Paramagnetic Carbon Nanosheets with Random Hole Defects and Oxygenated Functional Groups.

Ordered graphitic carbon nanosheets (GCNs) were, for the first time, synthesized by the direct condensation of multifunctional phenylacetyl building blocks (monomers) in the presence of phosphorous pentoxide. The GCNs had highly ordered structures with random hole defects and oxygenated functional groups, showing paramagnetism. The results of combined structural and magnetic analyses indicate that the hole defects and functional groups are associated with the appearance and stabilization of unpaired spins. DFT calculations further suggest that the emergence of stabilized spin moments near the edge groups necessitates the presence of functionalized carbon atoms around the hole defects. That is, both hole defects and oxygenated functional groups are essential ingredients for the generation and stabilization of spins in GCNs.

The surface functional groups-driven fast and catalytic degradation of naproxen on sludge biochar enhanced by citric acid.

In this work, a sludge biochar (CA-SBC-300) with efficient activation of peroxymonosulfate (PMS) was prepared by citric acid modification. CA-SBC-300 achieved efficient degradation of naproxen (NPX) (95.5%) within 10 min by activating PMS. This system was highly resilient to common disruptive factors such as inorganic anions, humic acid (HA) and solution pH. The results of XPS and Raman showed that the content of oxygenated functional groups (OFGs) and the degree of defects on the sludge biochar increased after citric acid modification, which may be an important reason for the enhanced catalytic performance of SBC. In the CA-SBC-300/PMS system, 1O2 and O2•- made the main contributions to the degradation of NPX. XPS analysis and DFT calculations demonstrated that C=O/C-O and pyridine N on CA-SBC-300 were the crucial active sites for PMS activation. According to the results of UPLC-MS analysis, three possible pathways for NPX degradation were inferred. This study provided a feasible strategy for sludge resource utilization combined with efficient catalytic degradation of toxic organic contaminants in wastewater.

Construction of carbon-doped iron-based nanozyme for efficient adsorption and degradation to synergistic removal of aflatoxin B1.

The multifunctional composites Fe3O4/GO/NH2-MIL-53(Fe) with excellent adsorption-degradation performance was prepared for the removal of Aflatoxin B1 (AFB1). The adsorption function of Fe3O4/GO/NH2-MIL-53(Fe) was based on the large specific surface area and abundant adsorption sites. The degradation function of Fe3O4/GO/NH2-MIL-53(Fe) was based on the activation of H2O2 by the catalytic active center formed by the coordination of metal ions and oxygen-containing groups in the system, resulting in hydroxyl radicals (·OH), superoxide anion radicals (O2-) and singlet oxygen (1O2). The adsorption of nanozyme accelerated the degradation reaction process, and the adsorption site was further exposed as the degradation process progressed. The synergistic effect realized the efficient removal of AFB1. Construction of Fe3O4/GO/NH2-MIL-53(Fe) as the carbon-doped iron-based nanozyme provided novel approaches of the removal for risks control of AFB1. Accompanied by the AFB1 adsorption, the advanced oxidation of nanozyme to the AFB1 degradation provided a promising way for the synergistic removal of AFB1.

Diesel soot combustion in air-NO environment: Evolution of functional groups on soot surfaces.

It is inevitable for NO to be involved in the soot combustion in diesel particulate filters (DPFs), so giving full play to the NO oxidation activity is one of the most effective means to improve the DPF regeneration performance. In this work, based on the results of programmed temperature oxidation (TPO) experiments, Fourier transfer inference spectroscopy, and X-ray photoelectron spectroscopy, the evolution of surface functional groups was seriously analyzed to explore the soot oxidation mechanism. The results revealed that with the presence of NO in the air atmosphere, the concentration of -ONO2 groups showed an increasing trend in the early oxidation stage of 0-20 % oxidation degree (OD) and then slowly decreased during 20-80 % OD, while the variations in CH functional group concentration were directly related to the concentration NO in the air atmosphere. COO functional group is easy to decompose, and NO promotes COO's generation and decomposition. The sp3/sp2 hybrid ratio is strongly correlated with CO (carbon­oxygen double bond), but the content of CO is also affected by the desorption of COO functional groups. It is worth noting that when the soot oxidation degree is at 50 %-80 % OD, CO groups are converted to CO functional groups.

The critical impacts of pyrochar during 2,4,6-trichlorophenol photochemical remediation process: Cooperation between persistent free radicals and oxygenated functional groups.

The widespread use of polychlorophenols poses enormous environmental challenges. Biochar has the potential to accelerate the transformation of polychlorophenols. But the biochar-triggered photochemical decomposition mechanism of polychlorophenols still remains unclear. Herein, the photochemical behavior of pyrochar was comprehensively investigated in 2,4,6-trichlorophenol (TCP) remediation. Researches revealed that persistent free radicals (PFRs) and oxygenated functional groups (OFGs) on the surface of pyrochar cooperatively promoted ROS generation for TCP degradation. PFRs performed a key role of electron-donating and energy transfer in ROS conversion, especially in the activation of H2O2 into •OH. The hydroxyl groups of photosensitive components of pyrochar were photo-excited and provided electrons for enhanced ROS formation as well. With photogenerated ROS involved, more TCP was decomposed through dechlorination under light irradiation than that in the dark, in which 1O2, •OH, and •O2- were the dominant active species. During this process, stronger light intensities (3 W/m2) and shorter light wavelengths (400 nm) can provide more energy for the activation of PFRs and OFGs, promoting the decomposition of TCP. This work casts a new light on the environmental roles of pyrochar in the photochemical removal of polychlorophenol pollutants.

Heterogeneous Fenton-like surface properties of oxygenated graphitic carbon nitride.

The photo-Fenton activity of graphitic carbon nitride (g-C3N4) has been widely studied, nevertheless, its Fenton-like catalytic behavior in the dark has not yet been demonstrated. In the present work, it is shown that oxygenated g-C3N4 obtained at different temperatures (500-600 °C) can degrade indigo carmine with hydrogen peroxide in the dark by a reaction similar to a conventional Fenton's reaction. Based on an extensive characterization of g-C3N4, we conclude that Fenton-like activity is directly related to the oxygenated functional groups on g-C3N4 structure, mainly by -OH functional groups. Oxygenated functional groups (e.g., hydroquinone-like groups) can reduce the H2O2 and generate oxidizing hydroxyl radicals, just like in the Fenton reaction performed by metals. In addition to new information on g-C3N4 surface reactivity revealed by this study, the metal-free oxygenated g-C3N4 catalyst may be an alternative to traditional metal catalysts used in Fenton-like reactions for advanced oxidation.

Impact of carbon chain length of alcohols on the physicochemical properties and reactivity of exhaust soot.

Particle is the main pollutant in diesel engine exhaust, which seriously endangers human health and the atmospheric environment. The use of alcohol fuels in diesel engines can effectively reduce particle emissions, but alcohol fuels with different carbon chain lengths will affect the generation process of particles, which in turn changes the physicochemical properties and oxidation characteristics of the particles. Therefore, it is particularly important to study the properties of particle emitted by diesel engines fueling alcohol fuels with different carbon chain lengths. The physicochemical properties of soot emitted from commercial diesel engines were studied by thermogravimetric analyzer, HRTEM (high-resolution transmission electron microscopy), and XPS (X-ray photoelectron spectroscopy) in this paper, respectively. The diesel engine used alcohol-diesel blends of different carbon chain lengths with the same oxygen content as fuels, such as methanol/diesel blend (M10), n-butanol/diesel blend (NB25), and n-octanol/diesel blend (NO45), and pure diesel fuel was used as a reference. The results showed that the use of alcohols reduced the fractal dimension (Df) of particles, and the NB25 particles had the smallest Df. Moreover, the particles of blended fuels had smaller primary particle diameter (dp) compared to pure diesel. However, with the use of short-chain to long-chain alcohols, an increasing tendency of dp was observed. In terms of the nanostructure, as the use of short-chain to long-chain alcohols, the La (fringe length) increased, both the d (fringe separation distance) and Tf (fringe tortuosity) reduced, which was not favorable for the oxidation of the particles. In addition, in terms of oxygenated surface functional groups (SFGs), the CO group occupied a higher proportion in most working conditions relative to the groups of CO and COO. Further analysis showed that the dp and nanostructure had more influence on the oxidation behavior of soot than Df and oxygenated SFGs.

Effect of the degree of oxidation of graphene oxide on As(III) adsorption.

The study of the interaction between graphene oxide (GO) and arsenic is of great relevance not only in the design of adsorbent materials to remove this contaminant but also in the understanding of its combined nanotoxicity. In this work, we show that As(III) adsorption, primarily H3AsO3, by graphene oxide is affected by its degree of oxidation. Three types of GO with C/O ratios between 1.35 and 1.98 were produced, resulting in important variations in the concentration of COH and COC functional groups. The less oxidized material reached a maximum As(III) adsorption capacity of 123 mg/g, whereas the GO with the highest degree of oxidation reached a value of 288 mg/g at pH 7, the highest reported in the literature. We also show that sulfates and carbonates present in water strongly inhibit As(III) adsorption. The interaction between graphene oxide and As(III) was also studied by Density Functional Theory (DFT) computer models showing that graphene oxide interacts with As(III) primarily through hydrogen bonds, having interaction energies with the hydroxyl and epoxide groups of 1508.6 and 1583.6 kJ/mol, respectively. Finally, cytotoxicity tests showed that the graphene oxide maintained cellular viability of 57% with 50 µg/ml, regardless of its degree of oxidation.

Safety and efficacy of 8-mercapto-p-menthan-3-one and p-menth-1-ene-8-thiol belonging to chemical group 20 when used as flavourings for all animal species.

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of two compounds belonging to chemical group 20 (aliphatic and aromatic mono- and di-thiols and mono-, di-, tri-, and polysulfides with or without additional oxygenated functional groups). 8-Mercapto-p-menthan-3-one [12.038] and p-menth-1-ene-8-thiol [12.085] are currently authorised as flavours in food. The FEEDAP Panel concludes that the two compounds are safe for the target species at the proposed maximum use level (0.05 mg/kg complete feed). No safety concern would arise for the consumer from the use of 8-mercapto-p-menthan-3-one and p-menth-1-ene-8-thiol up to the highest safe level in feedingstuffs for all animal species. Both compounds should be considered as irritants to skin and eyes, and 8-mercapto-p-menthan-3-one [12.038] also as irritant to the respiratory tract. No conclusions can be drawn on skin sensitisation potential. No environmental risk is foreseen for these compounds at the maximum proposed use level in feed. Since the two compounds are used as flavourings in food and their function is essentially the same as that in food, no further demonstration of efficacy is necessary.

Japan Flavour and Fragrance Materials Association's (JFFMA) safety assessment of food-flavouring substances uniquely used in Japan that belong to the class of aliphatic primary alcohols, aldehydes, carboxylic acids, acetals and esters containing additional oxygenated functional groups.

We performed a safety evaluation using the procedure devised by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) of the following four flavouring substances that belong to the class of 'aliphatic primary alcohols, aldehydes, carboxylic acids, acetals, and esters containing additional oxygenated functional groups' and are uniquely used in Japan: butyl butyrylacetate, ethyl 2-hydroxy-4-methylpentanoate, 3-hydroxyhexanoic acid and methyl hydroxyacetate. Although no genotoxicity study data were found in the published literature, none of the four substances had chemical structural alerts predicting genotoxicity. All four substances were categorised as class I by using Cramer's classification. The estimated daily intake of each of the four substances was determined to be 0.007-2.9 µg/person/day by using the maximised survey-derived intake method and based on the annual production data in Japan in 2001, 2005 and 2010, and was determined to be 0.250-600.0 µg/person/day by using the single-portion exposure technique and based on average-use levels in standard portion sizes of flavoured foods. Both of these estimated daily intake ranges were below the threshold of toxicological concern for class I substances, which is 1800 µg/person/day. Although no information from in vitro and in vivo toxicity studies for the four substances was available, these substances were judged to raise no safety concerns at the current levels of intake.