Sorption Capacity Of Material Research Articles

Magnetic Materials Based on Layered Double Hydroxides

Composite materials that contain tetracationic hydrotalcite-like layered double hydroxide and a cobalt-iron spinel phase were prepared by coprecipitation from a solution of a mixture of magnesium, aluminum, cobalt(II), and iron(III) salts followed by hydrothermal treatment. The iron and cobalt contents in the samples were varied within a broad range. The thermal transformations of the prepared composites were examined by high-temperature X-ray diffraction, and the layered hydroxide phase was found to remain when heated up to 300°C. The specific magnetization and magnetic susceptibility of the materials were determined using a vibrating sample magnetometer; a rise in the iron and cobalt contents was found to increase the magnetization up to a certain limit. The obtained samples can be used as magnetic sorbents. The sorption capacity of materials was estimated using Congo red anionic dye as an example.

Получение низкогорючего сорбента на основе пенополиуретана для улавливания радиоактивных форм иода

The composite sorption material based on a highly porous polyurethane foam matrix with a layer of impregnated activated carbon powder applied to its surface has been developed. The reticulated polyurethane foam Regicell was used as a base for the sorbent samples. The compounds that most effectively inhibit the combustion process were: phosphates, sulfates, borates and pyrosulfates. The selection of the optimal amount of the fire retardant was carried out, and the sorption capacity of the material samples in relation to radioactive methyl iodide was studied. It became clear that the sorbent treated with a 20 % solution of ammonium sulfate can be classified as a material with low combustibility. The study of the sorption capacity was carried out on a certified stand under conditions corresponding to the standard test method for nuclear power plants iodine sorbents. During the tests, more than 99.9 % radioactive methyl iodide trapping efficiency was achieved, which exceeds that for the industrial granular sorbent selected as a comparison. It was found that the gas flow hydraulic resistance corresponding to the manufactured samples is lower than that of the industrial one. The relative sorption capacity index was used as a criterion for comparing the sorption capacity of materials characterized by different free volume fractions.

Study of the Pt(IV) sorption on the Aspergillus niger O-5 biomass for remediation and/or analytical purposes

The use of Pt (IV) salts in different processes generates, even at low concentrations, toxic residuals that contaminate natural waters. For this reason, the improvement of limit of detection in Pt(IV) quantification for control and monitoring purposes, as well as, the development of methodologies for remediation is convenient. This study was aimed at the assessment of the dead Aspergillus niger O-5 biomass without treatment and chemically treated as sorbents for Pt(IV) concentration. The influence of pH and volume of dissolution, sorbent mass and contact time on the Pt(IV) sorption capacity of materials was studied. At optimized experimental conditions, a maximum sorption capacity of 79.63 ± 0.03 mg·g−1 was achieved using cetyltrimethylammonium bromide (CTAB)- treated biomass. A good fitting of the pseudo-second-order model of Ho to the experimental kinetic data suggested that chemisorption or chemical reactivity processes are involved in the biosorption. Those processes could be explained via the substitution of the hydrogen present in N-H bonds of amide groups on the biomass surface for Pt(IV) species in dissolution. This hypothesis was supported by the XPS analysis results. The best Pt(IV) desorption equal to 99% was achieved, when 15% (m/v) thiourea dissolution was used as eluent.

Removal of 2,4-D herbicide from aqueous solution by aminosilane-grafted mesoporous carbons

2,4-Dichlorophenoxyacetic acid (2,4-D) is the most commonly used herbicide in plant protection products. 2,4-D is poorly biodegradable and it is often found in aquatic environment. The development of an effective way to reduce the amount of this toxic contaminant from aqueous solution became an urgent issue. Therefore, in this study series of aminosilane-grafted mesoporous carbons were synthesized, characterized and then applied as adsorbents for 2,4-D. The impact of various factors such as the contact time (0–360 min) of herbicide with adsorbents, pH (2–11), temperature (25, 45, 60 °C) and initial concentration (6.25–150 mg/l) of the 2,4-D on the sorption capacity of materials was analyzed. The results proved that functionalization of mesoporous carbons with aminosilane increased the sorption capacity (qe = 142–191 mg/g) towards herbicide compared to pristine material (qe = 109 mg/g). The functional groups presented on the surface of materials enhanced the interaction between mesoporous carbons and herbicide. The most effective adsorbent for 2,4-D was the material that had the highest amount of basic groups on the surface (2.79 mmol/g) of all samples tested (0.06–0.52 mmol/g). For all studied materials the Langmuir model was the most suitable to describe the isotherms of 2,4-D adsorption (R2 = 0.999). While the kinetics of herbicide adsorption on the functionalized mesoporous carbons were best fitted to the pseudo-second-order model. The presented study proved that the aminosilane-grafted mesoporous carbons could be promising adsorbents for effective removal of 2,4-D from aqueous environment.

Determination of the size of particles of highly dispersed materials by low temperature nitrogen adsorption

The average size of particles of highly dispersed materials (Al2O3, TiO2, Y2O3) is calculated from their specific surface areas. The latter is determined with the analysis of sorption capacity of materials with nitrogen at −196°C in the ranges of relative equilibrium pressures of 0.05–0.35 (the Brunauer-Emmett-Teller method, BET) and 0.4–0.7 (the comparative method). Good agreement is obtained between results produced with the comparative method and familiar methods of analysis such as scanning and transmission electron microscopy and small-angle X-ray scattering.

Determination of the sorption capacity of needle-punch material

The method of determining the sorption capacity of a material is selected as a function of the shape of the samples and conditions of runoff of excess liquid. The maximum height of runoff of liquid from the sample must not exceed 5 cm. The sorption capacity is a function of the size of the cross section of the capillaries in the space between the fibre tufts and in the bulk of the tufts.

Deuterium trapping by carbon materials for tokamak plasma-facing components

The experiments on large tokamaks on measuring the hydrogen isotope pressure in the near-wall or divertor plasma are briefly described. Based on the analysis of exchange fluxes between the plasma and the wall it is stated that the plasma action, with respect to hydrogen sorption by graphite components of the tokamak first wall, is identical to materials exposure in the atmosphere of molecular hydrogen at pressures of 1–10 3 Pa and temperatures of 1200–1700 K. Within these ranges of pressures and temperatures RG-Ti-91 and USB-15 graphites are shown to be impermeable to molecular hydrogen in contrast to easily permeable POCO-AXF-5Q. Sorption capacity of well-treated dense graphites is about 10 2 appm. Sorption capacity of materials is increased to (1–3)×10 4 appm with defects like unsaturated carbon bonds, introduced into the above materials by mechanical treatment, ion irradiation, graphite gasification (exposure at 1200 K, 133 Pa during 1 h). At the same time permeability of graphites is increased to molecular hydrogen. Graphite modification by boron retards the rise of sorption capacity. The hydrogen sorption process is described as the filling of two sets of traps, i.e. weak traps arranged over the boundaries of carbon materials and deep traps arranged in the volume of separate crystallises. Russian-made graphites RG-Ti-91 and USB-15 can be used in large tokamaks as divertor and first wall tiles, respectively.

The absorption of deuterium by carbon-based facing materials on components in contact with the plasma in a thermonuclear reactor

The conditions have been proposed for performing modeling experiments making it possible to predict the accumulation of hydrogen isotopes in carbon materials which are in contact with a tokamak plasma acting as a source of particles having a flux density of between 3×1016 and 3×1019 cm−2·sec−1. By analyzing the reemission fluxes formed in the stopping zone of the particles implanted from the plasma it is suggested that the action of the plasma as regards the sorption of hydrogen is identical to that of annealing the material in an atmosphere of hydrogen isotopes at a pressure of 1–103 Pa and a temperature of 1200–1700 K. The quantity of absorbed deuterium in POCO, UAM, RGT-B, and USB increases as the temperature is lowered and the pressure is raised (1500 K, 0.66 Pa→1200 K, 133 Pa). As regards their sorption of deuterium, POCO, UAM, and RGT behave similarly. There is a tendency for the sorption capacity of materials doped with boron to be reduced. In a class of itself is the isotropic material USB, whose sorption capacity is a factor of 10–100 lower than that of undoped graphite. The introduction into these materials of radiation-induced defects (T=300 K) by means of ion irradiation in the range 0.1–1 dpa results in a continuous rise in the deuterium sorption capacity by a factor of 10–100 (up to 10−2 atomic fraction). The USB graphite demonstrates record low increments in the sorption capacity. In the fluence range identical to 1–10 dpa the sorption capacity of carbon materials for hydrogen is almost constant. The process of the sorption of hydrogen isotopes can be described as the filling of two ensembles of traps, deep traps which are difficult to access and readily accessible Langmuir traps. In the RGT-B materials containing 0.1% of boron, the traps introduced by irradiation with 300-keV neon ions vanish on annealing in a vacuum (T=1800 K, t=1 min).