Sorption Characteristics Research Articles

Moisture Sorption Characteristics of Wheat-Mango Flake

In this study, the moisture sorption characteristics of wheat-mango flakes in relation to their shelf-life in high-density polyethylene material were studied. A preliminary research work was done to ascertain the optimum acceptable levels of Mango pulp addition to wheat flake production using 0 to 80 % (w/v) of wheat and mango pulp. Sensory evaluation was done and the most accepted flake samples were selected, the main research, the level of mango pulp was the varied ratio of 0 to 50 giving rise to a total of 5 samples. Moisture sorption characteristics of the flakes were studied using standard methods. The goodness of fit of the various models was evaluated using the percentage root mean square of the errors (%RMS) for adsorption and desorption. In the adsorption mode, the RMS ranged from 14.36 to 43.62 (GAB), 13.82 to 67.69(BET), 2.69 to 12.97(OSWIN), 4.10 to 16.35 (HENDERSON) in W: M 100:0 sample. For W:M 90:10, the RMS ranged from 38.12 to 43.76 (GAB) 34.04 to 95.33 (BET), 3.24 to 4.48 (OSWIN), 1.89 to 13.85 (HENDERSON). For W: M 80:20, the RMS ranged from 29.48 to 90.85 (GAB), 18.10 to 68.72 (BET), 1.91 to 4.75 (OSWIN), 4.40 to 15.46 (HENDERSON). For W: M 70:30, the RMS ranged from 35.22 to 47.91 (GAB), 14.51 to 40.56 (BET), 2.81 to 4.20 (OSWIN), 2.32 to 13.78 (HENDERSON). For W:M 60:40, the RMS ranged from 23.59 to 55.91 (GAB), 14.41 to 42.96 (BET), 2.96 to 5.97 (OSWIN), 1.95 to 15.28 (HENDERSON). And for W:M 50:50, the values ranged from 41.20 to 55.10 (GAB),13.85 to 60.53 (BET), 1.78 to 5.65 (OSWIN), 1.25 to 14.35 (HENDERSON) respectively. Wheat-mango flakes sorption isotherm obeys type II curve and Oswin and Henderson model fits better and shelf-life for wheat-mango flake is greater than 12 months in high density polyethylene packaging film used as packaging material. Sensory evaluation revealed that acceptable flakes can be produced from wheat supplemented with mango fruit pulp. Blend formulation wheat: mango at 50:50 was mostly acceptable

Selecting Reference States in Thermodynamic Descriptions of Non-Exchangeable Sorption

Selecting standard and reference states for a thermodynamic description of the non-exchange sorption of substances by ion exchangers is considered a stoichiometric process. It is shown that it is best to choose different reference states for free and sorption centers associated with the absorbed substance, since this allows calculations of the thermodynamic constants and energy characteristics of sorption. Results from calculating thermodynamic characteristics of sorption are presented and discussed for systems with the participation of amino acids (glycine and phenylalanine).

Sorption comparative study of nectarine powder and flour mixtures with its participation

The current paper presented the sorption comparative study of nectarine powder and four mixtures with its participation. Four mixtures were made replacing 30% of the basic flour (white wheat, whole wheat, einkorn, and oat) with nectarine fruit powder of Bulgarian origin. Sorption characteristics were done at temperatures 10°C, 25°C, and 40°C, and the water activities (aw) in the interval 0.112 to 0.868 by the gravimetric-static method. For all compared products, augmentation in the temperature leads to a diminution in the sorption capacity. Using the statistical software “Statistica”, it was evaluated four models of Oswin, Chung-Pfost, Henderson, and Halsey. According to the obtained coefficients of each model and the criteria – P and SEM, the most appropriate model is the Halsey (for nectarine powder, white wheat, whole wheat, and einkorn mixtures). The Oswin model was suggested for the satisfactory description of the oat flour mixture with nectarine powder. The results showed that the monolayer moisture content varied in the large limits from 5.78% d.b. to 11.38% d.b. for water activities below 0.5.

Physicochemical and Sorption Characteristics of the Cuticle of the Pupae of the Fly Hermetia illucens

Physicochemical and Sorption Characteristics of the Cuticle of the Pupae of the Fly Hermetia illucens

Extraction and Physicochemical Characterization of <i>Adansonia digitata L.</i> Mucilage

Background: Adansonia digitata leaves are edible and they contain a significant amount of mucilage that has shown potentials for pharmaceutical application. However, there is paucity of information on this mucilage contained in its leaves.
 Objective: This study aimed to determine a suitable method for extraction of Adansonia digitata mucilage (ADM) as well as to characterize its physicochemical properties.
 Materials and Methods: ADM was extracted from the aqueous dispersion of the dried leaves powder of Adansonia digitata L. in water via precipitation with ethanol. Physicochemical characterization of ADM was based on viscosity, chemical composition, particle size characterization via QICPIC, Scanning Electron Microscopy (SEM), Attenuated Total Reflectance Fourier Transforms Infrared (ATR -FTIR) spectroscopy, Nuclear magnetic resonance (NMR), moisture content and Dynamic vapor sorption (DVS) studies as well as pH and aqueous solubility tests. In addition to this, colour of the mucilage and thermal analysis via DSC were used as criteria for selection of the most suitable method for extraction of ADM.
 Results: Colour and thermal analysis revealed a level of purity in the extraction process. The irregular needle like structures of ADM revealed by SEM was found to be mildly acidic with a high viscosity that is concentration dependent in aqueous medium. Thermal characterization revealed a glass transition (Tg) and melting temperatures (Tm) of 55.61 °C and 179.10 °C respectively. Finger prints of functional groups revealed azo aromatic groups and other chemical constituents of sugars including glucose, galactose, arabinose and rhamnose, and sugar acid form of galacturonic acid were identified by NMR. Moisture sorption provided insight into water sorption mechanism, processing, packaging and storage conditions of the mucilage.
 Conclusion: Extraction of ADM via a heat free method improved its colour and purity based on the technique used. The mucilage was found to be a highly viscous and hydrates rapidly with good gelling properties. In addition its moisture sorption characteristics and glass transition temperature gave insight into its stability, storage and packaging conditions. These properties reveal its potential for many pharmaceutical applications including binding, coating, gelling agents as well as matrix forming.

Innovative receiving phase for Chemcatcher® passive sampler for phosphorus in the water environment: Calibration of sampling rate by water temperature and pH

Passive sampling is a technique for monitoring orthophosphate (PO4-P) in the water environment. Compared with traditional grab sampling followed by PO4-P quantification, kinetic-type passive samplers such as Chemcatcher® express representative concentrations of PO4-P as time-weighted average concentrations (CTWA). They can also potentially evaluate much lower PO4-P concentrations, but the available receiving phases of Chemcatcher® used for PO4-P were extremely limited. We developed a new receiving phase, the PSfZS sheet, comprising a zirconium sulfate–surfactant micelle mesostructure and polysulfone matrix. We examined its performance in terms of PO4-P sorption characteristics, PO4-P selectivity, and PO4-P sampling rate (Rs). Its capacity was adequate (12.0 μg-P/cm2) and selectivity for PO4-P uptake was good. The Rs for PO4-P increased with increasing water temperature (8.1–29.1 °C) and decreasing pH (4.1–9.7) in a laboratory calibration, and ranged from 5.27 × 10−2 L/d to 1.66 × 10−1 L/d. We placed the samplers in a municipal wastewater treatment plant, a shallow eutrophic lake, and an oligotrophic caldera lake. The Rs in the deployment sites was calibrated by monitored water temperature and pH. The estimated CTWA of PO4-P in the municipal wastewater treatment plant was similar to the averaged concentration of soluble reactive phosphorus determined by multiple grab samplings. In the lake deployments, we found that the new sampler can quantify CTWA values of PO4-P below 10 μg/L, and thus it provides more technical monitoring options and contributes to the conservation and management of the water environment.

Investigating the influence of bentonite colloids on strontium sorption in granite under various hydrogeochemical conditions

The disposal of high-level radioactive waste in deep geological repositories is a critical environmental issue. The presence of bentonite colloids generated in the engineering barrier can significantly impact the transport of radionuclides, but their effect on radionuclide sorption in granite remains poorly understood. This study aimed to investigate the sorption characteristics of strontium (Sr) on granite as well as on the coexistence system of granite and colloids under various hydrogeochemical conditions, through batch experiments. Fourier transform infrared spectroscopy was employed to analyze the sorption forms of Sr on granite before and after sorption. Several hydrogeochemical factors were examined, including contact time, pH, ionic strength, coexisting ions, and bentonite and humic acid colloid concentration. Among these factors, the concentration of bentonite colloids exhibited a significant effect on Sr sorption. Within a specific range of colloid concentration, the sorption of Sr on the solid system increased linearly with the bentonite colloid concentration. pH and ionic strength were also found to play crucial roles in the sorption process. At low pH, Sr sorption primarily occurred through the outer sphere's surface complexation and Na+/H+ ion exchange. However, at high pH, inner sphere surface complexation dominated the process. As the ionic strength increased, electrostatic repulsion gradually increased, resulting in fewer binding sites for particle aggregation and Sr sorption on bentonite colloids. The results also indicate that with increasing pH, the predominant forms of Sr in the solution transitioned from SrHCO3+ and SrCl+ to SrCO3 and SrCl+. This was mainly due to the ion exchange of Ca2+/Mg2+ in plagioclase and biotite, forming SrCO3 precipitation. These findings provide valuable insights into the transport behavior of radionuclides in the subsurface environment of the repository and highlight the importance of considering bentonite colloids and other hydrogeochemical factors when assessing the environmental impact of high-level radioactive waste disposal.

RATIONAL CONDITIONS OF PRODUCING THE ACTIVATED CARBON WITH WELL-DEVELOPED NANOPOROUS STRUCTURE FOR THE TREATMENT OF NATURAL AND WASTE WATERS

Rational conditions for the activation of coal of a high stage of metamorphism (anthracite) have been determined, which allow the development of a nanoporous structure. Obtained activate carbon with nanoporous structure can be use for the treatment of natural and waste waters have been carried out. The structurally sorptive characteristics and granulometric size composition of obtained samples were determined. It was established that in order to obtain a sorbent with specified properties, it is necessary to introduce oxygen into the reacting mixture at the second stage of anthracite activation and control the activation time. The activation in the first stage was carried out with steam at a temperature of 750–800 °C, and in the second stage – with steam in the presence of air oxygen at 280–300 °C. The rational content of oxygen in the activating mixture is in the range of 2.7–4.4 %, while the specific surface area of activated carbon increases, which corresponds to nano-sized pores and, accordingly, the volume of the adsorption space of coal. The process led to the development of mesoporosity ~ 0.2–0.3 cm3/g, after which the microporous sample of activated carbon was impregnated with a surfactant solution. Thus, the rational conditions of activation are the duration of the process of 1.5 hours in the presence of 4.4 % oxygen in the activating mixture. It is shown that the largest values of the total specific surface area and the specific surface area of mesopores are achieved when using ionic surfactants with alkyl chain length n = 10–16 as modifiers. In particular, the use of sodium dodecyl sulfate СН3(СН2)11SO3Na as a modifier allows to obtain the largest value of the total surface Stot 1030 m2/g and the surface of mesopores Smе 334 m2/g. It was established that the activation of modified samples of activated carbon leads to a decrease in the size of granules.The content of fractions with a size of 1.0–2.0 mm and 0.5–1.0 mm is 80–85 %, which are rational for use for water purification from organic compounds.

Silicas with Polyoxyethylene Branches for Modification of Membranes Based on Microporous Block Copolymers.

We have synthesized cubic and linear polysiloxanes containing polyoxyethylene branches (ASiP-Cu) using tetraethoxysilane, polyoxyethylene glycol, and copper chloride as precursors; the products are stable to self-condensation. The effect of copper chloride content on the chemical structure of ASiP-Cu has been established. A special study was aimed at defining the modifying effect of ASiP-Cu on the sorption characteristics of membranes based on microporous, optically transparent block copolymers (OBCs). These OBCs were produced using 2,4-toluene diisocyanate and block copolymers of ethylene and propylene oxides. The study demonstrated significantly increased sorption capacity of the modified polymers. On the basis of the modified microporous block copolymers and 1-(2-pyridylazo)-2-naphthol (PAN) analytical reagent, an analytical test system has been developed. Additionally, the modified OBCs have the benefit of high diffusion permeability for molecules of organic dyes and metal ions. It has been shown that the volume of voids and structural features of their internal cavities contribute to the complex formation reaction involving PAN and copper chloride.

Physicochemical and Sorption Characteristics of the <i>Hermetia illucens</i> Fly Pupal Cuticle

Physicochemical and sorption characteristics of the Black Soldier fly pupal cuticle have been studied. The qualitative and granulometric compositions of chitin material were determined, and the surface microrelief of chitin particles was studied by scanning microscopy. The sorption properties of the material were studied using the methylene blue dye. It was found that the sorption capacity of the material is 0.118 mmol/g, or about 38 mg/g. Mathematical processing of the sorption isotherm using the Langmuir, Freindlich, Dubinin-Radushkevich models showed that the process is best described by the Dubinin-Radushkevich model (R2 = 0.8031), and the sorption process has a physical nature (E = 5.534 kJ/mol).

Moisture absorption of 3D-printed PETG plastic samples

Introduction. The additive manufacturing method implies the emergence of emergent properties in the final product, not inherent in the original elements of the system individually. Performance properties of products obtained by FDM-printing are defined not only by the material properties, but also by printing parameters — nozzle and table temperature, layer thickness, printing speed, the direction of laying layers, their relative positioning, etc. Thus, when designing 3D-printed polymer products with the required characteristics one should consider the material – printing parameters system together. The results of the study of the effect of sorption characteristics of 3D-printed PETG plastic samples made by FDM-printing on their elastic-strength properties are presented.
 
 Materials and methods. Three groups of FDM-printed PETG 3D specimens were studied. Collection, preprocessing, analysis, statistical processing and visualization of the data were performed using Python programming language in an interactive Jupyter Notebook development environment.
 
 Results. It was found that the moisture content of 3D-printed polymer samples could be conventionally divided into the superstructural and microstructural levels. A comparison of moisture content limits in different moisture saturation conditions shows that the former exceeds the latter by 2 to 6 times depending on the specimen printing parameters. Moisture content of superstructure level has no statistically significant (for α = 0.01) effect on the ultimate tensile strength of the samples, regardless of the printing parameters of the samples. The moisture sorbed by the level of substructure presumably can act as a stress concentrator preventing the free flow of specimens beyond the ultimate tensile strength, which is reflected in the reduction of elongation at rupture.
 
 Conclusions. The obtained results allow taking into account the influence of moisture state on the elastic-strength properties of 3D printed articles and structures on the basis of PETG-plastics. This, in its turn, contributes to more accurate prediction of their behavior under real operating conditions.

Obtaining biochar from rice husk and straw

This paper presents the results of research on obtaining biochar from agricultural plant waste such as rice husk and straw. The selection of the optimal conditions for thermolysis, such as the duration and temperature of the process, has been conducted. The thermolysis products are characterized for iodine adsorption activity, cumulative water pore volume, and for bulk density. The porous structure of the obtained products has been studied by scanning electron microscopy. Based on the results of the research conducted, it has been found that biochars obtained from husk and straw with a thermolysis duration of 30 minutes have low iodine sorption characteristics and water pore volumes. With an increase in the duration of thermolysis, the sorption characteristics improve, the optimal for the husk is the thermolysis duration of 60 minutes at a temperature of 500°C, and for straw, the optimal thermolysis duration is 60 minutes at a temperature of 300°C. The best option is biochar obtained from rice straw at a duration of 60 minutes and a thermolysis temperature of 300°C, having an iodine adsorption activity of 54.61%, a cumulative water pore volume of 0.941 cm3 /g and a bulk density of 169.29 g/dm3. The obtained biochars from rice husk and straw have been studied by scanning electron microscopy at 4300 and 5000 times magnification, and they have a developed porous structure.

Bituminous Coal Sorption Characteristics and Its Modeling of the Main Coal Seam Gas Component in the Huaibei Coalfield, China

Knowledge of the gas sorption and permeability characteristics of a coal provides an essential basis for the evaluation of coalbed methane reserves and their recoverability. Thus, the gas excess sorption capacities of the main gas component of coal seam gas (CSG) in bituminous coal samples derived from the Xutuan Coal Mine in the Huaibei Coalfield, in the Anhui Province of China, were measured using a volumetric method. The results showed that under the same equilibrium pressure, the order of excess sorption capacity was CO2 > CH4 > N2. Furthermore, the sorption capacity ratios of coal from the Xutuan Mine for CO2, CH4, and N2 were approximately 6.0:2.3:1. It was also demonstrated that the sorption capacity during depressurization was always larger than that of the adsorption process, which is indicative of desorption hysteresis. The behaviors of three adsorption models, Langmuir, BET, and D-R, all of which include two parameters, are considered in this paper. The different gas sorption measurement data were fitted by the three models. For the bituminous coal samples, the fits of the D-R equation of all three different gases are higher than 0.99, the fits of the Langmuir equation are higher than 0.985, while the fits of the BET equation for CH4 and N2 absorption are higher than 0.95. However, the fits of the BET equation for CO2 absorption are only about 0.5. Coal sorption has an apparent influence on coal permeability; the permeability of the same coal sample to N2, CH4, and CO2 gases was tested and analyzed. The result shows that the permeability of CO2 was found to be lower than that of other coal seam gas constituents, CH4 and N2, due to their different adsorption abilities.

Higher allochthonous organic carbon increases polycyclic aromatic hydrocarbon concentration whereas fossil fuel combustion alters the composition: Evidence from a eutrophic plateau lake in southwest China

Understanding the source of polycyclic aromatic hydrocarbons (PAHs) is crucial for determining their structural, degradational, and burial characteristics in lake sediments. Here, we used a sediment core to determine the changing sources and burial characteristics of 16 PAHs from Dianchi Lake, southwest China. The ∑16PAH concentrations ranged from 105.10 to 1248.05 ng g−1 (448.97 ± 351.25 ng g−1), exhibiting a sharp increase since 1976. Our results showed that the depositional flux of PAHs has increased by approximately 3.72 times over the past 114 years (1895–2009). The C/N ratio, stable isotopes (δ13Corg and δ15N), and n-alkanes data all indicated that allochthonous contributors of organic carbon have substantially increased since the 1970s, playing an important role in the increase in sedimentary PAHs. Positive matrix factorization indicated that petrogenic sources, coal and biomass combustion, and traffic emissions were the main sources of PAHs. The relationships between PAHs from different sources and total organic carbon (TOC) varied with the sorption characteristics. The effect of TOC on the absorption of high-molecular-weight aromatic PAHs from fossil fuels was significant. A higher risk of lake eutrophication is accompanied by higher allochthonous organic matter imports, which might stimulate an increase in sedimentary PAHs through algal biomass blooms.

Moisture sorption, thermal, and caking characteristics of l-lysine-carbonate granules

l-Lysine, an essential amino acid, is often produced in the granular form of l-lysine-monohydrochloride (l-lysine-HCl). To address chemical waste and processing cost concerns associated with the production of l-lysine-HCl granules, an alternative process has been recently developed for the production of l-lysine as granules of l-lysine-carbonate (l-lysine-CO3). In the present study, the moisture sorption, thermal, and caking properties of l-lysine-CO3 granules were investigated in comparison with commercial l-lysine-HCl granules. l-Lysine-CO3 granules showed a popcorn-like surface structure (59.0% crystallinity), while l-lysine-HCl granules exhibited an angular crystalline structure (72.9% crystallinity). l-Lysine-CO3 granules had a less compact structure than l-lysine-HCl granules and showed excellent initial flowability comparable to l-lysine-HCl granules. l-Lysine-CO3 granules were more hygroscopic than l-lysine-HCl granules, probably due to their lower crystallinity and less compact structure. l-Lysine-CO3 granules began to undergo thermal decomposition at 192 °C, probably due to CO2 release, followed by melting at 234 °C and further decomposition, while l-lysine-HCl granules underwent melting at 251 °C, and then began to undergo thermal decomposition at 260 °C. No glass transition was observed for either lysine-CO3 or l-lysine-HCl granules. Storage test under pressurized and accelerated conditions showed that l-lysine-CO3 granules were more prone to caking and formed harder agglomerates than l-lysine-HCl granules. The results showed that l-lysine-CO3 granules were more hygroscopic, less thermally stable, and more prone to caking, compared to commercial l-lysine-HCl granules. However, these properties of l-lysine-CO3 granules were at acceptable levels for commercial use, thus l-lysine-CO3 granules have high potential for commercial development.

Physicochemical, Sorption, and Morphological Characteristics of Bombyx Mori Silkworm Cocoon Fibroin and a Multifunctional Hemosorbent Obtained on Its Basis

Physicochemical, Sorption, and Morphological Characteristics of Bombyx Mori Silkworm Cocoon Fibroin and a Multifunctional Hemosorbent Obtained on Its Basis

Assessment of Dispersed Oil Sorption in Oily Wastewater onto Hydrophobized/Oleophilized Autoclaved Aerated Concrete (AAC) Grains

The discharge of untreated oily wastewater into the environment has serious impacts on human health, living nature, and ecosystems and leads to significant economic losses. Many engineering techniques have been proposed and applied to treat oily wastewater, but limited studies have investigated low-cost and effective techniques using by-products and waste/scrap materials from the construction industry. Materials to treat oily wastewater are needed not only to mitigate environmental pollution but also to promote the reuse and recycling of industrial by-products, especially in developing countries. This study, therefore, examined the sorption capacity of dispersed oil in wastewater (dispersed soybean oil in water; initial oil concentrations, Ci = 10–1000 mg/L; oil droplet size in water <2 μm) onto the hydrophobized/oleophilized autoclaved porous aerated concrete (AAC) grains made from waste scrap in Vietnam by using batch sorption tests in the laboratory. The AAC grains (sizes 0.106–0.25, 0.25–0.85, and 0.85–2.00 mm) were hydrophobized/oleophilized using oleic and stearic acids (coating concentrations of 1.0, 5.0, and 10 g/kg), and two sands (0.18–2.00 and 0.30–2.00 mm) were used as control samples. The results showed that the hydrophobized/oleophilized AAC grains had high sorption capacity for dispersed oil (i.e., high oil removal efficiency) compared to the control sands. Especially, the removal of AAC grains coated with stearic acid was >80% in high oil concentration solutions (Ci = 100 and 1000 mg/L), indicating that the hydrophobized/oleophilized AAC grains have high potential as useful adsorbents to trap dispersed oil in oily wastewater. Moreover, adsorption isotherms were drawn to examine the sorption characteristics of dispersed oil onto AAC grains. For all tested samples, the sorption of dispersed oil increased linearly with increasing equilibrium concentration. The commonly used Langmuir model, on the other hand, did not capture the measured isotherms.

Long-term manure and cropping systems effect on soil water vapour sorption characteristics is controlled by soil texture

Increasing studies indicate that long-term experiments (LTEs) involving manure application and optimal cropping systems can significantly improve soil physicochemical properties, which may also affect the soil water retention curve (WRC) in the wet region (pF < 4.2). However, few studies have explored the effect of long-term manure application and cropping systems on soil WRC in the dry region (water vapour sorption isotherms, WSIs) (pF > 4.2) as well as the associated soil physicochemical properties. To overcome this knowledge gap, we investigated the effect of long-term manure application (24 to 177 years) and different cropping systems (71 to 82 years) on soil organic carbon (SOC) content, WSIs, hysteresis, and specific surface area (SSA). Soil samples were collected from five long-term manure experiments in Sweden, the United Kingdom, Spain, Germany, and Denmark, and two long-term cropping systems experiments in the United Kingdom. The five manure LTEs comprised three soil textures (silty clay, silt loam, and sandy loam) with one to four crops grown in the fields, including wheat, barley, maize, and grass/clover. The cropping system LTEs comprised silt loam and sandy loam including bare fallow (BF), arable rotation, ley–arable rotation, and permanent grass. Results showed that long-term manure application increased SOC content in each site, but it had little effect on the soil WSIs, hysteresis, and SSA in silty clay soils. The changes of soil WSIs, hysteresis, and SSA in silt loam and sandy loam arising from manure application largely depend on the crops grown in the field. For the long-term cropping systems experiments, permanent grass had the most significant effect in increasing SOC content, soil WSIs in silt loam and sandy loam, and hysteresis and SSA in silt loam compared to other treatments. Compared to BF, arable rotation and ley-arable rotation had no effect on SOC and soil WSIs in silt loam, and on hysteresis and SSA in silt loam and sandy loam. Multiple linear regression models including SOC, clay, and silt contents sufficiently explained the variabilities observed in the soil WSIs, hysteresis, and SSA for both manure and cropping systems LTEs.

Active carbon-based waste packaging materials for uranium sorption from aqueous solution

Waste (packaging plastic and industrial water) accumulation is one of the great global challenges over the world. Combining waste recycling science and water treatment knowledge are fascinating as applied sciences add value to the safe disposal of waste plastic packaging materials and wastewater. Active carbons (ACs) are prepared from polyethylene terephthalate (PET) at two pyrolysis temperatures (i.e. 450 and 500 °C) and compressed in well-defined designed molds to form cylinder shapes as applied in industry. Particle size (817 and 1074 nm), zeta potential (− 7.17 and − 25.6 mV), surface area (544 and 632 m2/g), and topography of prepared ACs were investigated and discussed. Zeta potential exhibited nice dispersion in accordance to charge value and surficial SEM images prove space hole filling with adsorbed materials after treatment. The prepared activated carbon sorbents have been applied for the removal of radioactive elements from wastewater. The displayed data declare that both sorbents have the same sorption performance, whereas the uranium sorption process using both sorbents is obeyed to pseudo-second-order kinetic model and Langmuir isotherm model. Nevertheless, it is worth noting that the prepared AC at a pyrolysis temperature of 500 °C exhibits higher sorption capacity (38.9 mg g−1) than that prepared at lower temperature, i.e., 450 °C (36.2 mg g−1) which indicates that the increase in pyrolysis temperature improves the sorption characteristics of the yield-activated carbon.

Hydrogen sorption by nanostructures at low temperatures (Review article)

The features of hydrogen sorption by a wide range of nanostructures — fullerite C60, carbon nanotubes, graphene structures, nanodispersed carbon, including Pd-containing nanoclusters, ordered silicon-oxide-based nanostructures (the MCM-41 family) and silicon-oxide aerogel — have been reviewed. Special attention is given to the sorption characteristics of carbon nanostructures that have been exposed to various modifying treatments (oxidation, gamma-ray irradiation in gas atmosphere, action of pulsed high frequency gas discharge). Two mechanisms of physical low-temperature sorption of hydrogen have been revealed to predominate in such nanostructures in different temperature intervals. At the lowest temperatures (8–12 K), the sorption can actually proceed without thermal activation: it is realized through the tunnel motion of hydrogen molecules along the nanostructure surfaces. The periodic structure of the potential relief, allowed by the surface frame of carbon and silicon-oxide nanostructures, along the rather low interpit barriers are beneficial for the formation of low-dimensional (including quantum) hydrogen-molecule systems practically without thermally activated diffusion. In such nanostructures, the hydrogen diffusion coefficients are actually independent of temperature at 8–12 K. At higher temperatures (12–295 K), a thermally activated mechanism of hydrogen diffusion prevails. The periodic structure of fullerite C60 contains periodic interstitial cavities, separated by rather low potential barriers. Their sizes are sufficient to accommodate impurity hydrogen molecules and, thus, allow diffusion processes, which can also have a tunnel nature. It is shown that gamma-irradiation and high-frequency gas discharge processing increase markedly the quantity of hydrogen strongly bonded to carbon nanostructures.