Specific Surface Area Values Research Articles

Natural clays as adsorbents for the efficient removal of antibiotic ciprofloxacin from wastewaters: Experimental and theoretical studies using DFT method

Natural clays were used as adsorbent to remove ciprofloxacin from aqueous solutions by adsorption. The textural, structural, and morphological properties were examined, finding low-moderate specific surface area values (9.9–50.1 m2g−1) and a structure coincident with the smectite phase. Adsorption kinetic studies revealed that clay 3 and 4 reached a CIP removal around 70–80 % in 7–8 h. Elovich and pseudo-second-order models were the most suitable to describe the kinetics. The highest equilibrium adsorption capacities (qe = 150.2–193.7 mg g−1) were obtained for clay 1, 3, and 4; the lowest (qe = 30.6 mg g−1) was found for clay 2, which showed the highest-ordered structure. The Freundlich adsorption model led to the best-fitting results. From pH studies, working at solution pH = 4.0 led to the best adsorption results. The estimated thermodynamic parameters suggested that the adsorption process can be considered of physical nature. It was found that the high concentration of CO32– salts in the hospital wastewater effluent enhanced the CIP adsorption capacity, showing a CIP removal of about 95 % for the clay 3. Therefore, the adsorbent with the greatest compromise situation among all the variables was clay 3, presenting the maximum CIP removal after 7 h at pH 4.0, 50 °C and real matrices. The reusability of natural clays can be successfully regenerated by NaOH treatment using the adsorption/desorption process, an indication of its excellent reusability and stability during the regeneration. Finally, DFT molecular studies were performed to clarify the particularities of the adsorption of CIP onto clays.

Ethyl palmitate decarboxylation using colloidal SiO2- templated mesoporous Ni-ZrO2 catalysts

A series of 10 wt% NiO-xSiO2-ZrO2 (x = 0–30 wt%) catalysts were synthesized using a one-pot coprecipitation method with different of colloidal SiO2 contents, as a hard template, in order to imprint mesoporous cavities after a post-synthesis selective alkaline NaOH/H2O lixiviation. The final catalysts were characterized by XRD, HRTEM, textural measurements, 29Si-MAS NMR, FTIR, and XPS; the lixiviated, calcined and H2-reduced powders, were evaluated in the decarboxylation (DCO2) of ethyl palmitate as a liquid-solid phase model reaction at 300 °C, and 20 kg/cm2 H2 pressure. Optimal amount of colloidal SiO2 was 10 wt%. SiO2 effect (as colloid in fresh preparations and/or residual SiO2, after lixiviation) on ZrO2 is twofold. (i) to upgrade mesoporosity and (ii) to stabilize the porous structure. Residual SiO2 (from incomplete lixiviation) plays a beneficial role as examined by 29Si-NMR, being chemically bonded to ZrO2 and acting as props of the mesopores. Total pore volume and specific surface area values increased 5 and 6 times, respectively, when using a 30 wt% SiO2 in comparison with a non-silicated NiO-ZrO2 preparation. DCO2 of ethyl palmitate benefit from better mesoporosity and a great number of oxygen vacancies from Ni isomorphic substitution into cubic ZrO2 (as indicated by XPS); being at the origin of the reaction mechanism. For instance, a 10 wt% SiO2 NiO-ZrO2 catalyst is 1.6 times more selective (to n-pentadecane) and 1.2 times more active than a non-silicated NiO-ZrO2, yielding decarboxylated (i.e., deoxygenated) renewable linear hydrocarbons similar to those in a Diesel composition. However, DFT calculations indicate that adsorbed CO2 (as a formate species) desorbs, once fully hydrogenated, as methane regenerating the oxygen vacancies but consuming H2 as well, in agreement with the high methane concentration detected in gas phase.

Using machine learning to explore oxyanion adsorption ability of goethite with different specific surface area

In this study, we developed prediction models for the adsorption of divalent and trivalent oxyanions on goethite based on machine learning algorithms. After verifying the reliability of the models, the importance of goethite specific surface area (SSA) and the average oxyanion adsorption capacities of goethite with different SSAs were calculated by shapley additive explanations (SHAP) importance analysis and partial dependence (PD) analysis. Despite there were differences in the feature importance of divalent and trivalent oxyanions, the contribution of goethite's SSA to the adsorption amount ranked the fourth based on SHAP importance, indicating SSA played the important role in oxyanion adsorption. Meanwhile, the PD values of SSA and the optimized complexation constants from surface complexation modeling (SCM) both indicated a non-monotonic relationship between the goethite with different SSA and its oxyanions binding capacity. When the total site concentration and crystal face composition were used as the machine learning model input features, the SHAP importance values of crystal faces and the PD decomposition results indicated that the (001) face showed the crucial influence on oxyanions adsorption amount. These findings demonstrated the important role of crystal face composition in goethite's adsorption ability, and provided a theoretical explanation for the variations of oxyanions adsorption amount on different SSA goethite.

Dual function of ultra-laminated hydrotalcite in environmental remediation: Adsorption of water contaminant BP-4 and reutilization of the adsorption product for photocatalytic NOx air decontamination

UV filters are a class of emerging water pollutants used in cosmetics to protect the skin from ultraviolet radiation. This work appraises the uptake of benzophenone-4 (BP-4), widely used and highly soluble sunscreen agent, by its adsorption on hydrotalcite based compounds. The studied adsorbents were hydrotalcite Mg3Al-CO3 (HT), ultra-laminated hydrotalcite (UHT) prepared by “Aqueous Miscible Organic Solvent Treatment” and their calcined products (HT500 and UHT500, respectively). Adsorbents were characterised by different techniques such as XRD, TEM, FT-IR, BET, XRF and TGA. The most remarkable feature was the enhancement in the specific surface area (SSA) of the ultra-laminated hydrotalcite samples, UHT and UHT500 with values of 212 m2·g─1 and 247 m2·g─1, respectively. Adsorption capacities decreased from very high for UHT500 to low values for HT in order UHT500 > HT500 > UHT > HT. The results showed that not only the SSA values were relevant for adsorbing BP-4, but also other factors such as anionic exchange capacity (AEC) and surface charge. In addition, the adsorption product (UHT-BP4) was evaluated as a photocatalyst for air purification, exhibiting good efficiency for the removal of atmospheric pollutants such as NOx gases.

Effect of Amino-Functionalized Polyhedral Oligomeric Silsesquioxanes on Structure-Property Relationships of Thermostable Hybrid Cyanate Ester Resin Based Nanocomposites.

Nanocomposites of cyanate ester resin (CER) filled with three different reactive amino-functionalized polyhedral oligomeric silsesquioxane (POSS) were synthesized and characterized. The addition of a small quantity (0.1 wt.%) of amino-POSS chemically grafted to the CER network led to the increasing thermal stability of the CER matrix by 12-15 °C, depending on the type of amino-POSS. A significant increase of the glass transition temperature, Tg (DSC data), and the temperature of α relaxation, Tα (DMTA data), by 45-55 °C of the CER matrix with loading of nanofillers was evidenced. CER/POSS films exhibited a higher storage modulus than that of neat CER in the temperature range investigated. It was evidenced that CER/aminopropylisobutyl (APIB)-POSS, CER/N-phenylaminopropyl (NPAP)-POSS, and CER/aminoethyl aminopropylisobutyl (AEAPIB)-POSS nanocomposites induced a more homogenous α relaxation phenomenon with higher Tα values and an enhanced nanocomposite elastic behavior. The value of the storage modulus, E', at 25 °C increased from 2.72 GPa for the pure CER matrix to 2.99-3.24 GPa for the nanocomposites with amino-functionalized POSS nanoparticles. Furthermore, CER/amino-POSS nanocomposites possessed a higher specific surface area, gas permeability (CO2, He), and diffusion coefficients (CO2) values than those for neat CER, due to an increasing free volume of the nanocomposites studied that is very important for their gas transport properties. Permeability grew by about 2 (He) and 3.5-4 times (CO2), respectively, and the diffusion coefficient of CO2 increased approximately twice for CER/amino-POSS nanocomposites in comparison with the neat CER network. The efficiency of amino-functionalized POSS in improving the thermal and transport properties of the CER/amino-POSS nanocomposites increased in a raw of reactive POSS containing one primary (APIB-POSS) < eight secondary (NPAP-POSS) < one secondary and one primary (AEAPIB-POSS) amino groups. APIB-POSS had the least strongly pronounced effect, since it could form covalent bonds with the CER network only by a reaction of one -NH2 group, while AEAPIB-POSS displayed the most highly marked effect, since it could easily be incorporated into the CER network via a reaction of -NH2 and -NH- groups with -O-C≡N groups from CER.

Enhanced dispersing properties of kaolin due to high-strength kneading process

In this study, the influence of high-strength kneading process on the dispersibility of kaolin was investigated. Various factors including crystallinity, shape and interaction energy of kaolin particles were investigated systematically based on XRD, SEM, FTIR, Zeta potential and DLVO analyses. The results showed that the high-strength kneading treatments increased the proportion of kaolinite (001) planes, reducing the friction between kaolin particles but increasing their crystallinity. In addition, this treatment promoted the tendency of kaolin to a pseudo-hexagonal shape. DLVO analyses further showed that the electrostatic repulsion energy between kaolin particles was proportional to the kneading time due to the increased specific surface area (e.g., increased from 14.63 to 18.24 m2·g−1) and negative charge value (e.g., decreased from −15 to −32 mV) of kaolin sample. This correspondingly led to a lower viscosity of kaolin pulp with better dispersing properties, e.g., the viscosity of kaolin samples decreased by 65.41% when kneading time was extended from 0 to 6 h. This study therefore provides a new strategy to reutilize kaolin sources with low dispersing properties and crystallinity after a high-strength kneading process.

Electrochemical Performance of Activated Graphene-Based Materials for Electrodes of Double-Layer Supercapacitors

Activated graphene oxide seems to be a promising electrode material for electrochemical double-layer capacitors, also known as supercapacitors or ultracapacitors, and other energy storage purposes. This article summarizes the results of our research about the effect of graphene oxide KOH-catalyzed activation on their specific surface area (SSA) and their capacitance, both strongly related to their electrochemical performance. KOH-catalyzed activation increased the SSA values of the reduced graphene oxide (rGO) from ∼783 m2 g−1 to ∼2144 m2 g−1; it is important to note that the SSA and oxygen-containing groups are two important factors determining electrochemical performance. Moreover, the highest capacitance value was 50.08 F g−1, using 1.0 M H2SO4 as an aqueous electrolyte. Activated graphene-based materials with high SSA support conductive networks decorated with oxygen groups synergistically improve charge storage capability in EDLCs.

Ab-initio study of structural, morphological and optical properties of multiferroic La2FeCrO6

The current research is concerned with the structure, morphology, and physical properties of a double perovskite La2FeCrO6. The crystallite size of the sample was determined to be 22.46 nm using the modified Scherrer equation. The elemental composition of La2FeCrO6 was confirmed through X-ray photoelectron-spectroscopy (XPS), which detected La, Fe, Cr, and oxygen, as well as oxygen deficiencies that significantly impact the observed ferroelectric behavior in the investigated sample. High-resolution transmission electron microscopy (HRTEM) verified the nanoscale preparation of the sample with an average particle size of 33.32 nm. Thermogravimetric analysis (TGA) was employed to investigate the thermal properties of the sample including the calculation of thermodynamic functions such as changes in enthalpy (ΔH) and entropy (ΔS) for La2FeCrO6. The material exhibits an optical direct transition with a band gap value of 3.4 eV and an Urbach energy of 2.5 eV. Due to its large specific surface area and band gap value, La2FeCrO6 shows promise in applications such as photocatalysis and water purification. The ac conductivity of La2FeCrO6 follows the universal dielectric response (UDR), and the P-E loop of the sample demonstrates its ferroelectric behavior.

Freestanding Carbon Nanofibers Derived from Biopolymer (Kraft Lignin) as Ultra-Microporous Electrodes for Supercapacitors

Lignin-derived carbon nanofibers (LCNFs) formed via the solution blowing of a biopolymer are developed here as a promising replacement for polyacrylonitrile (PAN)-derived carbon nanofibers (PCNFs) formed via electrospinning for such applications as supercapacitor (SC) electrodes. Accordingly, it is demonstrated here that a biopolymer (kraft lignin, which is, essentially, a waste material) can substitute a petroleum-derived polymer (PAN). Moreover, this can be achieved using a much faster and safer fiber-forming method. The present work employs the solution blowing of lignin-derived nonwovens and their carbonization to form electrode materials. These materials are characterized and explored as the electrodes in supercapacitor prototypes. Given the porosity importance of carbon fibers in SC applications, N2 gas adsorption tests were performed for characterization. LCNFs revealed the specific surface area (SSA) and capacitance values as high as 1726 m2/g and 11.95 F/g, which are about one-half of those for PCNFs, 3624 m2/g and 25.5 F/g, respectively. The capacitance values of LCNFs are comparable with those reported in the literature, but the SSA observed here is much higher. Moreover, no further post-carbonization activation steps were performed here in comparison with those materials reported in the literature. It was also found here that fiber pre-oxidation in air prior to carbonization and the addition of zinc chloride affect the SSA and capacitance values of both LCNFs and PCNFs. The electrochemical tests of the SCs prototypes were used to evaluate their capacitance at different charging rates, voltage windows, and the number of cycles. The capacitance of PCNFs decreased by about 47% during fast charging, while the capacitance of LCNFs improved during fast charging, bringing them to the level of only 21% below that of PCNFs. These changes were correlated with the packing density of the electrodes. It should be emphasized that LCNFs revealed a much higher mass yield, which was 4–5 times higher than that of PCNFs. LCNFs also possess a higher packing density, a lower price, and cause a significantly lower environmental impact than PCNFs. The best cell supercapacitor delivered a maximum specific energy of 1.77 Wh/kg and a maximum specific power of 156 kW/kg, surpassing conventional electrochemical supercapacitors. Remarkably, it retained 95.2% of its initial capacitance after 10,000 GCD cycles at a current density of 0.25 A/g, indicating robust stability. Accordingly, kraft lignin, a bio-waste material, holds great promise as a raw material for supercapacitor electrodes.

Comparative Study of the Physico-Chemical Properties of Sorbents Based on Natural Bentonites Modified with Iron (III) and Aluminium (III) Polyhydroxocations

A comparative study of the physicochemical properties of natural bentonite clays of Pogodayevo (Republic of Kazakhstan, mod. 1) and Dash-Salakhli (Republic of Azerbaijan, mod. 2) deposits and modification of the bentonite clay with polyhydroxocations of iron (III) and aluminium (III). The amount of bentonite in the concentration of iron (aluminum) was 5 mmol Me3+/g. It was established that the modification of natural bentonites using polyhydroxocations of iron (III) (mod. 1_Fe_5-c, mod. 2_Fe_5-c) and aluminum (III) (mod. 1_Al_5-c, mod. 2_Al_5-c) by the method of “co-precipitation” leads to a change in their chemical composition, structural and sorption properties. The results showed that hydroxy-aluminum cations ([Al3O4(OH)24(H2O)12]7+) and poly-hydroxyl-Fe or polyoxo-Fe were intercalated into clay layers, which led to an increase in the values of d001 and specific surface areas compared to those of the original bentonite, from 37 to 120 m2/g for the Pogodaevo bentonite and from 51 to 172 m2/g respectively, for bentonite from the Dash-Salakhli deposit. It is shown that modified sorbents based on natural bentonite are finely porous objects with a predominance of pores of 1.5–8.0 nm in size. As a result, there is a significant increase in the specific surface area of sorbents. Modification of bentonite with polyhydroxocations of iron (III) and aluminum (III) by the “co-precipitation” method also leads to an increase in the sorption capacity of the sorbents obtained with respect to nickel (II) cations. Modified bentonites were used for the adsorption of Ni (II) ions from the model solution. Ni (II) was absorbed in a neutral pH solution. The study of equilibrium adsorption showed that the data are in good agreement with the Langmuir isotherm model. The maximum adsorption capacity of the Ni (II) obtained from the Langmuir equation was 25.0 mg/g (mod. 1_Al_5-c), 18.2 mg/g (mod. 2_Al_5-c) for Al-bentonite and 16.7 mg/g (mod. 1_Fe_5-c), 10.1 (mod. 2_Fe_5-c) for Fe-bentonite. The kinetics of adsorption is considered. The high content of Al-OH anion exchange centers in them determines the higher sorption activity of Al-modified bentonites.

Microwave-Assisted hydrothermal carbonization and characterization of Amazonian biomass as an activated carbon for methane adsorption

Activated carbons were prepared from Amazonian biomass by means of microwave-assisted hydrothermal carbonization and activated with CO2. These materials were investigated as methane adsorption sorbents. The prepared samples were submitted to textural investigations and comprehensive characterizations using scanning electron microscopy, Transmission electron microscopy, energy dispersive X-ray diffraction, Raman and FTIR spectroscopy. Values of specific surface areas and pore volume ranged from 0.35 cm3/g to 0.50 cm3/g and from 840 to 1096 m2/g respectively, this value is likely attributed to the high selectivity of CO2/CH4 and methane adsorption by combining large surface area, narrow micropores. The results of the stability tests attested to the robustness of activated carbon as an adsorbent under the specified operating conditions The assessment, which included measurements after the first cycle as well as the fifth, tenth, and fifteenth cycles, revealed a remarkable consistency in its adsorption behavior, with a maximum recorded standard deviation of 0.05. Isosteric heat showed a decline in Qst from 21 to 20 as surface coverage increases from 0.1 to 0.5, indicating the energetic transformation occurring during the adsorption process. Activated carbon AC C shows the highest methane capture capacity of 150 V/V at 40 bar pressures and CH4/CO2 0.49 selectivity up to 1 bar.

Synthesis and Properties of Rubidium Salts of Phosphotungstic Acid

The work is devoted to the study of the influence of synthesis conditions on the properties of water-insoluble rubidium salts of phosphotungstic acid (PTA). Such heteropoly compounds have a wide range of applications, including in the field of electrocatalysts and solid electrolytes for various electrochemical devices. The acid salts of PTA with high activity of acid sites on the particle surface are of particular interest. It is known that the properties of water-insoluble PTA salts strongly depend on synthesis conditions, such as the ratio of reagents, temperature, concentrations, and other parameters. The work examines the influence of the ratio and concentration of reagents on the sizes of crystallites and agglomerates, specific surface area (SSA), porosity, water content, and ionic conductivity of the synthesized PTA salts. The SSA value of the obtained samples varied in the range of 84–123 m2 g−1, and the ionic conductivity was 13–90 mS cm−1 at room temperature and 75% RH. An increase in the acid concentration and the degree of proton substitution led to an increase in SSA, accompanied by an increase in particle sizes without changing the size of crystallites. The results of the work may be useful for the development of new materials based on the obtained salts in many fields, including hydrogen energy.

Efficient removal of amoxycillin antibiotics onto magnetic graphene oxide: adsorption performance, mechanism, and regeneration exploration

ABSTRACT The present study was done to synthesise an adsorbent, i.e. magnetic graphene oxide (MGO) nanocomposite, which was performed based on a facile precipitation method and was utilised in experiments for removing amoxycillin (AMX). The characteristics of the prepared adsorbent were defined based on commonly utilised analyses (SEM, XRD, BET, TEM, FTIR, VSM, and pHpzc). According to kinetic studies, the PSO model was found as an applicable model for describing data. Moreover, the two-step diffusion process, i.e. diffusion in the boundary layer and the porous structures, was perceived for the evaluated process based on the IPD model. The isotherm models, including Langmuir, Freundlich, Temkin, and D–R, were employed for fitting data and calculating AMX adsorption capacity, among which Langmuir was the best one; using this model, the maximum adsorption capacities for MGO were 91.4, 103.9, 112.3, and 122.5 mg/g, which were achieved at 20, 30, 40, and 50°C. In addition, a feasible, spontaneous, and endothermic process was found for the adsorption of AMX ions, according to thermodynamic studies. The highest percentage of removal (100%) was obtained for the initial concentration of 25 mg/L at 50°C using the adsorbent dose of 1.5 g/L at a pH of 5 and a contact time of 90 min. The values of 74.4 m2/g and 27.74 emu/g were detected for the specific surface area and saturation magnetisation values of the MGO, respectively. The overall results were representative of the suitability of the MGO as an adsorbent for removing AMX from aqueous media.

Tuning the surface area of reduced graphene oxide by modulating graphene oxide concentration during hydrazine reduction

In this study, we explore the impact of graphene oxide (GO) concentration in aqueous suspension on the specific surface area (SSA) of multilayered reduced graphene oxide (RGO). A series of GO suspensions were prepared, and subsequently subjected to reduction using hydrazine hydrate. Particle size for all obtained RGO samples does not exceed 10 μm averagely consisting of 2–3 graphene layers. Our findings demonstrate that, under consistent synthetic conditions, the variation in GO concentration predominantly influences the SSA values while other structural characteristics do not change significantly. We observe a concentration-dependent trend in SSA, displaying a peak value with highest SSA for RGO of 600 m2/g obtained from the GO suspension with a concentration of 4 mg/mL.

In English

Various 2D carbons demonstrate significant effects of surface oxidation, heating, suspending–drying, cryogelation, swelling, and adsorption of polar and nonpolar compounds on the morphological, structural, and textural characteristics. Heating at 120–150 °C could result in collapse of pores not only between carbon sheets in stacks but also between neighboring stacks; therefore, the specific surface area (SSA) decreases by a factor of 30–100 for preheated graphene oxides (GO). According to the TEM and XRD data, the GO structure is rather amorphous, since only small X-ray coherent scattering regions demonstrate a certain order giving broad XRD (001) and (002) lines. In the Raman spectra, the D line (disordered defect structures with sp3 hybridized C atoms) intensity for GO is similar to that of the G line (ordered structures with sp2 hybridized C atoms). The graphite oxide (GtO) structure, which is closer to that of graphite than that of GO, is characterized by intensive G and low D lines, and the main XRD peak at 26.4° (characteristic for graphite) is broadened similar to the XRD peak of GO at 10°. Despite the GO stacks have a tendency to collapse upon heating, the collapsed stacks can be swollen not only in water (strongly) but also in liquid nitrogen (relatively weakly). Therefore, the use of GO in aqueous media can provide great SSA values in contact with the solvent and solute molecules. This could provide high efficiency of the GO use for purification of wastewater, separation of solutes, etc. MLGO produced from natural flake graphite as a precursor (flakes &lt; 0.2 mm in size) using a modified method of ionic hydration and freeze–drying is characterized by typical light brown color, low bulk density, flexible sheet stacks easily collapsed, but its interaction with water results in strong swelling. Interaction between the carbon sheets in preheated MLGO is strong and nonpolar molecules, such as benzene, n–decane, poorly penetrate between the sheets, i.e., intercalation adsorption is small. However, water molecules can effectively penetrate (this is rather intercalation adsorption resulting in swelling) between the sheets, but the swelling effect of water adsorbed from the gas phase could be weaker than that in the aqueous suspensions. Thus, the proposed synthesis method of MLGO using natural graphite is effective and appropriate for preparation of the materials for various practical applications.

Adsorption behavior of triclosan on polystyrene nanoplastics: The roles of particle size, surface functionalization, and environmental factors

Nanoplastics (NPs) contribute substantially to the transport of waterborne pollutants. Triclosan (TCS) has a high potential to contact with NPs because of their prevalence in natural waters. Herein, this study investigated the adsorption behavior of TCS on differently sized and functionalized polystyrene (PS) NPs. The effects of environmental factors such as pH, salinity, and dissolved organic matter (DOM) were also evaluated. Results suggest that the adsorption equilibrium constant (kd) of TCS in pristine PSNP suspensions followed the order as: PSNPs-50 nm (4.39 L·g−1) > PSNPs-100 nm (2.78 L·g−1) > PSNPs-200 nm (2.59 L·g−1) > PSNPs-500 nm (1.36 L·g−1) ≈ PSNPs-900 nm (1.36 L·g−1). For the functionalized PSNPs (i.e., PSNPs-COOH, PSNPs-NH2), the values of specific surface area normalized kd called kd, SSA were higher than those of pristine PSNPs. Meanwhile, TCS adsorption on two functionalized PSNPs remained stable and then decreased as salinity increased, while an opposite trend was observed toward pristine PSNPs. All these suggested that physicochemical properties of PSNPs (e.g., particle size and surface functional groups) are important factors influencing their adsorption capacity. When the solution pH raised, the adsorbed amounts of TCS on all tested PSNPs prone to decline. However, DOM only affected the adsorption behavior of PSNPs-50 nm, probably owing to its aggregation with tiny PSNPs and the induced secondary adsorption.

Electric arc pyrolysis of different fractions derived from waste tire pyrolysis oil

The paper reports the experimental results on extraction and characterization of different fractions (light (<180 °C), middle (180–350 °C), and heavy (>350 °C)) derived from pyrolysis oil of waste tires of mining vehicles, followed by their electric arc pyrolysis in order to produce nanosized carbon material. The released gas was found to contain 20.4–37.1 vol% hydrogen, 7.4–24.9 vol% methane, and 24.7–27.9 vol% carbon monoxide. The carbon material obtained was presented by an array of nanosized particles (30–250 nm) with a graphite-like structure and a wide range of specific surface area values (Ssf = 38.8–79.7 m2/g). The content of carbon and sulfur was 98.3–99.1 wt% and 0.1–0.3 wt%, respectively. Transmission electron microscopic analysis of the test samples revealed two types of carbon nanostructures of different morphology: polyhedral graphite and carbon nano-onions. Characteristics of the samples obtained from pyrolysis oil and its fraction with a boiling point exceeding 350 °C were the closest to those of carbon black.

Synthesis of Crosslinked Microparticles Based on Glycidyl Methacrylate and N‐Vinylimidazole

AbstractIn this study, suspension polymerization technique is used to obtain 3D porous networks based on two monofunctional monomers (glycidyl methacrylate and N‐vinylimidazole) and one of the following difunctional monomers known as crosslinking agents: mono‐, di‐, and triethylene glycol dimethacrylate or divinylbenzene. The influence of various operational parameters like: monomer molar ratio, amount and type of crosslinkers, composition of stabilization system, stirring speed, amount of porogenic agent on the reaction yield, surface morphologies, particle size distribution, and porous characteristics are investigated in order to find the optimal conditions for the synthesis of microparticles possessing the desired properties for further chemical modification. Crosslinked porous microparticles are structurally characterized by Fourier transform inrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy, and elemental analysis by determination of nitrogen and epoxy groups. The microparticle morphologies as a function of investigated parameters are revealed by scanning electron microscopy, whereas the porous structure is highlighted by mercury porosimetry and dynamic water vapor sorption methods. All the crosslinked networks exhibit porous structures with different surface morphologies and specific surface area values (1.15–48.32 m2 g−1) depending on the operational parameters. These microparticles can be considered precursors for the preparation of various functional polymeric materials.

Directed thermocatalytic CO2 reduction over NiAl4 layered double hydroxide precursors − activity and selectivity control using different interlayer anions

The use of rare nickel-poor and aluminum-rich layered double hydroxides (LDHs) as catalyst precursors in CO2 hydrogenations has revealed the key importance of chemical quality of the interlayer anions for the achievable CO2 conversion and CH4/CO selectivity. At atmospheric pressures between 300 and 700 °C, the obtained CH4 and CO formation rates varied widely, reaching up to the remarkable 76.8 (LDH-NO3) and 47.7 μmol/gcats (LDH-NH2SO3), respectively, competing with Pt and Co containing catalysts. Depending on thermal stability of the interlayer anions, their partial or complete removal resulted in significant differences in LDH transformation and thus in reducibility of Ni(II) and specific surface area values of the resulting metal oxides. Moreover, clear correlation was found between the conversion, selectivity and the abundance, strength of base and acid sites presented in the calcined LDHs related to the nature of starting interlamellar anions. Incorporation of nitrate and perchlorate ions into the precursors helped the formation of weak basic sites, while sulphate and sulphamate ions resulted in a large number of strong acid and base sites. The high-resolution quasi in situ X-ray photoelectron spectra revealed the effect of the anions on chemical composition of the forming catalytic interfaces. Meantime, the in situ diffuse reflectance infrared spectroscopy measurements indicated multifarious CO2 hydrogenation pathways via formate (LDH-NO3, -Br, -I), carboxylate (LDH-Cl, -ClO4) intermediates and CO2 dissociation (LDH-SO4, -NH2SO3).

Conversion of waste biomass to designed and tailored activated chars with valuable properties for adsorption and electrochemical applications.

Waste biomass, a renewable energy source, is inexpensive material that has great potential in sorption and electrochemical application. The selected waste materials (corncobs, coconut shells, walnuts, and pistachio husks) allow to close the production cycle and enable material recycling, which are important aspects in the hierarchy of waste management. The proposed methodology for production and activation of biochars can be used industrially due to highly porous structure, developed surface area, and sorption ability of the obtained activated carbons (AC). A significant increase (from 4 up to more than 10 times) in specific surface area (SSA) is observed for all samples after the CO2 activation process (0.5 h at 800 °C) up to 725 m2 g-1 for corncobs, 534.9 m2 g-1 for pistachio husks, 523 m2 g-1 for coconut shells, and 393 m2 g-1 for walnut husks. The highest value of SSA is achieved for the AC derived from corncobs. This material is evaluated for use as an adsorbent, revealing 99% removal of Rhodamine B (dye/AC ratio of 0.0017) and 69% removal of chromium (dye/AC ratio of 0.0028). Based on the adsorption kinetics analysis, it is demonstrated that the Cr(VI) undergoes physical adsorption, while RhB undergoes chemisorption. In addition, corncob-derived AC exhibits superior electrochemical performance in 6 M KOH compared to the nonactivated biochar. A specific capacitance of 70 F g-1 at 5 A g-1 is achieved, along with outstanding rate capability (45 F g-1 at 50 A g-1) and cycling stability (94% at 10 A g-1 after 10,000 cycles). In contrast, the nonactivated sample shows only 34 F g-1 at 5 A g-1 and 13 F g-1 at 50 A g-1, with a stability of 91.4%.