Indoor air quality improvement with filtration and UV-C on mitigation of particulate matter and airborne bacteria: Monitoring and modeling.

Indoor air, especially with suspended particulate matter (PM), can be a carrier of airborne infectious pathogens. Without sufficient ventilation, airborne infectious diseases can be transmitted from one person to another. Indoor air quality (IAQ) significantly impacts people's daily lives as people spend 90% of their time indoors. An industrial-grade air cleaner prototype (filtration + ultraviolet light) was previously upgraded to clean indoor air to improve IAQ on two metrics: particulate matter (PM) and viable airborne bacteria. Previous experiments were conducted to test its removal efficiency on PM and airborne bacteria between the inlet and treated air. However, the longer-term improvement on IAQ would be more informative. Therefore, this research focused on quantifying longer-term improvement in a testing environment (poultry facility) loaded with high and variable PM and airborne bacteria concentrations. A 25-day experiment was conducted to treat indoor air using an air cleaner prototype with intermittent ON and OFF days in which PM and viable airborne bacteria were measured to quantify the treatment effect. The results showed an average of 55% reduction of total suspended particulate (TSP) concentration between OFF days (110 µg/m3) and ON days (49 µg/m3). An average of 47% reduction of total airborne viable bacteria concentrations was achieved between OFF days (∼3200 CFU/m3) and ON days (∼2000 CFU/m3). A cross-validation (CV) model was established to predict PM concentrations with five input variables, including the status of the air cleaner, time (h), ambient temperature, indoor relative humidity, and day of the week to help simulate the air-cleaning effect of this prototype. The model can approximately predict the air quality trend, and future improvements may be made to improve its accuracy.

Thermally persistent carbonyl nitrene: FC(O)N.

Transient carbonyl nitrenes RC(O)N, formed during thermal- or photoinduced decomposition of carbonyl azides RC(O)N3, are highly liable to the Curtius rearrangement, producing isocyanates RNCO in almost quantitative yield. Contrary to common belief, we found a thermally persistent triplet carbonyl nitrene, FC(O)N, that can be produced by flash pyrolysis of FC(O)N3 in 49% yield. The computed CBS-QB3 activation barrier for the thermal decomposition of FC(O)N3 to FC(O)N is 29 kJ mol(-1) lower than that for a concerted pathway producing FNCO.

Computational rationalization for the observed ground-state multiplicities of fluorinated acylnitrenes.

Computational methods are used to investigate the mechanism by which fluorination of acetylnitrene reduces the stabilization of the singlet configuration. ΔEST is made more positive (favoring the triplet state) by 1.9, 1.3, and 0.7 kcal/mol by the addition of the first, second, and third fluorine, respectively, at the CR-CC(2,3)/6-311(3df,2p)//B3LYP/6-31G(d,p) level of theory. Smaller effects observed with substitution of ß-fluorines in propanoylnitrene derivatives and examination of molecular geometries and orbitals demonstrate that the effect is due to inductive electron withdrawal by the fluorines, rather than hyperconjugation.

Computational investigation of the photochemical deoxygenation of thiophene-S-oxide and selenophene-Se-oxide.

CASSCF and multireference MP2 calculations were carried out on thiophene-S-oxide (TO) and selenophene-Se-oxide (SeO), comparing the energies of the ground state to the first two electronically excited singlet and triplet states, using constrained optimizations and multiple fixed S-O or Se-O distances. For both molecules, one of the two triplet states smoothly dissociates to yield O((3)P) with little or no barrier. Single point calculations are consistent with the same phenomenon occurring for dibenzothiophene-S-oxide (DBTO). This provides an explanation for the inefficient unimolecular photochemical dissociation of O((3)P) from DBTO despite a phosphorescence energy below that of S-O dissociation, i.e., that S-O scission probably occurs from a spectroscopically unobserved triplet (T2) state.

Laboratory-scale investigation of UV treatment of ammonia for livestock and poultry barn exhaust applications.

The feasibility of using deep ultraviolet (UV) treatment for abatement of ammonia (NH(3)) in livestock and poultry barn exhaust air was examined in a series of laboratory-scale experiments. These experiments simulated moving exhaust air through an irradiation chamber with variables of UV wavelength and dose, NH(3) concentrations, humidity, and presence of hydrogen sulfide (H(2)S). Ammonia, initially at relevant barn exhaust concentrations in air, was substantially or completely reduced by irradiation with 185 nm light. Reactions were monitored using chemiluminescence detection, gas chromatography with mass spectrometry detection, and Fourier transform infrared spectrometry, of which the latter was found to be the most informative and flexible. Detected nitrogen-containing products included N(2)O, NH(4)NO(3), and HNO(3). It was presumed that atomic oxygen is the primary photochemical product that begins the oxidative cascade. The data show that removal of NH(3) is plausible, but they highlight concerns over pollution swapping due to formation of ozone and N(2)O.

Evaluation of an Air Cleaning Device Equipped with Filtration and UV: Comparison of Removal Efficiency on Particulate Matter and Viable Airborne Bacteria in the Inlet and Treated Air.

Since the COVID-19 pandemic, improving indoor air quality (IAQ) has become vital for the public as COVID-19 and other infectious diseases can transmit via inhalable aerosols. Air cleaning devices with filtration and targeted pollutant treatment capabilities can help improve IAQ. However, only a few filtration/UV devices have been formally tested for their effectiveness, and little data is publicly available and UV doses comparable. In this research, we upgraded a particulate matter (PM) air filtration prototype by adding UV-C (germicidal) light. We developed realistic UV dose metrics for fast-moving air and selected performance scenarios to quantify the mitigation effect on viable airborne bacteria and PM. The targeted PM included total suspended particulate (TSP) and a coarse-to-fine range sized at PM10, PM4, PM2.5, and PM1. The PM and viable airborne bacteria concentrations were compared between the inlet and outlet of the prototype at 0.5 and 1.0 m3/s (low and high) air flow modes. The upgraded prototype inactivated nearly 100% of viable airborne bacteria and removed up to 97% of TSP, 91% of PM10, 87% of PM4, 87% of PM2.5, and 88% of PM1. The performance in the low flow rate mode was generally better than in the high flow rate mode. The combination of filtration and UV-C treatment provided 'double-barrier' assurance for air purification and lowered the risk of spreading infectious micro-organisms.

Evaluation of TiO2 Based Photocatalytic Treatment of Odor and Gaseous Emissions from Swine Manure with UV-A and UV-C.

It is essential to mitigate gaseous emissions that result from poultry and livestock production to increase industry sustainability. Odorous volatile organic compounds (VOCs), ammonia (NH3), hydrogen sulfide (H2S), and greenhouse gases (GHGs) have detrimental effects on the quality of life in rural communities, the environment, and climate. This study's objective was to evaluate the photocatalytic UV treatment of gaseous emissions of odor, odorous VOCs, NH3, and other gases (GHGs, O3-sometimes considered as by-products of UV treatment) from stored swine manure on a pilot-scale. The manure emissions were treated in fast-moving air using a mobile lab equipped with UV-A and UV-C lights and TiO2-based photocatalyst. Treated gas airflow (0.25-0.76 m3∙s-1) simulates output from a small ventilation fan in a barn. Through controlling the light intensity and airflow, UV dose was tested for techno-economic analyses. The treatment effectiveness depended on the UV dose and wavelength. Under UV-A (367 nm) photocatalysis, the percent reduction of targeted gases was up to (i) 63% of odor, (ii) 51%, 51%, 53%, 67%, and 32% of acetic acid, propanoic acid, butanoic acid, p-cresol, and indole, respectively, (iii) 14% of nitrous oxide (N2O), (iv) 100% of O3, and 26% generation of CO2. Under UV-C (185 + 254 nm) photocatalysis, the percent reductions of target gases were up to (i) 54% and 47% for p-cresol and indole, respectively, (ii) 25% of N2O, (iii) 71% of CH4, and 46% and 139% generation of CO2 and O3, respectively. The results proved that the UV technology was sufficiently effective in treating odorous gases, and the mobile lab was ready for farm-scale trials. The UV technology can be considered for the scaled-up treatment of emissions and air quality improvement inside livestock barns. Results from this study are needed to inform the experimental design for future on-farm research with UV-A and UV-C.

Design and Testing of Mobile Laboratory for Mitigation of Gaseous Emissions from Livestock Agriculture with Photocatalysis.

Livestock production systems generate nuisance odor and gaseous emissions affecting local communities and regional air quality. There are also concerns about the occupational health and safety of farmworkers. Proven mitigation technologies that are consistent with the socio-economic challenges of animal farming are needed. We have been scaling up the photocatalytic treatment of emissions from lab-scale, aiming at farm-scale readiness. In this paper, we present the design, testing, and commissioning of a mobile laboratory for on-farm research and demonstration of performance in simulated farm conditions before testing to the farm. The mobile lab is capable of treating up to 1.2 m3/s of air with titanium dioxide, TiO2-based photocatalysis, and adjustable UV-A dose based on LED lamps. We summarize the main technical requirements, constraints, approach, and performance metrics for a mobile laboratory, such as the effectiveness (measured as the percent reduction) and cost of photocatalytic treatment of air. The commissioning of all systems with standard gases resulted in ~9% and 34% reduction of ammonia (NH3) and butan-1-ol, respectively. We demonstrated the percent reduction of standard gases increased with increased light intensity and treatment time. These results show that the mobile laboratory was ready for on-farm deployment and evaluating the effectiveness of UV treatment.

Designing and Testing of a System for Aerosolization and Recovery of Viable Porcine Reproductive and Respiratory Syndrome Virus (PRRSV): Theoretical and Engineering Considerations.

Porcine reproductive and respiratory syndrome virus (PRRSV) infections cause significant economic losses to swine producers every year. Aerosols containing infectious PRRSV are an important route of transmission, and proper treatment of air could mitigate the airborne spread of the virus within and between barns. Previous bioaerosol studies focused on the microbiology of PRRSV aerosols; thus, the current study addressed the engineering aspects of virus aerosolization and collection. Specific objectives were to (1) build and test a virus aerosolization system, (2) achieve a uniform and repeatable aerosol generation and collection throughout all replicates, (3) identify and minimize sources of variation, and (4) verify that the collection system (impingers) performed similarly. The system for virus aerosolization was built and tested (Obj. 1). The uniform airflow distribution was confirmed using a physical tracer (<12% relative standard deviation) for all treatments and sound engineering control of flow rates (Obj. 2). Theoretical uncertainty analyses and mass balance calculations showed <3% loss of air mass flow rate between the inlet and outlet (Obj. 3). A comparison of TCID50 values among impinger fluids showed no statistical difference between any two of the three trials (p-value = 0.148, 0.357, 0.846) (Obj. 4). These results showed that the readiness of the system for research on virus aerosolization and treatment (e.g., by ultraviolet light), as well as its potential use for research on other types of airborne pathogens and their mitigation on a laboratory scale.

Selenium-modified TiO2 and its impact on photocatalysis.

This work describes the preparation of a selenium-modified TiO(2) photocatalyst and a preliminary evaluation of its photocatalytic activity. Se-TiO(2) displayed greater visible absorption than undoped TiO(2) and was still capable of degrading quinoline at a slightly faster rate than undoped TiO(2) under UV light. Se-TiO(2) was also able to degrade organic molecules under purely visible light by a single electron transfer pathway. Irradiation with >435 nm light showed no evidence of efficient production of HO•-like species. Se-TiO(2) was also examined under hypoxic conditions, where the Se atoms were capable of trapping photogenerated electrons as evidenced by XPS.

A simple and mild synthesis of 1H-isochromenes and (Z)-1-alkylidene-1,3-dihydroisobenzofurans by the iodocyclization of 2-(1-alkynyl)benzylic alcohols.

A variety of iodo-substituted isochromenes, dihydroisobenzofurans, and pyranopyridines are readily prepared in good to excellent yields under mild conditions by the iodocyclization of readily available 2-(1-alkynyl)benzylic alcohols or 2-(1-alkynyl)-3-(hydroxymethyl)pyridines. Reactions are carried out in MeCN at 25 degrees C with 3 equiv of I(2) as the iodine source and NaHCO(3) (3 equiv) as the base. The regiochemical outcome of the reaction strongly depends on the substitution pattern of the starting material. In particular, the 5-exo-dig cyclization mode, leading to dihydroisobenzofurans, is observed in the case of substrates bearing a tertiary alcoholic group, owing to the gem-dialkyl effect, while the 6-endo-dig cyclization mode, leading to isochromene or pyranopyridines, is the usually preferred pathway in the case of substrates bearing a primary or secondary alcoholic group.

Pilot-Scale Testing of UV-A Light Treatment for Mitigation of NH3, H2S, GHGs, VOCs, Odor, and O3 Inside the Poultry Barn.

Poultry farmers are producing eggs, meat, and feathers with increased efficiency and lower carbon footprint. Technologies to address concerns about the indoor air quality inside barns and the gaseous emissions from farms to the atmosphere continue to be among industry priorities. We have been developing and scaling up a UV air treatment that has the potential to reduce odor and other gases on the farm scale. In our recent laboratory-scale study, the use of UV-A (a less toxic ultraviolet light, a.k.a. "black light") and a special TiO2-based photocatalyst reduced concentrations of several important air pollutants (NH3, CO2, N2O, O3) without impact on H2S and CH4. Therefore, the objectives of this research were to (1) scale up the UV treatment to pilot scale, (2) evaluate the mitigation of odor and odorous volatile organic compounds (VOCs), and (3) complete preliminary economic analyses. A pilot-scale experiment was conducted under commercial poultry barn conditions to evaluate photocatalyst coatings on surfaces subjected to UV light under field conditions. In this study, the reactor was constructed to support interchangeable wall panels and installed on a poultry farm. The effects of a photocatalyst's presence (photocatalysis and photolysis), UV intensity (LED and fluorescent), and treatment time were studied in the pilot-scale experiments inside a poultry barn. The results of the pilot-scale experiments were consistent with the laboratory-scale one: the percent reduction under photocatalysis was generally higher than photolysis. In addition, the percent reduction of target gases at a high light intensity and long treatment time was higher. The percent reduction of NH3 was 5-9%. There was no impact on H2S, CH4, and CO2 under any experimental conditions. N2O and O3 concentrations were reduced at 6-12% and 87-100% by both photolysis and photocatalysis. In addition, concentrations of several VOCs responsible for livestock odor were reduced from 26 to 62% and increased with treatment time and light intensity. The odor was reduced by 18%. Photolysis treatment reduced concentrations of N2O, VOCs, and O3, only. The initial economic analysis has shown that LEDs are more efficient than fluorescent lights. Further scale-up and research at farm scale are warranted.

Reaction of dicarbomethoxycarbene with thiophene derivatives.

Photolysis of derivatives of dimethylmalonate thiophene-S,C-ylide provides dicarbomethoxycarbene, which can react with thiophene to form dimethyl (2-thienyl)malonate. By generation of dicarbomethoxycarbene from the dibenzothiophene-based ylide in neat thiophene, it is shown that the thienylmalonate is not a product of rearrangement of the thiophene ylide, in contrast to thermolysis results. Formation of the thienylmalonate is suppressed by substitution of any sort in the 2- and 5-positions on the thiophene and by substitution with an electron-withdrawing substituent.

Simultaneous chemical and sensory characterization of volatile organic compounds and semi-volatile organic compounds emitted from swine manure using solid phase microextraction and multidimensional gas chromatography-mass spectrometry-olfactometry.

Swine manure is associated with emissions of odor, volatile organic compounds (VOCs) and other gases that can affect air quality on local and regional scales. In this research, a solid phase microextraction (SPME) and novel multidimensional gas chromatography-mass spectrometry-olfactometry (MDGC-MS-O) system were used to simultaneously identify VOCs and related odors emitted from swine manure. Gas samples were extracted from manure headspace using Carboxen/polydimethylsiloxane (PDMS) 85-microm SPME fibers. The MDGC-MS-O system was equipped with two columns in series with a system of valves allowing transfer of samples between columns (heartcutting). The heartcuts were used to maximize the isolation, separation, and identification of compounds. The odor impact of separated compounds was evaluated by a trained panelist for character and intensity. A total of 295 compounds with molecular weights ranging from 34 to 260 were identified. Seventy one compounds had a distinct odor. Nearly 68% of the compounds for which reaction rates with OH* radicals are known had an estimated atmospheric lifetime <24 h.

S,C-sulfonium ylides from thiophenes: potential carbene precursors.

Photolysis of S,C-sulfonium ylides derived from thioanisol, thiophene, benzothiophene, or dibenzothiophene provides products deriving from dicarbomethoxycarbene. In methanol, no rearrangement of the carbene to the ketene derivative is observed. Formation of dibenzothiophene and benzothiophene is quantitative. For the thiophene-based ylide, insertion of the carbene into the alpha-CH bond of thiophene is observed. Evidence is presented that supports formation of both singlet and triplet carbene.

Use of chiral ionic liquids as solvents for the enantioselective photoisomerization of dibenzobicyclo[2.2.2]octatrienes.

[Reaction: see text] Six chiral ionic liquids were prepared and evaluated as "chiral induction solvents" in which two different dibenzobicyclo[2.2.2]octatrienes were photoisomerized to chiral products. Enantiomeric excesses from 3 to 12% were obtained from the photochemical di-pi-methane rearrangement. Results indicate that the chiral induction derives from an ion pairing interaction of the deprotonated diacids with the ionic liquid cation. This is the first report on chiral induction via a chiral IL for an irreversible, unimolecular photochemical isomerization.

Improved quantification of livestock associated odorous volatile organic compounds in a standard flow-through system using solid-phase microextraction and gas chromatography-mass spectrometry.

Aerial emissions of odorous volatile organic compounds (VOCs) are an important nuisance factor from livestock production systems. Reliable air sampling and analysis methods are needed to develop and test odor mitigation technologies. Quantification of VOCs responsible for livestock odor remains an analytical challenge due to physicochemical properties of VOCs and the requirement for low detection thresholds. A new air sampling and analysis method was developed for testing of odor/VOCs mitigation in simulated livestock emissions system. A flow-through standard gas generating system simulating odorous VOCs in livestock barn emissions was built on laboratory scale and tested to continuously generate ten odorous VOCs commonly defining livestock odor. Standard VOCs included sulfur VOCs (S-VOCs), volatile fatty acids (VFAs), and p-cresol. Solid-phase microextraction (SPME) was optimized for sampling of diluted odorous gas mixtures in the moving air followed by gas chromatography-mass spectrometry (GC-MS) analysis. CAR/PDMS 85µm fiber was shown to have the best sensitivity for the target odorous VOCs. A practical 5-min sampling time was selected to ensure optimal extraction of VFAs and p-cresol, as well as minimum displacement of S-VOCs. Method detection limits ranged from 0.39 to 2.64ppbv for S-VOCs, 0.23 to 0.77ppbv for VFAs, and 0.31ppbv for p-cresol. The method developed was applied to quantify VOCs and odorous VOC mitigation with UV light treatment. The measured concentrations ranged from 20.1 to 815ppbv for S-VOCs, 10.3 to 315ppbv for VFAs, and 4.73 to 417ppbv for p-cresol. Relative standard deviations between replicates ranged from 0.67% to 12.9%, 0.50% to 11.4%, 0.83% to 5.14% for S-VOCs, VFAs, and p-cresol, respectively. This research shows that a simple manual SPME sampler could be used successfully for quantification of important classes of odorous VOCs at concentrations relevant for real aerial emissions from livestock operations.

Separation of racemic sulfoxides and sulfinate esters on four derivatized cyclodextrin chiral stationary phases using capillary gas chromatography.

The separation of 17 chiral sulfoxides and eight chiral sulfinate esters by gas chromatography (GC) on four derivatized cyclodextrin chiral stationary phases (CSPs) (Chiraldex G-TA, G-BP, G-PN, B-DM) is presented. Many of these compounds are structural isomers or part of a homologous series. Differences in enantioselectivity of the methyl phenyl sulfoxide isomers on the derivatized gamma cyclodextrin and the heptakis 2,6-di-O-methyl-beta-cyclodextrin (i.e. B-DM) CSPs are discussed. Under the conditions of this study, the molecular mass cut-off for the GC separation of these compounds was approximately 230. Compounds of higher molecular mass were not eluted from the CSPs at reasonable times and temperatures, but these higher molecular mass enantiomers can be separated by liquid chromatography and capillary electrophoresis. The enantiomeric separation and elution order of a sulfinate ester containing two stereogenic centers as well as 15 chiral sulfoxides is presented. The G-TA and B-DM CSPs generally gave opposite elution orders for most of the compounds studied.

Separation of chiral sulfoxides by liquid chromatography using macrocyclic glycopeptide chiral stationary phases.

A set of 42 chiral compounds containing stereogenic sulfur was prepared. There were 31 chiral sulfoxide compounds, three tosylated sulfilimines and eight sulfinate esters. The separations were done using five different macrocyclic glycopeptide chiral stationary phases (CSPs), namely ristocetin A, teicoplanin, teicoplanin aglycone (TAG), vancomycin and vancomycin aglycone (VAG) and seven eluents, three normal-phase mobile phases, two reversed phases and two polar organic mobile phases. Altogether the macrocyclic glycopeptide CSPs were able to separate the whole set of the 34 sulfoxide enantiomers and tosylated derivatives. Five of the eight sulfinate esters were also separated. The teicoplanin and TAG CSPs were the most effective CSPs able to resolve 35 and 33 of the 42 compounds. The three other CSPs each were able to resolve more than 27 compounds. The normal-phase mode was the most effective followed by the reversed-phase mode with methanol-water mobile phases. Few of these compounds could be separated in the polar organic mode with 100% methanol mobile phases. Acetonitrile was also not a good solvent for the resolution of enantiomers of sulfur-containing compounds, neither in the reversed-phase nor in the polar organic mode. The structure of the chiral molecules was compared to the enantioselectivity factors obtained with the teicoplanin and TAG CSP. It is shown that the polarity, volume and shape of the sulfoxide substituents influence the solute enantioselectivity factor. Changing the oxidation state of the sulfur atom from sulfoxides to sulfinate esters is detrimental to the compound's enantioselectivity. The enantiomeric retention order on the teicoplanin and TAG CSPs was very consistent: the (S)-(+)-sulfoxide enantiomer was always the less retained enantiomer. In contrast, the (R)-(-)-enantiomer was less retained by the ristocetin A, vancomycin and vancomycin aglycone columns, showing the complementarity of these CSPs. The macrocyclic glycopeptide CSPs provided broad selectivity and effective separations of chiral sulfoxides.

Modulation of carbene spin state population through precursor photophysics.

Dicarbomethoxycarbene can be generated by photolysis of S-C sulfonium ylides derived from thiophene. By manipulating the thiophene (leaving group) portion of the ylide, the initial spin distribution of the carbenes can be strongly influenced. With certain carbene traps, product distributions from dicarbomethoxycarbene depend on the initial spin state distribution in which the carbene is generated and this is used as a means to report on the initial spin state distributions. This approach should be general for other carbenes generated from analogous precursors.