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High-biomass sweet sorghum is considered a promising energy crop suitable for the production of energy, first- and second-generation biofuels and biobased chemicals. Processing in a typical sugar cane mill or dedicated sorghum mill is challenged by the presence of trash (leaves and panicles). The separation of leaves and panicles could generate additional value streams, and the reduction of trash is considered beneficial for juice extraction and juice quality. A two-stage trash removal system for the separation of leaves, and panicles was designed and tested. The pneumatic leaf separation stage allowed the removal of up to 56% of leaves in a single pass and the second stage, a novel rotating-disk separator, demonstrated the feasibility of the panicle separation. The basic design parameters were optimized for both systems, and the impact of trash removal tested on Ceres® Inc. “Durasweet” sorghum in 2015 and 2016. Trash removal from the feedstock allowed practically identical recovery (97.3–99.9%) of soluble solids, while up to 19.1% less feedstock with significantly less fiber (82.6% of original feedstock) was processed.

Sweet sorghum (Sorghum bicolor L. Moench) is a promising bioenergy crop for the production of ethanol and bio-based products. Sugarcane billet harvesters can be used to harvest sweet sorghum. Multiple extractor fan speed settings of these harvesters allow for separating the extraneous matter in the feedstock, which has been associated with increased milling throughput and better juice quality at the processing facility. This removal is not completely selective, and some stalk material is also lost. These losses can be higher for sweet sorghum than sugarcane due its lower weight. This paper presents an assessment of how the speed of the primary extractor fan of a sugarcane billet combine used for harvesting sweet sorghum affects the biomass yield, biomass losses, and quality at delivery for the production of ethanol from extracted juice and fiber. Three primary extractor fan speeds (0, 800, and 1100 rpm) were evaluated. Higher fan speeds decreased fresh biomass yields by up to 28.3 Mg ha−1. Juice quality was not significantly different among treatments. Ethanol yield calculated from sweet sorghum harvested at 0 rpm was 6075 L ha−1. This value decreased by about half for material harvested at 1100 rpm due to the differences in biomass yield.

Initial feasibility evaluations of utilizing sugarcane as a renewable fuel source was fostered by high fossil fuel prices in the 1970s. Ethanol production from corn grain, however, was found to be more economical than from sugarcane feedstocks. Despite an effort made by the federal government to create a favorable environment for research and development into the use of sugarcane and energy cane feedstocks for biofuel production, the US Department of Energy and the US Department of Agriculture list no production in 2018 of either conventional or second-generation biofuel derived from these crops in the USA. Currently, the principal energy provided by sugarcane is from the combustion of bagasse to produce steam and electricity to power the sugar factory with some excess cogenerated electricity supplied to the electric grid.

Aldehydes and ketones, ubiquitous air, cloud, and fog water pollutants, are precursors to secondary organic aerosol formation and photochemical smog. Traditional aldehyde and ketone determination methods involve the addition of 2,4-dinitrophenylhydrazine (DNPH) as a derivatization agent, but many require a large sample volume or a lengthy extraction/concentration process. For fog water, where the sample size is inherently small, a DNPH derivatization method, based on U.S. EPA Method 8315A, was developed to combat this issue. In this method, a manual injection online concentration system in conjunction with HPLC was used, eliminating all liquid-liquid extraction and concentration steps and reducing the required sample volume. Hence, concentration and separation were combined in a single step. Using this injection method shortened the procedure time and also lowered the limit of detection to the nanomolar range. In this study, fourteen fog water samples, collected from October 2012 through April 2014 in Baton Rouge, LA, were analyzed for the concentration of aldehydes and ketones in order to test the feasibility of this method. Dissolved organic content (DOC), ionic concentration, and pH were measured. Formaldehyde, acetaldehyde, acrolein, butyraldehyde, benzaldehyde, and acetone were quantified. The DOC of the collected fog samples varied between 6.2 and 262.2 mgC/L. The wide range of organic content in the fog water samples corresponds to a diverse sample set, highlighted by the large variation of observed acetone concentration (under 5 nM to 1.05 mM). However, formaldehyde had a relatively stable concentration between each event (0.5 to 4.5 μM).

Green leaf volatiles (GLVs) are a group of biogenic volatile organic compounds (BVOCs) released into the atmosphere by vegetation. BVOCs produce secondary organic aerosol (SOA) via gas-phase reactions, but little is known of their aqueous-phase oxidation as a source of SOA. GLVs can partition into atmospheric water phases, e.g., fog, mist, dew or rain, and be oxidized by hydroxyl radicals (˙OH). These reactions in the liquid phase also lead to products that have higher molecular weights, increased polarity, and lower vapor pressures, ultimately forming SOA after evaporation of the droplet. To examine this process, we investigated the aqueous, ˙OH-mediated oxidation of methyl jasmonate (MeJa) and methyl salicylate (MeSa), two GLVs that produce aqueous-phase SOA. High performance liquid chromatography/electrospray ionization mass spectrometry (HPLC-ESI-MS) was used to monitor product formation. The oxidation products identified exhibit higher molecular mass than their parent GLV due to either dimerization or the addition of oxygen and hydroxyl functional groups. The proposed structures of potential products are based on mechanistic considerations combined with the HPLC/ESI-MS data. Based on the structures, the vapor pressure and the Henry's law constant were estimated with multiple methods (SPARC, SIMPOL, MPBPVP, Bond and Group Estimations). The estimated vapor pressures of the products identified are significantly (up to 7 orders of magnitude) lower than those of the associated parent compounds, and therefore, the GLV oxidation products may remain as SOA after evaporation of the water droplet. The contribution of the identified oxidation products to SOA formation is estimated based on measured HPLC-ESI/MS responses relative to previous aqueous SOA mass yield measurements.

In this study we have investigated the effect of surfactant, sodium dodecyl sulfate (SDS), on the dynamics of a single crude oil droplet, rising in a quiescent water column. Experiments were conducted in a tank, in which an oil droplet was released into a stagnant water column through a nozzle. The droplets ranging from 0.3 to 0.85 cm were produced from three different sized nozzles. The shape adopted by the emanating droplets varied from spherical to oblate. SDS concentrations were varied from 0 to 750 ppm in water. The adsorption of surfactant reduced the interfacial tension at oil-water interface which resulted in generation of smaller sized droplets at the nozzle and caused the droplet to flatten. Consequently, the rise velocities of droplets decreased. A numerical model based on finite volume method was developed using commercial CFD package ANSYS Fluent®. The model employed volume of fluid method, suggested by Hirt and Nichols (Journal of Computational Physics 1981, 39, 201), with an interface reconstruction technique based on piecewise linear representation for tracking the oil-water interface. The influence of surface tension on the droplet dynamics was captured by including Continuum Surface force (CSF) approach suggested by Brackbill, Kothe, and Zemach (Journal of Computational Physics 1992, 100, 335). The shape and rise velocities predicted from model were in good agreement with experimental data. The results from simulations were used, to analyze the wake structure and pressure distribution around the droplet. It was found that the smaller droplets which ascended in rectilinear path were associated with an axisymmetric wakes whereas larger and intermediate sized droplets in high SDS concentration wobbled as they ascended because of asymmetric wakes.

Green leaf volatiles (GLVs) are a family of oxygenated hydrocarbons emitted in large quantities by plants, especially those under mechanical stress or damage. GLVs can significantly contribute to the formation of secondary organic aerosols (SOAs) by reacting with oxidants in atmospheric water droplets (fog, mist, and rain). Here we investigated the properties of four GLVs, 2-methyl-3-buten-2-ol (MBO), methyl salicylate (MeSA), cis-3-hexen-1-ol (HxO), and cis-3-hexenylacetate (HxAc) in air/water systems at 298 K using a combination of experiments and molecular simulations. Good agreement between simulation and experimental results of the 1-octanol/water partition coefficients and the free energy of hydration of the GLVs ensure the suitability of our molecular models for these systems; likewise, surface concentrations determined from experimental measurements of the surface tensions of these systems compared favorably against trends determined from molecular simulations. Our simulations indicate that all fo...

Oil spills in the deep-sea environment such as the 2010 Deep Water Horizon oil spill in the Gulf of Mexico release vast quantities of crude oil into the sea-surface environment. Various investigators have discussed the marine transport and fate of the oil into different environmental compartments (air, water, sediment, and biota). The transport of the oil into the atmosphere in these previous investigations has been limited to only evaporation, a volatility dependent pathway. In this work, we studied the aerosolization of oil spill matter via bursting bubbles as they occur during whitecaps in a laboratory aerosolization reactor. By evaluating the alkane content in oil mousse, crude oil, the gas phase, and particulate matter we clearly demonstrate that aerosolization via bursting bubbles is a solubility and volatility independent transport pathway for alkanes. The signature of alkane fractions in the native oil and aerosolized matter matched well especially for the less volatile alkanes (C20-C29). Scanning electron microscope interfaced with energy dispersive X-ray images identified the carbon fractions associated with salt particles of aerosols. Theoretical molecular dynamics simulations in the accompanying paper lend support to the observed propensity for alkanes at air-salt water interfaces of breaking bubbles and the produced droplets. The presence of a dispersant in the aqueous phase increased the oil ejection rate at the surface especially for the C20-C29 alkanes. The information presented here emphasizes the need to further study sea-spray aerosols as a possible transport vector for spilled oil in the sea surface environment.

In order to assess the degradation of aromatic compounds in fog, the reaction of benzene with hydroxyl radicals was studied in a bulk aqueous system. The effects of temperature, oxygen content, ionic strength, and pH were investigated in a batch reactor by following the two main products, phenol and biphenyl. The reaction rate increased with temperature, but was not significantly affected by ionic strength and pH. The overall phenol yield also did not significantly change with the removal of oxygen from the system. Conversely, the formation of biphenyl was more favorable under conditions of low oxygen content, high ionic strength, and low pH. The pH of the solution decreased during the reaction due to the formation of oxidation products of phenol; thus, we found that biphenyl did not form in detectable concentrations unless the pH was at or below 4.50–4.80.

The adsorption of gas-phase phenanthrene on atmospheric water and ice films was investigated in a flow-tube reactor with a view to understanding the processing of semi-volatile organic compounds by fog and snow. Air-water (ice) interface partition constants were obtained by measuring the mass uptake of phenanthrene vapor on thin water and ice films with varying thickness. Adsorption enthalpies and entropies were obtained from the temperature dependence of the interfacial partition constants. The surface adsorption is the predominant mechanism for the uptake of phenanthrene in water and ice films with small film thickness or at low temperature. The adsorption of phenanthrene to ice resembles that to sub-cooled water and there's no significant difference between the adsorption of phenanthrene to water and that to quasi liquid layer (QLL) if we take into account the uncertainties on the thermodynamic quantities measured. Molecular dynamics simulations of phenanthrene at air/water and air/ice interfaces suppo...

The Clar reaction of 7H-benz[de]anthracen-7-one (20) was reinvestigated as a source for C34H18 polycyclic aromatic hydrocarbons (PAH). The utilization of a ternary sodium chloride/potassium chloride/zinc chloride melt with zinc dust as reducing agent yielded tetrabenzo[a,cd,j,lm]perylene (11) (10.7% yield), dibenzo[a,cd]naphtho[1,8-jk]perylene (16) (10.2% yield), and dibenzo[a,cd]naphtho[3,2,1-lm]perylene (14) (7.4% yield) as main products. Tetrabenzo[a,cd,lm,o]perylene (26) as a minor product of the Clar reaction was purified via semi-preparative high performance liquid chromatography, and its unequivocal identification was demonstrated through NMR data and a microscale-cyclization reaction.

Experiments have been conducted to study the effects of NiO, a prevalent form of nickel in combustion-generated ash particles, on polycyclic aromatic hydrocarbons (PAH) and other hydrocarbons in a fuel product mixture. The fuel product mixture is generated from the gas-phase pyrolysis, in N 2 , of the model fuel catechol in a quartz tube reactor at 1100 K and 5 s, a condition that ensures full conversion of the catechol and produces a mixture—of PAH, hydrocarbon gases, and oxygen-containing species—that is representative of the products of practical liquid and solid fuels in pyrolysis and fuel-rich combustion environments. Once formed, the product mixture is passed, at the same temperature, through a bed of ultrafine NiO particles held in place by quartz wool, in the contact zone of the reactor. The products exiting the reactor are quenched, collected, and analyzed by non-dispersive infrared analyzers, gas chromatography, and high-pressure liquid chromatography with diode-array ultraviolet–visible absorbance detection. The results from the experiments at 1100 K show that—compared to the case of no inorganics in the contact zone—when NiO is present: PAH yields are reduced 86% (from 10.8% to 1.48% fed carbon); all of the highly mutagenic 5- and 6-ring PAH are eliminated; and all of the acetylene, the highest-yield hydrocarbon product when NiO is absent, and other hydrocarbons with carbon–carbon triple bonds are eliminated from the gas phase. Most of the surface-bound carbon is released as CO. Similar experiments at 1275 K show that—except for the release of the surface-bound carbon as CO—the selective surface effects of NiO bring about similar results at higher temperature: 89% reduction in PAH yield, elimination of mutagenic 5- and 6-ring PAH, removal of acetylene and acetylenic species, as well as a decrease in the production of solid carbon (not formed at 1100 K).

Atmospheric aerosols contain a significant quantity of water in the form of both bulk water and thin water films. These provide very high surface areas and adsorptive surfaces for organic compounds of low solubility and low vapor pressures. They also provide highly active sites for oxidation reactions with hydroxyl, singlet oxygen, and ozone species in the gaseous atmosphere. Thus, organic compounds are transformed readily by the reaction at the air–water interface of fog/cloud droplets and in the thin water film in atmospheric aerosols. Mathematical models suggest that the reactions in fog and cloud droplets are not limited by gas phase diffusion or mass accommodation at the surface; rather, they primarily depend on the partition constant and reaction rates at the surface. Laboratory data on both the latter parameters are available in the literature for a variety of organic compounds and they are also supported by field data. Considerable data already exist on the aqueous processing of organic species that are highly water soluble in atmospheric aerosols. However, our works suggest that aqueous processing of organic chemicals (possessing low solubility and low vapor pressure) at the interface should also be considered in fate models for secondary organic aerosols in the atmosphere.

The adsorption and photochemical reaction of naphthalene vapor at the air-water interface of water films (22 microm and 450 microm) were studied in a horizontal flow reactor. Experiments were conducted in the regime where gas-phase mass transfer resistance did not limit the uptake. The equilibrium uptake was dependent on water film thickness only below 1 microm. Bulk water-air and air-to-interface partition constants were estimated from the experiments. The equilibrium partition constant between the water film and air decreased with increasing temperature. Photochemical reaction products were isolated in the water film after exposure to UV light. Four main oxygenated products were identified (1,3-indandione, 1(3H)-isobenzofuranone (phthalide), 2H-1-benzopyran-2-one (coumarin), and 1-naphthol). The initial rates of product formation were 46 to 154% larger for the thin film (22 microm) compared to both a thick film (450 microm) and bulk aqueous phase photooxidation. The atmospheric implications of reactions in water films are discussed.

Nanofibers with excellent activities in surface-enhanced Raman scattering (SERS) were developed through electrospinning precursor suspensions consisting of polyacrylonitrile (PAN), silver nanoparticles (AgNPs), silicon nanoparticles (SiNPs), and cellulose nanocrystals (CNCs). Rheology of the precursor suspensions, and morphology, thermal properties, chemical structures, and SERS sensitivity of the nanofibers were investigated. The electrospun nanofibers showed uniform diameters with a smooth surface. Hydrofluoric (HF) acid treatment of the PAN/CNC/Ag composite nanofibers (defined as p-PAN/CNC/Ag) led to rougher fiber surfaces with certain pores and increased mean fiber diameters. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirmed the existence of AgNPs that were formed during heat and HF acid treatment processes. In addition, thermal stability of the electrospun nanofibers increased due to the incorporation of CNCs and AgNPs. The p-PAN/CNC/Ag nanofibers were used as a SERS substrate to detect p-aminothiophenol (p-ATP) probe molecule. The results show that this substrate exhibited high sensitivity for the p-ATP probe detection.

Potential of mean force (PMF) calculations and molecular dynamics (MD) simulations were performed to investigate the properties of oil n-alkanes [i.e., n-pentadecane (C15), n-icosane (C20) and n-triacontane (C30)], as well as several surfactant species [i.e., the standard anionic surfactant sodium dodecyl sulfate (SDS), and three model dispersants similar to the Tween and Span species present in Corexit 9500A] at air/salt water interfaces. This study was motivated by the 2010 Deepwater Horizon (DWH) oil spill, and our simulation results show that, from the thermodynamic point of view, the n-alkanes and the model dispersants have a strong preference to remain at the air/salt water interface, as indicated by the presence of deep free energy minima at these interfaces. The free energy minimum of these n-alkanes becomes deeper as their chain length increases, and as the concentration of surfactant species at the interface increases. The n-alkanes tend to adopt a flat orientation and form aggregates at the bare air/salt water interface. When this interface is coated with surfactants, the n-alkanes tend to adopt more tilted orientations with respect to the vector normal to the interface. These simulation results are consistent with the experimental findings reported in the accompanying paper [Ehrenhauser et al., Environ. Sci.: Processes Impacts 2013, in press, (DOI: 10.1039/c3em00390f)]. The fact that these long-chain n-alkanes show a strong thermodynamic preference to remain at the air/salt water interfaces, especially if these interfaces are coated with surfactants, makes these species very likely to adsorb at the surface of bubbles or droplets and be ejected to the atmosphere by sea surface processes such as whitecaps (breaking waves) and bubble bursting. Finally, the experimental finding that more oil hydrocarbons are ejected when Corexit 9500A is present in the system is consistent with the deeper free energy minima observed for the n-alkanes at the air/salt water interface at increasing concentrations of surfactant species.

Methyl salicylate (MeSA) is a green leaf volatile (GLV) compound that is emitted in significant amounts by plants, especially when they are under stress conditions. GLVs can then undergo chemical reactions with atmospheric oxidants, yielding compounds that contribute to the formation of secondary organic aerosols (SOAs). We investigated the adsorption of MeSA on atmospheric air/water interfaces at 298 K using thermodynamic integration (TI), potential of mean force (PMF) calculations, and classical molecular dynamics (MD) simulations. Our molecular models can reproduce experimental results of the 1-octanol/water partition coefficient of MeSA. A deep free energy minimum was found for MeSA at the air/water interface, which is mainly driven by energetic interactions between MeSA and water. At the interface, the oxygenated groups in MeSA tend to point toward the water side of the interface, with the aromatic group of MeSA lying farther away from water. Increases in the concentrations of MeSA lead to reductions in the height of the peaks in the MeSA-MeSA g(r) functions, a slowing down of the dynamics of both MeSA and water at the interface, and a reduction in the interfacial surface tension. Our results indicate that MeSA has a strong thermodynamic preference to remain at the air/water interface, and thus chemical reactions with atmospheric oxidants are more likely to take place at this interface, rather than in the water phase of atmospheric water droplets or in the gas phase.

Green leaf volatiles (GLVs) are oxygenated hydrocarbons that are emitted by plants, especially under stress conditions such as mechanical damage and local weather changes. GLVs can react with photochemically-generated oxidants (e.g., OH radicals) in atmospheric water drops, and contribute to the formation of secondary organic aerosols (SOAs). Here we investigated the adsorption of a gas phase GLV, 2-methyl-3-buten-2-ol (MBO) and OH radicals on atmospheric air/water interfaces using classical molecular dynamics (MD) simulations and potential of mean force (PMF) calculations. Our models can reproduce experimental values of the free energy of hydration of MBO and ˙OH, as well as 1-octanol/water partition coefficients of MBO determined experimentally in this study. Both MBO and ˙OH have a strong thermodynamic incentive to remain at the air/water interface, with their density profiles overlapping significantly at the interface. These results suggest that chemical reactions between MBO and ˙OH are more likely to take place at the interface, rather than inside the bulk of water droplets or in the vapor phase. We found a significant number of contacts between MBO and ˙OH in our simulations, which could lead to reactions between these two species.

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants in the atmosphere, predominantly known for their toxicity. Although there has been substantial work on the atmospheric degradation of PAH, little is known about how the presence of atmospheric droplets (e.g., a fog cloud) affects the fate of PAH. In order to assess the processing of PAH and their corresponding oxidation products during a fog event, two field-sampling campaigns in Fresno, CA and Davis, CA were conducted. The simultaneous evaluation of concentrations of the PAH and oxygenated polycyclic aromatic compounds (OPAC) in the gas phase, particulate matter and fog water droplets before, during and after fog allows for the characterization of transformative and transport processes in a fog cloud. By tracking the ratio of OPAC to PAH in the individual atmospheric phases, two major polycyclic aromatic compounds-processing pathways can be identified: (i) the dissolution of OPAC from particulate matter and (ii) the uptake and oxidation of PAH in the fog water droplets. Wet deposition steadily decreases the pollutant concentration in the fog cloud droplets during a fog event; however, uptake and concentration via evaporative water loss upon the dissipation of a fog cloud cause an increase in the atmospheric pollutant concentration.

Atmospheric-pressure photoionization (APPI) mass spectrometry benefits from the addition of an ionization-enhancing dopant such as benzene. A passive dopant-delivery system has therefore been designed for use with the orthogonal APPI source within a commercial liquid chromatographic instrument with mass spectrometric detector. By providing the dopant in the gas phase, the newly designed equipment avoids mixing problems and other difficulties associated with liquid dopant addition. The system is a simple and durable design that can reliably deliver virtually any dopant with sufficient vapor pressure in the temperature range of 20 to 120 degrees C. At the optimum dopant flow rate (10% of the mobile phase flow rate) for high-performance liquid chromatography with narrow-bore (2.1 mm) columns, the system allows for uninterrupted routine analysis for up to two weeks. The performance of the device has been evaluated with benzene as dopant and with a test mixture consisting of four polycyclic aromatic hydrocarbons (PAH): naphthalene, 9H-fluorene, anthracene, and phenanthrene. All four PAH can be detected with an excellent signal-to-noise ratio in the scanning mode and a limit of detection down to 0.42 ng on column (51 pg in single-ion monitoring mode). The concentration calibration curves are linear over a range of three orders of magnitude, with correlation coefficients greater than 0.99. The utilization of benzene as dopant not only increases the sensitivity significantly - 20-fold, compared with dopant-free operation - but the low m/z values of the background ions observed also allow for the effective quantitative and qualitative analysis of PAH.