Model Organic Compounds Research Articles

Hydrothermal Liquefaction of Organic Waste Model Compounds: The Effect of the Heating Rate on Biocrude Yield and Quality from Mixtures of Cellulose-Albumin-Sunflower Oil.

Hydrothermal liquefaction (HTL) is a promising technology for the conversion of high-moisture biomass into a liquid biofuel precursor without predrying treatment. This study investigated the effects of the heating rate (20-110 °C/min) and feedstock composition on phase repartition of the HTL products. HTL tests were carried out using as feedstocks cellulose, egg albumin, and sunflower oil as model compounds for carbohydrates, proteins, and lipids, alone and in binary mixtures. The biocrude, solid residue, and aqueous phase were characterized in terms of composition and elemental percentage. The effects of binary interactions were studied in terms of product yields and compositions. It was observed that higher heating rates resulted in lower solid yields from all the cellulose-containing feedstocks and, in most cases, in higher biocrude yields and higher energy recovery. The results showed that the heating rate influences also the oil composition. Biocrude and solid yields were compared with their prediction based on the combination of the yields of single model compounds, showing a general increase in biocrude yields and a decrease in solid yields. The most significant deviation is observed with the mixture cellulose-albumin both for the biocrude and solid yields. In fact, the main interactions were recognized for carbohydrate-protein mixtures followed by carbohydrate-lipid and protein-lipid mixtures.

The effects of dissolved organic carbon and model compounds (DOC analogues) on diffusive water flux, oxygen consumption, nitrogenous waste excretion rates and gill transepithelial potential in Pacific sanddab (Citharichthys sordidus) at two salinities.

Many flatfish species are partially euryhaline, such as the Pacific sanddab which spawn and feed in highly dynamic estuaries ranging from seawater to near freshwater. With the rapid increase in saltwater invasion of freshwater habitats, it is very likely that in these estuaries, flatfish will be exposed to increasing levels of dissolved organic carbon (DOC) of freshwater origin at a range of salinities. As salinity fluctuations often coincide with changes in DOC concentration, two natural freshwater DOCs [Luther Marsh (LM, allochthonous) and Lake Ontario (LO, autochthonous) were investigated at salinities of 30 and 7.5 ppt. Optical characterization of the two natural DOC sources indicate salinity-dependent differences in their physicochemistry. LO and LM DOCs, as well as three model compounds [tannic acid (TA), sodium dodecyl sulfate (SDS) and bovine serum albumin (BSA)] representing key chemical moieties of DOC, were used to evaluate physiological effects on sanddabs. In the absence of added DOC, an acute decrease in salinity resulted in an increase in diffusive water flux (a proxy for transcellular water permeability), ammonia excretion and a change in TEP from positive (inside) to negative (inside). The effects of DOC (10mg C L-1) were salinity and source-dependent, with generally more pronounced effects at 30 than 7.5 ppt, and greater potency of LM relative to LO. Both LM DOC and SDS increased diffusive water flux at 30 ppt but only SDS had an effect at 7.5 ppt. TA decreased ammonia excretion at 7.5 ppt. LO DOC decreased urea-N excretion at both salinities whereas the stimulatory effect of BSA occurred only at 30 ppt. Likewise, the effects of LM DOC and BSA to reduce TEP were present at 30 ppt but not 7.5 ppt. None of the treatments affected oxygen consumption rates. Our results demonstrate that DOCs and salinity interact to alter key physiological processes in marine flatfish, reflecting changes in both gill function and the physicochemistry of DOCs between 30 and 7.5 ppt.

Anchored Ru nanoclusters strategy enhances hydrogen spillover effect for high-efficiency hydrogen storage

Enhancing the hydrogen spillover effect of catalysts is an effective method for optimizing hydrogen storage reactions. In this study, we report a catalyst consisting of Ru nanoclusters (1.2–2.7 nm) anchored on nitrogen-doped carbon (NC) that are highly dispersed on an Al2O3 substrate. Both experimental and density functional theory-based calculations indicate that these constrained, highly dispersed ultrafine nanoclusters significantly improve the intrinsic catalytic activity of Ru and reduce the reaction barriers. Moreover, the electron transfer between NC and Ru clusters increases the adsorption inertness of Ru with hydrogen, enhances hydrogen desorption, and promotes hydrogen spillover, synergistically improving the activity of catalytic hydrogen storage. Notably, the aromatic compounds in the ethylene tar narrow fraction were effectively converted at a low temperature of 80 °C, and the total cycloalkanes yield reached 99.04 %. The hydrogen storage capacity can be about 5.70 wt%. Liquid Organic Hydrogen Carriers model compounds were fully hydrogenated at temperatures no higher than 70 °C with low Ru loading (2 wt%). This work provides a potential utilization strategy of ethylene tar narrow fraction as hydrogen carriers based on its hydrogenation over the highly active and stable Ru nanocluster catalysts.

Screening ionic liquids based on COSMO-SAC model for extracting organic sulfur from coal and mechanism study

Screening suitable ionic liquids（ILs） for removing organic sulfur compounds from coal and discovering new, effective and environmentally friendly coal desulfurization additives is crucial. The solubility properties (SP) of six organic sulfur model compounds (OSMCs) in imidazole ILs were calculated based on the COSMO-SAC model. The results showed that 2-thiophenecarboxylic acid and 2-aminophenyl phenyl sulfone exhibited favorable solubility properties in certain ILs. The solubility properties of partial imidazole ILs consisting of [Cl]- were significantly better than other anions. Through the σ -profiles analysis of ILs anions, cations and OSMCs, it showed that [Cl]- had a higher tendency to be hydrogen bond acceptor than other anions. The polar groups in OSMCs increased the hydrogen bond donor or acceptor sites for interactions with ILs, while extended the optional range of ILs for hydrogen bond interactions with OSMCs. The extraction efficiencies of 2-thiophenecarboxylic acid by ILs were above 25%, with [DMIM][Cl] displaying the highest efficiency at 47.5%. Meanwhile, [DMIM][Cl] was the most effective extractant for removing all OSMCs except benzothiophene, which was basically consistent with the calculation results. Electrostatic potential analysis was used to obtain the sites where OSMCs are the most likely to form hydrogen bond interactions with [DMIM][Cl]. And characterization of hydrogen bond formation between ILs and OSMCs was obtained by FTIR analysis. The hydrogen bond formed by p-thiocresol with [DMIM][Cl] is weak, and the hydrogen bonds formed by 2-thiophenecarboxylic acid, 2-aminophenyl phenyl sulfone with [DMIM][Cl] are relatively strong. The analysis of intermolecular hydrogen bond interactions verified the mechanism underlying the excellent extraction performance for specific OSMCs by the selected ILs.

Hollow sphere CuCo2O4 as highly efficient catalyst of microwave-assisted Fenton-like reaction for water treatment

In industries with high-value addition, the demand for rapid pollutant breakdown through advanced water treatment techniques is growing. The microwave (MW)-assisted Fenton-like reaction is notable for its exceptionally fast reaction rate, providing enhanced economic benefits, especially in the context of limited factory space. In this research, hollow sphere-shaped CuCo2O4 was synthesized at the various temperature (200 °C, 250 °C, 300 °C, 350 °C, 400 °C, 450 °C, and 500 °C) and used in a MW-assisted Fenton-like reaction to break down the organic model compound, methyl orange (MO). Unlike typical Fenton reactions that are most effective in acidic conditions (around pH 3), the synthesized CuCo2O4 in this study demonstrated its highest efficiency at a circumneutral pH level (pH 6). It was observed that the majority of MO was oxidized by ∙OH within just 3.5 min under the optical condition (10 mg/L MO, 300 mg/L H2O2, 200 mg/L catalyst, pH 6, 20 °C, 200 W, and total volume of 50 mL). Ex-situ analysis confirmed the gradual generation of oxygen vacancies (OV) with each repeated cycle. The formation of OV enhances the catalyst's MW absorption and oxidation potential, resulting in the superior MO decomposition performance even after the 5th cycle. Although there were minor changes in the shell thickness and smoothness, along with some leaching (1.17 mg Cu/L and 0.01 mg Co/L per cycle), the catalyst continued to comply with the US Environmental Protection Agency (EPA) guidelines for drinking and discharge water.

Supramolecular Polymer Network based on Electrophilic Substitution (ES) Adduct of Furan-Triazolinedione.

Polymers with furan functionality have been the subject of extensive research on developing sustainable materials applying a limited number of dynamic covalent approaches. Herein, we introduce a facile, dynamic non-covalent approach to make a furan polymer readily accessible for self-healing applications based on its electrophilic substitution (ES) with a commercially available 1,2,4-triazoline-3,5-dione (TAD) derivative, 4-phenyl-TAD (PTAD). A tailor-made furan polymer, poly(furfuryl methacrylate) (PFMA), considering it an initial illustrative example, was rapidly ES modified with PTAD to produce furfuryl-tagged triazolidine that subsequently associated via inter-molecular hydrogen (H-) bonding to produce a thermally reversible supramolecular polymer network under ambient conditions. The H-bonded network was experimentally quantified via ATR-IR analysis and theoretically rationalized via the density functional theory (DFT) study using smaller organic model compounds analogous to the macromolecular system. Thermoreversible feature of the H-bonded triazolidine-derived supramolecular polymer network enabled the solution reprocessing and self-healing of the polymer material.

Effect of adding biochar from prickly pear skin to aluminium sulphate to improve the coagulation-flocculation process during the elimination of humic substances present in the Laghrous drainage canal Water, Zab El-gharbi region (SE Algeria)

The objective of this research is to enhance the elimination of humic substances found in agricultural drainage water using a two-fold approach: coagulation-flocculation using aluminum sulfate both separately and in combination with powdered activated carbon made from prickly pear skin. To attain our goal, laboratory jar test were conducted on synthetic solutions. Several reaction parameters were examined, including the impact of changing coagulant dosage, impact of temperature, and adjusting pH levels. The results obtained demonstrated that the flocculation process is more effective in reducing compounds with higher molecular masses. Compared to a 49% removal rate with aluminum sulfate alone, the addition of an adjuvant powdered activated carbon made from the skin of prickly pears greatly improved the elimination process, resulting in removal rates of 92%, 84%, and 79% for powdered activated carbon masses of 0.50 g/L, 0.20 g/L, and 0.10 g/L, respectively. Throughout this investigation, we will showcase the outcomes derived from the tests performed on synthetic solutions containing model organic compounds (commercial products) dissolved in distilled water, alongside the analysis of agricultural drainage waters. The study investigates the influence of various reaction parameters on the removal efficiency of humic substances through coagulation-flocculation using aluminum sulfate. The results show also that in the presence or in the absence of powdered activated carbon derived from the skin of prickly pear, the coagulation is more eficient at low pH (5 to 6). In addition, we have show that simple coagulation flocculation remove only 66% of Chemical oxygen demand (COD) of initial value and the presence of powdered activated carbon (40 mg.L-1) increases efficiency up to 82%. To enhance this process, the addition of a water additive is considered to improve treatment efficiency.

Annealing Effects of ZnO Thin Film on Photocatalytic Performances of Graphene Composites

The hybrid structure of Graphene and ZnO (Graphene/ZnO) is emerging as a novel material used to achieve the high performance of photocatalysis. In this study, we examined the ZnO characteristics that affect the photocatalytic activity of graphene/ZnO using a lamellar structure of graphene and ZnO thin films. Graphene samples were synthesized via chemical vapor deposition, and a typical wet process was applied to transfer them on sputter-deposited ZnO thin films with and without annealing. We confirmed that graphene-deposited ZnO demonstrated more efficient photocatalytic behavior toward the decomposition of methylene blue (as a model organic compound) with ordinary sputtered ZnO thin films. Again, ZnO thin films annealed at 1000 °C in an N2 gas atmosphere with graphene performed better than unannealed films. XRD analysis confirmed that pre-thermal treatment of a ZnO thin film promoted re-crystallization, which had less impact on the photocatalytic improvement. The attachment of graphene to the film is considered to contribute to the enhancement. Raman analysis revealed that the graphene coverage areas on the post-annealed ZnO increased by two times compared to that of an unannealed film where the unannealed film had a higher graphene layer. The results presented in this study demonstrate that an annealed ZnO thin film forms a better attachment with graphene, resulting in a larger graphene coverage area with fewer multilayers, which effectively improves the photocatalytic activity in composite structures.

Photoelectrocatalytic chemical oxygen demand analysis using a TiO2 nanotube array photoanode

The chemical oxygen demand (COD) is a widely used parameter to evaluate the quality of water for industrial applications. Currently, the standardized method for COD analysis employs expensive and harmful reagents that require a special treatment for disposal upon use. The photoelectrocatalytic COD detection, based on the photocatalytic activity of a reduced TiO2 nanotube array photoanode (Ti|NT-TiO2) under supply of a low bias potential, represents a fast, cheap and eco-friendly alternative to the standard COD method (CODSTD). Here, Ti|NT-TiO2 was synthesized by the anodization method followed by heat treatment and electrochemical reduction. Potassium hydrogen phthalate, glucose and acetic acid were used as model organic compounds. The photoelectrocatalytic detection of COD (CODPEC) is based on the photoelectrocatalytic oxidation of target compounds on the surface of the reduced Ti|NT-TiO2 under UV illumination. Photocurrent transients were recorded using chronocoulometry, and the net charge (Δq) was plotted as a function of the theoretical COD (CODTH). A linear relationship was found between these two parameters regardless of the model compound. That relationship was used to determine the CODPEC for acetylsalicylic acid and Terasil Blue dye solutions at concentrations within the range of 0–15 mg L−1. A good agreement between CODPEC and CODSTD was achieved. The limit of detection of the method was 3.6 mg L−1 COD, with the linear range established from 0 to 50 mg L−1.

Insights into the shape-dependent effects of polyethylene microplastics on interactions with organisms, environmental aging, and adsorption properties

The shape-dependent effects of microplastics have been studied in the context of ingestion but have not been considered in other environmental processes. Therefore, we investigated how the shape of polyethylene microplastics (spheres, fragments, and films) affects interactions with plants, aging, and their adsorption properties. The shape had no effect on the growth rate and chlorophyll content of duckweed Lemna minor, but the fragments strongly adhered to the plant biomass and reduced the root length. The adsorption process of the model organic compound (methylene blue dye) was described by the same kinetic model for all shapes—the experimental data best fit the pseudo-second order model. However, twice as much methylene blue was adsorbed on films as on fragments and spheres. During environmental aging, most biofilm developed on films. The biofilm on spheres contained significantly less photosynthetic microorganisms, but twice as much extracellular polymeric substances (EPS) as on fragments and films. This suggests that the attachment of microorganisms to spherical particles is limited and therefore more intensive production of EPS is required for stable biofilm formation. From the results of this study, it is evident that the shape of microplastics significantly affects not only ecotoxicity but also other environmentally relevant processes.

Bismuth-doped TiO2 enable solar photocatalytic water treatment

Sol-gel coprecipitation method provides a facile and affordable synthesis methodology for bismuth-doped TiO2 photocatalysts. The effective doping of TiO2 widens the photoactivity of the catalyst enabling effective electron excitation under visible light irradiation. Different doping percentages of bismuth can modulate the photocatalytic response and provide engineered control over the bandgap energy of the semiconductor. Characterization demonstrated that 5 % doping provides an optimum balance on the photocatalytic properties as well as the effectiveness in the treatment of indigo carmine (IC) used as a model organic pollutant compound. This by increasing the size of the anatase crystals to 65.87 nm, improving the specific surface to 116.3 m2/g, and lowering the Egap of TiO2 to 2.98 eV.

Scavenging Efficiency of Activated Charcoal of Sweet Corn Cop and Areca Nut Shell for Carcinogenic Salicylic Acid and Methylene Blue

Activated plant charcoal plays major role in adsorption chemistry and finds a huge application in industry, pharmaceuticals, cosmetics and water treatment. Present work planned to utilize waste sweet corn cop and areca nut husk to prepare charcoal by chemical method. The charcoal was carbonized at 8000C using muffle furnace. The adsorption efficiency of the experimental activated carbon adsorbents towards the model organic compounds methylene blue and salicylic acid were assessed by UV-Vis spectrophotometric method. Experimental results clearly indicates that sweet corn cop charcoal recorded maximum absorption for salicylic acid 640ppm/g in compare to areca nut shell husk charcoal 480ppm/g. Sweet corn cop charcoal recorded optimum absorption for methylene blue 240 ppm/g in compare to areca nut shell husk charcoal 240ppm/g. The experimental charcoal projects noticeable results in scavenging salicylic acid and methylene blue from polluted samples. This experimental results and affordable cost the raw material made the sweet corn cop and areca nut husk activated carbon a powerful alternative for the adsorption of carcinogenic organic compounds salicylic acid and methylene blue.

Nanoextraction from a flow of a highly diluted solution for much-improved sensitivity in offline chemical detection and quantification

Preconcentration of the target compound is a critical step that ensures the accuracy of the subsequent chemical analysis. In this work, we present a straightforward yet effective liquid-liquid extraction approach based on surface nanodroplets (i.e., nanoextraction) for offline analysis of highly diluted sample solutions. The extraction and sample collection were streamlined in a 3-m microcapillary tube. The concentration of the target analyte in surface nanodroplets was significantly increased compared to the concentration in the sample solution, reaching several orders of magnitude. A limit of detection (LOD) was decreased by a factor of ∼103 for an organic model compound in Fourier-transform infrared spectroscopy (FTIR) measurements and ∼105 for a model fluorescent dye in fluorescence detection. The quantitative analysis of the organic compound was also achieved in a wide concentration region from 10−3 M to 10−4 M. The total volume of surface nanodroplets can be manipulated to further enhance extraction efficiency, according to the principle that governs droplet formation by solvent exchange. Additionally, our method exhibited significantly improved sensitivity compared to traditional dispersive liquid-liquid microextraction (DLLME). The LOD of the fluorescent dye and the organic model compound obtained with DLLME was 3 orders of magnitude and 20 times higher than the LOD achieved through nanoextraction approach. The nanoextraction developed in this work can be applied to preconcentrate multi-compounds from river water samples, without clear interference from each other. This can further extend its applicability for the detection and quantification of target analytes in complex aqueous samples by common analytical instruments.

Relationships between char reactivity and char structure from a suite of organic model compounds

In order to better understand the impact of the carbon structure of char on its combustion reactivity, 14 types of organic model compounds were pyrolyzed under temperatures of 530 °C, 800 °C and 1028 °C at heating rates of 10 °C/min and 65 °C/s, respectively. The carbon structure and the oxidation reactivity of the produced char were determined by respective Raman spectroscopy and thermogravimetric analysis (TGA) methods. The relationships between different reactivity indexes and Raman spectral parameters have been assessed. The results reveal that changes in pyrolysis temperature and heating rate would result in certain evolution of the graphitization degree of char. Good correlations have been discovered between the Raman spectral parameters (AD/AALL, AGL/AALL, A(S+R+SL+VR+VL)/AD, and A(GR+VL+VR)/AD) and the combustion characteristic temperatures (Ti, Tb, T50, and Tmax). From the correlations above, Raman spectral parameter A(GR+VL+VR)/AD is found to be the best correlated to the char combustion characteristic temperature Tb with R2 of around 0.76.

Nickel-Passivating element selection in FCC process and mechanistic study on the passivation of nickel by lanthanum and phosphorus

Motivated by the dehydrogenation activity of nickel (Ni) and the toxicity of free nickel oxide (NiO) in the fluid catalytic cracking (FCC) catalysts, this study aims to reveal the appropriate elements to in-situ passivate nickel during the cracking reactions of oil by conducting hydrocarbon dehydrogenation tests of Y-zeolite loaded with Ni and passivating elements in a Pyro-probe micro-reactor coupled with GC-TCD and MS. The conditions were chosen as 550 °C with a catalyst-to-hydrocarbon mass ratio of 5:1. Additionally, hydrogen-temperature programmed reduction (H2-TPR) was conducted. In supporting the experimental observation, thermodynamic calculations were also performed to assist the selection of possible Ni-passivating elements in terms of the free Gibbs energy for their reactions with NiO. Lanthanum (La) and phosphorus (P) were found to exert the most effective effects on nickel passivation. The use of twice the quantity of La or P more than Ni, or the combined use of La and P each in equimolar ratio to Ni is able to decrease the dehydrogenation extent by 97%. La can passivate the free NiO species by chemically bonding with NiO which, otherwise, would bond with alumina in zeolite. Instead, P is preferentially coated on the Ni-bearing particles, which leads to the formation of phosphate that is inactive in the dehydrogenation of the model organic compounds when compared to the free NiO.

Inorganic Skeleton Reinforcement-A Generic Approach to Improve the Mechanical Properties of Biochar.

Biochar is considered as a promising candidate for emerging sustainable energy systems and environmental technology applications. However, the improvement of mechanical properties remains challenges. Herein, we propose a generic strategy to enhance the mechanical properties of bio-based carbon materials through inorganic skeleton reinforcement. As a proof-of-concept, silane, geopolymer, and inorganic gel are selected as precursors. The composites' structures are characterized and an inorganic skeleton reinforcement mechanism is elucidated. Specifically, two types of reinforcement of the silicon-oxygen skeleton network formed in situ with biomass pyrolysis and the silica-oxy-al-oxy network are constructed to improve the mechanical properties. A significant improvement in mechanical strength was achieved for bio-based carbon materials. The compressive strength of well-balanced porous carbon materials modified by silane can reach up to 88.9 kPa, geopolymer-modified carbon material exhibits an enhanced compressive strength of 36.8 kPa, and that of inorganic-gel-polymer-modified carbon material is 124.6 kPa. Moreover, the prepared carbon materials with enhanced mechanical properties show excellent adsorption performance and high reusability for organic pollutant model compound methylene blue dye. This work demonstrates a promising and universal strategy for enhancing the mechanical properties of biomass-derived porous carbon materials.

Electrochemical Determination of Chemical Oxygen Demand Based on Boron-Doped Diamond Electrode

A rapid and environment-friendly electrochemical sensor to determine the chemical oxygen demand (COD) has been developed. The boron-doped diamond (BDD) thin-film electrode is employed as the anode, which fully oxidizes organic pollutants and provides a current response in proportion to the COD values of the sample solution. The BDD-based amperometric COD sensor is optimized in terms of the applied potential and the solution pH. At the optimized conditions, the COD sensor exhibits a linear range of 0 to 80 mg/L and the detection limit of 1.1 mg/L. Using a set of model organic compounds, the electrochemical COD sensor is compared with the conventional dichromate COD method. The result shows an excellent correlation between the two methods.

Study on the effect of biomass on sulfur release behavior from dyeing sludge incineration: Focusing on in-situ sulfur fixation mechanism based on model compounds

Although incineration is a recommended disposal strategy for dyeing sludge (DS), sulfurous gases problem is severe. Wood sawdust (WS) and rice husk (RH) are eco-friendly and CO2-neutral additives to relieve sulfur emission from DS incineration. However, the interaction between organic sulfur and biomass is uninterpreted. This study explores the effect of WS and RH on the combustion behavior and sulfur evolution from organic sulfur model compound combustion via thermogravimetry (TG) with mass spectrometry (MS). Results indicated that the sulfone and mercaptan combustion activities in DS were more drastic than in other forms. WS and RH additives generally deteriorated the combustibility and burnout performance of model compounds. The combustion of mercaptan and sulfone in DS contributed to most gaseous sulfur pollutants, where CH3SH and SO2 were the predominant forms. WS and RH minimized the sulfur release from mercaptan and sulfone incineration, whose in-situ retention ratios reached 20.14 % and 40.57 %. The retention mechanism to sulfur could be divided into: (1) Diffusion stage: the closed structure of biomass residue restrained sulfurous gases from escaping. (2) Chemical reaction stage: multiple sulfation occurred and inhibited sulfur release. Ca/K sulfate and compound sulfates were predisposed and thermostable sulfur-fixing products for the mercaptan–WS and sulfone–RH co-combustion systems.

Liquid metal enabled reformation of ethylene glycol

Having showcased intriguing features in a vast range of catalytic applications, liquid metals (LMs) are continuously ticking boxes of pathways that are conventionally only associated with transitional metals. Herein, we report a gallium-ethylene glycol system where gallium is utilized to interact and break down organic bonds. Ethylene glycol is selected as a model organic compound, as it has been extensively studied for the reformation mechanisms and the potential to produce hydrogen gas. With mechanical agitation applied to the LM-based reaction system, we establish an in-situ monitoring approach for the gaseous products and also perform a series of characterizations on the post-reaction mixture. We reveal that the hydrogen gas production from the system is continuous and highly selective. Gaseous alkanes and alkenes are also observed in the output. Our analyses demonstrate that gallium induces structural reformations of ethylene glycol following a complex pathway. The process generates methyl, aldehyde, carbonyl, and other groups. We further reveal the formation of polymer products with repeating methylene groups in the system. The process for reforming ethylene glycol signifies the capability of LMs to efficiently break down organic bonds. As such, this study provides a platform to explore environment-friendly and alternative strategies for hydrogen production and organic transformation toward valuable products.

Reactivity of Bromine Radical with Dissolved Organic Matter Moieties and Monochloramine: Effect on Bromate Formation during Ozonation.

Bromine radical (Br•) has been hypothesized to be a key intermediate of bromate formation during ozonation. Once formed, Br• further reacts with ozone to eventually form bromate. However, this reaction competes with the reaction of Br• with dissolved organic matter (DOM), of which reactivity and reaction mechanisms are less studied to date. To fill this gap, this study determined the second-order rate constant (k) of the reactions of selected organic model compounds, a DOM isolate, and monochloramine (NH2Cl) with Br• using γ-radiolysis. The kBr• of all model compounds were high (kBr• > 108 M-1 s-1) and well correlated with quantum-chemically computed free energies of activation, indicating a selectivity of Br• toward electron-rich compounds, governed by electron transfer. The reaction of phenol (a representative DOM moiety) with Br• yielded p-benzoquinone as a major product with a yield of 59% per consumed phenol, suggesting an electron transfer mechanism. Finally, the potential of NH2Cl to quench Br• was tested based on the fast reaction (kBr•,NH2Cl = 4.4 × 109 M-1 s-1, this study), resulting in reduced bromate formation of up to 77% during ozonation of bromide-containing lake water. Overall, our study demonstrated that Br• quenching by NH2Cl can substantially suppress bromate formation, especially in waters containing low DOC concentrations (1-2 mgC/L).