Search

A number of new micro-mesoporous carbon materials (FHU100N, FHU100K, FHU70N30K, FHU50N50K and FHU20N80K) based on a mixture of furfural, hydroquinone, and urotropine have been synthesized by the alkaline activation method using a combination of activating agents (KOH and NaOH). The influence of the porous structure of the synthesized adsorbents has been studied with particular attention to the pore size distribution, in particular, to the pore volume in which MG can be adsorbed most efficiently from aqueous solutions. Subsequently, among the tested carbons, the FHU100N has excellent porosity (total pore volume, micropore volume and mesopore volume: 1.136, 0.632 and 0.504 cm3 /g, respectively) with the highest surface area (2575 m2 /g). The adsorption capacity of FHU100N (1300 mg/g) for malachite green (MG) was superior to other micro mesoporous carbons (500–918 mg/g). The results obtained showed that the key contribution to the adsorption of the MG dye is made by pores ranging in size from 2 to 3.5 nm. The FHU100N adsorbent, which showed the highest MG adsorption activity, was characterized by nitrogen adsorption, FTIR, Raman spectroscopy, and XRD techniques. To understand the adsorption mechanisms on the obtained material, detailed mathematical analysis of experimental sorption data was carried out using the existing kinetic (pseudo-first order and pseudo-second order) models and diffusion (Weber-Morris and Boyd) models, along with adsorption equilibrium isotherms (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich). [ABSTRACT FROM AUTHOR]

The paper describes the adsorption of toluene and benzene on a new sorption material—coconut activated carbon (AC) modified with carbon nanotubes. The new material was characterized using Raman spectroscopy, scanning and transmission electron microscopy, X-ray diffractometry and FTIR. Also, the parameters of the porous space and the specific surface area were determined. The adsorption capacity for toluene and benzene was 123.53 and 84.92 mg g−1, respectively, the contact time was 60 min. The kinetic data were described using intraparticle diffusion, and the results of isothermal studies were described using the Langmuir, Freundlich, and Dubinin-Radushkevich equations. It was found that the adsorption of toluene and benzene considered Weber-Maurice model, that conform to a diffusion with fluid phase film resistance. In addition, the physical nature of adsorption is confirmed by the values of free energy (E = 6.92 and 8.41 kJ moL−1 for benzene and toluene, respectively). According to a thermodynamic study, the Gibbs energy values for nanomodified AC were − 16.32 kJ moL−1 for benzene and − 33.33 kJ moL−1 for toluene, which corresponds to the range of values for physical sorption. Thus, the material can be considered as a promising adsorbent for removing organic pollutants from aqueous media. [ABSTRACT FROM AUTHOR]

Carbon porous materials obtained through KOH activation of a furfural + hydroquinone + urotropine mixture were applied as adsorbent for the remediation of methylene blue (MB). The impact of porous structure with special attention to pore size distribution along with well-known pore volume and specific surface area on the remediation of MB was well investigated and elucidated. Findings obtained revealed that pore size distribution plays a crucial role in the liquid-phase adsorption of organic dyes like MB. By varying the synthesis mode parameters, in particular, the activating agent/precursor mass ratio, with the composition and initial components ratios remaining unchanged, samples with different pore size distribution were obtained. It was found that the material predominantly containing pores with an average equivalent diameter of ~ 3.5 nm appears to be the efficient MB adsorbent. The resulting highly porous carbon materials demonstrated high MB adsorption capacity (up to 2555 mg/g). Furthermore, to fully elucidate the adsorption mechanisms occurring on the obtained materials, a comprehensive mathematical processing of experimental data was performed out using the known kinetic and diffusion models (pseudo-first- and pseudo-second order, and intraparticle diffusion), as well as adsorption equilibrium isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich). It can be concluded that the porous carbon materials obtained and described in the present work are effective adsorbents for the removal of MB and may possess great potential for the treatment of dye-containing wastewater. [ABSTRACT FROM AUTHOR]

The possibility of stabilizing aqueous dispersions of carbon nanotubes (CNTs) using phenol-formaldehyde resin (PFR) and aminocumulene (AC) is shown. The preliminary oxidation of CNTs contributes to their higher solubility in the presence of these stabilizing agents. The concentration of pristine and oxidized CNTs in weakly alkaline solutions containing 2.5 g/L of PFR is 3.0 and 11.4 g/L, respectively. AC promotes the formation of stable dispersions in acidic media with the concentrations of pristine and oxidized CNTs, respectively, 3.3 and 20.4 g/L. A decrease in the effective sizes of agglomerates of both pristine and oxidized CNTs in the presence of PFR and AC has been shown by dynamic light scattering method. According to TG/DSC analysis and Raman spectroscopy data, it was concluded that the oxygen-containing groups of oxidized CNTs interact with the surfactants used. Schemes for the formation of hydrogen and chemical bonds between CNTs and PFR or AС were proposed, which made it possible to explain the effect of dispersion. [ABSTRACT FROM AUTHOR]

This article discusses the nature of the distribution of intact polyaniline-functionalized graphene nanoplatelets (GNPs) in the surface layer of nanomodified films of ultra-high molecular weight polyethylene (UHMWPE) using a Raman mapping method. On the Raman maps, D, G, and 2D peaks can be observed for the 0.1 wt.% GNPs content in the UHMWPE. In the surface layer of the films containing 1.0 wt.% GNPs, these signals are not detected, thereby indicating the displacement of the nanomodifier into the polymer bulk. In contrast, the polyaniline-functionalized GNPs tend to migrate to the surface of the UHMWPE nanocomposite film and evenly distribute in the surface layer as the concentration increases from 0.1 to 2.0 wt.%. [ABSTRACT FROM AUTHOR]

In the present paper, the features of obtaining a metal oxide Fe–Co/Al2O3 catalyst for the synthesis of carbon nanostructured materials through thermal decomposition are considered. It was experimentally proved that the temperature and duration of the stage of thermal decomposition of the initial components solution significantly affect the catalyst activity in the synthesis of carbon nanostructured materials by the CVD method. It was found that controlling the mode parameters of the thermal decomposition of the initial components solution of the Fe–Co/Al2O3 catalyst, one can not only obtain a catalyst with the required characteristics but also directionally synthesize carbon nanostructured materials over the resulting catalytic systems. During the experiments, rational modes for the implementation of the method for producing catalysts were determined, allowing to form a metal oxide system with a specific surface area of 108 m2/g, the use of which in the synthesis of carbon nanostructured materials leads to the formation of multi-walled carbon nanotubes with an external diameter of 30 nm. [ABSTRACT FROM AUTHOR]

The results of a study on the homogeneity of suspensions are described considering the effect of different types of surfactant stabilizers and their concentrations on the uniform distribution of a carbon nanotubes (CNTs)-based modifying additive to construction materials in an aqueous medium. This problem was solved herein by using surfactants and ultrasound. The sonication treatment of CNTs particle agglomerates allowed for dispersing their globules and achieving a 15-20-fold decrease in their average size, for which it became possible to make better use of the CNTs as cement modifier. As a result of the experimental studies carried out, the effect of the surfactant type and concentration promoting uniform distribution of the CNTs in the bulk of the suspension and, correspondingly, in the structural composite matrix was revealed. The CNTs-based additive improved the physical-mechanical and operational characteristics of the material. [ABSTRACT FROM AUTHOR]

The effect of ultrasonic activation on the performance of a mixed oxide-based (Ni/Mg) catalyst in the synthesis of multiwalled carbon nanotubes via chemical vapor deposition was studied. The molecular geometry of the solution of initial catalyst components (feed solution) was calculated and simulated according to a molecular mechanics method. Activation of the catalyst performed for 10 s during its preparation stage resulted in a considerable increase (of about 40 %) in the specific yield of nanotubes due to enhanced catalytic activity. Moreover, the kinetics of nanotube synthesis over the activated catalyst was studied, and the morphology of the obtained nanoproduct was investigated. Finally, the possibility of employing the present method for catalyst activation in experimental-industrial production of nanotubes was evaluated. [ABSTRACT FROM AUTHOR]