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• Facile method for effective modification of asphaltenes by nitro groups. • Surface properties are determined by inverse gas chromatography (IGC). • Nitrated asphaltenes exhibits outstanding adsorption properties. • Nitrated asphaltenes are comparable with activated carbon, zeolites and alumina. • IGC revealed changes in the Lewis acid-base properties of aphaltenes by nitration. A novel nitrated asphaltene-derived adsorbent (Asf-Nitro) was prepared using facile isolation and modification procedures. The successful modification was confirmed by Fourier-transform infrared spectroscopy (FTIR). The nitrated adsorbent was evaluated in terms of dispersive and specific interactions, Lewis acid-base properties and adsorption isotherms by means of inverse gas chromatography (IGC). Nitration was found to be extremely effective in enhancing adsorption properties of asphaltenes towards variety of chemical compounds. Asf-Nitro adsorbent exhibits superior dispersive interactions (197.50 ± 1.12 mJ m−2 at 423 K), as compared to unmodified asphaltenes, which are comparable with activated carbons, zeolites or alumina. Examination of the specific interactions revealed a shift from basic to acidic character of the surface, what will be beneficial for adsorption of alkaline gases. Additionally, adsorption isotherms revealed that developed surface properties of the Asf-Nitro results in more than doubled monolayer adsorption capacity. Obtained results demonstrates the applicability of the asphaltene-derived materials in adsorption processes as highly effective and low cost adsorbents. This studies revealed a highly effective adsorption of environmentally important VOCs, e.g. n -butanol (odorous compound), trichloromethane (chlorinated hydrocarbon) and benzene (carcinogenic). [ABSTRACT FROM AUTHOR]

• Unprecedented selectivity towards volatile organic compounds (VOCs). • NADES based approach for separation techniques. • Comparable performance and stability with commercially available phases. • Green analytical chemistry approach for gas chromatography. • High applicability in environmental analysis. The paper presents a new kind of stationary phase for gas chromatography based on deep eutectic solvents (DES) in the form of a mixture of L-proline (protonated with hydrochloric acid) as a hydrogen bond acceptor (HBA) and xylitol as a hydrogen bond donor (HBD) in a molar ratio of HBA:HBD 5:1. DES immobilized on a silanized chromatographic support was tested by gas chromatography (GC) in order to determine its resolving power for volatile organic compounds. Studies have demonstrated the suitability of this type of DES as a stationary phase for GC. The Rohrschneider-McReynolds constants were determined for the synthesized DES, revealing that it is a polar stationary phase (Σ(ΔI) = 1717). The selectivity of DES is influenced by the presence of hydroxyl groups in the xylitol structure capable of forming hydrogen bonds of a donor nature and the proton acceptor properties of the protonated L-proline structure. The presence of additional interactions is brought about by the presence of the carboxyl group. As a result, the retention of alcohols is several times higher (200-670%) than the expected value based on their boiling points. A significant increase in retention (400-970%) was also found for pyridine derivatives. The developed DES stationary phase is characterized by very good repeatability of retention and stability (up to 140°C). The efficiency of the prepared columns (6300-11300 theoretical plates/m) and the selectivity of the DES stationary phase are competitive with the commercial products. [ABSTRACT FROM AUTHOR]

We present the results of investigations on the possibility of the application of the asphaltene fraction isolated from the oxidized residue from vacuum distillation of crude oil as a stationary phase for gas chromatography. The results of the investigation revealed that the asphaltene stationary phases can find use for the separation of a wide range of volatile organic compounds. The experimental values of Rohrschneider/McReynolds constants characterize the asphaltenes as stationary phases of medium polarity and selectivity similar to commercially available phases based on alkyl phthalates. Isolation of asphaltenes from the material obtained under controlled process conditions allows the production of a stationary phase having reproducible sorption properties and chromatographic columns having the same selectivity. Unique selectivity and high thermal stability make asphaltenes attractive as a material for stationary phases for gas chromatography. A low production cost from a readily available raw material (oxidized petroleum bitumens) is an important economic factor in case of application of the asphaltene stationary phases for preparative and process separations. [ABSTRACT FROM AUTHOR]

We present the results of investigations of the chromatographic (sorptive) properties of silanized silica gel as a stationary phase for gas chromatography used for simulated distillation. Commercially available silanized sorbent (particle diameter range 63-200 μm, average pore size 60 Å) was sieved to obtain the 80-100 mesh fraction (180-150 μm). The obtained results revealed that silanized silica gel allows the complete separation of a mixture of n- and iso-alkanes in the C1-C7 range. Such a separation is achieved with a temperature program starting with an initial temperature of 50˚C, which is advantageous because the gas chromatograph oven does not have to be cooled below room temperature. The use of temperature programming with a final temperature of 300˚C ensures separation and elution of all mixture components from C1 to n-C28 in one run. This study confirms the applicability of silanized silica gel as a stationary phase for the investigation of distillation temperature distribution of gasoline and diesel fuel based on the simulated distillation procedure according to ASTM D2887. The deviations of individual points of distillation curve obtained using ASTM D2887 and columns packed with silanized silica gel were within the reproducibility range of the standard procedure. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient and economical adsorbent for waste gases treatment. • Remarkable enhancement of adsorption capacity by nitrated asphaltenes. • Over 2 times higher adsorption capacity for benzene comparing to Carbotrap adsorbent. • Detailed examination by inverse gas chromatography explained VOCs adsorption. • Step forward in design of adsorbents for removal of environmental pollutants. Asphaltenes isolated from bitumen possess unusual adsorption characteristics that can be further enhanced by chemical modifications to promote interactions with VOCs'. Herein, nitrated asphaltenes are used as an active layer coated on a surface of a diatomaceous earth, in order to prepare an efficient adsorbent (AsfNitro). Breakthrough experiments with benzene, pyridine, and 1-nitropropane revealed significant increase in adsorption capacity, after deposition of nitrated asphaltenes, by 26, 12, and 8 times respectively. The adsorption capacity of AsfNitro for benzene per square meter of surface area is far more superior than for other adsorbents in use. Moreover, the AsfNitro exhibited excellent efficiency. For adsorption of 1-nitropropane and pyridine, almost 100% of the adsorbent's bed was effectively used. Inverse gas chromatography measurements proved that nitrated asphaltenes were exclusively responsible for the adsorption properties, and the role of the diatomaceous earth was only to provide the surface area. Presented findings can be extended to other support materials and their inherent limitations for adsorption of VOCs can be overcome. Comparison of adsorption enthalpies demonstrated that common adsorbents e.g. activated carbons, cannot compete with AsfNitro in terms of sorbate-sorbent interactions. Additionally, contribution of chemisorption mechanism was recognized for AsfNitro, which indicate catalytic properties, and opens a new research field about asphaltenes' novel practical applications. Application of asphaltenes in adsorption processes can be an effective procedure for risk mitigation of hazardous VOCs, accompanied by effective waste management and materials' valorisation. Wasted adsorbent can be easily regenerated (without deterioration of surface properties), or blended in bitumen-aggregates mixes for road paving applications. [ABSTRACT FROM AUTHOR]

• First deep eutectic solvents (DES) based GC stationary phase • Unexpected selectivity towards volatile organic compounds (VOCs) • High applicability of developed DES in separation techniques The paper presents the first application of deep eutectic solvents (DES) as stationary phases for gas chromatography. DES obtained by mixing tetrabutylammonium chloride (TBAC) as a hydrogen bond acceptor (HBA) with heptadecanoic acid being a hydrogen bond donor (HBD) in a mole ratio of HBA:HBD equal to 1:2 was characterized by its ability to separate volatile organic compounds (VOCs). The Rohrschneider – McReynolds constants determined reveal that the synthesized DES is a stationary phase of medium polarity. A detailed retention characteristic was determined for a number of groups of chemical compounds, including aromatic hydrocarbons, alcohols, ketones, sulfides and thiophene derivatives. The synthesized DES was found to have a high selectivity towards alcohols. At the same time, the investigated stationary phase was found to have specific interactions with some analytes. For example, a stronger retention was observed for 1-hexanol and 1-heptanol compared to other alcohols. Retention times of these two alcohols are longer by 191% and 300%, respectively, relative to the expected value based on their boiling point. Such an increased retention is caused by a synergistic effect of various kinds of interactions – the possibility of formation of hydrogen bonds between the DES and the hydroxyl group of alcohols and hydrophobic interactions of alkyl chains of the DES with the alkyl chain of alcohols. The ability to modify properties of DESs by replacement of HBA or HBD with a different chemical compound or by dissolving in DES macromolecular substances makes the proposed stationary phase highly flexible. In addition to using the developed DES in chromatographic techniques, the retention data collected indicate the possibility of its application to other separation techniques, i.e. extractive distillation. [ABSTRACT FROM AUTHOR]

• Phenol catabolism among three psychrotolerant yeast strains was examined. • For this, enzymatic and chromatographic (GC–MS) techniques were applied. • The impact of cell inoculum preparation on the enzymatic activity was examined. • All yeast strains utilized phenol via the ortho -cleavage pathway. • None of the yeast strains utilized phenol via the meta -cleavage pathway. In this study, three psychrotolerant phenol-degrading yeast strains Candida subhashii (strain A01 1), Candida oregonenis (strain B02 1) and Schizoblastosporion starkeyi-henricii (strain L01 2) isolated from Rucianka peatland were examined to determine which alternative metabolic pathway for phenol biodegradation is used by these microorganisms. All yeast strains were cultivated in minimal salt medium supplemented with phenol at 500, 750 and 1000 mg l−1 concentration with two ways of conducting phenol biodegradation experiments: with and without the starving step of yeast cells. For studied yeast strains, no catechol 2,3-dioxygenase activities were detected by enzymatic assay and no products of catechol meta -cleavage in yeast cultures supernatants (GC–MS analysis), were detected. The detection of catechol 1,2-dioxygenase activity and the presence of cis,cis -muconic acid in the analyzed samples revealed that all studied psychrotolerant yeast strains were able to metabolize phenol via the ortho -cleavage pathway. Therefore, they may be tested in terms of their use to develop biotechnology for the production of cis,cis -muconic acid, a substrate used in the production of plastics (PET) and other valuable goods. [ABSTRACT FROM AUTHOR]

In the present study, the extracts of Cytinus hypocistis (L.) L using both traditional solvents (hexane, ethyl acetate, dichloromethane, ethanol, ethanol/water, and water) and natural deep eutectic solvents (NADESs) were investigated in terms of their total polyphenolic contents and antioxidant and enzyme-inhibitive properties. The extracts were found to possess total phenolic and total flavonoid contents in the ranges of 26.47–186.13 mg GAE/g and 0.68–12.55 mg RE/g, respectively. Higher total phenolic contents were obtained for NADES extracts. Compositional differences were reported in relation to antioxidant potential studied by several assays (DPPH: 70.19–939.35 mg TE/g, ABTS: 172.56–4026.50 mg TE/g; CUPRAC: 97.41–1730.38 mg TE/g, FRAP: 84.11–1534.85 mg TE/g). Application of NADESs (choline chloride—urea 1:2, a so-called Reline) allowed one to obtain the highest number of extracts having antioxidant potential in the radical scavenging and reducing assays. NADES-B (protonated by HCl L-proline-xylitol 5:1) was the only extractant from the studied solvents that isolated a specific fraction without chelating activity. Reline extract exhibited the highest acetylcholinesterase inhibition compared to NADES-B and NADES-C (protonated by H2SO4 L-proline-xylitol 5:1) extracts, which showed no inhibition. The NADES extracts were observed to have higher tyrosinase inhibitory properties compared to extracts obtained by traditional organic solvents. Furthermore, the NADES extracts were relatively better inhibitors of the diabetic enzymes. These findings provided an interesting comparison in terms of total polyphenolic content yields, antioxidant and enzyme inhibitory properties (cholinesterase, amylase, glucosidase, and tyrosinase) between traditional solvent extracts and NADES extracts, used as an alternative. While the organic solvents showed better antioxidant activity, the NADES extracts were found to have some other improved properties, such as higher total phenolic content and enzyme-inhibiting properties, suggesting functional prospects for their use in phytonutrient extraction and fractionation. The obtained results could also be used to give a broad overview of the different biological potentials of C. hypocistis. [ABSTRACT FROM AUTHOR]

The unplanned anthropogenic activities and raced industrial revolution detrimentally causes serious threat to terrestrial and aquatic life. A high discharge of wastewater from industries using dyes affects living organisms and the environment. This paper presents studies on polycationic selenides (PCS) synthesized by hydrothermal methods for photocatalytic degradation of dyes. The synthesized PCS were confirmed by various characterization techniques such as FTIR, SEM, EDX, UV/Vis, and XRD. The FTIR spectra revealed characteristic band at 843, 548 cm−1, and 417 cm−1 due to the M − Se stretching and intrinsic stretching vibrations, respectively. The optical bandgap of polycationic selenide lies in the visible light region (2.36 eV). The SEM images showed that PCS has a spherical shape with an average crystallite size of 29.23 nm calculated from XRD data using Scherer's equation. The PCS has a point of zero charge (PZC) at pH 7. The efficiency of synthesized PCS photocatalyst was confirmed in terms of its activity towards Eosin (EY) and Crystal violet (CV) dyes mineralization. The photocatalytic degradation for EY and CV dyes at optimum conditions was 99.47% and 99.31% and followed second order reactions kinetics with 1.4314 and 0.551 rate constant, respectively. The polynomial quadratic model is the best-fitted response surface methodology (RSM) model having a maximum desirability factors value and significant terms, with R2 (0.9994) and adj R2 values (1.0). [Display omitted] • Green fabrication of new ternary metallic selenides nanostructured materials. • Structural/morphological characteristics of ternary metallic selenides by advanced techniques. • Efficient photocatalytic degradation of textile contaminants under sunlight irradiation. • Operating factors influencing the degradation phenomena are investigated. [ABSTRACT FROM AUTHOR]