Guzman Lab Publications

Valorisation of Bourbon Distillery Waste into Single-source Hybrid Lithium-ion Capacitors Authors: Josiel Barrios Cossio, Juan Luis Gómez‑Urbano, Sandesh Darlami Magar, Ignacio Martin‑Gullon, Rodney Andrews, Andrea Balducci, and Marcelo I. Guzman Journal: Materials Advances (Royal Society of Chemistry) Publication status: Accepted and published online (Open Access, CC BY) DOI: https://doi.org/10.1039/D6MA00297H Graphical Abstract Abstract Bourbon, an iconic American whiskey, is primarily produced in Kentucky, which accounts for 95% of the world’s supply. Between 2000 and 2024, bourbon output in Kentucky increased sixfold, creating significant sustainability challenges—particularly the disposal of spent grains (stillage), a high‑volume by‑product generated at six to ten times the volume of bourbon produced. This study presents a scalable strategy to upcycle bourbon stillage into high‑performance carbon materials for energy‑storage applications. The pr...

Our group is excited to share our newest article published in ACS ES&T Air (March 2026), titled “Methane Emissions from Underground Coal Mines.” The study provides the first coordinated, multiplatform evaluation of methane emissions from underground coal mines across Kentucky. Between 2021 and 2022, the team surveyed 14 active, 4 inactive, and 4 abandoned mines using vehicle‑mounted near‑infrared spectrometers, GHGSat aircraft overflights, and a small uncrewed aerial system (sUAS). These complementary methods were deployed to evaluate detection performance, quantify methane emissions, and compare results with historical EPA and MSHA data. Vehicle-based surveys proved highly effective, detecting methane anomalies at 9 of 13 accessible mines, with emissions reaching up to 665 ± 229 kg h⁻¹ at major ventilation fans. In contrast, aircraft surveys detected anomalies at only 3 of 14 mines, largely due to complex terrain and horizontally oriented fans that weaken vertical column si...

A new study from the Guzman Lab has just been published in Environmental Science: Water Research & Technology (Royal Society of Chemistry), offering fresh insights into the environmental risks of iodinated compounds in urban wastewater systems. Title: Iodinated Disinfection Byproduct Formation from Iohexol in Sunlit and Chlorinated Urban Wastewaters Authors: Reagan P. Witt & Marcelo I. Guzman 🔗 Read the full article This research explores how iohexol, a common medical imaging agent, undergoes chemical transformations when exposed to sunlight and chlorination during wastewater treatment. The study reveals the formation of iodinated disinfection by-products (I-DBPs)—a group of toxic compounds associated with serious health risks, including bladder cancer and miscarriages. By mapping the transformation pathways of iohexol, the Guzman Lab provides critical knowledge that can help healthcare facilities and wastewater treatment plants minimize the formation of hazardous byproducts a...

O ur latest open-access publication in Science of The Total Environment was published on August 18, 2025. The study investigates the ozonolysis of phenolic aldehydes from industrial lignin wastewaters. We identify hydroxylated and acidic products formed via OH radical pathways, and propose a mechanism for pollutant degradation that enhances water quality. This work contributes to advancing sustainable wastewater treatment technologies and understanding the chemistry behind pollutant transformation. Abstract: Phenolic aldehydes are widespread pollutants in water and soil, originating from lignin-based agro-industries. With increasing wastewater pollution, improved treatment systems are necessary to degrade phenolic aldehydes into less hazardous compounds. Over the past two decades, ozonolysis wastewater treatment has been implemented in the United States, Japan, and South Korea. However, the mechanistic understanding of phenolic aldehyde ozonolysis in water remains ...

Summary: As the Special Issues “Feature Papers in Photochemistry” and “Feature Papers in Photochemistry II” conclude, it is crucial to acknowledge the remarkable progress and persistent gaps that continue to shape the journey of photochemistry research. The field of photochemistry has seen unprecedented advancements, driven by novel techniques and interdisciplinary approaches. The study of light-induced molecular transformations, the application of photochemical processes in organic synthesis, the development of high-efficiency photocatalysts, and the discovery of novel environmental photochemical mechanisms have all marked significant progress in recent years. Moreover, photochemical reactions in astrochemical mimics have been investigated to understand the chemical evolution of interstellar environments. Reference: Feature Papers in Photochemistry . M.I. Guzman . Photochem (2024), 4 (4), 511-517; DOI: 10.3390/photochem4040032 .  ...

Abstract: Semiconductor photocatalysis with commercial TiO 2 (Degussa P25) has shown significant potential in water treatment of organic pollutants. However, the photoinduced reactions of adsorbed catechol, a phenolic air pollutant from biomass burning and combustion emissions, at the air–solid interface of TiO 2 remain unexplored. Herein we examine the photocatalytic decay of catechol in the presence of water vapor, which acts as an electron acceptor. Experiments under variable cut-off wavelengths of irradiation (λ cut-off ≥ 320, 400, and 515 nm) distinguish the mechanistic contribution of a ligand-to-metal charge-transfer (LMCT) complex of surface chemisorbed catechol on TiO 2 . The LMCT complex injects electrons into the conduction band of TiO 2 from the highest occupied molecular orbital of catechol by visible light (≥2.11 eV) excitation. The deconvolution of diffuse reflectance UV–visible spectral bands from LMCT complexes of TiO 2 with catechol, o -semiquinone ...

Abstract: Landfills for disposing of solid waste are designed, located, managed, and monitored facilities expected to comply with government regulations to prevent contamination of the surrounding environment. After the average life expectancy of a typical landfill (30 to 50 years), a large investment in the construction, operation, final closure, and 30-year monitoring of a new site is needed. In this case study, we provide a holistic explanation of the unexpected development of elevated temperature landfills (ETLFs), such as that in the city of Bristol (United States) on the border of the states of Virginia and Tennessee, including the initial role played by coal ash. Despite the increasing frequency of ETLF occurrence, there is limited knowledge available about their associated environmental problems. The study uses mixed (qualitative, quantitative, and mapping) methods to analyze (1) the levels of odoriferous reduced sulfur compounds, ammonia, and volatile organic com...

  Abstract: Climate change is a complex, global issue that is impacting human health in various ways, with healthcare being a significant contributor to carbon emissions in the United States. This review discusses the environmental impact of important aspects of gynecologic oncology care, including surgery, anesthesia care, radiology, chemotherapy, and radiation oncology. Operating room energy and material use is highlighted, with a focus on the environmental impact of robotic surgery. The contribution of certain anesthetic gases in increasing greenhouse gas emissions is addressed. Additionally, the environmental impacts of radiologic imaging, chemotherapy, and radiation oncology are also discussed. Despite the complexity of climate change, there are multiple strategies on the individual and institutional level that can help mitigate the environmental impact of gynecologic oncology care. Individual efforts include practicing red bag stewardship, limiting single use-s...

Abstract: Formate (HCOO – ) is the most dominant intermediate identified during carbon dioxide electrochemical reduction (CO 2 ER). While previous studies showed that copper (Cu)-based materials that include Cu(0), Cu 2 O, and CuO are ideal catalysts for CO 2 ER, challenges to scalability stem from low selectivity and undesirable products in the −1.0–1.0 V range. There are few studies on the binding mechanism of intermediates and products for these systems as well as on changes to surface sites upon applying potential. Here, we use an in situ approach to study the redox surface chemistry of formate on Cu thin films deposited on Si wafers using a VeeMAX III spectroelectrochemical (SEC) cell compatible with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Spectra for surface species were collected in real time as a function of applied potential during cyclic voltammetry (CV) experiments. Results showed the reproducibility of CV curves on freshly...

Abstract: Catechol is a widespread atmospheric dihydroxybenzene present in vehicle emissions, biomass burning, and combustion pollution plumes. Although the daytime reactivity of catechol is controlled by ozone (O 3 ) and hydroxyl radicals (HO), the action of nitrate radicals (NO 3 ) on the surface of aqueous atmospheric particles should become significant at night. This work simulates nighttime interfacial chemistry between hydrated catechol and adsorbed NO 3 to form 4-nitrocatechol during experiments lasting ≤1 μs. Surface-sensitive online electrospray ionization mass spectrometry (OESI-MS) examines the reaction on the water surface under variable ratios of [NO 2 ] and [O 3 ]. The produced 4-nitrocatechol is quantified by a standard addition in real-time experiments under [NO 2 ]:[O 3 ] ratios of 1:1, 2:1, 3:1, and 4:1. Three mechanisms contribute to produce 4-nitrocatechol: (1) electron and proton transfers from catechol to NO 3 , forming a semiquinone radical, (2) ele...

Abstract: Biomass burning emissions contain abundant phenolic aldehydes (e.g., syringaldehyde, vanillin, and 4-hydroxybenaldehyde) that are oxidized during atmospheric transport, altering the physicochemical properties of particulates. Herein, the oxidative processing of thin films made of syringaldehyde, vanillin, and 4-hydroxybenaldehyde is studied at the air–solid interface under a variable O 3 (g) molar ratio (410 ppbv–800 ppmv) and relative humidity (0–90%). Experiments monitored the absorption changes of C═C, C═O, and ─COOH vibration changes during the oxidation of thin films by transmission Fourier transform infrared spectroscopy (FTIR). Selected spectroscopic features of aromatic ring cleavage by O 3 (g) revealed the production of carboxylic acids. Instead, monitoring O─H stretching provided a comparison of a hydroxylation channel from in situ produced hydroxyl radical. The overall oxidation reactivity trend syringaldehyde > vanillin > 4-hydroxybenzladehyde...

Abstract: Abundant substituted catechols are emitted to, and created in, the atmosphere during wildfires and anthropogenic combustion and agro-industrial processes. While ozone (O 3 ) and hydroxyl radicals (HO • ) efficiently react in a 1 μs contact time with catechols at the air–water interface, the nighttime reactivity dominated by nitrate radicals (NO 3 ) remains unexplored. Herein, online electrospray ionization mass spectrometry (OESI-MS) is used to explore the reaction of NO 3 (g) with a series of representative catechols (catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol) on the surface of aqueous microdroplets. The work detects the ultrafast generation of nitrocatechol (aromatic) compounds, which are major constituents of atmospheric brown carbon. Two mechanisms are proposed to produce nitrocatechols, one (equivalent to H atom abstraction) following fast electron transfer from the catechols (QH 2 ) to NO 3 , forming NO 3 – and QH 2 •+ ...

Abstract: Potassium is used extensively as a promoter with iron catalysts in Fisher–Tropsch synthesis, water–gas shift reactions, steam reforming, and alcohol synthesis. In this paper, the identification of potassium chemical states on the surface of iron catalysts is studied to improve our understanding of the catalytic system. Herein, potassium-doped iron oxide (α-Fe 2 O 3 ) nanomaterials are synthesized under variable calcination temperatures (400–800 °C) using an incipient wetness impregnation method. The synthesis also varies the content of potassium nitrate deposited on superfine iron oxide with a diameter of 3 nm (Nanocat ® ) to reach atomic ratios of 100 Fe: x K ( x = 0–5). The structure, composition, and properties of the synthesized materials are investigated by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Fourier-transform infrared, Raman spectroscopy, inductively coupled plasma-atomic emission spectroscopy, and X-ray phot...

Abstract: The heterogeneous reaction between thin films of catechol exposed to O 3 (g) creates hydroxyl radicals (HO • ) in situ, which in turn generate semiquinone radical intermediates in the path to form heavier polyhydroxylated biphenyl, terphenyl, and triphenylene products. Herein, the alteration of catechol aromatic surfaces and their chemical composition are studied during the heterogeneous oxidation of catechol films by O 3 (g) molar ratios ≥ 230 ppbv at variable relative humidity levels (0% ≤ RH ≤ 90%). Fourier transform infrared micro-spectroscopy, atomic force microscopy, electrospray ionization mass spectrometry, and reverse-phase liquid chromatography with UV–visible and mass spectrometry detection provide new physical insights into understanding the surface reaction. A Langmuir–Hinshelwood mechanism is accounted to report reaction rates, half-lives, and reactive uptake coefficients for the system under variable relative humidity levels. The reactions reported...

  Abstract: Nitrogen-containing organic carbon (NOC) in atmospheric particles is an important class of brown carbon (BrC). Redox active NOC like aminophenols received little attention in their ability to form BrC. Here we show that iron can catalyze dark oxidative oligomerization of o - and p -aminophenols under simulated aerosol and cloud conditions (pH 1–7, and ionic strength 0.01–1 M). Homogeneous aqueous phase reactions were conducted using soluble Fe(III), where particle growth/agglomeration were monitored using dynamic light scattering. Mass yield experiments of insoluble soot-like dark brown to black particles were as high as 40%. Hygroscopicity growth factors (κ) of these insoluble products under sub- and super-saturated conditions ranged from 0.4–0.6, higher than that of levoglucosan, a prominent proxy for biomass burning organic aerosol (BBOA). Soluble products analyzed using chromatography and mass spectrometry revealed the formation of ring coupling produc...

Abstract: Substantial amounts of phenolic aldehydes, represented by the structures of syringaldehyde, vanillin, and 4-hydroxybenzaldehyde, are emitted to the atmosphere during biomass burning. The oxidative transformation of phenolic aldehydes during atmospheric transport has the potential to modify the physicochemical properties of particulates, which play a vital role in Earth’s climate and human health. Herein, thin solid films made of syringaldehyde, vanillin, and 4-hydroxybenzaldehyde are oxidized in contact with O 3 (g) under a relative humidity of 74% representative of average global conditions. New physical insights into the surface reactions are achieved by analyzing isopropanol-extracted films before and during oxidation by multiple techniques. Changes in electronic transitions at 220, 310, and 350–400 nm registered by UV–vis spectroscopy show that the oxidized films have enhanced mass absorption coefficients at λ > 300 nm. Electrospray ionization (ESI) mass ...

Abstract: Solid waste components can be recycled in waste paper and cardboard sorting plants (WPCSP) through a multistep process. This work collected 15 samples every six days from each of the 9 points selected to study the processes taking place in a WPCSP (135 particulate matter samples total). Examining the concentration and size fraction of particulate matter (i.e., PM 1 , PM 2.5 and PM 10 ) in WPCSP is an essential issue to notify policy makers about the health impacts on exposed workers. The major activities for increasing of the concentration of PM in various processing units in the WPCSP, especially in hand-picking routes I and II were related to manual dismantling, mechanical grinding, mechanical agitation, and separation and movement of waste. The results of this work showed that a negative correlation between temperature and particulate matter size followed the order PM 10  > PM 2.5  > PM 1 . Exposure to PM 2.5 and PM 10 in the WPCSP ...

Abstract: Oxidative degradation in amine based post-combustion carbon capture (PCCC) leads to solvent losses and decreased solvent performance. Oxygen (O 2 ) in the flue gas is dissolved into the aqueous solvent and can reactively degrade the amine component. Advanced aqueous amine solvents are designed to contain additional surfactant and anti-foam additives as well as two types of corrosion inhibitors. These additives contribute to improve the solvent performance while reducing foaming and corrosion of expensive equipment. This work examines the impact of these additives on oxygen solubility (or dissolved oxygen - DO) in various aqueous amines used in PCCC including ethanolamine (MEA), 1-amino-2-propanol (A2P), 2-amino-1-propanol (2A1P), 2-(methylamino)-ethanol (NMEA), 2-(ethylamine)-ethanol (2EAE), diethanolamine (DEA), methyl-diethanolamine (MDEA), dimethylethanolamine (DMEA), piperazine (PZ), 1,2-ethyldiamine (EDA), and 1,6 hexadiamine (HDA). The impact of carbon lo...

  Abstract: Examining the concentration and types of airborne bacteria in waste paper and cardboard sorting plants (WPCSP) is an urgent matter to inform policy makers about the health impacts on exposed workers. Herein, we collected 20 samples at 9 points of a WPCSP every 6 winter days, and found that the most abundant airborne bacteria were positively and negatively correlated to relative humidity and temperature, respectively. The most abundant airborne bacteria (in units of CFU m −3 ) were: Staphylococcus sp. (72.4) >  Micrococcus sp. (52.2) >  Bacillus sp. (30.3) >  Enterococcus sp. (24.0) >  Serratia marcescens (20.1) >  E. coli (19.1) >  Pseudomonas sp. (16.0) >  Nocardia sp. (1.9). The lifetime average daily dose (LADD) for the inhalation and dermal routes for the intake of airborne bacteria ranged from 3.7 × 10 −3 ≤ LADD Inhalation ≤ 2.07...

Abstract: Atmospheric organic aerosols play a major role in climate, demanding a better understanding of their formation mechanisms by contributing multiphase chemical reactions with the participation of water. The sunlight driven aqueous photochemistry of small 2-oxocarboxylic acids is a potential major source of organic aerosol, which prompted the investigations into the mechanisms of glyoxylic acid and pyruvic acid photochemistry reviewed here. While 2-oxocarboxylic acids can be contained or directly created in the particles, the majorities of these abundant and available molecules are in the gas phase and must first undergo the surface uptake process to react in, and on the surface, of aqueous particles. Thus, the work also reviews the acid-base reaction that occurs when gaseous pyruvic acid meets the interface of aqueous microdroplets, which is contrasted with the same process for acetic acid. This work classifies relevant information needed to understand the photoc...