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.     

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.     

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.     

Magnetic manganese dioxide as an amphoteric adsorbent for removal of harmful inorganic contaminants from water

Manganese dioxide (δ-MnO₂) with magnetic properties has been synthesized by precipitation of MnO₂ in the presence of magnetite. The resulting material has a particle size distribution between 0.5 and 5 μm. Magnetization of the material is in the order of magnitude of that of magnetite. Therefore a solid–liquid separation by means of moderate magnetic fields is possible. Due to the properties of δ-MnO₂ the point of zero charge of the surface is about 2.5. Therefore, the adsorbent is almost exclusively a cation exchanger although sorption of oxoanions is also possible. Sorption experiment with Cd²⁺, Ni²⁺, and Pb²⁺ ions revealed a preferred sorption. Alkaline earth ions such as Ca²⁺ affect the uptake only at high concentrations. Because of the small particles and the respective large specific surface, sorption is fast.     

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.     

Gravimetric and volumetric study of the sorption of gases and vapors in poly(vinyl chloride) powders

The sorption of a variety of gases and organic vapors in poly(vinyl chloride) (PVC) powders has been studied gravimetrically with a recording microbalance and volumetrically with a gas pycnometer and an automatic surface area analyzer. For nitrogen, carbondioxide, vinyl chloride, methanol, acetone, n-butane, and benzene at low penetrant activities and temperatures below T_g, sorption isotherms exhibit the downward curvature characteristic of dual-mode sorption. The solubility of each of these penetrants is lower in heat-treated PVC samples than in samples recovered from the polymerization without additional heating. It has been possible to estimate the parameters of the dual-mode sorption model for carbondioxide, vinyl chloride, and methanol. The results indicate that the history-dependence of gas or vapor solubility is associated only with the “hole-filling” term of the dual-mode model; the normal dissolution or Henry's Law term is essentially unaffected by the prior heat treatment of the PVC.     

Photocatalytic degradation of flexible PVC/TiO2 nanohybrid as an eco-friendly alternative to the current waste landfill and dioxin-emitting incineration of post-use PVC

Photo-degradable poly(vinyl chloride) (PVC)/titanium dioxide (TiO₂) nanohybrid has been investigated to be utilized as an eco-friendly alternative strategy to the current waste landfill and toxic byproduct-emitting incineration of PVC wastes. Thus, the present study suggests a novel idea related to preparing the photocatalytically degradable nanohybrid through TiO₂ nanoparticle-integrated hyperbranched poly(ε-caprolactone) (HPCL-TiO₂). The main aim of this study is to find a solution to the unresolved problem in the conventional PVC/TiO₂ composites related to the poor dispersion of the nanoparticles in PVC polymer. First, TiO₂ nanoparticles are prepared by a sol-gel process, and the size of the particle is about 5-10 nm in diameter as measured by using a transmission electron microscopy (TEM) and dynamic light scattering (DLS). The hyperbranched poly(ε-caprolactone) (HPCL) with numerous COOH groups and good miscibility with PVC as a binder for TiO₂ nanoparticles is prepared from moisture-sensitive catalyst-free polymerization of 2,2-bis[ω-hydroxy oligo(ε-caprolactone)methyl]propionic acids followed by modification reaction using pyridinium dichloromate (PDC), then characterized with ¹H NMR and ¹³C NMR analyses. The integration of TiO₂ nanoparticles onto HPCL is carried out by a dip-coating method based on the spontaneous self-assembly between TiO₂ nanoparticles and HPCL, and the loading amount of the nanoparticles in the HPCL-TiO₂ is determined to be ca. 3.3 wt% by X-ray photoelectron spectroscopy (XPS). Then, the HPCL-TiO₂ is blended with PVC by solution blending in THF as solvent, and the resulting dispersibility of TiO₂ nanoparticle in PVC is characterized by field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectrometry (EDS), which exhibits the TiO₂ nanoparticles are well-dispersed in PVC matrix, while some agglomerates are observed in the PVC/TiO₂ sample prepared from TiO₂ nanoparticle itself. The photocatalytic degradation of the samples are examined and verified from the change of surface morphology, chemical structure, molecular weight, and molecular-level structure after UV irradiation through field-emission scanning electron microscopy (FESEM), UV-visible spectroscopy, gel permeation chromatography (GPC), and positron annihilation lifetime spectroscopy (PALS). The remarkable photocatalytic degradation is observed in the PVC/HPCL-TiO₂, and the structural change accompanied by the degradation of the irradiated sample can clearly explained.     

Uptake of tridodecylmethylammonium chloride by PVC

The uptake of tridodecylmethylammonium chloride (TDMAC) by poly(vinyl chloride) has been investigated to provide a more quantitative basis for the preparation of blood-compatible surfaces based on TDMAC–heparin coatings. Sorption isotherms of TDMAC from toluene–cyclohexane and toluene–methanol mixtures have been measured. In toluene–cyclohexane mixtures, the TDMAC uptake is proportional to the degree of swelling of the polymer. From ion-exchange experiments with ³⁶Cl^?, it appears that only a small fraction of the TDMAC remains near the PVC surface to provide the heparin binding capacity. Methanol forms a strong H-bonded complex with TDMAC in toluence and prevents its sorption by PVC.     

Improvement of the dispersity of micro-nano particles for PP/PVC composites using gas-assisted dispersion in a controlled foaming process

Polyvinyl chloride (PVC) and nanosilicon dioxide (nano-SiO₂) were blended with neat polypropylene (PP) to improve its flame retardancy and cellular foam structure, and the dispersal effects of PVC and nano-SiO₂ and the foaming effect of the PP/PVC composites were investigated. PP/PVC samples with different compositions and foaming degrees were first fabricated by conventional injection molding with and without a blowing agent. Tensile testing, differential scanning calorimetry, scanning electron microscopy, limiting oxygen index testing, and vertical burn testing were used to study the mechanical properties, thermal features, microstructures, and flame-retardant properties of the molded samples, and the samples with different degrees of foaming were compared. The results suggest that the foaming process facilitates the dispersion of PVC and nano-SiO₂, while the presence of PVC and nano-SiO₂ improves the foamability of PP. A method for a gas-assisted dispersion technology to control the foaming process was hence proposed. Considering that the mechanical properties of PP/PVC could be retained with satisfactory flame retardancy and weight loss, convenient processing, and low-cost materials; the technology presented can be directly applied for lightweight engineering and the manufacture of fire-resistant material and can act as a reference for other micro-nano processing involving the dispersion of particles. POLYM. ENG. SCI., 60:524–534, 2020. © 2019 Society of Plastics Engineers     

Toluene and n-heptane sorption in Matrimid asymmetric hollow fiber membranes

Equilibrium and transient sorption isotherms were obtained for toluene and n-heptane in both annealed and non-annealed Matrimid^® asymmetric hollow fiber membranes at 35 °C. Equilibrium sorption follows the dual mode model except for toluene sorption into annealed fibers above a pressure of 0.5 psia. Except at the highest toluene exposure pressure, the equilibrium uptake of penetrant in annealed fibers was signigicantly less than in non-annealed fibers at a given pressure due to the significant reduction of excess free volume. Changes in the dual mode model parameters for the annealed samples may reflect not only reductions in sample free volume, but also charge transfer formation. The Berens-Hopfenberg model successfully describes all of the various transient sorption behaviors observed for toluene and n-heptane in Matrimid^® with a significant relaxation-controlled contribution to the overall mass uptake over much of the experimental range explored. Purely diffusion-controlled (Fickian) uptake was seen only for toluene sorption in annealed fibers for a change in activity from 0 to 0.05, while purely relaxation-controlled (non-Fickian) uptake was observed for n-heptane sorption in non-annealed fibers for a change in activity from 0 to 0.09. A reduced value of D_A/L², the effective Fickian diffusion time, in non-annealed fibers for toluene at a low activity level provides evidence of antiplasticization, while at intermediate to high activity, the value of D_A/L² increases with activity for all of the systems studied in this work indicating plasticization.     

Evaluation of Nickel Sulphide Prepared by Different Routes for Removal of 106Ru from Alkaline Radioactive Liquid Waste

An attempt has been made to synthesize nickel sulphide (NiS) compound by different routes. The NiS material thus obtained was coated on polymethyl metha acrylate (PMMA) beads to form a composite material, which was subjected to its performance evaluation for uptake of ¹⁰⁶Ru from low level radioactive liquid waste (LLW) stream. Distribution Coefficient (K_d) of ¹⁰⁶Ru from LLW using NiS–PMMA composite beads was found to be in the range of 9000–12000 (ml/g). The effect of various parameters viz. pH, ionic strength, temperature, time equilibration, etc. towards the uptake of ¹⁰⁶Ru was investigated. The sorption mechanism was also studied. The ΔG, ΔH, and ΔS value for sorption were evaluated. The sorption was observed to be spontaneous and endothermic in nature. From the practical utilization point of view, the rate of uptake of ¹⁰⁶Ru by the composite material was studied. The data of sorption was investigated with Lagergren first-order, pseudo-first-order, and second-order plots. Its intraparticle diffusion mechanism was studied with the Weber Morris model. The kinetics was found to follow a pseudo-first-order pattern with intraparticle diffusion. However, intraparticle diffusion is not the rate controlling step.     

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.     

Low rank coals sulphur functionality study by AP-TPR/TPO coupled with MS and potentiometric detection and by XPS

Atmospheric pressure-temperature programmed reduction (AP-TPR) and X-ray photoelectron spectroscopy (XPS) techniques were applied to low rank coals sulphur study. Coal samples were pyrolysed in a flow of water vapor (WV). It was demonstrated that this treatment influenced mainly aliphatic sulphur. Samples were characterised by two methods and data were interpreted within the limits of the techniques. XPS measurements registered sulphur 2p spectra with two main signals for organic and inorganic sulphur compounds. The AP-TPR set-up, with potentiometric detection of the formed H₂S as S²⁻ using an ion selective Ag₂S-electrode, gives quantitative data about the presence of different sulphur species. The AP-TPR equipment on-line coupled with a mass spectrometer (MS) gives extra qualitative information about different reductive and oxidative organic sulphur forms. Using MS not only H₂S but also SO₂, COS, CS₂, and all other volatile sulphur and organic compounds can be monitored, giving more information for the initial presence of the different sulphur forms and to the mechanisms involved in the pyrolytic process. This AP-TPR-MS experiment is subsequently followed by AP-TPO-MS measurement (in an oxidated atmosphere) to study sulphur presence in the residue (tar and char) in the reactor. Comparing all these AP-TPR profiles results in a better assignment of the different signals to specific sulphur functionalities.     

Tetraalkylphosphonium Ionic Liquid Encapsulation in Alginate Beads for Cd(II) Sorption from HCl Solutions

Cyphos IL 105 (tetraalkylphosphonium dicyanamide) was immobilized in alginate capsules (IL vesicle entrapped in a biopolymer layer, as shown by SEM-EDX analysis). This material was tested for efficient Cd(II) sorption from HCl solutions. The concentration of HCl and chloride ions hardly influenced metal sorption that proceeds through ion exchange between Cd(II) (under the form of CdCl₄^2?) and 2 dicyanamide groups. The sorption capacity (at saturation of the resin) proportionally increased with IL content (respecting the 1:2 stoichiometry between Cd(II) and the phosphonium cation). The uptake kinetics are well described by the Crank’s equation (resistance to intraparticle diffusion) and by the pseudo-second order rate equation (chemical reaction rate).     

Investigation of sorption and diffusion of supercritical carbon dioxide into poly(vinyl chloride)

The interaction of supercritical carbon dioxide (scCO₂) with poly(vinyl chloride) (PVC) was systematically investigated. PVC films of 0.5 mm thickness were treated with CO₂ at pressures between 5 and 40 MPa, at temperatures between 40 and 70°C and soaking times between 0.5 and 7 h. The gravimetric desorption data were kinetically and thermodynamically evaluated assuming Fickian diffusion and the morphology changes due to the CO₂ treatment investigated by microscopic methods. The sorbed amount of CO₂, q (q=g_CO2/g_polymer) ranged between 0.03 (5 MPa, 70°C) and 0.13 (15 MPa, 40°C). The desorption diffusivities, D_d, were in the order of 0.1×10⁻¹¹ m²/s and decreased with decreasing amounts of CO₂. In contrast, the sorption diffusivities, D_s, were markedly higher and varied between 0.7×10⁻¹¹ and 2.5×10⁻¹¹ m²/s (20 MPa, 40–70°C). The CO₂ treatment changed the polymer chain structure, macroscopically visualized by the film opaqueness and by the density decrease to 1.05 g/cm³. Microcellular structures were not detected.     

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.     

Hypercrosslinked microporous organic polymer networks derived from silole-containing building blocks

Three silole-containing hypercrosslinked microporous organic polymer networks were designed and synthesized via Friedel–Crafts alkylation promoted by anhydrous FeCl₃. The results demonstrated that the substitution of methyl group connected with silicon atom by benzene has negligible effect on the surface area and gas uptake ability of the polymer networks. The network-1 produced from 1,1-dimethyl-2,3,4,5-tetraphenylsilole shows a surface area up to 1236 m² g⁻¹ with the hydrogen uptake ability of 1.33 wt% (77.3 K/1.13 bar) and a carbon dioxide capture capacity of 2.94 mmol g⁻¹ at 273 K/1.13 bar. The isosteric heats of carbon dioxide sorption for all of the polymer networks exceed 25 kJ/mol at the zero coverage because the introduction of silicon atom into the polymer skeleton enhanced the binding affinity between the adsorbent and CO₂ molecules. In addition, the selectivity of the polymer networks for CO₂/N₂ and CO₂/CH₄ were found to be around 35 and 6 at 273 K, respectively. These results show that these materials are potential candidates for applications in post-combustion CO₂ capture and separation.     

Effect of Thermal Activation on the Kinetics of Cd2+ Ions Sorption by AlPO4

Abstract

The kinetics of Cd²⁺ uptake on two different samples of AlPO₄ activated at 105°C and 400°C is studied as a function temperature, which shows an increase in the optimum time for the maximum uptake of Cd²⁺ ions with activation. The mechanism of the uptake is observed to change from ion exchange to sorption inside the pores with activation. The rate constants calculated from the first order Lagergren's plots are observed to decrease while activation energy, enthalpy, entropy, and free energy of activation are observed to increase with activation. All the activation parameters are found to be higher for the activated AlPO₄ as compared to the non-activated AlPO₄.     

Swelling characteristics of NR/PU block copolymers and the effect of NCO/OH ratio on swelling behaviour

A series of (NR/PU) block copolymers (BCs) was prepared from toluene diisocyanate (TDI), 1,3-butane diol (1,3-BDO), and hydroxyl-terminated liquid natural rubber (HTNR), by solution polymerisation. The swelling characteristics of the BCs were investigated. Diffusion profile in various solvents and the sorption kinetics were studied. Arrhenius and thermodynamic parameters were evaluated from the diffusion data. Finally, the influence of NCO/OH ratio on the swelling behaviour was also studied. The equilibrium sorption value (Q_∞) decreased with increasing NCO/OH ratio for all the BCs. The samples have higher uptake of solvents with solubility parameter within a small range centred about 9 (cal/cm³)^1/2. Highly polar and non-polar solvents show minimum uptake. It was observed that polarity factor predominates in the solvent transport through the present block copolymer systems. The sorption behavior is also found to vary with the NCO/OH ratio employed in the preparation of polyurethane (PU) oligomers.