Sorption of sulphur dioxide by indoor surfaces II. Wood

The sorption of sulphur dioxide by untreated wood samples has been investigated at a concentration of 90 μg/m³ by use of ³⁵SO₂. The softwoods sorbed less sulphur dioxide than the hardwoods and the sites of sorption were different in each class. Most of the sorbed sulphur dioxide was found in the outermost 0.05 mm of each sample and a large portion of it was water-soluble. The possible role of sulphur dioxide in the weathering of woods is discussed.     

The sorption of sulphur dioxide by indoor surfaces. IV. Flooring materials

The sorption of sulphur dioxide by a number of carpet and solid flooring material samples has been investigated at a concentration of 50 to 60 μg/m³ using ³⁵S-labelled sulphur dioxide. The amount of sulphur dioxide sorbed by the samples varied little with their chemical composition and was of such a magnitude as to suggest a low affinity of the surfaces for sulphur dioxide. The sorption of sulphur dioxide by artificial fibre carpet pile was shown to be significantly reduced by the application of dyes.     

Sorption of sulphur dioxide by indoor surfaces I. Wallpapers

The sorption of sulphur dioxide by PVC wallcoverings and conventional wallpaper samples has been measured at a maximum sulphur dioxide concentration of 150 μg/m³ by use of ³⁵SO₂. The sorption was found to be influenced by the surface finish and design pattern of the wallpapers. Sweat deposits on the samples also influenced the pattern of uptake. The conventional wallpapers showed a greater uptake than did PVC wallcoverings in all cases.     

Sorption of sulphur dioxide by paper

Sulphur dioxide is sorbed by paper and slowly converted to sulphuric acid; the presence of this severely reduces the useful life of the material. The sorption (‘pick-up’) of sulphur dioxide has been investigated for a representative range of papers for exposures lasting many months at concentrations approaching those found in polluted urban atmospheres. It was found that the relative humidity does not significantly affect the long-term pick-up rate and that this rate remains constant for prolonged exposures, being proportional to the square root of the gas phase sulphur dioxide concentration. Rosin size increases markedly the long-term rate while certain other paper additives, e.g. Turkey Red Oxide and Anatase, have no such effect.     

Molecular probe chromatography of selected lignites

The properties of selected lignites have been studied by a molecular probe technique using several probes. Following the sorption of air components and carbon dioxide at ambient temperature, interesting flow disturbance peaks were observed due to swelling and shrinkage of the packing mass. Both the retention and peak asymmetry of carbon dioxide increase significantly upon column conditioning. Irrespective of their chemical identity, the probe molecules are sorbed on the surface of lignite by an adsorptive mechanism alone up to 175 °C. The probes are retained in the column both by specific and non-specific interaction forces, the former being very large. Water and methanol sorbed in monolayer or submonolayer coverage can only be eluted easily at a temperature of ≈ 175 °C. As well as hydrogen bonding, dative linkages of polar ligands with transition elements associated with brown coal have also been considered to contribute to the observed retention behaviour. The column permeability may depend on the sulphur content of lignites. The very large stationary phase non-equilibrium coefficient for carbon dioxide mass transfer has been ascribed to the slow interfacial mass transport within the micropores.     

The effect of temperature,light and some transitional metal ions on the sorption of sulphur dioxide by paper

The sorption of sulphur dioxide by a series of laboratory-made paper handsheets of typical furnishes was investigated. The gas phase SO₂ concentrations used approached those found in city atmospheres. It was found that at fixed gas phase SO₂ concentration, increase in temperature decreased the “pick-up” rate. Copper and manganese ions were found to catalyse the fixation of sulphur dioxide but iron ions were found to be much less effective in this respect. Experiments conducted to assess the effect of light indicated that the rate of “pick-up” was increased when the samples were exposed to sunlight; an effect most marked in the samples containing groundwood.     

Transport phenomena in gas permeation through glassy polymer membranes with concentration-dependent sorption and diffusion parameters

The modified dual-mode mobility model for permeation of a gas in glassy polymer membranes was combined with the extended dual-mode sorption model to take account of the plasticization effect of sorbed gas molecules on both sorption and diffusion processes. The combined model was further simplified by the introduction of a concentration of the mobile gas species. However, the observed pressure dependence of mean permeability coefficients of carbon dioxide in methylmethacrylate-n-butyl acrylate copolymer and polymethylmethacrylate films at 30°c and also that of oxygen in a polycarbonate film at 50°C and 60°C showed that a plasticization action of sorbed gas species has an influence on the diffusion process rather than on the sorption process, that is, were simulated by the modified dual-mode mobility model combined with the conventional dual-mode sorption model.     

The sorption of poly(vinyl acetate) on cellulose. I. The nature and extent of the sorbed layer

The sorption of poly(vinyl acetate) from benzene solution onto cellulose fibers has been investigated with particular attention to the nature and extent of the sorbed layer of polymer. The cellulose substrate has been varied by swelling pretreatments with water, ethylenediamine, and 18% sodium hydroxide. The density of the sorbed polymer after drying was found to be similar to that of the bulk polymer (1.19–1.20 g/cm³). Water vapor sorption isotherms were used to evaluate the internal surface of cellulose and the decrease in the surface area accessible to water after sorption of the polymer. This decrease was considered equivalent to the area covered by sorbed polymer. The amount of polymer sorbed per unit area (5.0–5.5 mg PVAc sorbed from benzene per 1 m² of cellulose surface) was found to be substantially independent of the amount of sorbed polymer and of the swelling pretreatment, indicating that the thickness of the sorbed layer was quite uniform (40–50 Å). A comparison of the thickness of the sorbed layer in the dry state with the thickness of a monolayer with polymer molecules lying flat on the solid surface indicated that the fraction of the polymer segments attached directly to the surface was about 0.10. The amount of polymer sorbed per unit area of cellulose and consequently the thickness of the sorbed layer and the fraction of attachment can be affected by the nature of the solvent from which the polymer is sorbed.     

Sorption and migration of organic liquids in poly(ethylene terephthalate)

Sorption kinetics of organic liquids in amorphous poly(ethylene terephthalate) (APET) and biaxially oriented PET (BPET) were determined at 34°C. With heptane and 1,2 propanediol, no sorption or swelling was observed. Estimated diffusion coefficients based on analysis from pseudo-Fickian sorption data are 3.7 ± 1.0 × 10⁻⁹ cm²/sec for toluene sorption in APET, 12.7 ± 4.1 × 10⁻⁹ cm²/sec for benzyl alcohol in APET, 0.44 ± 0.4 × 10⁻⁹ cm²/sec for toluene in BPET, and 0.33 ± 0.4 × 10⁻⁹ cm²/sec for benzyl alcohol in BPET. Weight gain of sorbed APET samples at equilibrium was 11.4 ± 0.1% in toluene and 21.7 ± 0.8% in benzyl alcohol. BPET weight gain at equilibrium was 9.5 ± 0.1% in toluene and 13.5 ± 0.2% in benzyl alcohol. Subsequent migration of sorbed toluene from APET samples into water at 34°C was measured by gas chromatography. Migration from toluene-sorbed APET films sandwiched between virgin APET layers was two orders of magnitude less than from sorbed films placed directly in water.     

Interaction of Copper,Zinc, and Manganese Cations with Lignite and Humic Acids

By IR Fourier spectroscopy, EPR, and ¹³C NMR analysis in solids, the sorption of copper, zinc, and manganese cations by various materials from aqueous solutions is studied. The materials considered are Tyul’gansk lignite, Tisul’sk lignite in unoxidized and oxidized forms, humic acids, and the coal residues remaining after separation of the humic acids. The zinc cations are sorbed by ion exchange; copper and manganese cations are sorbed by a mixed mechanism: ion exchange and complex formation. All the samples are selective in terms of sorption of the cations: Cu²⁺ > Zn²⁺ > Mn²⁺.     

Sorption of water vapour by atactic and isotactic poly (methyl methacrylate)

For the purpose of studying the relation between the stereoregularity and the sorption properties of atactic (a-PMMA) and isotactic (i-PMMA) poly(methyl methacrylate) samples, the isotherms for the sorption of water vapour by these polymers were determined. The glass transition temperatures, T_g and the densities of both PMMA samples were also measured under different conditions of moisture content. The amount of water vapour sorbed by i-PMMA was found, in this study, to be greater than that by a-PMMA. This is rather peculiar when we consider that the former has a high crystallinity (76%) and the latter is non-crystalline in nature. It was concluded that water vapour is sorbed by a-PMMA by a mechanism whereby the water molecules sorbed, fill pre-existing sites (polar groups) and spaces occupied by microvoids or free volumes in the polymer without causing any swelling in the latter; and that the extra sorption of water vapour by i-PMMA was due to a mechanism by which the water molecules sorbed cause the polymer to swell, and thus increase its sorption capacity.     

Exchangeable and non-exchangeable phosphate sorption in Portuguese soils

Total amounts of phosphate (P) sorbed were measured for 6 Portuguese soils of widely varying properties.³²P was used to assess the isotopically exchangeable and non-exchangeable sorbed P. Total sorbed and exchangeable P were described by modified Freundlich equations and non-exchangeable P by a Temkin equation. The Langmuir equation also proved to fit the data for non-exchangeable P well. The amount of total sorbed P required to attain 0.2 mg P 1^–1 in solution ranged from 5.3 to 819 mg P kg^–1. At this concentration exchangeable and non-exchangeable P values varied from 62.4 to 536.6 and from 0.4 to 322.1 mg P kg^–1 respectively.There were highly significant (p < 0.01) correlations between soil organic matter and all forms of sorbed P (total sorbed, exchangeable and non-exchangeable). The P sorption parameters with correlation coefficients greater than 0.967 were parametersa andb of the modified Freundlich equation b_n of Temkin and parametersa of the Langmuir equation. Aluminium extracted by acid oxalate (Al_ox) and dithionite (Al_di) showed highly significant correlation coefficients (r = 0.972) with the same sorption parameters. But P sorption was not closely related to the clay content Fe_ox and Fe_di. It was concluded that extractable aluminium (Al_ox and Al_di) had the most important effects on P sorption in these soils.     

Predicting external sulphur requirement of alfalfa from sulphate sorption isotherm of Tanzanian soils

For Tanzanian soils dominant in hydrous oxides of iron and amorphous ferri-alumino silicate, a 48-hour (hr) mixing period with the sulphate (SO₄) solution was adequate for a near-equilibrium condition. Although differing in their SO₄ sorption capacity, all the soils sorbed SO₄ at or beyond 1µg ml^–1 sulphur (S) concentration in the supernatant. Hydroxyl (OH) ions were displaced during SO₄ sorption as indicated by a significant positive correlation between the amount of sorbed SO₄ and the difference in pH values determined in 0.1N K₂ SO₄ and 0.1N KCl, i.e. the dpH values.In a greenhouse experiment, alfalfa was grown on eight soils at six adjusted S concentrations. Sulphur deficiency symptoms appeared in the control pots of those soils which were low in native sorbed SO₄, SO₄ sorption capacity and initial soil solution S concentration. Sulphur fertilization increased dry matter (DM) yield as well as response to applied S. The external S concentration, i.e. adjusted S concentration required for 95% of the maximum DM yield, ranged from 0.8 to 8.2µg S ml^–1 with values less than 2.0 on most of the soils. The external S concentration decreased hyperbolically as the SO₄ sorption capacity of the soils increased. The total amount of fertilizer S required to obtain the external S concentration in solution, and at the same time satisfy the SO₄ sorption capacity of the soil at the external S concentration (determined from the sorption isotherm) was defined as the external S requirement for the specified yield level of alfalfa. The external S requirement for 95% of the maximum yield of alfalfa varied from soil to soil due to differences in their capacity and intensity for S nutrition.Part of a thesis by the senior author for the MSc (Agric) degree of the University of Dar es Salaam     

Reactive polymers,XXXVIII. Sorption of acid gases on macroporous 2,3-epoxypropyl methacrylate copolymers modified by a reaction with amines

Macroporous copolymers of 2,3-epoxypropyl methacrylate and ethylenedimethacrylate modified by aminolysis yielded sorbents with various contents of amino and hydroxy groups. The dependences of structural characteristics of these sorbents and of the sorption of sulphur dioxide on the content of crosslinking agent and on the cyclohexanol/dodecanol ratio used as the porogenic medium in the preparation of copolymers were investigated. The sorption of sulphur dioxide depends on the geometrical structure of the sorbent, concentration, chemical structure and accessibility of functional groups.     

Sorption and permeation behavior of water vapor and carbon dioxide gas through ethylene ionomer membranes

Sorption and permeation of water vapor and carbon dioxide gas through ethylene ionomer membranes were studied as a function of pressure. Water sorption increased with an increase of the acid content and especially degree of neutralization of ethylene ionomers. The sodium salt ionomer enhanced water sorption compared to the zinc salt ionomer. However, there was no remarkable difference of permeability coefficient of water vapor through the sodium and zinc ionomer membranes. Diffusion coefficient of the sodium salt ionomer is one order smaller than that of zinc salt ionomer, corresponding to an immobilized water structure in the sodium salt ionomer. Differential scanning calorimetry studies on water sorbed to membrane manifested that water sorbed was almost nonfreezable. Sorption of carbon dioxide gas in ethylene ionomers was a dual-mode type. The pressure dependence of permeability coefficient of carbon dioxide gas was interpreted in terms of a partial immobilization model, independent of the kind of the metal salt in ethylene ionomer.     

The sorption of monovalent cations onto norway spruce: Model studies using wood flour and LiCl solution

The transport of chemicals in a porous material such as wood is very complex and involves several processes: the diffusion of chemicals in the cell pores (lumen and pit pores), through the cell walls at certain conditions, and sorption of wood tissue. In the present study, batch sorption experiments were performed to examine the sorption of Li⁺ ions from an aqueous LiCl solution onto Norway spruce wood flour samples. The experimental methodology employed is suitable for differentiating the amount of ions sorbed onto the wood tissue and dissolved in the solution in wood pores. The apparent equilibrium sorption data were analyzed using two widely applied isotherm models: Langmuir and Freundlich. The results suggest that the sorption was spontaneous, and for the experimental conditions studied, probably involved several interaction types between the different functional groups of the wood and the Li⁺/Cl^? ions.     

Evidence of dual mobility in sulfur dioxide-polyarylate system: An integral sorption analysis

Integral sorption/desorption measurements were carried out for the sulfur dioxide-glassy polyarylate polymer system at 25°C, 40°C, 55°C, and 63°C. The transport of sulfur dioxide in the glassy polyarylate polymer was governed by Fickian diffusion. The effective diffusion coefficient of sulfur dioxide increased with increasing penetrant concentration. The concentration dependence of the effective diffusion coefficient is explained on the basis of the partial-immobilization model developed by Paul and Koros. The mobility of the molecules sorbed in the Langmuir mode is shown to be significantly lower than the mobility of the molecules in Henry's law dissolution mode. The predictions of permeability values as a function of upstream gas pressure are presented. The equilibrium sorption isotherms for this system are well represented by the dualmode sorption model. The eltergetics and the temperature dependence of the dual-mode parameters are also discussed.     

Enhanced sorption of phenanthrene on activated carbon in surfactant solution

Distribution of a hazardous hydrophobic organic compound (HOC) and a nonionic surfactant in aqueous/activated carbon systems was investigated. Phenanthrene was selected as a representative HOC and Triton X-100 as a surfactant. Three activated carbons that differed in size (Darco 20-40, 12-20 and 4-12 mesh sizes) were used in the adsorption experiments. The system was analyzed using a mathematical partitioning model and compared with intrinsic sorption of phenanthrene without the effect of sorbed surfactant. Phenanthrene was sorbed onto activated carbon in a greater amount than an estimated value by intrinsic sorption, even though surfactant molecules covered most of surfaces. The sorbed surfactant was much more effective as a sorbent for phenanthrene, in the range of 1.2-98 for effectiveness factor, than was activated carbon, particularly at high surfactant doses. We introduced surface molar solubilization ratio (MSR_s) for sorbed micelles of surfactant and mathematically estimated using effectiveness factor and available carbon fraction of activated carbon after surfactant sorption. The MSR_s for sorbed surfactant was 5-46 times higher than the MSR for micellar surfactant in bulk solution. The sorbed surfactant onto activated carbon can more effectively remove hazardous organic compounds in liquid environmental samples.     

Supercritical carbon dioxide‐assisted loosening preparation of dry leather

The physical modification of the dry leather using supercritical carbon dioxide (SC‐CO₂) was studied in this article. A series of loosening processes of the leather fibers were carried out by changing the experimental conditions such as experimental pressure, experimental temperature, and time. The samples were characterized by scanning electronic microscopy (SEM), Brunauer–Emmett–Teller (BET) and X‐ray diffraction (XRD). SEM images show that samples were loosened by SC‐CO₂ and the leather fibers in micron size arrange more orderly after treatment. The BET surface area of treated samples increase from 1.67 m²/g to 6.33 m²/g with the changing of conditions. The optimal treatment conditions were determined. Moreover, XRD patterns indicate that aggregation structure of collagen fibers in the sample was altered by SC‐CO₂, and it can be found that the loosening of leather mostly happened in amorphous regions of collagen fibers. Besides, the percent breaking elongation of the samples was examined by means of a tensile analyzing test, and it indicates that the elongation at break of all the treated samples in SC‐CO₂ can increase to 128.2% compared with 95.9% of the original ones. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Selective Separation of Uranium using Alizarin Red S (ARS)-Modified Anion-Exchange Resin or by Flotation of U-ARS Chelate

ABSTRACT

An alizarin red S (ARS)-modified anion-exchange resin was prepared by a simple reaction of ARS with the anion exchanger Doulite A101 and used for the efficient sorption of uranium from aqueous media. The effect of various parameters on the sorption of U(VI) (pH effect, sorption kinetics, resin capacity and breakthrough curves) was investigated. The modified resin sorbs U(VI) over a wide range of pH (2·8–5) with a maximum sorption capacity of 0·68 mmol.g^?1 at pH 3·2 to 4·0. Iron (III), Zr(IV), Ti(IV), Cu(II), and Th(IV) ions are also sorbed to different extents, but Be(II), Bi(III), Ca(II), Mg(II), Pb(II), Hg(II), Zn(II), Cd(II), AI(III), Mn(II), Co(II) and Ni(II) are not sorbed; thus, conditions for separating U(VI) from these metal ions have been identified. For eluting U(VI) from the resin, 0·2 mol.L^?1 HCl was used and the recovery recorded was as high as 99.9%. The use of ARS is extended to float uranium quantitatively and selectively from aqueous media at pH = 4 by using oleic acid as a surfactant. The different parameters affecting the flotation process have also been investigated. Uranium(VI) has been effectively separated from natural water samples and certified uranium ores using both procedures.