Advanced remediation in the presence of ferrous iron and carbonate-containing water by oxygen-induced oxidation of organic contaminants.

Mechanistic investigations of an environmentally friendly and easy-to-implement oxidation method in the remediation of contaminated anoxic waters, i.e. groundwater, through the sole use of oxygen for the oxygen-induced oxidation of pollutants were the focus of this work. This was achieved by the addition of O2 under anoxic conditions in the presence of ferrous iron which initiated the ferrous oxidation and the simultaneous formation of reactive •OH radicals. The involvement of inorganic ligands such as carbonates in the activation of oxygen as part of the oxidation of Fe2+ in water was investigated, too. The formation of •OH radicals, was confirmed in two different, indirect approaches by a fluorescence-based method involving coumarin as •OH scavenger and by the determination of the oxidation products of different aromatic VOCs. In the latter case, the oxidation products of several typical aromatic groundwater contaminants such as BTEX (benzene, toluene, ethylbenzene, xylenes), indane and ibuprofen, were determined. The influence of other ligands in the absence of bicarbonate and the effect of pH were also addressed. The possibility of activation of O2 in carbonate-rich water i.e. groundwater, may also potentially contribute to oxidation of groundwater contaminants and support other primary remediation techniques.

Photocatalytic degradation process of antibiotic sulfamethoxazole by ZnO in aquatic systems: a dynamic kinetic model based on contributions of OH radical, oxygenated radical intermediates and dissolved oxygen.

The photocatalytic degradation process of sulfamethoxazole (SMX) using ZnO in aquatic systems has been systematically studied by varying initial SMX concentration from 0 to 15 mgL-1, ZnO dosage from 0 to 4 gL-1 and UV light intensity at the light source from 0 to 18 W(m-lamp length)-1 at natural pH. Almost complete degradations of SMX were achieved within 120 min for the initial SMX concentration ≤15 mgL-1 with ZnO dosage of 3 gL-1 and UV light intensity of 18 W(m-lamp length)-1. The photocatalytic degradation process was found to be interacted with the dissolved oxygen (DO) consumption. With oxygen supply through the gas-liquid free-surface, the DO concentration decreased significantly in the initial SMX degradation phase and increased asymptotically to the saturated DO concentration after achieving about 80% SMX degradation. The change in DO concentration was probably controlled by the oxygen consumption in the formation of oxygenated radical intermediates. A novel dynamic kinetic model based on the fundamental reactions of photocatalysis and the formation of oxygenated radical intermediates was developed. In the modeling the dynamic concentration profiles of OH radical and DO are considered. The dynamics of SMX degradation process by ZnO was simulated reasonably by the proposed model.

Top-down versus bottom-up oxidation of a neonicotinoid pesticide by OH radicals.

Emerging contaminants (EC) distributed on surfaces in the environment can be oxidized by gas phase species (top-down) or by oxidants generated by the underlying substrate (bottom-up). One class of EC is the neonicotinoid (NN) pesticides that are widely distributed in air, water, and on plant and soil surfaces as well as on airborne dust and building materials. This study investigates the OH oxidation of the systemic NN pesticide acetamiprid (ACM) at room temperature. ACM on particles and as thin films on solid substrates were oxidized by OH radicals either from the gas phase or from an underlying TiO2 or NaNO2 substrate, and for comparison, in the aqueous phase. The site of OH attack is both the secondary >CH2 group as well as the primary -CH3 group attached to the tertiary amine nitrogen, with the latter dominating. In the case of top-down oxidation of ACM by gas phase OH radicals, addition to the -CN group also occurs. Major products are carbonyls and alcohols, but in the presence of sufficient water, their hydrolyzed products dominate. Kinetics measurements show ACM is more reactive toward gas phase OH radicals than other NN nitroguanidines, with an atmospheric lifetime of a few days. Bottom-up oxidation of ACM on TiO2 exposed to sunlight outdoors (temperatures were above 30 °C) was also shown to occur and is likely to be competitive with top-down oxidation. These findings highlight the different potential oxidation processes for EC and provide key data for assessing their environmental fates and toxicologies.

Influence of pesticide mixture on their heterogeneous atmospheric degradation by ozone and OH radicals.

Pesticides in the atmosphere can exist in both gaseous and particulate phases due to their semi-volatile properties. They can undergo degradation when exposed to atmospheric oxidants like ozone and hydroxyl radicals. The majority of studies on the atmospheric reactivity of pesticides study them in combination, without considering potential mixture effects that could induce uncertainties in the results. Therefore, this study aims to address this gap, through laboratory studies using a flow reactor, and by evaluating the degradation kinetics of pendimethalin mixed with folpet, tebuconazole, and S-metolachlor, which were simultaneously adsorbed on hydrophobic silica particles that mimic atmospheric aerosols. The comparison with other mixtures, including pendimethalin, from the literature has shown similar reactivity with ozone and hydroxyl radicals, indicating that the degradation kinetics of pesticides is independent of the mixture. Moreover, the degradation rates of the four pesticides under study indicate that they are not or slightly degraded by ozone, with half-lives ranging from 29 days to over 800 days. In contrast, when exposed to hydroxyl radicals, tebuconazole exhibited the fastest reactivity, with a half-life of 4 days, while pendimethalin had a half-life of 17 days.

Atmospheric chemistry of 2-nitrobenzaldehyde: Initiated by photo-excitation, OH-oxidation, and small TiO2 clusters adsorption catalysis.

The fate of 2-nitrobenzaldehyde (2-NBA) is of interest in atmospheric chemistry as it is a semi-volatile organic compound with high photosensitivity. This study presents a quantum chemical study of the gas-phase reactions of 2-NBA photo-excitation and OH-oxidation in the absence and presence of small TiO2 clusters. To further understand the unknown photolysis mechanism, the photo-reaction pathways of ground singlet state and the lying excited triplet state of 2-NBA were investigated including the initial and subsequent reactions of proton transfer, direct CO, NO2, and HCO elimination routes in the presence of O2 and NO. Meanwhile, the OH-mediated degradation of 2-NBA proceeded via five H-extraction and six OH-addition channels by indirect mechanism, which follows a succession of reaction steps initiated by the formation of weakly stable intermediate complexes. The H-extraction from the -CHO group was the dominant pathway with a negative activation energy of -1.22 kcal/mol. The calculated rate coefficients at 200-600 K were close to the experimental data in literature within 308-352 K, and the kinetic negative temperature independence was found in both experimental literature and computational results. Interestingly, 2-NBA was favored to be captured onto small TiO2 clusters via six adsorption configurations formed via various combination of three types of bonds of Ti···O, Ti···C, and O···H between the molecularly adsorbed 2-NBA and TiO2 clusters. Comparison indicted that the chemisorptions of aldehyde oxygen have largest energies. The results suggested adsorption conformations have a respectable impact on the catalysis barrier. This study is significant for understanding the atmospheric chemistry of 2-nitrobenzaldehyde.

Biocompatible copper formate-based nanoparticles with strong antibacterial properties for wound healing.

Copper-based antibacterial materials have emerged as a potential alternative for combating bacterial infections, which continue to pose significant health risks. Nevertheless, the use of copper-based nanoparticles as antibacterial agents has faced challenges due to their toxicity towards cells and tissues. To overcome this obstacle, we propose a new approach using a contact-active copper-based nanoparticles called polydopamine (PDA)-coated copper-amine (Cuf-TMB@PDA). The positively charged surface of Cuf-TMB@PDA enables efficient targeting of negatively charged bacteria, allowing controlled release of Cu(II) into the bacterial cell membrane. Moreover, Cuf-TMB@PDA exhibits similar ·OH signals as Cuf-TMB suspensions in previous work. In cytotoxicity assays conducted over 72 h, Cuf-TMB@PDA demonstrated an efficacy of 98.56%, while releasing lower levels of Cu(II) that were less harmful to cells, resulting in enhanced antimicrobial effects. These antimicrobial properties are attributed to the synergistic effects of charge-contact activity of PDA, controlled release of Cu(II), and free radicals. Subsequent in vivo experiments confirmed the strong antimicrobial potency of Cuf-TMB@PDA and its ability to promote wound healing.

Cold Plasma for Green Advanced Reduction/Oxidation Processes (AROPs) of Organic Pollutants in Water.

Cold plasma is gaining increasing attention as a novel tool to activate energy demanding chemical processes, including advanced reduction/oxidation processes (AROPs) of organic pollutants in water. The very complex milieu generated by discharges at the water/plasma interface comprises photons, strong oxidants and strong reductants which can be exploited for achieving the degradation of most any kind of pollutants. Despite the complexity of these systems, the powerful arsenal of mechanistic tools and chemical probes of physical organic chemists can be usefully applied to understand and develop plasma chemistry. Specifically, the added value of air plasma generated by in situ discharge with respect to ozonation (ex situ discharge) is demonstrated using phenol and various phenol derivatives and mechanistic evidence for the prevailing role of hydroxyl radicals in the initial attack is presented. On the reduction front, the impressive performance of cold plasma in inducing the degradation of recalcitrant perfluoroalkyl substances, which do not react with OH radicals but are attacked by electrons, is reported and discussed. The widely different reactivities of perfluorooctanoic acid (PFOA) and of perfluorobutanoic acid (PFBA) underline the crucial role played in these processes by the interface between plasma and solution and the surfactant properties of the treated pollutants.

Oxidation 1-methyl naphthalene based on the synergy of environmentally persistent free radicals (EPFRs) and PAHs in particulate matter (PM) surface.

Studies of the environmental fate through the interactions of particle-associated polycyclic aromatic hydrocarbons (PAHs) with environmentally persistent free radicals (EPFRs) are presented. The formation of PAHs and EPFRs typically occurs side by side during combustion-processes. The laboratory simulation studies of the model PAH molecule 1-Methylnaphthalene (1-MN) interaction with model EPFRs indicate a transformational synergy between these two pollutants due to mutual and matrix interactions. EPFRs, thorough its redox cycle result in the oxidation of PAHs into oxy-/hydroxy-PAHs. EPFRs have been shown before to produce OH radical during its redox cycle in aqueous media and this study has shown that produced OH radical can transform other PM constituents resulting in alteration of PM chemistry. In model PM, EPFRs driven oxidation process of 1-MN produced 1,4-naphthoquinone, 1-naphthaldehyde, 4-hydroxy-4-methylnaphthalen-1-one, and various isomers of (hydroxymethyl) naphthalene. Differences were observed in oxidation product yields, depending on whether EPFRs and PAHs were cohabiting the same PM or present on separate PM. This effect is attributed to the OH radical concentration gradient as a factor in the oxidation process, further strengthening the hypothesis of EPFRs' role in the PAH oxidation process. This finding is revealing new environmental role of EPFRs in a natural degradation process of PAHs. Additionally, it points to implications of such PM surface chemistry in the changing mobility of PAHs into an aqueous medium, thus increasing their bioavailability.

New insight into the removal process of benzotriazole UV stabilizers by UV/H2O2: Integrating quantum chemical calculation with CFD simulation.

Benzotriazole UV stabilizers (BT-UVs) are important UV absorbers. As high-production chemicals and potential hazards, their ubiquitous presence in aquatic environments is of greatly pressing concern. Herein, the removal of six typical BT-UVs by UV/H2O2 was comprehensively investigated by quantum chemistry calculation integrated with CFD simulation. Utilizing such a micro and macro incorporated model in treating contaminants is the first report. From the micro-view, degradation mechanisms of BT-UVs by •OH oxidation were determined, and corresponding rate constants were obtained with values of 109∼1010 M-1s-1. In a macroscopic aspect, combining the established kinetic model and CFD simulation, the effects of UV lamp power (P), volumetric flow rate (Qv), and H2O2 dosage ([H2O2]0) on removal yields of BT-UVs were expounded, increasing P or [H2O2]0 or decreasing Qv are effective in improving removal yields of BT-UVs, but the enhancement was abated when P or [H2O2]0 increased to a certain level. When [H2O2]0 is 5 mg/L and Qv is decreased from 0.1 to 0.05 m3/h, the removal yields of BT-UVs could achieve more than 95% (P = 150 W) and 99% (P = 250 W), respectively. This work provides a new interdisciplinary insight for investigating organic contaminant removal in potential industrial applications of UV/H2O2 systems.

Fe(II)/LXQ-10 bifunctional resin materials for boosting synergistic adsorption/oxidation of benzene in industrial waste gas.

A series of adsorption/oxidation bifunctional material with different Fe(II) loading amounts was prepared by using ultrahigh crosslinking adsorption resin (LXQ-10) as a carrier and FeCl2 as an impregnating solution. The bifunctional material was characterized by BET, SEM, XRD, XPS, and EPR. The effects of Fe loading, reaction temperature, and space velocity on benzene adsorption efficiency were investigated using self-made experimental equipment to explore the optimal reaction condition. The adsorption results were fitted and analyzed by using four typical models: the quasi-first-order kinetic model, the quasi-second-order kinetic model, Elovich's kinetic model, and the Weber and Morris kinetic model. The quasi-first-order kinetic model had the highest R2 value (0.998) and the best applicability. The fitting effect of the Freundlich equation (R2 = 0.997) was better than that of the Langmuir equation (R2 = 0.919). Furthermore, the effects of Fe loading, H2O2 concentration, benzene inlet concentration, and temperature on the catalytic oxidation efficiency of benzene were studied. The catalytic oxidation efficiency of 3-Fe(II)/LXQ-10 was maintained at about 95% at a temperature of 303 K and an H2O2 concentration of 150 mmol/L. Compared with the adsorption efficiency, the catalytic oxidation efficiency of bifunctional resin materials in a heterogeneous Fenton system was remarkably improved and had excellent stability. A possible migration and transformation path during benzene removal was proposed according to the results of the analysis of GC-MS intermediates. This study provided a novel process for the adsorption and oxidative degradation of VOCs.

3D Characterization of the Molecular Neighborhood of •OH Radical in High Temperature Water by MD Simulation and Voronoi Polyhedra.

Understanding the properties of the •OH radical in aqueous environments is essential for biochemistry, atmospheric chemistry, and the development of green chemistry technologies. In particular, the technological applications involve knowledge of microsolvation of the •OH radical in high temperature water. In this study, the classical molecular dynamics (MD) simulation and the technique based on the construction of Voronoi polyhedra were used to provide 3D characteristics of the molecular vicinity of the aqueous hydroxyl radical (•OHaq). The statistical distribution functions of metric and topological features of solvation shells represented by the constructed Voronoi polyhedra are reported for several thermodynamic states of water, including the pressurized high-temperature liquid and supercritical fluid. Calculations showed a decisive influence of the water density on the geometrical properties of the •OH solvation shell in the sub- and supercritical region: with the decreasing density, the span and asymmetry of the solvation shell increase. We also showed that the 1D analysis based on the oxygen-oxygen radial distribution functions (RDFs) overestimates the solvation number of •OH and insufficiently reflects the influence of transformations in the hydrogen-bonded network of water on the structure of the solvation shell.

Flocculation synergistic with nano zero-valent iron augmented attapulgite @ chitosan as Fenton-like catalyst for the treatment of landfill leachate.

In this study, nano-zero-valent iron (NZVI) was added to attapulgite/chitosan and used as a catalyst in the heterogeneous Fenton process to degrade stabilized landfill leachate. Landfill leachate has serious environmental impacts due to the complexity and diversity of its pollutants. A magnetic catalyst (NZVI@PATP/CS) was prepared by a liquid-phase reduction method. The NZVI@PATP/CS were characterized by XRD, FTIR and SEM. The pH of leachate and the dosage of catalyst and H2O2 were changed to determine the best-operating conditions for the effective removal of chemical oxygen demand (COD) and total phosphorus(TP). To understand the adsorption degradation mechanism, the quenching experiments of free radicals were carried out. The results showed that the degradation rates of COD and TP were 66% and 92%, respectively, under the optimum pH value of 8, the dosage of H2O2 of 5 mL, and the dosage of the catalyst of 0.25 g for 60 min.

Vertical distributions of atmospheric HONO and the corresponding OH radical production by photolysis at the suburb area of Shanghai, China.

Nitrous acid (HONO) is considered as one of the main sources of the hydroxyl radical (OH), the most relevant oxidant in the atmosphere. Multi-AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were conducted to obtain the vertical profiles of aerosol and HONO from November 1, 2020 to January 31, 2021 at a suburb site of Shanghai, China. HONO was mainly distributed near the surface, but high values HONO occasionally occurred around 0.7 km, indicating an unaccounted source of daytime HONO at high altitudes. The positive correlation between HONO and aerosols suggested that the photo-enhanced heterogeneous reactions on the aerosol surface were an important source of daytime HONO at high altitudes. To obtain the vertical distribution of OH production by HONO photolysis (P(OH)HONO), the vertical profiles of photolysis rate of HONO (JHONO) were calculated by establishing a method of combining observations with empirical relationship based on heterogeneous atmospheric and radiative transfer models. The JHONO increased approximately linearly with increasing altitudes and the noontime averages value of JHONO near the ground were 6.68 × 10-4 s-1, which was strongly negatively affected by aerosols in the morning and afternoon. The P(OH)HONO profile varied in different months (November, December, January) that the changes were mainly affected by HONO and JHONO. P(OH)HONO was more positively affected by JHONO at high altitude and noon but greatly influenced by HONO concentrations in the morning and afternoon.

Fabrication of Ni/TiO2 visible light responsive photocatalyst for decomposition of oxytetracycline.

Nickel-impregnated TiO2 photocatalyst (NiTP) responding to visible light was prepared by the liquid phase plasma (LPP) method, and its photoactivity was evaluated in degrading an antibiotic (oxytetracycline, OTC). For preparing the photocatalyst, nickel was uniformly impregnated onto TiO2 (P-25) powder, and the nickel content increased as the number of LPP reactions increased. In addition, the morphology and lattice of NiTP were observed through various instrumental analyses, and it was confirmed that NiO-type nanoparticles were impregnated in NiTP. Fundamentally, as the amount of impregnated nickel in the TiO2 powder increased sufficiently, the band gap energy of TiO2 decreased, and eventually, the NiTP excited by visible light was synthesized. Further, OTC had a decomposition reaction pathway in which active radicals generated in OTC photocatalytic reaction under NiTP were finally mineralized through reactions such as decarboxamidation, hydration, deamination, demethylation, and dehydroxylation. In effect, we succeeded in synthesizing a photocatalyst useable under visible light by performing only the LPP single process and developed a new advanced oxidation process (AOP) that can remove toxic antibiotics.

The Effect of Human Occupancy on Indoor Air Quality through Real-Time Measurements of Key Pollutants.

The primarily emitted compounds by human presence, e.g., skin and volatile organic compounds (VOCs) in breath, can react with typical indoor air oxidants, ozone (O3), and hydroxyl radicals (OH), leading to secondary organic compounds. Nevertheless, our understanding about the formation processes of the compounds through reactions of indoor air oxidants with primary emitted pollutants is still incomplete. In this study we performed real-time measurements of nitrous acid (HONO), nitrogen oxides (NOx = NO + NO2), O3, and VOCs to investigate the contribution of human presence and human activity, e.g., mopping the floor, to secondary organic compounds. During human occupancy a significant increase was observed of 1-butene, isoprene, and d-limonene exhaled by the four adults in the room and an increase of methyl vinyl ketone/methacrolein, methylglyoxal, and 3-methylfuran, formed as secondary compounds through reactions of OH radicals with isoprene. Intriguingly, the level of some compounds (e.g., m/z 126, 6-methyl-5-hepten-2-one, m/z 152, dihydrocarvone, and m/z 194, geranyl acetone) formed through reactions of O3 with the primary compounds was higher in the presence of four adults than during the period of mopping the floor with commercial detergent. These results indicate that human presence can additionally degrade the indoor air quality.

[Characteristics and Reactivity of VOCs in a Typical Industrial City in Summer].

To investigate the ambient pollution caused by volatile organic compounds (VOCs) in a typical industrial city in summer, the characteristics and chemical reactivity from VOCs and the causes of ozone (O3) pollution were analyzed using online VOCs measurements during polluted and non-polluted periods in Zibo city in July 2020. The results showed that the average hourly concentration of total volatile organic compounds (TVOC) during the polluted period[(50.6±28.3)] µg·m-3 was 32.5% higher than that during the non-polluted period[(38.2±24.9) µg·m-3]. The contribution of all VOCs categories were as follows:alkanes>aromatics>alkenes>alkynes, and the diurnal averages of TVOC and O3 concentrations were opposite during the polluted and non-polluted period. Ozone formation potential (OFP),·OH radical loss rate (L·OH), and secondary organic aerosol formation potential (SOAp) during the polluted period were higher than those during the non-polluted period. Alkenes contributed most to OFP and L·OH, whereas aromatics contributed most to SOAp. The tendency of the diurnal average of OFP and SOAp was overall consistent with that of TVOC. The priority species of OFP, L·OH, and SOAp were alkenes and aromatics. The VOCs/NOx method was applied to identify the O3-VOC-NOx sensitivity during the polluted and non-polluted periods, and the results showed that the photochemical regimes were VOCs-limited and transition regions. In addition, the smog production model (SPM) was employed to identify the O3 formation regime, and the results showed that those during the polluted period were identified as VOCs-limited and transition regions from 08:00 to 16:00, whereas the non-polluted period was mainly considered to be VOCs-limited. To mitigate the O3 pollution in summertime, the synergistic control of VOCs (especially alkenes and aromatics) and NOx emissions should be enforced.

Emission Characteristics and Health Risks of Volatile Organic Compounds (VOCs) Measured in a Typical Recycled Rubber Plant in China.

The continued development of the automotive industry has led to a rapid increase in the amount of waste rubber tires, the problem of "black pollution" has become more serious but is often ignored. In this study, the emission characteristics, health risks, and environmental effects of volatile organic compounds (VOCs) from a typical, recycled rubber plant were studied. A total of 15 samples were collected by summa canisters, and 100 VOC species were detected by the GC/MS-FID system. In this study, the total VOCs (TVOCs) concentration ranged from 1000 ± 99 to 19,700 ± 19,000 µg/m3, aromatics and alkanes were the predominant components, and m/p-xylene (14.63 ± 4.07%-48.87 ± 3.20%) could be possibly regarded as a VOCs emission marker. We also found that specific similarities and differences in VOCs emission characteristics in each process were affected by raw materials, production conditions, and process equipment. The assessment of health risks showed that devulcanizing and cooling had both non-carcinogenic and carcinogenic risks, yarding had carcinogenic risks, and open training and refining had potential carcinogenic risks. Moreover, m/p-xylene and benzene were the main non-carcinogenic species, while benzene, ethylbenzene, and carbon tetrachloride were the dominant risk compounds. In the evaluation results of LOH, m/p-xylene (25.26-67.87%) was identified as the most key individual species and should be prioritized for control. In conclusion, the research results will provide the necessary reference to standardize the measurement method of the VOCs source component spectrum and build a localized source component spectrum.

[Comparison of VOCs Pollution Characteristics Between an Urban Site and a Background Site in Summer in Zibo].

To study the differences in volatile organic compound (VOCs) pollution characteristics between an urban site and a background site in summer, ambient VOCs were monitored using an online gas chromatograph (GC) at an urban site and a background site (Mt. Lu) in Zibo in July 2020. The VOCs pollution characteristics and chemical reactivity were analyzed, and the sources of VOCs were identified using the positive matrix factorization model(PMF). The results showed that ρ(TVOC) and ρ(NOx) were higher at the urban site, but ρ(O3) was higher at the background site. Diurnal average characteristics of ρ(TVOC) and ρ(NOx) were high at night and low during the day at the urban site, and there were no obvious variation characteristics at the background site. The diurnal average characteristics of ρ(O3) were consistent at the urban and background sites, showing low level at night and high level during the day; however, the peak in the background site was later than that at the urban site. The average ρ(TVOC) at the urban site and background site were (44.9±27.5) µg·m-3 and (17.3±9.1) µg·m-3, respectively, and the mass fraction of each component was ordered as alkanes>aromatics>alkenes>alkynes in both sites. The average ozone formation potentials(OFP)were (115.5±63.1) µg·m-3 and (38.0±20.2) µg·m-3, and the contribution of each component was ordered as alkenes>aromatics>alkanes>alkynes. The respective average values of·OH radical loss rate(L·OH) were (3.9±2.3) s-1 and (1.0±0.6) s-1, with the highest contribution of alkenes and the lowest contribution of alkynes in both sites. The average values of secondary organic aerosol formation potential(SOAp) were (0.5±0.3) µg·m-3 and (0.2±0.06) µg·m-3, respectively, with aromatic being the most abundant group. According to the source appointment by the PMF model, the main source of VOCs in the urban site was traffic sources (52.4%), followed by petroleum evaporation (19.2%), solvent evaporation (17.3%), and oil and biological sources (11.1%). The source of VOCs in the background site mainly came from traffic sources (40.2%), followed by solvent evaporation (31.3%), combustion sources (19.3%), and biological sources (9.2%). Zibo City should strengthen the management and control of motor vehicle emissions, petroleum evaporation, and the use of industrial solvents.

Review of component designs for post-COVID-19 HVAC systems: possibilities and challenges.

The globally occurring recurrent waves of the COVID-19 pandemic, primarily caused by the transmission of aerosolized droplets from an infected person to a healthy person in the indoor environment, has led to the urgency of designing new modes of indoor ventilation. To prevent cross-contaminations due to airborne viruses, bacteria, and other pollutants in indoor environments, heating ventilation and air-conditioning (HVAC) systems need to be redesigned with anti-pandemic components. The three vital anti-pandemic components for the post-COVID-19 HVAC systems, as identified by the authors, are: a biological contaminant inactivation unit, a volatile organic compound decomposition unit, and an advanced air filtration unit. The purpose of the current article is to provide an overview of the latest research outcomes toward designing these anti-pandemic components and pointing out the future promises and challenges. In addition, the role of personalized ventilation in minimizing the risk of indoor cross-contamination by employing various air terminal devices is discussed. The authors believe that this article will encourage HVAC designers to develop effective anti-pandemic components to minimize the indoor airborne transmission.

Inactivation behavior and intracellular changes in Escherichia coli during electro-oxidation process using Ti/Sb-SnO2/PbO2 anode: Elucidation of the disinfection mechanism.

This study investigates the behavior and intracellular changes in Escherichia coli (model organism) during electro-oxidation with Ti/Sb-SnO2/PbO2 anode in a chlorine free electrochemical system. Preliminary studies were conducted to understand the effect of initial E. coli concentration and applied current density on disinfection. At an applied current density 30 mA cm-2, 7 log reduction of E. coli was achieved in 75 min. The role of reactive oxygen species' (ROS) in E.coli disinfection was evaluated, which confirmed hydroxyl (•OH) radical as the predominant ROS in electro-oxidation. Observations were carried out at cell and molecular level to understand E.coli inactivation mechanism. Scanning electron microscopy images confirmed oxidative damage of the cell wall and irreversible cell death. Intracellular and extracellular protein quantification and genetic material release further confirmed cell component leakage due to cell wall rupture and degradation due to •OH radical interaction. Change in cell membrane potential suggests the colloidal nature of E. coli cells under applied current density. Plasmid deoxyribonucleic acid degradation study confirmed fragmentation and degradation of released genetic material. Overall, effective disinfection could be achieved by electro-oxidation, which ensures effective inactivation and prevents regrowth of E. coli. Disinfection of real wastewater was achieved in 12 min at an applied current density 30 mA cm-2. Real wastewater study further confirmed that effective disinfection is possible with a low cost electrode material such as Ti/Sb-SnO2/PbO2. Energy consumed during disinfection was determined to be 4.978 kWh m-3 for real wastewater disinfection at applied current density 30 mA cm-2. Cost of operation was estimated and stability of the electrode was studied to evaluate the feasibility of large scale operation. Relatively low energy and less disinfection time makes this technology suitable for field scale applications.