence electrons in solids

Valence electrons contribute a small fraction of the total electron density of materials, but they determine their essential chemical, electronic and optical properties. Strong laser fields can probe electrons in valence orbitals^1-3 and their dynamics^4-6 in the gas phase. Previous laser studies of solids have associated high-harmonic emission^7-12 with the spatial arrangement of atoms in the crystal lattice^13,14 and have used terahertz fields to probe interatomic potential forces¹⁵. Yet the direct, picometre-scale imaging of valence electrons in solids has remained challenging. Here we show that intense optical fields interacting with crystalline solids could enable the imaging of valence electrons at the picometre scale. An intense laser field with a strength that is comparable to the fields keeping the valence electrons bound in crystals can induce quasi-free electron motion. The harmonics of the laser field emerging from the nonlinear scattering of the valence electrons by the crystal potential contain the critical information that enables picometre-scale, real-space mapping of the valence electron structure. We used high harmonics to reconstruct images of the valence potential and electron density in crystalline magnesium fluoride and calcium fluoride with a spatial resolution of about 26 picometres. Picometre-scale imaging of valence electrons could enable direct probing of the chemical, electronic, optical and topological properties of materials.

Emission characteristics for co-combustion of leather wastes, sewage sludge, and coal in a laboratory-scale entrained flow tube furnace

Four different mixed fuels consisted of leather waste, coal, and sewage sludge were combusted in a lab-scale entrained flow fluidized bed furnace. The influence of blending ratio on emission characteristics of SO₂, NO_x, HCl, particulate matter (PM), heavy metals, and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was studied. Results showed that the mixing of coal with sewage sludge had a complex effect on the emission characteristics. On the one hand, with more sewage sludge blending in the mixed fuel, the acid gas pollutant (SO₂, NO_x) decreased a lot, and the recovery of volatile heavy metals (Cd, Pb) increased at the same time. Furthermore, the leaching toxicity of Cr in the fly ash and bottom ash went down below the national standard with the adding of sewage sludge. On the other hand, the mixing of sewage sludge which consisted of more ash content resulted in the increase of the PM emission. Moreover, the high content of Cu and chlorine in the sewage sludge can promote the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) when the fuel 3 and 4 were combusted. Most importantly, the concentration of toxic PCDD/Fs in the flue gas produced from fuel 3 and fuel 4 was successfully controlled down below 0.20 ng I-TEQ/Nm³ by the active carbon.

Cost-effectiveness analysis of the addition of bevacizumab to chemotherapy as induction and maintenance therapy for metastatic non-squamous non-small-cell lung cancer

BACKGROUND

The BEYOND trial found that the addition of bevacizumab (B) to paclitaxel-carboplatin (PC) chemotherapy provided a significant clinical benefit to Chinese patients with metastatic non-squamous non-small-cell lung cancer (NSCLC). This study aimed to evaluate the cost-effectiveness of adding B to first-line PC induction and continuation maintenance therapy from a Chinese perspective.

METHODS

A Markov model was developed to estimate the cost and effectiveness of B + PC in the induction and maintenance therapy of patients with metastatic non-squamous NSCLC. Costs were calculated in the Chinese setting, and health outcomes derived from the BEYOND trial were measured as quality-adjusted life years (QALYs). A one-way sensitivity analysis was conducted to explore the impact of various parameters in the study.

RESULTS

The B + PC treatment was more costly ($112,943.40 versus $32,171.43) and more effective (1.07 QALYs versus 0.80 QALYs) compared with the PC treatment. Adding B to the PC regimen for non-squamous NSCLC results in an incremental cost-effectiveness ratio of $299,155.44 per QALY, which exceeded the accepted societal willingness-to-pay threshold ($23,970.00) for China. In the sensitivity analysis, the duration of progression-free survival (PFS) for the B + PC group, the cost of the PFS state for B + PC group and the price of B were considered the most sensitive factors in the model.

CONCLUSIONS

The addition of B to first-line PC induction and maintenance therapy was not determined to be a cost-effective strategy for metastatic non-squamous NSCLC in China, even when an assistance program was provided.