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University of Texas at Austin. — In: Lake, C.B., R.K. Rowe 2005: A comparative assessment of volatile organic compound (VOC) sorption to various types of potential GCL bentonites. — Geotextiles and Geomembrans, 23, pp. 323 – 347

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The aim of the presented study was to prepare the phosphate sorption isotherms of 20 European volcanic soil profiles and some other Hungarian and German volcanic soils (n = 114) used in the experiment and to establish the soil characteristics determining the phosphate sorption capacity of these soils. The Langmuir isotherm well describes the phosphate sorption of European volcanic soils at bright concentration interval 0–600 mg·dm -3 P. The calculated phosphate adsorption maximum (P max ) is an excellent soil property for characterizing the surface activity of soils developed on volcanic parent material. The calculated phosphate sorption maxima of soils included in the experiment ranged from 0 to 10.000 mg P·kg -1 . Some of the volcanic soils sorbed a high ratio of the added phosphate at low concentrations, while others sorbed somewhat less. The difference in the phosphate binding affinity of soils caused the differences in the shape of the Langmuir adsorption isotherms. P retention % is a WRB diagnostic requirement of andic soil horizon. It was supposed that the phosphate sorption maximum (P max ) gives a better characterization of the surface reactivity of volcanic soils. As it was predicted, oxalate soluble Al is the most important soil property, which dominantly (in 73%) explained the phosphate sorption ability of European volcanic soils.

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Abstract  

Two types of films consisting of sodium salt of carboxymethyl cellulose (NaCMC) and hydroxypropyl cellulose (HPC) as film forming materials and glycerin as plasticizer were prepared, characterized and their water vapour sorption properties were determined. The water sorption isotherms of the films were measured using a magnetic suspension balance. Results show that diffusion of water vapour in NaCMC based film is faster than that in HPC based films, due to the heterogeneous structure and larger pore dimensions of the NaCMC films.

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The origin of kinks (steps) on sorption isotherms was examined for the sorption of benzene and n-hexane on silicalite-1. In both cases sorption revealed the existence of two different binding sites. There was no equilibrium (or a very slow one), between molecules bound at different sites. Sorption energies within particular centres display more or less wide overlapping distributions leading to a single resultant isotherm. Depending on differences in binding energies and degree of overlapping, the resulting isotherms exhibit steps (benzene) or no steps (n-hexane). In fact, the sorption isotherm of benzene being a sum of two elemental isotherms (Ω1 and Ω2) of different shapes is characterized by a ‘kink’, in contrast to n-hexane the elemental isotherms of which are of the same shape.

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Abstract  

Jntti published in 1970 a method to obtain values of the sorption parameters at an early stage of gravimetric sorption measurements. In the present paper we apply that method to volumetric sorption measurements to discuss its applicability. A method is presented to cope with inaccuracies when using Jntti’s method. This will be of special importance for volumetric measurements where accuracy plays a major part. In the paper a second order regression method is used. We use a computer simulation as well as experimental data on desorption of nitrogen from a silica aerogel at 77 K.

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Abstract  

In sorption measurements, volumetric or gravimetric procedures are commonly used to determine the amount adsorbed. At low pressures, thermomolecular flow and pressure differences according to Knudsen's law disturb measurements. In volumetry, calibration of the dead space is required; in gravimetry, the influence of buoyancy has to be taken into account. In both cases, adsorption of the calibrating gas, usually helium, may disturb the measurements [1]. From the calibration measurements, the density of the sample can in principle be calculated. However, it has been observed in many experiments that its value depends on the calibrating gas.

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Summary Anhydrous lactitols (A1, α- and β-lactitol), lactitol monohydrate, lactitol dihydrate and lactitol trihydrate were kept for varying times in atmospheres of different relative humidity at 20°C in equivalent size plastic desiccators. The relative humidities (8-95%) were maintained with saturated salt solutions and drying agents (silica gel and phosphorous pentoxide). The composition of the samples was monitored by thermogravimetry, differential scanning calorimetry and X-ray powder diffraction. According to these measurements both lactitol monohydrate and lactitol dihydrate were substantially stable under the conditions used. Lactitol monohydrate converts to lactitol dihydrate at the highest relative humidity used. All phases of anhydrous lactitol convert into a form of lactitol monohydrate but not to lactitol dihydrate, even at the highest relative humidity used. At a high relative humidity lactitol trihydrate easily loses part of its crystal water and converts partly to lactitol dihydrate. At a lower relative humidity, the phase forming from trihydrate is difficult to identify.

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Journal of Thermal Analysis and Calorimetry
Authors: A. Barros, S. Prasad, V. Leite, A. Souza, G. Marino, Crislene Morais, and Marta Conceição

Abstract  

The present study was carried out for evaluating the retention behavior of sanitary sewage in relation to cadmium and cobalt ions in an ascendant continuous-flow reactor. It was found that the studied sludge presented a high assimilation of the metals, probably due to the presence of anionic groups, which favors adsorption and complexation processes. Thermal analyses of the samples showed a shift in the thermal decomposition of the ‘in natura’ sludge, when compared with those of the samples spiked with the metals, confirming the possibility of interactions between the heavy metals and the anionic groups present in the sludge.

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Abstract  

The time necessary for the measurement of gas adsorption on a solid can be substantially reduced by using Jäntti's directions for data interpretation. This procedure already delivers results after measuring only a few values of the adsorbed mass. In earlier papers we introduced a second order adaptation to Jäntti's method to broaden its applicability. In the present paper we apply this second order treatment to the adsorption of water vapour from moistened air. Specially we pay attention to the diffusion delay caused by the boundary layer around the sample.

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Macalady L. D., Smith S. K., Ranville F. J. Acid mine drainage; streambed sorption of copper, cadmium and zinc, Colorado Water Resources Research Institute, Completion Report , No. 154, 1990. Clement R. E., Eiceman G

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