Organic By-products Research Articles

Formation of carbonyl compounds during ozonation of lake water and wastewater: Development of a non-target screening method and quantification of target compounds

Ozonation of natural waters is typically associated with the formation of carbonyl compounds (aldehydes, ketones and ketoacids), a main class of organic disinfection byproducts (DBPs). However, the detection of carbonyl compounds in water and wastewater is challenged by multiple difficulties inherent to their physicochemical properties. A non-target screening method involving the derivatisation of carbonyl compounds with p-toluenesulfonylhydrazine (TSH) followed by their analysis using liquid chromatography coupled to electrospray ionisation high-resolution mass spectrometry (LC-ESI-HRMS) and an advanced non-target screening and data processing workflow was developed. The workflow was applied to investigate the formation of carbonyl compounds during ozonation of different water types including lake water, aqueous solutions containing Suwannee River Fulvic acid (SRFA), and wastewater. A higher sensitivity for most target carbonyl compounds was achieved compared to previous derivatisation methods. Moreover, the method allowed the identification of known and unknown carbonyl compounds. 8 out of 17 target carbonyl compounds were consistently detected above limits of quantification (LOQs) in most ozonated samples. Generally, the concentrations of the 8 detected target compounds decreased in the order: formaldehyde > acetaldehyde > glyoxylic acid > pyruvic acid > glutaraldehyde > 2,3-butanedione > glyoxal > 1-acetyl-1-cyclohexene. The DOC concentration-normalised formation of carbonyl compounds during ozonation was higher in wastewater and SRFA-containing water than in lake water. The specific ozone doses and the type of the dissolved organic matter (DOM) played a predominant role for the extent of formation of carbonyl compounds. Five formation trends were distinguished for different carbonyl compounds. Some compounds were produced continuously upon ozonation even at high ozone doses, while others reached a maximum concentration at a certain ozone dose above which they decreased. Concentrations of target and peak areas of non-target carbonyl compounds during full-scale ozonation at a wastewater treatment plant showed an increase as a function of the specific ozone dose (sum of 8 target compounds ∼ 280 µg/L at 1 mgO3/mgC), followed by a significant decrease after biological sand filtration (> 64–94% abatement for the different compounds). This highlights the biodegradability of target and non-target carbonyl compounds and the importance of biological post-treatment.

Insights into characterization of organophosphorus flame retardants transformation under thermal activation persulphate

Organophosphorus flame retardants (OPFRs) are widely used in consumer products and are frequently detected in water, thereby threatening public health. In the present study, we investigated the mechanism of degradation of two representative OPFRs, tri(2-chloroethyl) phosphate (TCEP) and tri-n-butyl phosphate (TnBP), by thermally activated persulphate (PS). First, the experimental data were in accordance with the modelling simulations. In the absence of Cl−, the instantaneous concentration of SO4–• was 3.12 × 10−15 M. When the concentration of Cl− increased from 7.5 mM to 450 mM, Cl2–• became the dominant radical, with its concentration increasing from 7.39 × 10−14 M to 7.91 × 10−13 M. Conversely, the concentration of SO4–• declined from 6.3 × 10−17 M to 2.6 × 10−19 M. Second, owing to the transition of dominant radicals from SO4–• to Cl2–•, the resultant pseudo-first-order decay rates (robs) of TCEP and TnBP were reduced. Without Cl−, robs of TCEP and TnBP were (1.8 ± 0.1)× 10−2 h−1 and (6.1 ± 0.4)× 10−2 h−1, respectively. When the Cl− concentration reached 450 mM, the robs of TCEP and TnBP dropped to (2.2 ± 0.2)× 10−3 h−1 and (2.4 ± 0.2)× 10−2 h−1, respectively. Additionally, despite the presence of oxidised Cl2–• compounds, when Cl− participated in PS oxidation, no primary organic chlorinated byproducts were detected. These results indicated that Cl− did not affect the toxicity of TCEP and TnBP transformation intermediates. Finally, the apparent kinetic isotope effects for carbon (AKIEC) and hydrogen (AKIEH) were detected to be 1.01 and 1.370–3.049, respectively. The results implied that the C-H split occurred during the PS-activated transformation of TCEP and TnBP. The present study combines quantitative steady-state radical calculation, transformation product identification, and isotope fractionation to characterise the radical transformation of typical OPFRs, thereby laying the foundation for regulating PS oxidation to eliminate OPFRs in real-world systems.

Overlooked Cytotoxicity and Genotoxicity to Mammalian Cells Caused by the Oxidant Peroxymonosulfate during Wastewater Treatment Compared with the Sulfate Radical-Based Ultraviolet/Peroxymonosulfate Process.

Byproduct formation (chlorate, bromate, organic halogen, etc.) during sulfate radical (SO4•-)-based processes like ultraviolet/peroxymonosulfate (UV/PMS) has aroused widespread concern. However, hypohalous acid (HOCl and HOBr) can form via two-electron transfer directly from PMS, thus leading to the formation of organic halogenated byproducts as well. This study found both PMS alone and UV/PMS can increase the toxicity to mammalian cells of wastewater, while the UV/H2O2 decreased the toxicity. Cytotoxicity of two wastewater samples increased from 5.6-8.3 to 15.7-29.9 mg-phenol/L, and genotoxicity increased from 2.8-3.1 to 5.8-12.8 μg 4-NQO/L after PMS treatment because of organic halogen formation. Organic halogen formation from bromide rather than chloride was found to dominate the toxicity increase. The SO4•--based process UV/PMS led to the formation of both organic halogen and inorganic bromate and chlorate. However, because of the very low concentration (<20 μg/L) and relatively low toxicity of bromate and chlorate, contributions of inorganic byproducts to toxicity increase were negligible. PMS would not form chlorate and bromate, but it generated a higher concentration of total organic halogen, thus leading to a more toxic treated wastewater than UV/PMS. UV/PMS formed less organic halogen and toxicity because of the destruction of byproducts by UV irradiation and the removal of byproduct precursors. Currently, many studies focused on the byproducts bromate and chlorate during SO4•--based oxidation processes. This work revealed that the oxidant PMS even needs more attention because it caused higher toxicity due to more organic halogen formation.

Transformation of microplastics by oxidative water and wastewater treatment processes: A critical review.

Microplastics (MPs) are contaminants of emerging concern that accumulate in various environments, where they pose threats to both the ecosystem and public health. Since MPs have been detected in drinking water resources and wastewater effluents, more efficient treatment is needed at wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). This review discusses the potential of biological, photochemical, Fenton (-like) systems, ozonation, and other oxidation processes in the treatment of MPs in terms of their indicators of oxidation such as mass loss and surface oxidation. The oxidation processes were further analyzed in terms of limitations and environmental implications. Most previous studies examining MPs degradation using conventional treatments-such as UV disinfection, ozonation, and chlorination-employed significantly higher doses than the common doses applied in DWTPs and WWTPs. Owing to such dose gaps, the oxidative transformation of MPs observed in many previous studies are not likely to occur under practical conditions. Some novel oxidation processes showed promising MPs treatment efficiencies, while many of them have not yet been applied on a larger scale due to high costs and the lack of extensive basic research. Health and environmental impacts related to the discharge of oxidized MPs in effluents should be considered carefully in different aspects: the role as vectors of external pollutants, release of organic compounds (including organic byproducts from oxidation) and fragmentation into smaller particles as MPs circulate in the ecosystem as well as the possibility of bioaccumulation. Future research should also focus on ways to incorporate developed oxidation processes in DWTPs and WWTPs to mitigate MPs contamination.

Heterobimetallic CoCeOx derived from cobalt partially-substituted Ce-UiO-66 for chlorobenzene efficient catalytic destruction

Here, a metal–organic framework (MOF)-templated strategy was applied to synthesize the CoCeOx bimetallic catalysts by calcining Co partially-substituted Ce-UiO-66. It is indicated that the substituted Co limited Ce cations in Ce-UiO-66 framework, which affects its growth and structure crystallinity to some extent. After pyrolysis treatment, the derived bimetallic oxide (CoCeOx-M) can basically keep the octahedral structure and the surface area is much higher than the bulk metal composite oxide (CoCeOx-B) prepared by traditional coprecipitation. Results reveal that CoCeOx-M performs the best chlorobenzene degradation capacity, superior stability and vapor tolerance compared with those of CeO2-M (derived from Ce-UiO-66) and CoCeOx-B. At the same time, it is favorable to inhibit the formation of CO during the oxidation reaction. The superior catalytic performance of CoCeOx-M is attributed to a good dispersion of metal cations, high surface area and active oxygen concentration, and good redox property. Moreover, the formation of organic byproducts especially chlorinated organics can be obviously prohibited over CoCeOx-M compared with that of CeO2-M. Mechanism study reveals that chlorobenzene dissociates on the surface of CoCeOx-M to form carboxylates such as acetate species, maleate and phenolate before finally oxidized into CO2, H2O, and HCl. The present work poses new insights into the fabrication of efficient catalysts for industrial CVOC purification.

Oxidation of ciprofloxacin by the synergistic effect of DBD plasma and persulfate: reactive species and influencing factors analysis

A synergistic system of water falling film dielectric barrier discharge (DBD) plasma and persulfate (PS) was set up and used for oxidizing ciprofloxacin (CIP) in water. Results of reactive species formation in the DBD-only system as well as the DBD–PS system verified the PS activation in the DBD system. Influencing factors on CIP degradation and the degradation process were also been studied. The obtained results showed that the presence of PS could greatly improve the degradation and mineralization of CIP and that the degradation efficiency could reach 97.73% after only 40 min treatment with 4 mM PS addition. The increase of PS concentration, the lower CIP concentration, the acidic solution pH and the addition of metal ions (Fe2+ and Cu2+) enhanced the CIP degradation, while the existence of Cl− and HC had a negative effect. The experiments related to scavenger addition confirmed the contribution of the main reactive species to the CIP oxidation. Three probable degradation pathways were proposed by analyzing the inorganic ions and organic byproducts formed during the CIP degradation. The toxicity evaluation results of the CIP and its intermediates confirmed the effectiveness of the DBD–PS synergistic system.

Monitoring of n-hexane degradation in a plasma reactor by chemical ionization mass spectrometry.

n-Hexane (C6H14) removal and conversion are investigated in a filamentary plasma generated by a pulsed high-voltage Dielectric Barrier Discharge (DBD) at atmospheric pressure and room temperature in a dry N2/O2 (20%) mixture with C6H14. The degradation of n-hexane and the by-product formation are analyzed in real-time using a high-resolution Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometer coupled with Chemical Ionization (CI). As alkanes are reacting slowly with H3O+ ions, two precursor ions were used: O2+ to follow the n-hexane mixing ratios and H3O+ to follow the mixing ratios of organic by-products. As the CI-FTICR technique can work at high mixing ratios, studies were made between 5 and 200 ppm of n-hexane. Absorption spectroscopy is also used to follow ozone and carbon dioxide molecules. We show that the DBD efficiency increases for lower n-hexane mixing ratios and a large number of by-products are identified, with the major compounds being: formaldehyde, acetaldehyde, propanal, carbon dioxide, and carbon monoxide along with nitrate compounds. Based on the nature of the by-products characterized, a mechanism accounting for their formation is proposed.

Synergistic Modification of PVC with Nitrogen-Containing Heterocycle and Tung-Oil Based Derivative for Enhanced Heat Stabilization and Plasticization Behavior

The additives present in polyvinyl chloride (PVC) materials are the major source of organic by-products during PVC degradation. The thermal stabilizer and plasticizer are the main additives that endow PVC with the required properties during its processing. However, these two additives easily migrate when samples are obtained by physical mixing of the additives with PVC. This causes the reduction of PVC sample efficacy and the increase in the formation of organic by-products in the radiolysis process. In this work, two kinds of grafted PVC samples (tung-oil derivative grafted PVC and Atz grafted PVC, abbreviated as P-GT4 and P-AZ3) were synthesized by chemical grafting of 3-amino-1,2,4-triazole (Atz) and tung-oil derivative on PVC, respectively. These two PVC samples were then blended at different mass ratios to obtain hybrid PVC materials with excellent plasticization, thermal stability and migration resistance ability. Differential scanning calorimetry (DSC), discoloration, Congo red test and thermogravimetric analysis (TGA) showed that when the mass ratio of P-GT4 to P-AZ3 in the mixed PVC resin was 1:3, the resulting P1:3-GT4-AZ3 (P4) presented the best plasticization and thermal stability. The kinetics of thermal decomposition showed that the activation energy of P4 was much higher than that of the reference material [PVC/DOTP/CaSt2/ZnSt2, PVC/CZ41 for short] at mass loss α = 20% and 80%. In addition, the leaching test showed that P4 material possessed excellent migration resistance ability.

THE INFLUENCE OF PROCESS PARAMETERS ON BROWN STOCK PULP WASHING AT NATRON-HAYAT MAGLAJ

Brown stock washing is one of the major unit operations within the pulp manufacturing business. Poor operating washers have the potential to significantly and negatively affect almost every other area of a pulp and paper mill, including the mill’s environmental performance. The objective of the pulp washing is to remove the soluble impurities such as organic solids (lignin), fines, inorganic solids (Na, Mg, Ca, and K ions), and byproducts after each processing step. The present paper attempts to look at various parameters influencing pulp washing at Natron-Hayat Maglaj to ensure a complete understanding of the process. The results showed for this mixture of raw materials (15 % pine and 85 % fir) that the most influential parameters are Kappa number and dilution factor. Working with a high Kappa number above 50 requires additional equipment. Online control of the dilution factor would further improve the quality of the washing process and provide additional saving water and savings at the Evaporation plant. The First step for the future to improve the washing of unbleached kraft pulp is the optimization of the washing process through advanced control.

Investigating solids present in the aqueous stream during STEX condensate upgrading—a case study

Abstract Steam explosion (STEX) of woody biomass is an efficient pretreatment method in the production of water-resistant wood pellets. The STEX process also generates an aqueous condensate stream containing dissolved organic compounds, with furfural as the most abundant and valuable component. An industrial-scale recovery process for furfural and other organic by-products is therefore in the process of being developed and built. One challenge in the process has turned out to be the formation of solid particulate matter that can clog filters in the process unit. We have analyzed both the solid deposits and the fluids present at different points in the process unit to try to identify the origin of the particles using spectroscopic and chromatographic analysis, elemental analysis, and scanning electron microscopy.The aqueous fluids deriving from condensed steam contain furfural and other small organic molecules, with a separate low-density organic layer occurring at some points. This layer largely consists of wood extractives, typically terpenoids. In addition, a heavy organic phase comprising mostly furfural was found at one sampling point. The particles comprise a black, largely insoluble material with a H/C ratio of 0.88 and an O/C ratio of 0.26 and a very low ash content. IR spectra show a low content of C–H functional groups, and chromatographic analysis supports an interpretation that the particles are dominantly furfural-sourced humin-like polymers with adsorbed or co-polymerized terpenoids. Particle formation has been reproduced in a laboratory setting with conditions similar to those in the full-scale process.

Simultaneously Constructing Active Sites and Regulating Mn-O Strength of Ru-Substituted Perovskite for Efficient Oxidation and Hydrolysis Oxidation of Chlorobenzene.

Chlorinated volatile organic compounds (CVOCs) are a class of hazardous pollutants that severely threaten environmental safety and human health. Although the catalytic oxidation technique for CVOCs elimination is effective, enhancing the catalytic efficiency and simultaneously inhibiting the production of organic byproducts is still of great challenge. Herein, Ru-substituted LaMn(Ru)O3+ δ perovskite with Ru-O-Mn structure and weakened Mn-O bond strength has been developed for catalytic oxidation of chlorobenzene (CB). The formed Ru-O-Mn structure serves as favorable sites for CB adsorption and activation, while the weakening of Mn-O bond strength facilitates the formation of active oxygen species and improves oxygen mobility and catalyst reducibility. Therefore, LaMn(Ru)O3+ δ exhibits superior low-temperature activity with the temperature of 90% CB conversion decreasing by over 90°C compared with pristine perovskite, and the deep oxidation of chlorinated byproducts produced in low temperature is also accelerated. Furthermore, the introduction of water vapor into reaction system triggers the process of hydrolysis oxidation that promotes CB destruction and inhibits the generation of chlorinated byproducts, due to the higher-activity *OOH species generated from the dissociated H2 O reacting with adsorbed oxygen. This work can provide a unique, high-efficiency, and facile strategy for CVOCs degradation and environmental improvement.

Characterization of a flow-through electrochemical reactor for the degradation of ciprofloxacin by photoelectro-Fenton without external oxygen supply

This work reports the experimental characterization of an innovative electrolyzer designed for self-sustained H2O2 production and synchronized degradation of the antibiotic ciprofloxacin (CIP) by photoelectro-Fenton (PEF) process tested in recirculation operation mode. The flow-through electrochemical reactor comprises an arrangement of two alternated anodes and cathodes, using the anodic O2 generated from water oxidation at Ti|IrO2-Ta2O5 anodes to produce H2O2 at graphite-felt cathodes from the oxygen reduction reaction (ORR). The influence of the most relevant operation conditions such as the initial Fe2+ concentration, applied current density, liquid flow rate (Q) and initial CIP concentration was systematically examined during the electrolytic trials by analyzing the CIP concentration decay, solution mineralization, and time course of Fe2+ content. It is demonstrated that the H2O2 concentration attained with this reactor configuration is sufficient to run the PEF treatment without needing an air pump or compressor. Complete elimination of CIP was reached at 40 min, with mineralization current efficiency and electrolytic energy consumption of 42% and 0.25 kWh (g TOC)-1, respectively. Oxalic and oxamic acids were the final organic by-products of the destruction of CIP, which also yielded nitrate, ammonium, and fluoride ions. PEF outperformed other processes like anodic oxidation with cathodic H2O2 and electro-Fenton (EF), as revealed by comparing the degradation and mineralization profiles.

Critical Review of the Recent Literature on Organic Byproducts in E-Cigarette Aerosol Emissions.

We review the literature on laboratory studies quantifying the production of potentially toxic organic byproducts (carbonyls, carbon monoxide, free radicals and some nontargeted compounds) in e-cigarette (EC) aerosol emissions, focusing on the consistency between their experimental design and a realistic usage of the devices, as determined by the power ranges of an optimal regime fulfilling a thermodynamically efficient process of aerosol generation that avoids overheating and "dry puffs". The majority of the reviewed studies failed in various degrees to comply with this consistency criterion or supplied insufficient information to verify it. Consequently, most of the experimental outcomes and risk assessments are either partially or totally unreliable and/or of various degrees of questionable relevance to end users. Studies testing the devices under reasonable approximation to realistic conditions detected levels of all organic byproducts that are either negligible or orders of magnitude lower than in tobacco smoke. Our review reinforces the pressing need to update and improve current laboratory standards by an appropriate selection of testing parameters and the logistical incorporation of end users in the experimental design.

Conversion of Oil Palm By-Products into Value-Added Products through Oyster Mushroom (Pleurotus ostreatus) Cultivation

The oyster mushroom (Pleurotus species) is a popular and widely cultivated edible mushroom that can be found worldwide, including in Malaysia. However, its local production is unable to fulfil the market demand, partly due to the limited availability of rubber wood sawdust (RWS) as the conventional cultivation substrate. Furthermore, the palm oil industry in Malaysia generates large volumes of organic by-products that have caused environmental concerns. Therefore, the potential utilisation of oil palm waste-based substrates in order to develop a substitute RWS for Pleurotus ostreatus mushroom production is evaluated in this study, based on their agronomic performance and nutritional properties. Empty fruit bunches (EFBs), oil palm fronds (OPFs), and oil palm trunks (OPTs) were used to formulate the substrates. The control used was 100% RWS. Generally, 100% EFB showed a better agronomic performance, and mushroom growth was 1.9 times faster compared to the control, with a comparable mushroom yield. The crude protein and beta glucan content of mushrooms grown on oil palm by-product-formulated substrates were significantly higher than those grown using the control. Additionally, the number of fruiting bodies, crude protein, and beta glucan content of the mushrooms were positively correlated with potassium in the substrate. Therefore, 100% EFB could be used as a potential substitute for RWS for the cultivation and production of P. ostreatus.

Clindamycin removal from aqueous solution by non-thermal air plasma treatment: performance, degradation pathway and ensuing antimicrobial activity.

The present study set out to investigate clindamycin (CLN) removal from aqueous solution using non-thermal plasma (NTP) under atmospheric air conditions and to address the effects of some variables including pH, initial concentration of CLN, and working voltage on CLN degradation. The result showed that the NTP system exhibited excellent degradation rate and mineralization efficiency on CLN in 15 min under neutral conditions, which exceeded 90 and 45%, respectively, demonstrating its conversion to other organic by-products. Furthermore, CLN degradation was largely dependent upon the initial pH of solution, applied voltage, and reaction time. Specifically, under acidic conditions (pH = 3), working voltage of 24 kV and after 15 min of reaction, almost 100% of CLN was degraded. NTP-initiated CLN degradation products through LC-MS/MS analysis, determined within 10 min of reaction, inferred that the complex structure of CLN has undergone deterioration by active radical species which subsequently generated small molecular organic compounds. Chemical processes involved in CLN degradation were found to be demethylation, desulfonylation, dechlorination, hydroxylation and deamination. Lastly, antimicrobial susceptibility tests revealed that the activity of CLN was reduced following NTP treatment, which is also in good agreement with the minimum inhibitory concentration (MIC) values obtained from microdilution analyses.

The Effects of Insect Frass Fertilizer and Biochar on the Shoot Growth of Chicory and Plantain, Two Forage Herbs Commonly Used in Multispecies Swards

Livestock farmers are seeking ways to lower their environmental footprints by reducing inputs, lowering greenhouse gas emissions, and enhancing carbon sequestration. To meet these objectives, farmers are investigating the value of diverse multispecies grazing swards and various organic by-products as alternative fertilizers and soil amendments. This study investigated the effects of HexaFrass™ [HexaFly, Meath, Ireland], an insect frass based organic fertilizer, and biochar, a form of charcoal, on the shoot dry matter accumulation of two forage plants, chicory and ribwort plantain. Under glasshouse conditions, HexaFrass™ generally increased the shoot growth of both chicory and plantain, although these positive effects were lost if an excessive amount of HexaFrass™ was applied, or the growing medium was already nutrient-rich. Importantly, it was found that HexaFrass™ also increased the re-growth of shoots after cutting, which is vital for plants that are destined to be successfully used in grazing or silage swards. Biochar had a less obvious effect on the shoot dry matter accumulation, although there was some evidence of a synergy between biochar and HexaFrass™, which caused an additional increase in the shoot growth. The results indicate that frass-based fertilizers could play a role in low-input mixed swards, whereas the potential of biochar as a soil amendment in these grazing systems requires further research.

Role and Control of Solid-Electrolyte Interphase in Lithium-Mediated Electrochemical Ammonia Synthesis

Lithium-mediated electrochemical ammonia synthesis (LiMEAS) is a way-to-go to reduce nitrogen at ambient pressure and temperature, thus avoiding harsh conditions of industrial standard Haber-Bosch process.1 Inspired by Tsuneto,2 we showed how the choice of electrolyte solvent has a considerable effect both in terms of ammonia yield and electrolyte degradation, which affects the long term stability.3 Recently, we introduced a strategy to improve LiMEAS by pulsed instead of constant current over time leading to considerably higher Faradaic efficiency.4 The pulsed current kept the electrode cleaner from deposit, which allowed the system to run for a longer time. The thinner deposit decreased the ohmic losses, thus increasing the energy efficiency of the electrosynthesis process. Including our discovery that small amounts of oxygen (O2) added to nitrogen (N2) enhance Faradaic efficiency of LiMEAS,5 the role of the solid-electrolyte interphase (SEI) has to be understood, in order to make LiMEAS stable, reliable, and more efficient.The SEI is responsible for performance and stability of Li-ion batteries (LIB).6 It grows on the working electrode (WE) once the deposited lithium contacts the electrolyte resulting in the materials from electrolyte decomposition. Inorganic, organic and polymeric compounds are the main components of this layer, which can be controlled. The same is expected in LiMEAS, since the organic byproducts in electrolyte are formed during electrosynthesis.3 In an ideal case, only Li+ and H+ should diffuse through this layer, shielding the reactive electrode against further reduction reactions.7 However, the composition, behavior and specific role of SEI in LiMEAS is not known, and the field lacks of studies on it.In this work we show what SEI in LiMEAS is and how its formation and properties can be tuned. An operando electrochemical quartz crystal microbalance (EQCM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), gas chromatography-mass spectrometry (GCMS) and nuclear magnetic resonance (NMR) were employed to determine dynamic, mechanical and chemical SEI properties as a function of time, electrolyte, gases, and additives. We focus on the physical behavior and chemical composition changes on the electrodes and in the electrolyte. The role of SEI was elaborated in detail by comparing electrochemical operation conditions, constant and pulsed current, introducing additives to the electrolyte or exchanging electrolyte components. When the current is pulsed, electrolyte decomposition triggers slower and more controllable interphase growth with some mass stripping during relaxation compared to rapid growth in constant current LiMEAS. Due to these (electro-)chemical processes, the interphase formed on cathodes with pulsed current is thinner, less rigid and more viscous than formed with constant current. Furthermore, addition of O2 to N2 suppresses the electrolyte degradation and chemical side reactions, leading to a more efficient and chemically stable LiMEAS. High performance of LiMEAS with optimal O2 was attributed to the formation of a stable and efficient SEI on the surface of the working electrode, and the subsequent suppression of HER from electrolyte. The main phases in SEI were lithium hydroxides (LiOH∙xH2O), carbonate (LiCO3), and ethoxide (LiOEt). However, larger masses in EQCM and NMR describe polytetrahydrofuran (polyTHF) network formation. This work additionally elaborates on the effect of LiMEAS and consequent SEI on the electrolyte decomposition. Our results point towards efficient, stable and robust LiMEAS with highly dynamic structure–activity–stability relationship of the electrode interphase for, but not limited to, LiMEAS. C. Li, T. Wang and J. Gong, Transactions of Tianjin University, 2020, 26, 67-91.A. Tsuneto, A. Kudo and T. Sakata, Chem. Lett., 1993, 22, 851-854.R. Sažinas, S. Z. Andersen, K. Li, M. Saccoccio, K. K., J. B. Pedersen, J. Kibsgaard, P. K. K. Vesborg, D. Chakraborty and I. Chorkendorff, Submitted, 2021.S. Z. Andersen, M. J. Statt, V. J. Bukas, S. G. Shapel, J. B. Pedersen, K. Krempl, M. Saccoccio, D. Chakraborty, J. Kibsgaard, P. C. K. Vesborg, J. Nørskov and I. Chorkendorff, Energy & Environ. Sci., 2020, 13, 4291-4300.K. Li, S. Z. Andersen, M. J. Statt, M. Saccoccio, V. J. Bukas, K. Krempl, R. Sažinas, J. B. Pedersen, V. Shadravan, Y. Zhou, D. Chakraborty, J. Kibsgaard, P. C. K. Vesborg, J. K. Nørskov and I. Chorkendorff, Science (New York, N.Y.), 2021, 374, 1593-1597.S. K. Heiskanen, J. Kim and B. L. Lucht, Joule, 2019, 3, 2322–2333.L. Wang, A. Menakath, F. Han, Y. Wang, P. Y. Zavalij, K. J. Gaskell, O. Borodin, D. Iuga, S. P. Brown, C. Wang, K. Xu and B. W. Eichhorn, Nat. Chem., 2019, 11, 789-796.

Exploring simultaneous elimination of dimethyl phthalate and nitrogen by a novel constructed wetlands coupled with dielectric barrier discharge plasma

Dimethyl phthalate (DMP) contamination, as an emerging pollutant, has posed acute health risks to humans due to its potential disruption in reproductive function and endocrine system disorders. In this study, the dielectric barrier discharge (DBD) plasma and constructed wetlands (CWs) were coupled to explore the simultaneous enhancement of DMP and nitrogen removal. The results showed that the coupling DBD plasm and CWs obtained an efficient elimination of DMP (87.7–97.3%), and nitrogen removal was also improved simultaneously with higher removal of ammonia nitrogen (97.7–98.6%) and total nitrogen (TN, 22.6–40.6%). TN removal efficiency was promoted gradually by increasing the concentration of influent DMP due to the DMP decomposition into small molecules by DBD plasma, which could provide carbon source to promote denitrification for subsequent CWs. The DMP degradation processes in the coupling system were reflected by three-dimensional excitation emission matrix fluorescence spectrum and gas chromatograph-mass spectrometer, which indicated that DMP solution was activated in the DBD plasma and more organic by-products were produced. Additionally, monomethyl phthalate and phthalic acid were main degradation intermediate products of DMP. It indicated that coupling DBD plasma and CWs broke the carbon–oxygen single bond of DMP and converted it into less toxic compounds with less-refractory substances. This study provides assistant information on the application of the coupling DBD plasma and CWs technology for treating wastewater containing toxic and non-biodegradable contaminants.

Using Au NPs anchored on ZrO2/carbon black toward more efficient H2O2 electrogeneration in flow-by reactor for carbaryl removal in real wastewater

In the present study, we designed a highly efficient catalyst for H2O2 production using gold nanoparticles (Au NPs) anchored on hybrid substrate composed of ZrO2 and Printex L6 carbon (Au-ZrO2/PL6C). The higher selectivity of Au-ZrO2/PL6C (97%) toward H2O2 electrogeneration and its improved activity in terms of ORR onset potential (140 mV for more positive values) compared to Au/PL6C (80%) were attributed to the synergism between Au NPs anchored on ZrO2/PL6C hybrid support. The results obtained from the application of the catalysts for H2O2 generation on gas diffusion electrode (GDE) after 120 min of electrolysis reflected the following order of efficiency: PL6C (∼140 mg L−1) < ZrO2/PL6C (∼235 mg L−1) < Au/PL6C (∼374 mg L−1) < Au-ZrO2/PL6C (∼600 mg L−1). Given that Au-ZrO2/PL6C exhibited the highest catalytic efficiency, this catalyst was employed for the removal of carbaryl (CBR) using different electrochemical advanced oxidation processes. The CBR degradation tests exhibited pseudo first-order kinetics, with the electro-Fenton (EF) and photoelectro-Fenton (PEF) processes recording the fastest removal kinetics (3.5 × 10−2 s−1 and 4.1 × 10−2 s−1, respectively). The PEF process exhibited the highest efficiency in terms of organic by-products mineralization; this was attributed to the additional photodecarboxylation of the Fe(III)-RCOOH complexes by UVC light. The aromatic by-products, short chain carboxylic acids, and ionic nitrogen species produced during the mineralization process contributed to the successful degradation of CBR. Apart from the analysis with synthetic water, the study also analyzed the treatment of urban wastewater spiked with CBR using a pre-pilot flow plant.

Experimental analysis of gas- and particle-phase organic byproducts formed by plasma-induced toluene destruction processes

• Organic byproducts were evaluated by NTP degradation of toluene at ambient temperature and atmospheric pressure. • PTR-TOFMS measurement showed that toluene degradation resulted in dozens of organic by-products. • Size distribution and number concentration of particles formed during toluene degradation were measured by SMPS. • NTP-induced polymerization and oxidation contribute to particle formation with diameters in the range of 10 and 100 nm. Non-thermal plasma (NTP) technology has great potential to treat volatile organic compounds (VOCs) at low concentrations and large volumes. In this work, toluene, one of the most stable VOCs, was employed as a model pollutant to study its degradation by double dielectric barrier discharge (DDBD) at ambient temperature and atmospheric pressure. The performance of the DDBD reactor was evaluated in terms of discharge power, removal efficiency, CO x selectivity, and byproduct formation. Online and continuous measurements by PTR-TOFMS showed that toluene degradation resulted in the formation of 12 major volatile organic byproducts as well as 7 minor ones with concentrations ranging from ppbv to ppmv. Moreover, the particle size distribution and number concentration of particles formed during toluene degradation were measured using a scanning mobility particle sizer, and the effects of discharge power, initial toluene concentration, gas flow rate and O 2 content on particle formation were systematically investigated. The results show that both NTP-induced polymerization and oxidation contribute to aerosol formation, and the total concentration of organic byproducts in the aerosol phase is about 10 7 cm −3 with diameters in the range of 10 and 100 nm. This pioneered investigation on gas- and particle-phase organic byproducts from toluene degradation by NTP would deepen the understanding of plasma degradation of VOCs and accelerate the practical application of NTP for VOCs treatment.