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.     

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 indoor surfaces III.—Leather

The sorption of sulphur dioxide by a wide range of leather samples has been investigated at a concentration of ～ 100 μg/m³ using sulphur-35 dioxide. In general, the sulphur dioxide was sorbed evenly over the leather surfaces, the sorbed sulphur being water-soluble. The position on the hide from which the leather was taken had no significant effect on the amount of sulphur dioxide sorbed. The total uptake of the gas was reduced by the application of a finish and by dyeing. The penetration of sulphur dioxides into the samples was influenced by the nature of the organic retanning process used, condensed tannins leading primarily to surface sorption. Leather greases were also shown to reduce penetration of sulphur dioxide. Some implications of these results in the degradation of leathers by atmospheric sulphur dioxide are discussed.     

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.     

Copolymerization of acrylamide with sulphur dioxide. Determination of the effect of copolymerization temperature on the monomer sequence distribution by 13C n.m.r.

Acrylamide was copolymèrized with sulphur dioxide at temperatures from ?78° to 60°C. The bulk monomer composition was fixed at 60 mol % sulphur dioxide, and both azobisisobutyronitrile and ⁶⁰Co gamma radiation were used as initiators. The ratio R of acrylamide to sulphur dioxide in the copolymers increased as the copolymerization temperature was raised; for example R was 1.97 at ?78°C and 29.3 4at 60°C. The microstructure of the copolymers was determined by ¹³C-{¹H} n.m.r. The carbonyl resonances were the most sensitive to structure, and they were assigned to monomer sequence pentads and configurational sequence dyads and triads. Only the backbone carbon resonance areas were quantitatively reliable under the observing conditions. The methine and methylene carbons revealed monomer sequence triad structure, and their relative areas allowed the monomer sequence distribution to be obtained as a function of temperature. A propagation-step mechanism was proposed to account for the effect of temperature on the monomer sequence distribution. No 1:1 alternating sequences were formed above 0°C, and this result suggested that depropagation of the sulphonyl radical was particularly facile when there was a pen-penultimate sulphone unit in the terminal chain sequence. The results were compared with those from other systems which form variable-composition polysulphones.     

Interaction of gases with ablative composites. I. Ar,CO2, and N2

The sorption of argon, carbon dioxide, and nitrogen on two heat shield composites SLA-561 and SLA-561V and the SLA components was measured over the pressure range of 10^?3 to 760 torr and in the temperature range of 30° to 50°C. The sorption of the gases by both the composites and the components varied directly with pressure. The sorption of CO₂ by the phenolic spheres and the silicone elastomer and of Ar by the silicone elastomer varied inversely with temperature. The mechanism involved in the gas sorption was primarily absorption.     

Spectroscopic and Thermodynamic Analysis of Cd2+ Ion Sorption Kinetics by Manganese Dioxide in the Presence of Oxyanions

The present study reports the effect of contact time, nature of electrolyte, and temperature on the sorption kinetics of Cd²⁺ by manganese dioxide, which is the most active oxide in soils and sediments. The sorption kinetics of Cd²⁺ by manganese dioxide is evaluated at pH 6 in different electrolytes in the temperatures range 293-323 K. The solid samples are equilibrated in 0.45 mmol.L^?1 Cd²⁺ and different electrolytes at pH 6. The results indicate that sorption of Cd²⁺ increases with time and temperature and the system attains equilibrium within 60 min in KNO₃ as the electrolyte. However, in the presence of 0.001 M KH2PO₄ sorption of Cd²⁺ increases and the time for equilibrium shifts to 90 min. The data second-order kinetics model and the calculated rate constant k and initial sorption rate h increases with increasing temperature phosphate treatment. Among the calculated thermodynamic activation parameters the positive values of ΔH^? and ΔG^? show the sorption process to be endothermic and nonspontaneous, while the ΔS^? being negative indicates a decrease in randomness of the system during sorption process at the solid-liquid interface. The free energy of activation decreases from 15.95 kJ.mol^?1 in nitrate to 8.76 kJ.mol^?1 in phosphate. These observations suggest that the rate controlling step in Cd²⁺ sorption is diffusionally controlled, a fact that has been proved by application of Fick’s law.     

Composition and volume of gas released by ‘melting’ coal from West Virginia and Alabama

Analyses of the composition and volume of gases released by ‘melting’ samples of coal from West Virginia and Alabama under vacuum have been made by mass spectrometric techniques. This was done by melting the coal in a quartz tube attached to the highvacuum inlet system of a research mass spectrometer. The gases observed were composed of C, S, H, O, N, He and Ar atoms. Hydrogen was the most abundant gas; others were helium, methane, ethylene, ethane, carbon monoxide, nitrogen, hydrogen sulphide, propane, argon, carbon dioxide and sulphur dioxide. Gas compositions were found to be a function of the source of the coal. For example, over 65% of the gas from Alabama coal was hydrogen, but West Virginia coal yielded only about 30% of hydrogen. All coals released about 100 cm³ g^?1 (STP) (about 2300 ft³ (short ton)^?1) of combustible gas. An additional observation was the fact that about 90% of the sulphur was physically separated from the coal in the vacuum melting process.     

High-rate discharge of poly 3-methylthiophene cathodes in inorganic electrolytes

Lithium cells with thin film electrodes of poly 3-methylthiophene were discharged at high current densities in electrolytes containing either sulphur dioxide, thionyl chloride, or sulphuryl chloride. Highest capactiy was obtained with thionyl chloride electrolyte for current densities as high as 30 mA cm^–2 (up to 600 W cm^–3). Cells containing sulphur dioxide electrolyte were rechargeable, but constant current discharge performance was less than in either thionyl chloride or sulphuryl chloride. However, pulse discharge in sulphur dioxide permitted comparable power densities to be achieved, and reproducible results were obtained over many cycles.     

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.     

Dependence of carbon dioxide sorption on the petrographic composition of bituminous coals from the Czech part of the Upper Silesian Basin, Czech Republic

The effect of the rank and of the maceral composition of bituminous coal on carbon dioxide sorption capacity was studied on the basis of samples from two coal mines (Darkov, ?SM) from the Czech part of the Upper Silesian Basin. The samples from the two mines cover a small but very significant section of coalification within the transition zone between high-volatile bituminous A coal and medium-volatile bituminous coal, where porosity and sorption properties pass through their minima. The coal porous system was characterized by the micropore volume evaluated using the sorption isotherm of carbon dioxide and the volumes of meso-, macro- and coarse pores were determined by high-pressure mercury porosimetry. The micropore fraction in the coal porous system ranged between 53% and 75%. It was particularly high in coals with high vitrinite content, namely collotelinite, and also in coals with high inertinite content. The carbon dioxide sorption capacity was determined from the carbon dioxide sorption isotherms measured using a gravimetric sorption analyzer at 298 K until a relative pressure of 0.015 p/p_s, and was interpreted by characteristic parameters of the Dubinin and Langmuir equations. It was found that the adsorbed amount of CO₂ in the ?SM coal increases with the content of vitrinite and collotelinite, whereas no increase or only a slight increase was observed for the Darkov coal. The tendency of adsorption capacity to depend on maceral composition, and also to some extent on coalification, observed for the ?SM coal, may be related to higher microporosity due to the coalification process or oxidative processes leading to the formation of pseudovitrinite.     

Uptake of Traces of Selenite by Manganese Dioxide from Aqueous Solutions

Abstract

Sorption of selenite onto manganese dioxide has been investigated with respect to shaking time, concentration of sorbent and sorbate, nature of electrolyte, and influence of cations and anions. The sorption of other metal ions has been studied using optimal conditions selected for maximum sorption of selenite. The surface area, average pore diameter, porosity, and solid phase density of the sorbent have been measured. The sorption data followed only the Dubinin–Radushkevich (D–R) sorption isotherm among all the isotherms tested. The sorption capacity of 51.2 nmol·g^?1 and a constant β related to sorption energy have been estimated to be ?0.007521 mol²·kJ^?2. The sorption energy is found to be 8.15 kJ·mol^?1. The kinetics of the sorption follows the Lagergren equation in the initial stages. The first-order rate constant, k′, was evaluated to be 0.498 min^?1 and of intraparticle diffusion rate 3.06 × 10^?5 mol·g^?1·min^?2. Among all the anions and cations tested, only carbonate, Fe(III), and citrate reduced the sorption significantly. The sorption data for other metal ions showed that Te(IV) can be separated from ions showing higher degree of sorption; especially Se(IV), As(III), Sb(V), and Eu(III). It can be concluded that manganese dioxide may be used for the separation of certain metal ions, their preconcentration from very dilute solutions, and for decontamination and treatment of industrial effluents.     

Modeling of Sorption Characteristics of Backfill Materials

ABSTRACT

Sorption data analysis was carried out using the Freundlich, Langmuir, and Modified Freundlich isotherms for the uptake of sodium and potassium in an initial concentration range of 10–100 mg/L on backfill materials, viz., bentonite, vermiculite, and soil samples. The soil samples were collected from a shallow land disposal facility at Kalpakkam. The Freundlich isotherm equation is validated as a preferred general mathematical tool for representing the sorption of K⁺ by all the selected backfill materials. The Modified Freundlich isotherm equation is validated as a preferred mathematical tool for representing the sorption of Na⁺ by the soil samples. Since a negative sorption was observed for the uptake of Na⁺ by commercial clay minerals (vermiculite and bentonite clay in the laboratory experiments), sorption analysis could not be carried out using the above-mentioned isotherm equations. Hill plots of the sorption data suggest that in the region of low saturation (10–40 mg/L), sorption of K⁺ by vermiculite is impeded by interaction among sorption sites whereas sorption by soil and bentonite clay is enhanced by interaction among sorption sites. In the region of higher saturation (60–100 mg/L), sorption of K⁺ by all three backfill materials is enhanced by interaction among sorption sites. The Hill plot of the sorption data for Na⁺ by soil suggests that irrespective of Na⁺ concentration, sorption of Na⁺at one exchange site enhances sorption at other exchange sites.     

Sorption kinetics of carbon dioxide onto rubidium carbonate

Rubidium carbonate was used as an adsorbent to capture carbon dioxide from gaseous stream of carbon dioxide, nitrogen, and moisture in a fixed-bed to obtain the breakthrough data of CO₂. Experiments were carried out at flow rates of carbon dioxide and nitrogen (5×10⁻⁶–35×10⁻⁶ m³/min), moisture (0.5×10⁻⁶–3.0×10⁻⁶ m³/h), amount of adsorbent (0.5×10⁻³–1.8×10⁻³ kg), mole fraction of carbon dioxide (0.03–0.22), and different sorption temperatures (323–353 K) at atmospheric pressure. The deactivation model in the non-catalytic heterogeneous reaction systems was used to analyze the sorption kinetics among carbon dioxide, carbonate, and moisture, employing the experimental breakthrough data that fit the deactivation model better than the adsorption isotherm models in the literature.     

Photoluminescence studies of stilbene laser dye incorporated mesoporous silica nanoparticle (MSN) with sulphur dioxide

Photoluminescence spectra of different concentration of laser grade dye stilbene dye solution and stilbene incorporated in mesoporous silica nanoparticle (MSN) had been studied and compared to determine maximum quantum yield. High quantum yield was obtained for 10^?3 M concentration stilbene incorporated MSN. This stilbene incorporated MSN silica is shown to give a fluorescence response to gaseous sulphur dioxide, with a response time of a few seconds and fluorescence emission intensity is proportional to the sulphur dioxide concentration, which are desirable properties for gas sensing. These features together make this MSN material very promising for optical sensing applications.     

The electrochemical oxidation of sulphur dioxide at porous catalysed carbon electrodes in sulphuric acid

The electrochemical oxidation of sulphur dioxide has been studied in sulphuric acid solution at porous carbon electrodes coated with catalysts consisting of aluminum-vanadium mixed oxides with traces of platinum.Catalyst activity and stability in acid electrolytes are determined by the preparation conditions and the V₂O₅: Al₂O₃ ratio.Potentiodynamic measurements were made for investigating the mechanism of the anodic oxidation of sulphur dioxide. When catalysts are present, sulphur dioxide is anodically oxidized at the porous carbon electrodes. Direct electron transfer from the sulphur dioxide to the anode takes place at low potentials, whereas at more positive potentials reaction takes place between the sulphur dioxide and the electrolytically produced surface oxides on the platinum.     

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.     

An ultrasound assisted reductive method for preparation of MnO2: modification of XAD and application in removal of arsenic

ABSTRACT

A sonochemical reduction method of permanganate (MnO₄^?) was utilized for preparation of manganese dioxide (MnO₂) coating on the surface of XAD-4 resin. Characterization of the modified MnO₂-coated XAD-4 resin (MX-4) was done and sorption studies were carried out using arsenic (⁷⁶As) radiotracer. The adsorption capacity for As(III) and As(V) using MX-4 were 5.5 mg/g and 7.6 mg/g, respectively. The MX-4 resin was successfully applied for quantitative removal of arsenic from two ground water samples collected from arsenic contaminated regions of North 24 Parganas, West Bengal, India. A schematic mechanism of removal of arsenic by MX-4 beads was also suggested.     

European inter-laboratory comparison of high pressure CO2 sorption isotherms. I: Activated carbon

In order to assess and improve the quality of high-pressure sorption isotherms of carbon dioxide (CO₂) on coals, an inter-laboratory study (“Round Robin”) has been conducted among four European research laboratories. In a first round of measurements, excess sorption isotherms were determined on Filtrasorb 400 (F400) activated carbon at 318 K using the manometric (TU Delft and RWTH Aachen University) and the gravimetric (FP Mons and INERIS) method up to 16 MPa. The study shows that CO₂ sorption in the supercritical range can be determined accurately with both gravimetric and manometric equipment but requires thorough optimization of instrumentation and measuring as well as proper sample preparation procedures. For the characterization of the activated carbon F400, which we used as benchmark, we have determined a surface area of 1063 m² g⁻¹, and Dubinin-Radushkevich (DR) micropore volume of 0.51 cm³ g⁻¹. Additionally, we analysed the elementary near-surface composition by energy dispersive X-ray spectroscopy (EDX). To characterise the bulk composition of the F400 activated carbon, a proximate and ultimate analysis was performed.The observed excess sorption maxima around 5 MPa have values around 8.0 mol kg⁻¹, which are consistently higher (by upto 0.8 mol kg⁻¹) than literature data.     

Absorption of sulphur dioxide by electrosprayed droplets

This paper describes and discusses experimental results on the absorption of sulphur dioxide in electrified water sprays, either when the polluted gas is treated as is or when the gas is exposed to a corona source to ionize the sulphur dioxide. The experiments revealed that an electrified spray with a charge-to-mass ratio of 50 μC · kg⁻¹ enabled the absorption rate of droplets to double, regardless of their polarities. Corona charging gave rise to an increase in the SO₂ depletion rate over the scrubber wall, while negligible effects appeared on the actual droplets absorption rate. These findings suggested that faster absorption rates mostly, though not uniquely, depend on the modifications on the morphological and interfacial properties of the sprayed droplets induced by the free electric charge imposed on their surface. Conversely, the absorption rates were negligibly affected by the electrical interactions between droplets (either charged or uncharged) and the sulphur dioxide ions/radicals originating from the corona source.