Nitrogen Sorption Research Articles

The Application of Clinoptilolite as the Green Catalyst in the Solvent-Free Oxidation of α-Pinene with Oxygen

In this work, we present the catalytic application of the naturally occurring zeolite, clinoptilolite, in the oxidation of α-pinene, a natural terpene compound. Clinoptilolites with different average particle sizes, designated as (in μm) clin_1 (20), clin_2 (50), clin_3 (200), and clin_4 (500–1000), were used as the green catalysts in the solvent-free oxidation of α-pinene with oxygen. Prior to their application in catalytic tests, the catalysts were characterized by the following methods: nitrogen sorption at 77 K, EDXRF, XRD, SEM, UV-Vis, and FTIR. The effects of the temperature, amount of the catalyst, and reaction time on the product’s selectivity and α-pinene conversion were determined. At the optimal conditions (a temperature of 100 °C, catalyst content (clin_4) in the reaction mixture of 0.05 wt%, and 210 min reaction time), the following compounds were obtained as the main products: α-pinene oxide (selectivity 29 mol%), verbenol (selectivity 17 mol%), and verbenone (selectivity 13 mol%). The conversion of α-pinene under these conditions amounted to 35 mol%. Additionally, the kinetic modeling of α-pinene oxidation over the most active catalyst (clin_4) was performed. The proposed method of oxidation is environmentally safe because it does not require the separation of products from the solvent. In addition, this method allows for managing the biomass in the form of turpentine, which is the main source of α-pinene. The catalytic application of clinoptilolite in the oxidation of α-pinene has not yet been reported in the literature.

Physicochemical, structural, and adsorption characteristics of DMSPS-co-DVB nanopolymers.

The aim of this work is the synthesis and characterization of the series of S,S'-thiodi-4,1-phenylene bis(thio-methacrylate)-co-divinylbenzene (DMSPS-co-DVB) nanomaterials. The series of new nanopolymers including three mixed systems with different ratios of DMSPS and DVB components, DMSPS-co-DVB = 1:1, DMSPS-co-DVB = 1:2, and DMSPS-co-DVB = 1:3, was synthesized in the polymerization reaction. The research task is to investigate the influence of the reaction mixture composition on morphological, textural, and structural properties of final nanosystems including size, shape, and agglomeration effect. The advanced biphasic nanomaterials enriched with thiol groups were successfully synthesized as potential sorbents for binding organic substances, heavy metals, or biomolecules. To determine the impact of the DMSPS monomer on the final properties of DMSPS-co-DVB nanocomposites, several techniques were applied to reveal the nano-dimensional structure (SAXS), texture (low-temperature nitrogen sorption), general morphology (SEM), acid-base properties (potentiometric titration), and surface chemistry and phase bonding effectiveness (FTIR/ATR spectroscopy). Finally, kinetic studies of aniline sorption on polymeric materials were performed.

Investigation of CO2 Adsorption on Avocado Stone-Derived Activated Carbon Obtained through NaOH Treatment.

Activated carbons were prepared from avocado stone through NaOH activation and subsequent carbonization. The following textural parameters were achieved: specific surface area: 817-1172 m2/g, total pore volume: 0.538-0.691 cm3/g, micropore volume 0.259-0.375 cm3/g. The well-developed microporosity resulted in a good CO2 adsorption value of 5.9 mmol/g at a temperature of 0 °C and 1 bar and selectivity over nitrogen for flue gas simulation. The activated carbons were investigated using nitrogen sorption at -196 °C, CO2 sorption, X-ray diffraction, and SEM. It was found that the adsorption data were more in line with the Sips model. The isosteric heat of adsorption for the best sorbent was calculated. It was found that the isosteric heat of adsorption changed in the range of 25 to 40 kJ/mol depending on the surface coverage. The novelty of the work is the production of highly microporous activated carbons from avocado stones with high CO2 adsorption. Before now, the activation of avocado stones using NaOH had never been described.

Formation and growth of anatase TiO2 nanocrystals under hydrothermal conditions

This work is devoted to the study of the processes of formation and growth of TiO2 nanoparticles under hydrothermal conditions. TiO2 nanocrystals were obtained during the dehydration of hydrated titanium dioxide by varying the temperature and duration of hydrothermal treatment, as well as the method of precipitation of the synthesis precursor. The study of various characteristics of the synthesized TiO2 nanoparticles by PXRD, SEM, TEM, and low-temperature nitrogen sorption made it possible to propose mechanisms for the formation of crystalline titanium dioxide from an X-ray amorphous precursor and the growth of titanium dioxide nanocrystals with an anatase structure under hydrothermal conditions. Within the scope of the chosen model of oriented attachment, the dependence of the sizes of TiO2 crystallites on the parameters of hydrothermal synthesis is mathematically described. It was concluded that the direct precipitation of the synthesis precursor from titanium tetrachloride is superior to the reverse. It is shown that the temperature of hydrothermal treatment largely determines the size and morphology of the formed crystallites and TiO2 nanoparticles, the rate of the crystallization process, and the preferred mechanisms of nanocrystal growth, while the duration of synthesis affects the agglomeration processes and the specific surface area of titanium dioxide powders.

Metal–Organic Frameworks with a Bioinspired Porous Polymer Coating for Sieving Separation

Polymer/metal-organic framework (MOF) composites have been widely studied for their favorable combination of polymer flexibility and MOF crystallinity. While traditional polymer-coated MOFs maximize the polymer properties at the surface, the dramatic loss of MOF porosity due to blockage by the nonporous polymeric coating remains a problem. Herein, we introduce intrinsically microporous synthetic allomelanin (AM) as a porous coating on the zirconium-based MOF (Zr-MOF) UiO-66 via an in situ surface-constrained oxidative polymerization of the AM precursor, 1,8-dihydroxynaphthalene (1,8-DHN). Transmission electron microscopy images verify the formation of well-defined nanoparticles with a core-shell morphology (AM@UiO-66), and nitrogen sorption isotherms indicate the porosity of the UiO-66 core remains constant and is not disturbed by the AM coating. Notably, such a strategy could be adapted to MOFs with larger pores, such as MOF-808 by generating porous AM polymer coatings from bulkier DHN oligomers, highlighting the versatility of this method. Finally, we showed that by tuning the AM coating thickness on UiO-66, the hierarchically porous structures of these AM@UiO-66 composites engender excellent hexane isomer separation selectivity and storage capacity.

Construction of 2D/2D Mesoporous WO3/CeO2 Laminated Heterojunctions for Optimized Photocatalytic Performance.

Photocatalytic elimination of antibiotics from the environment and drinking water is of great significance for human health. However, the efficiency of photoremoval of antibiotics such as tetracycline is severely limited by the prompt recombination of electron holes and slow charge migration efficacy. Fabrication of low-dimensional heterojunction composites is an efficient method for shortening charge carrier migration distance and enhancing charge transfer efficiency. Herein, 2D/2D mesoporous WO3/CeO2 laminated Z-scheme heterojunctions were successfully prepared using a two-step hydrothermal process. The mesoporous structure of the composites was proved by nitrogen sorption isotherms, in which sorption-desorption hysteresis was observed. The intimate contact and charge transfer mechanism between WO3 nanoplates and CeO2 nanosheets was investigated using high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy measurements, respectively. Photocatalytic tetracycline degradation efficiency was noticeably promoted by the formation of 2D/2D laminated heterojunctions. The improved photocatalytic activity could be attributed to the formation of Z-scheme laminated heterostructure and 2D morphology favoring spatial charge separation, confirmed by various characterizations. The optimized 5WO3/CeO2 (5 wt.% WO3) composites can degrade more than 99% of tetracycline in 80 min, achieving a peak TC photodegradation efficiency of 0.0482 min-1, which is approximately 3.4 times that of pristine CeO2. A Z-scheme mechanism is proposed for photocatalytic tetracycline by from WO3/CeO2 Z-scheme laminated heterojunctions based on the experimental results.

Solvent-Free Synthesis and Characterization of Bimetallic UiO-66(Zr/Sn) Heterogeneous Catalyst for Biodiesel Production

It has been verified that UiO-66(Zr) is an effective heterogeneous catalyst for the production of biodiesel. The construction of multimetal sites in the structure of UiO-66(Zr) can be a promising way to enhance the catalytic performance of UiO-66(Zr). In this contribution, UiO-66(Zr) with tin sites is simply fabricated under solvent-free conditions. The results from XRD, EDX, and XPS analyses indicate that tin species have been introduced into the structure of UiO-66(Zr). The nitrogen sorption data show that UiO-66(Zr/Sn)-5-130-24 obtained under optimized synthesis conditions maintains a large BET specific surface area (1170 m2/g) and pore volume (0.84 cm3/g). The NH3-TPD results reveal that UiO-66(Zr/Sn)-5-130-24 possesses more acid sites than UiO-66(Zr) probably because the introduction of tin species brought about the missing of linkers in the structure of UiO-66(Zr). As a consequence, UiO-66(Zr/Sn)-5-130-24 exhibits higher catalytic efficiency with an oleic acid conversion of 98.8% than UiO-66(Zr) (oleic acid conversion of 86.2%) at 333 K in the esterification reaction of oleic acid with methanol to obtain biodiesel. Furthermore, the reusability test demonstrates that such a catalyst can be readily recycled and reused.

Removal of Pb<sup>+2</sup> and Cd<sup>+2</sup> from Aqueous Solution by Using Faujasite

The excess amount of lead (Pb⁺²) and cadmium (Cd⁺²) in the drinking water system lead to affect immunity and kidney failure problems. To overcome such troubles by developing well-crystalline faujasite minerals that are synthesized from claystone by the hydrothermal process may be the current trend For the effective adsorption of these cations. The active functional group, thermal nature, crystallinity surface, texture properties, and porous surface nature of faujasite were investigated using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared, and nitrogen sorption 77k studies. The maximum removal of Pb⁺² and Cd⁺² was found to be 98% and 85% respectively using 60 mg and 70 mg from the adsorbent material. Moreover, the measured uptake capacity of Pb⁺² and Cd⁺² was 351.3 mg/g and 97.2 mg/g at equilibrium times of 50 min and 80 min respectively. Therefore, different adsorption isotherm and kinetic models were investigated. Accordingly, adsorption isotherms were the best fit for the Langmuir isotherm model. Moreover, the adsorption process for the two adsorbate cation was followed by the pseudo-second-order kinetics (R² >0.9), Elovich (R² >0.9 for Pb⁺² and 0.86 for Cd⁺²), and Langmuir (R² >0.9 for Pb⁺² and 0.85 for Cd⁺²). This indicates that the adsorption process via monolayer formation with chemical sharing or/and ion exchange process occurs on the energetically heterogeneous surface.

Phenanthrene sorption studies on coffee waste– and diatomaceous earth–based adsorbents, and adsorbent regeneration with cold atmospheric plasma

Phenanthrene (PHE) is a polycyclic aromatic hydrocarbon categorized as a high priority organic pollutant being toxic for the ecosystem and human health, and its sorption on natural organic or inorganic substances seems a well-promising method for its removal from water streams. The goals of the present work are (i) to assess the capacity of low-cost adsorbents fabricated by treating coffee wastes and diatomaceous earth to remove PHE from water; (ii) to elucidate the role of the pore structure on PHE sorption dynamics; and (iii) to assess the potential to regenerate adsorbents loaded with PHE, by using the novel technology of cold atmospheric plasma (CAP). Diatomaceous earth (DE) and DE pre-treated with sodium hydroxide (NaOH) or phosphoric acid (H3PO4) were chosen as inorganic adsorbents. Coffee waste (CW) and activated carbons (AC) produced from its pyrolysis at 800 °C (CWAC), either untreated (CWAC-800) or pre-treated with NaOH (CWAC-NaOH-800) and H3PO4 (CWAC-H3PO4-800), were chosen as organic adsorbents. The adsorbents were characterized with nitrogen adsorption–desorption isotherms, attenuated total reflectance-Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and mercury intrusion porosimetry. Based on the PHE sorption capacity and pore structure/surface characteristics, the CWAC-NaOH-800 was chosen as the most efficient adsorbent for further equilibrium and kinetic sorption studies. The multi-compartment model was used to describe the PHE sorption dynamics in CWAC-NaOH-800 by accounting for the pore/surface diffusion and instantaneous sorption. The CWAC-NaOH-800 exhibited remarkable values for (i) the specific surface area (SBET = 676.5 m2/g) and meso- and micro-pore volume determined by nitrogen sorption (VLN2 = 0.415 cm3/g); (ii) the macro- and meso-pore volume determined by mercury intrusion porosimetry (VMIP = 3.134 cm3/g); and (iii) the maximum PHE sorption capacity (qmax = 142 mg/g). The percentage of adsorbent recovery after its regeneration with CAP was found to be ~ 35%. From the simulation of sorption dynamics, it was found that at early times, the sorption kinetics is governed by the film diffusion towards the external surface of grains, but at late times, most of the adsorbed mass is transferred primarily to meso-/macro-pores via diffusion, and secondarily to micro-porosity via surface diffusion. Based on the adsorbent characteristics, effect of pH on sorption efficiency, and numerical analysis of sorption dynamics, it was concluded that probably the dominant adsorption mechanism is the π-π interactions between hydrophobic PHE aromatic rings and CWAC-NaOH-800 graphene layers. The high PHE removal efficiency of CWAC-NaOH-800, the successful interpretation of sorption dynamics with the multi-compartment model, and the potential to regenerate PHE-loaded adsorbents with the green and economic technology of CAP motivate a strategy for testing CWACs towards the adsorption of other PAHs, application of adsorbents to real wastewaters, and scaling-up to pilot units.Graphical

Large Degree of Variation in Sorption Properties within a System of Isoreticular, Mixed-Ligand Ni- and Co-Based 2-Periodic Metal–Organic Frameworks

Two Ni-based and two Co-based mixed-ligand metal–organic frameworks (MOFs), which are all isoreticular with each other, are shown to have a large variation in nitrogen, carbon dioxide, hydrogen, and water vapor sorption properties, despite their similar structures. The MOFs have 1,2-bis(4-pyridyl)ethane (bpe) as the common ligand with the second ligand being either 2-nitroterephthalate (2-nta) or 2-bromoterephthalate (2-bta) for the Ni-based MOFs or 2-nta or 2-aminoterephthalate (2-ata) for the Co-based MOFs. The four MOFs have the formula [Ni(2-nta)(bpe)(H2O)2]n·2(DMA)n (1), [Ni(2-bta)(bpe)(H2O)2]n·2.8(DMF)n (2), [Co(2-nta)(bpe)(H2O)2]n·2(DMA)n (3), and [Co(2-ata)(bpe)(H2O)2]n·3(DMA)n·(H2O)n (4), respectively, where DMA = N,N′-dimethylacetamide and DMF = N,N′-dimethylformamide. Variable-temperature powder X-ray diffraction (VT-PXRD) studies indicate that the activated MOF structures are different from those of the as-synthesized MOFs, showing that the 2-periodic layers are dynamic upon desolvation. For the same metal ion, the MOF involving the 2-nta ligand has higher sorption, while sorption for the Ni-based MOFs is higher than for the Co-based MOFs. MOF 1 has the highest sorption within the isoreticular series and also has the highest sorption (the highest for water vapor) compared to other MOFs with the same or related ligands.

The Reuse of Basic Oxygen Furnace Slag as Concrete Aggregate to Achieve Sustainable Development: Characteristics and Limitations

Basic oxygen furnace slag is considered a potential material for the replacement of natural aggregate in Portland cement concrete due to its similar physical characteristics. Therefore, in the present work, the slag was analyzed by Nitrogen sorption porosimetry, elemental analysis, mineralogical analysis, and volume stability. On the other hand, concrete mixtures were manufactured with basic oxygen furnace (BOF) slag aggregates and characterized mechanically and morphologically. The results showed superior compressive strength due to interfacial improvements in the slag aggregate. Statistically, there was no differentiation between the reference concrete and the slag concrete mixtures for tensile strength. Additionally, due to the porosity and low stiffness presented by the slag, the concrete elastic modulus showed a slight decrease. The replacement of sand with BOF slag as fine aggregate in Portland cement concrete presents itself as a sustainable alternative for the elimination and valorization of this environmental liability.

Internal microstructure of spray dried particles affects viral vector activity in dry vaccines

To maintain the activity of sensitive biologics during encapsulation by spray drying, a better understanding of deactivation pathways in dried particles is necessary. The effect of solid-air interfaces within dried particles on viral deactivation was examined with three binary excipient blends, mannitol/dextran (MD), xylitol/dextran (XD), and lactose/trehalose (LT). Particles encapsulating human serotype 5 adenovirus viral vector (AdHu5) were produced via both spray drying and acoustic levitation. The particles’ internal microstructure was directly visualized, and the location of a viral vector analogue was spatially mapped within the particles by volume imaging using focused ion beam sectioning and scanning electron microscopy. The majority of the viral vector analogue was found at, or near, the solid-air interfaces. Peclet number and crystallization kinetics governed the internal microstructure of the particles: XD particles with minimal internal voids retained the highest viral activity, followed by MD particles with a few large voids, and finally LT particles with numerous internal voids exhibited the lowest viral activity. Overall, AdHu5 activity decreased as the total solid-air interfacial area increased (as quantified by nitrogen sorption). Along with processing losses, this work highlights the importance of surface area within particles as an indicator of activity losses for dried biologics.

Borosilicate sol–gel bioactive glasses and the effect of borate content on structure-property relationships

AbstractBorate-doped silicate glasses with chemical compositions of (70 − x)SiO2–xB2O3–30CaO (x = 0, 5, 15, and 25, in mol%) were synthesized using the sol–gel method, intended to be used in tissue regeneration. The effects of borate content on the glass surface morphology, chemical structure, ion dissolution behavior, and fibroblast compatibility were investigated. 11B magic angle spinning-solid state nuclear magnetic resonance and Fourier transform infrared spectra demonstrated that borate, in the glasses, possessed both three- and four-coordinated structures. From nitrogen sorption, the specific surface area of the glasses decreased with increased borate content and calcination temperature, from 600 °C to 700 °C. In the case of glasses undergoing calcination at 700 °C, silicate and calcium ion released in a Tris–HCl buffer solution (pH = 7.4) at the early stage of the immersion test decreased as borate content increased. The decrease in surface area caused by stabilizing at 700 °C due to the effect of increasing borate concentration controlled the ion dissolution behavior of the glasses. The proliferation ability of fibroblasts cultured with the dissolution products of the glasses were improved as borate content increased in the glass composition. Graphical Abstract

Abattoir residues as nutrient resources: Nitrogen recycling with bone chars and biogas digestates

Abattoirs produce by-products that may become valuable resources for nutrient recycling and energy generation by including pyrolysis and biogas production in the value creation chain. This study investigated the potential of bone chars as sorbents for ammonium in order to produce a soil amendment useful for fertilizing purposes. Ammonium enriched from the digestate by membrane distillation or from pure ammonium sulphate solutions accommodated the nitrogen sorption to the bone chars. The plant availability of the sorbed nitrogen was studied by a standardized short-term plant test with rye (Secale cereale L.).The results showed that ammonium, both from biogas digestate and from pure salt solutions, could be sorbed successfully to the bone chars post-pyrolysis and increased the nitrogen concentration of the chars (1.6 ± 0.3%) by 0.2–0.4%. This additional nitrogen was desorbed easily and supported plant growth (+17 to +37%) and plant nitrogen uptake (+19–74%). The sorption of ammonium to the bone chars had a positive effect on the reversal of pure bone char phytotoxicity and on nitrogen availability. In summary, this study showed that abattoir wastes are useful pyrolysis input materials to produce bone chars and to provide ammonium source for sorption to the chars. This innovation offers the possibility to produce nitrogen-enriched bone chars as a new type of fertilizer that upgrades the known value of bone char as phosphorus fertilizer by an additional nitrogen fertilizer effect.

Enhanced visible-light photocatalytic oxidative desulfurization of model fuel over Pt-decorated carbon-doped TiO2 nanoparticles.

Modification of photocatalysts to improve their adsorption and photocatalytic activity in the oxidative desulfurization of liquid fuels has been reported by many investigators. In this study, Pt-decorated carbon-doped TiO2 nanoparticles were synthesized by hydrothermal and photo-deposition techniques and were subsequently used in photocatalytic oxidative desulfurization of dibenzothiophene (DBT) in n-heptane as a simulated liquid fuel with methanol as the extracting solvent. Carbon-doped TiO2 was first synthesized by a simple self-doping method. Pt was then loaded by a photo-deposition technique. The synthesized photocatalysts (labeled as YPt-CT where Y is percent Pt loading) were characterized by of X-ray diffraction (XRD), photoluminescence (PL), field emission scanning electron microscopy (FESEM), N2-physisorption, UV-Vis diffusive reflectance spectra (UV-Vis DRS), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), and nitrogen sorption measurements. The removal efficiency of DBT was 98% in the presence of 2 g/l of 0.5Pt-CT catalyst under visible-light irradiation (λ > 400 nm), ambient pressure, and reaction temperature of 40°C.

Mesoporous ZnCr2O4 Nanocatalyst with High Specific Surface Area for Facile Synthesis of Flavonoid Derivatives

ZnCr2O4 nanoparticles with a high specific surface area have been fabricated using a hydrothermal synthetic process and were used as an effective catalyst to synthesize flavonoid derivatives. The textural and structural properties of the spinel were studied by X-ray diffraction (XRD), Field Emission scanning electron microscope (FE-SEM), nitrogen sorption techniques, and Fourier transform infrared spectroscopy (FT-IR). XRD confirmed the formation of cubic Zinc Chromite spinel with a small crystallite size of 5.04 nm. While Transmission Electron Microscopy (TEM) illustrated the particle size of ∼8, 10, and 16 nm. Textural analysis by N2 sorption revealed a mesoporous system with a high specific surface of 215 m2/g for ZnCr2O4. Moreover, all desired flavonoids were obtained in high yields under solvent-free conditions with the aid of the ZnCr2O4 catalyst. Structures of all flavonoid derivatives were confirmed by 1H-NMR, 13C-NMR, FT-IR, and their melting points.

Solvent-dependent strategy to construct mesoporous Zr-based metal-organic frameworks for high-efficient adsorption of tetracycline

The accumulated antibiotics in the aquatic environment pose great threat to human and ecological health, boosting the development of porous materials for antibiotic removal. Mesoporous metal-organic frameworks (MOFs) have shown great promise in adsorption, which, however, usually need supramolecular design or cooperative template strategy for synthesis. Here we report the successful construction of mesoporous zirconium based metal-organic frameworks (Zr-MOFs) via a simple solvent-dependent strategy. Regulation of the ratio of water to N, N-dimethylacetamide during synthesis determined the porous structure of the synthesized MOFs. Systematic characterizations including SEM, FTIR, XRD and nitrogen sorption isotherm were carried out for structure analysis of the MOFs. With water fraction of 20% (v/v), the obtained Zr-MOF exhibited the highest adsorption capacity (Qmax of 337.0 mg⋅g−1) towards tetracycline (TC). The adsorption kinetics fitted the pseudo-second-order kinetics, and the adsorption isotherms fitted the Freundlich model well. Adsorption mechanism investigation revealed that the abundant Zr–OH groups stemming from coordination defects mainly accounted for TC adsorption. The hydrogen bonding interaction between TC and Zr-MOF and the generated mesopores contributed to the satisfactory adsorption capacity. This work is anticipated to provide insights on facile synthesis of mesoporous MOFs and application in environmental remediation.

Optimizing barium promoter for nickel catalyst supported on yttria‐stabilized zirconia in dry reforming of methane

AbstractBarium doping effect on the activity and stability of nickel‐based catalysts, supported on yttria‐stabilized zirconia (Ni‐YZr), was investigated in dry reforming of methane. Catalysts were characterized by several techniques (nitrogen sorption, X‐ray diffraction [XRD], scanning electron microscopy with energy dispersive X‐ray, transmission electron microscopy [TEM], thermogravimetric analysis [TGA], temperature programmed oxidation, CO2‐TPD, H2‐TPR) and were tested in a fixed‐bed reactor at 800°C and 42,000 mL/h gcat. Barium played a crucial role in enhancing catalyst reducibility and CO2 adsorption at high temperatures, as indicated by the activity and stability of the Ni‐YZr catalyst. The addition of 4.0 wt% of barium appeared to be the optimal loading, allowing for CH4 conversion of 82%, which remained constant for 7 h of reaction, compared with 72% of barium‐unpromoted Ni‐YZr at 800°C. TEM images of the spent catalysts revealed the formation of multiwalled carbon nanotubes on all samples. The TGA analysis showed, however, that an increase in baria loading significantly reduced the coke formation amount, indicating the inhibition of coke formation and the enhancement of the catalytic activity. Such improvement in activity and stability was attributed to the incorporation of barium into YZr support, as revealed by XRD analysis, which inhibited the sintering of the catalysts support.

Application of nata de coco as a biodegradable material for the aqueous adsorption of toxic metal cations

The bacterial fermentation of coconut water at ambient conditions produced bacterial cellulose in a jelly-like form which is widely known as nata de coco. X-ray diffraction, scanning electron microscopy and isothermal nitrogen sorption measurements confirmed that bacterial cellulose in nata de coco was arranged in a three-dimensional complex network with a high crystallinity and high porosity, which are highly promising for adsorption applications. In this study, as-synthesized nata de coco was directly applied as a bio-adsorbent for the removal of heavy metal ions from aqueous solutions without any further modification. The presence of numerous hydroxyl groups in cellulose could lead to strong affinities of nata de coco towards positively charged species. Upon a series of experiments screening the adsorption conditions for the single-metal solutions containing Cd(II) and Cr(III), respectively, it was found that the trapping process reached an equilibrium state after 60–120 min. Importantly, reducing the size of nata de coco via grinding for 6 min led to significant enhancements in the adsorption capacity of Cd(II) and Cr(III) to approx. 14 and 17 mg/g, respectively. Furthermore, in the solution containing 8 metal cations including Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II), Fe(III) and Cr(III), nata de coco could adsorb all of these cations with the uptakes in the range of 6.0–10.4 mg/g. The utilization of the biodegradable material facilely prepared from an abundant biomass resource, no chemical modifications required for the material, and trapping performances achieved for many different metal cations are highlights of this contribution.

The Influence of Physical Mixing and Impregnation on the Physicochemical Properties of Pine Wood Activated Carbon Produced by One-Step ZnCl2 Activation.

In this study, two different sample preparation methods to synthesize activated carbon from pine wood were compared. The pine wood activated carbon was prepared by mixing ZnCl2 by physical mixing, i.e., "dry mixing" and impregnation, i.e., "wet mixing" before high temperature carbonization. The influence of these methods on the physicochemical properties of activated carbons was examined. The activated carbon was analyzed using nitrogen sorption (surface area, pore volume and pore size distribution), XPS, density, Raman spectroscopy, and electrochemistry. Physical mixing led to a slightly higher density carbon (1.83 g/cm3) than wet impregnation (1.78 g/cm3). Raman spectroscopy analysis also showed that impregnation led to activated carbon with a much higher degree of defects than physical mixing, i.e., ID/IG = 0.86 and 0.89, respectively. The wet impregnated samples also had better overall textural properties. For example, for samples activated with 1:1 ratio, the total pore volume was 0.664 vs. 0.637 cm3/g and the surface area was 1191 vs. 1263 m2/g for dry and wet mixed samples, respectively. In the electrochemical application, specifically in supercapacitors, impregnated samples showed a much better capacitance at low current densities, i.e., 247 vs. 146 F/g at the current density of 0.1 A/g. However, the physically mixed samples were more stable after 5000 cycles: 97.8% versus 94.4% capacitance retention for the wet impregnated samples.