Mechanism of persulfate decomposition in aqueous solution at 50°C in the presence of vinyl acetate and nitrogen

The rate of the thermal decomposition of potassium persulfate has been studied in an unbuffered aqueous solution at 50°C in nitrogen atmosphere in the presence of vinyl acetate (VA) monomer (M). It has been found that the initial rate of persulfate decomposition may be written as in the concentration range of persulfate (1.85 × 10^?2–1.85 × 10^?3 m/dm³) and VA (0.054–0.27 m/dm³). The pH of the aqueous solution of persulfate was found to decrease continuously at 50°C, but there was no measurable change of pH of the aqueous solution containing persulfate and VA at 50°C in the presence of nitrogen at the early stages of the reaction. VA, methyl acetate, and ethyl acetate have been found to undergo very slow hydrolysis in aqueous solution at 50°C. The partition coefficient (β) of the monomer between the polymer phase and the aqueous phase was found to be 21 ± 2 in the presence and absence of electrolytes (K₂SO₄, 10^?4–10^?3 m/dm³) by the bromometric estimation of the monomer present in the aqueous phase containing known amounts of monomer [1.80–2.20%, w/v] and freshly prepared polymer (0.3–0.5 g/100 mL). Above 10^?2 (m/dm³) persulfate, the polymer obtained was found to be insoluble in common solvents, viz., acetone, benzene, etc. Highly purified sodium dodecyl sulfate (0.5–5.0 × 10^?3 m/dm³) had no measurable effect on the rate of persulfate decomposition.     

Synthesis and characterization of moisture‐cured polyurethane membranes and their applications in pervaporation separation of ethyl acetate/water azeotrope at 30°C

NCO‐terminated polyurethane membranes were prepared using diisocyanate, diol, and trimethylolpropane (TMP) using an NCO/OH ratio of 1.6 : 1. Prepolymer was chain‐extended using cellulose acetate butyrate (CAB) in the ratios of 2 : 1, 4 : 1, and 3 : 1 of NCO/OH. Polyurethane (PU) membranes were characterized by differential scanning calorimeter (DSC) and thermogravimetry (TGA) to investigate their thermal properties. Equilibrium sorption studies were carried out at 30°C in water and ethyl acetate media as well as in their binary mixtures. The influence of CAB on pervaporation (PV) separation of an ethyl acetate/water (92/8, w/w, i.e., azeotropic composition) mixture was investigated. Membranes in this study showed a selectivity of 42.42 with a flux value of 0.187 kg/m/h for 3 : 1% NCO/OH containing PU membrane. In order to gain a more detailed picture of the molecular transport phenomenon, we performed the sorption gravimetric experiments at 30°, 35°, 40°, and 50°C to compute diffusion, swelling, sorption, and permeability coefficients of PU membranes in the azeotropic mixture of ethyl acetate and water. Activation parameters for diffusion and permeation were computed from the Arrhenius equation to understand the polymer/solvent interactions. Sorption trends and diffusion anomalies were established through an empirical equation after estimating the diffusion parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3405–3414, 2007     

Low-pressure CO2 sorption in poly(vinyl benzoate) conditioned to high-pressure CO2

Sorption of CO₂ in poly(vinyl benzoate) was gravimetrically measured at pressures up to 1 atm. Sorption isotherms were determined above and below the glass transition temperature T_g from 5 to 85°C. The isotherms were analyzed by the dual-mode sorption model assuming that the plasticizing effect of sorbed CO₂ is negligible at this pressure range. The solubilities and Henry's law dissolution parameters were compared with those obtained by the high-pressure sorption and permeation measurements. Henry's law dissolution parameters were in good agreement with one another. However, the solubilities first determined here were smaller than those determined by the high-pressure sorption experiment at the same temperature. It was clear that the Langmuir capacity of the present specimen was smaller in spite of similar high-pressure CO₂ exposure. Relaxation of the polymer was expected to be one of the reasons. This expectation was confirmed from the observation and analysis of sorption isotherms after two kinds of treatments. After annealing above T_g, the Langmuir capacity was shown to be decreased to 1/2 or even to 1/3 from the sorption isotherms below 45°C. This means that the conditioning to the high-pressure CO₂ surely has a large effect on the nature of glassy polymer. Just after high-pressure CO₂ exposure at 25°C, increased solubility was observed. Furthermore, the slow decrease of solubility, that is, the decrease of conditioning effect, was also followed from the continual measurements at 25°C. This result reflects not only the characteristic of sorption capacity after high-pressure CO₂ exposure, but also the relaxation of polymer in glassy state.     

Development of renewable resource–based cellulose acetate bioplastic: Effect of process engineering on the performance of cellulosic plastics

This paper deals with the development of a cellulose acetate biopolymer. Plasticization of this biopolymer under varying processing conditions to make it a suitable matrix polymer for bio‐composite applications was studied. In particular, cellulose acetate was plasticized with varying concentrations of an eco‐friendly triethyl citrate (TEC) plasticizer, unlike a conventional, petroleum‐derived phthalate plasticizer. Three types of processing were used to fabricate plasticized cellulose acetate parts: compression molding, extrusion followed by compression molding, and extrusion followed by injection molding. The processing mode affected the physicomechanical and thermal properties of the cellulosic plastic. Compression molded samples exhibited the highest impact strength, tending towards the impact strength of a thermoplastic olefin (TPO), while samples that were extruded and then injection molded exhibited the highest tensile strength and modulus values. Increasing the plasticizer content in the cellulosic plastic formulation improved the impact strength and strain to failure while decreasing the tensile strength and modulus values. The coefficient of thermal expansion (CTE) of the cellulose acetate increased with increasing amounts of plasticizer. Plasticized cellulose acetate was found to be processable at 170–180°C, approximately 50°C below the melting point of neat cellulose acetate.     

Adsorption characteristics of carbonized bark for phenol and pentachlorophenol

The potential of using carbonized slash pine bark as a substitute for activated carbon was examined in this study. The bark was carbonized by slow heating in nitrogen for 6·5 h to 672°C. The BET-N₂ surface area, average micropore and mesopore diameter, and micropore volume were 332 m² g⁻¹ 21·7 Å, and 0·125 cm³ g⁻¹, respectively. The adsorption capacities for phenol and pentachlorophenol (PCP) at pH 2 and pH 8 were evaluated. The Langmuir equation provided a slightly better fit than the Freundlich equation to two sets of phenol data. The calculated Freundlich constants, K = 0·41–0·58 mmol/g/(mmol dm⁻³)^1/n and 1/n = 0·30–0·41, were lower and higher, respectively, than literature values for activated carbons. The adsorption capacity of the carbonized bark was much lower for PCP than for phenol. The protonated and anionic PCP isotherms were Type II or III, respectively, in the Brunauer classification. The BET equation provided the best fit to protonated PCP isotherm data. The anionic PCP data were fitted to both the BET model and an equation used in the literature to represent phosphate adsorption on activated carbons. Non-linear regression of the data for both phenol and PCP adsorption with the Freundlich, Langmuir and BET equations generally gave more accurate param-eters, compared with the use of linearized equations to obtain the parameters. © 1998 SCI.     

Permeability of phenol through cellulose acetate membranes by reverse osmosis in various alcoholic systems

Reverse osmosis separation of phenol in various alcoholic solutions using porous cellulose acetate membranes was investigated. The permeation behavior of phenol was measured for cellulose acetate membranes having various pore size distributions which were prepared by annealing at four different temperatures. Some differences were found between the aqueous and the alcoholic solutions in solute permeabilities and product rates. Membranes annealed at 90°C showed higher permselectivity than membranes annealed at lower temperatures. The pore character was classified into two types according to the relation of the product rate of 1-propanol and that of water. It was found in a series of alcoholic solutions that the permeability of phenol, the product rate, and the apparent partition coefficient are closely related to the carbon number of the alcohols, but the values of J_v × η (ca. 1.25 × 10^?4 poise·m³/m²·day) and of the permselectivity coefficient (ca. 0.83) remain constant. The result was analyzed by using the three-dimensional solubility parameter to obtain some information for the partition mechanism of solutes in aqueous and alcoholic solutions.     

Adsorption equilibrium,thermodynamics, kinetics,mechanism and process design of zinc(II) ions onto cashew nut shell

Cashew nut shell (CNS) is an agricultural waste was investigated as a new adsorbent for the removal of zinc(II) from aqueous environment. Effects of solution pH, CNS dose, contact time, initial zinc(II) concentration and temperature on removal efficiency were tested and optimum conditions were evaluated. The equilibrium data were fitted well with Langmuir isotherm model and pseudo‐second‐order kinetic model. Langmuir monolayer adsorption capacity of CNS was examined as 24.98 mg/g. Changes in standard Gibbs free energy (?G°), standard enthalpy (?H°) and standard entropy (?S°) showed that the sorption of zinc(II) ions onto CNS are spontaneous and exothermic at 303–333 K. Sorption process was found to be controlled by both surface and pore diffusion. A batch adsorber was designed for different CNS dose to effluent volume ratios using Langmuir equation. Effective diffusivity values were found to be 1.927 × 10^?11 (10 mg/L), 2.135 × 10^?11 (20 mg/L), 2.267 × 10^?11 (30 mg/L), 2.305 × 10^?11 (40 mg/L) and 2.362 × 10^?11 (50 mg/L) m²/s. © 2011 Canadian Society for Chemical Engineering     

Ageing Effect on Ethyl Cellulose Films

The effect of physical ageing on the electrical properties, such as thermally stimulated discharge currents (TSDC) and conduction currents, of ethyl cellulose (EC) has been analysed. The TSDC thermograms of EC samples, poled with 100kVcm^-1 at different poling temperatures (i.e. 50, 70 and 90°C) consist of two peaks located at 70±5°C and 110±5°C, respectively. The conductivity measurements were made over a time period of 10¹–10³min in the temperature range 30–125°C with a poling field of 100kVcm^-1. It has been observed that physical ageing considerably affects the magnitude of the thermally stimulated depolarization and conduction currents of EC films. This ageing effect, which has been attributed to continuous vitrification of a polymer, is considered to enhance the life-time of a polymer electret. © of SCI.     

SORPTION BEHAVIOR OF PERTECHNETATE ION ON REILLEXTM-HPQ ANION EXCHANGE RESIN FROM HANFORD AND MELTON VALLEY TANK WASTE SIMULANTS AND SODIUM HYDROXIDE/SODIUM NITRATE SOLUTIONS

ABSTRACT

The batch distribution coefficients (K_d, mL solution /g dry resin) for pertechnetate (TcO₄) between Reillex^TMHPQ anion exchange resin and various caustic solutions have been determined. The average K_d value in 1.5 M NaNO₃/l.0 M NaOH solution is (262.2 ± 12.6) mL7sol;g for TcO₄ ^? ranging from 1.0 × 10^TM M to 5.0 × 10^?4 M. Pertechnetate K_d values were measured in a series of NaOH7sol;NaNO₃ solutions. The series are: 1.00 M NaOH with 0.010 to 5.00 M NaNO₃; 0.100 M NaOH with 0,010 to 5.00 M NaNO₃; 0.100 MNaNO₃ with 0.10 to 5.00M NaOH; 1.00MNaNO₃ with 0.10 to 5.00 M NaOH; 1.50 M NaNO₃ with 0.10 to 5.00 M NaOH; 3.50 M NaNO₃ With 0.10 to 5.00 M NaOH. The K_d values are described by the following equation.

This equation was used to predict the K_d values for a series of tank waste simulants. The predicted K_d values are different from the measured values with an average absolute difference of (29 ± 10)%.

Pertechnetate k_dvalues for 101-SY, 103-SY, DSS, DSSF-2.33, DSSF-5, DSSF7, 101-AW, and Melton Valley simulants have been determined as a function of time. A first order approach to equilibrium is observed. The K_d values at two hours are (1066±45), (870± 102), (346± 18), (296± 15), (245 ±6), (209± II), (218±5), and (167 ± 5) mL/g, respectively.     

Barrier properties of poly(lactic acid) and its morphological changes induced by aroma compound sorption

The barrier properties of poly(lactic acid) (PLA) play a key role in food packaging applications. For their optimization, the influence of crystallinity on the barrier properties of PLA and the interaction of PLA with the aroma compound ethyl acetate were investigated. PLA film samples with various crystallinities were fabricated by flat die extrusion and thermocompression and compared to PLA Biophan^?. The degree of crystallinity had no effect on the oxygen permeability. However, an increase of crystallinity caused a decrease in ethyl acetate sorption. The sorption isotherm of ethyl acetate obtained using microgravimetry showed a steep increase with increasing aroma activity, a form which is consistent with a plasticization effect. This behaviour was verified using differential scanning calorimetry and dynamic mechanical analysis. Sorption caused a marked decrease in the glass transition temperature well below room temperature to approximately 0 °C. Furthermore, PLA underwent a solvent‐induced crystallization when equilibrated in ethyl acetate atmosphere at an activity of 0.5. The results obtained show the importance of considering possible interactions between polymer and foodstuff during the optimization step of polymeric materials for food packaging applications. Copyright © 2010 Society of Chemical Industry     

Shear degradation of poly(vinyl acetate) in toluene solutions by high-speed stirring

A poly(vinyl acetate) (PVAc) of M?_w 750,000 and M?_w/M?_n 5.10 in toluene solution was sheared in a Virtis-60 homogenizer. The polymer concentration was 3.0 to 12.0 g/100ml, and test temperature was 10 ± 0.5°C. The extent of degradation was measured by gel permeation chromatography (GPC). It was concluded that on shearing (i) the molecular weight decreases rapidly at the beginning of shearing and thereafter decreases ever more slowly toward a limiting value, (ii) the molecular weight distribution is narrowed, (iii) no degradation occurs up to 5000 rpm and thereafter increases with stirring speed, (iv) degradation is more at lower concentrations but concentration is not a sensitive variable, and (v) the chain scission occurs randomly. The Mark-Houwing relationship for PVAc in THF at 25°C was derived as [η] = 2.47 × 10^?4 × M?_v^0.644.     

Polyallylamine-conjugated thermo-responsive polymers for the rapid removal of phenolic compounds from water

Polyallylamine-conjugated thermo-responsive polymer (PNIPAAm-PAA) was readily prepared by the condensation of polyallylamine and poly(N-isopropylacrylamide-co-acrylic acid) with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The synthesized polymer was water-soluble below the lower critical solution temperature (LCST, ca. 34 °C) but deposited to form a condensed coagulate by heating the solution above the LCST. In the presence of phenol oxidation enzymes, phenolic compounds was oxidized and spontaneously bound to the amino group of PNIPAAm-PAA. Almost complete removal of 300 mg l⁻¹ phenol was achieved by the use of 1 g l⁻¹ PNIPAAm-PAA. However, long time was required for the oxidation of phenol by using mushroom tyrosinase. On the other hand, combined use of horseradish peroxidase and hydrogen peroxidase allowed rapid phenol removal. Furthermore, the proposed method was applicable to the removal of a wide range of phenolic compounds including estrogenic hormones. The applicability to wastewater treatment was successfully demonstrated using spiked effluents.     

Synthesis and testing of cellulose acetate nicotinate as adsorbent for rhodamine B dye

The esterification of cellulose hydroxyl groups with natural carboxylic acids in mild conditions represents an adequate pathway in obtaining cellulose derivatives with different useful properties. In this article, authors report the synthesis of new mixed ester of cellulose and cellulose acetate nicotinate (CAN) , in a homogenous medium using DMF as solvent, cellulose acetate (CA) as starting cellulosic material, and nicotinic acid as an esterification agent in the presence of p-toluenesulfonyl chloride and pyridine. FTIR and NMR techniques were used to prove the binding of nicotinoyl group at free hydroxyl groups of CA. The obtained CAN was electrospun by electrospinning technique to obtain adsorbent ultrafine fibers, evidenced by SEM images, with high specific surface area. Monolayer Langmuir and empirical Leundrich isotherms were used to assess the adsorption capacity for rhodamine B dye of electrospun CAN in comparison with that of electrospun CA used as starting material. Langmuir isotherm led to a better assessment of experimental data suggesting that the adsorption is mainly determined by hydrogen bonds formed between carboxylic OH hydrogen bonding donor and pyridine N hydrogen bonding acceptor. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47772.     

Catalytic removal of phenol from aqueous solutions in a trickle‐bed reactor

The degradation of high concentrations of phenol (1g/dm^?3) in aqueous media at high temperatures (100–190 °C) and pressures (2.0 MPa) has been studied by catalytic wet air oxidation in a trickle‐bed reactor. The effect of reaction temperature, weight hourly space velocity (WHSV) and hydrogen peroxide concentration on phenol concentration, total organic carbon (TOC) and chemical oxygen demand (COD) conversion by using a commercial copper catalyst has been investigated. At 150 °C, TOC removal increased by 28% with the WHSV of 62.5 h^?1. The addition of hydrogen peroxide as a free radical promoter significantly enhanced the depletion rate of phenol. A kinetic study has been carried out leading to the determination of the kinetic constants for the removal of TOC. Copyright © 2005 Society of Chemical Industry     

CYPHOS IL 101 (Tetradecyl(Trihexyl)Phosphonium Chloride) Immobilized in Biopolymer Capsules for Hg(II) Recovery from HCl Solutions

Abstract

A composite polymer (made of gelatin and alginate) was used for the synthesis of Cyphos IL 101-immobilized resins. These resins (with varying size and different ionic liquid (IL) content) have been tested for the recovery of mercury from concentrated HCl solutions (0.1–5 M HCl concentrations). Prior to the study of sorption performance on resins, the reactivity of Cyphos IL 101 versus mercury was tested using solvent extraction methodology. These results showed that the extraction was hardly affected by the concentration of HCl and that an ion exchange mechanism was probably involved in metal recovery (binding of HgCl₄ ^2-). The performance of these resins for Hg(II) recovery was tested through sorption isotherms and uptake kinetics, investigating the effect of resin size, ionic liquid content, metal concentration, agitation speed, and resin state (dry state versus wet state). Sorption capacity (which was proportional to the IL content) can reached up to 150 mg Hg g^?1 in 1 M HCl; this sorption capacity was decreased by increasing chloride concentration. The kinetics were described well by the pseudo-second order equation and by the intraparticle diffusion equation (the so-called Crank's equation). The intraparticle diffusion coefficient was in the range of 10^?11–1.2 × 10^?10 m² min^?1. The kinetic profiles were controlled by the IL content, sorbent dosage, and the sorbent particle size. Drying of the resins significantly decreased diffusion rates in the resins. The presence of competitor metals did not affect sorption capacity except when stable chloro-anionic species such as in the case of Zn(II) were formed. Mercury can be desorbed using 6 M nitric acid solutions; and the sorbent can be recycled for at least six sorption/desorption cycles without significant decrease in the sorption performance.     

Dilute-solution behavior of aeromonas gum, a heteropolysaccharide

Summary Fifteen fractions of aeromonas gum, a heteropolysaccharide produced by the strain Aeromonas nichidenii, have been studied by static light scattering and viscometry with dimethylsulfoxide containing 0.2 M LiCl at 25°C as the solvent. Data for the z-average radius of gyration and the intrinsic viscosity covering a molecular weight range from 4.5 × 10⁵ to 2 × 10⁶ show the polymer to behave like a semiflexible chain in this solvent, and are analyzed on the basis of the wormlike chain by coarse-graining the heteropolysaccharide molecule. It is shown that these data and those for the particle scattering function are consistently explained by this model with a (mean) persistence length of 10 (± 1) nm and a (mean) linear mass density of 1450 (± 100) nm⁻¹, and that the heteropolysaccharide chain is as stiff as cellulose derivatives. Received: 5 April 2002 / Accepted: 4 June 2002     

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.     

Thermodynamic,kinetic, and equilibrium studies on phenol removal by use of cashew nut shell

Adsorption of phenol from aqueous solution onto cashew nut shell (CNS) was investigated to assess the possible use of this adsorbent. The influence of various parameters such as contact time, phenol concentration, adsorbent dose, pH, and temperature has been studied. Studies showed that the pH of aqueous solutions affected phenol removal as a result of decrease in removal efficiency with increasing solution pH. The experimental data were analysed by the Langmuir equation. Equilibrium data fitted well with the Langmuir model with maximum monolayer adsorption capacity of 5.405 mg/g. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° have also been evaluated and it has been found that the sorption process was feasible, spontaneous, and exothermic in nature. The pseudo‐first‐order and pseudo‐second‐order kinetic models were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of phenol could be described by the pseudo‐second‐order equation, suggesting that the adsorption process is presumable a chemisorption. The CNS investigated in this study showed good application potential for the removal of phenol from aqueous solution.     

Sorption and transport of benzene in poly(ethylene terephthalate)

The kinetics and equilibria of benzene sorption in poly(ethylene terephthalate) were measured at 40°C, 50°C, and 60°C, with benzene activities ranging from 0.02 to 0.3. At most experimental conditions, diffusion was found to be Fickian; however, evidence of non-Fickian transport was found at the highest activity levels. Values of the diffusion coefficient of benzene range from 10^-14 cm²/s at 40°C to 10^?12 cm²/s at 60°C in the limit of low concentrations. Nonlinear isotherms observed for benzene sorption were successfully interpreted in terms of the dual mode model for sorption in glassy polymers, whereby the sorbed penetrant exists as two populations: one sorbed according to Henry's law and the other following a Langmuir isotherm. Non-Fickian transport data were correlated with a model that superimposes diffusion of both the Henry's law and Langmuir populations (the “partial immobilization” model) upon first-order relaxation of the polymer matrix.     

Iron and hydrogen electrodes in liquid ammonia

Equilibrium potentials of the iron(II)—iron electrode vs TlTlCl; 0.1 M NH₄Cl in liquid ammonia are determined from intersections of Tafel lines for iron deposition and dissolution. The hydrogen electrode is shown to behave reversibly at palladium hydride, but not at platinum with respect to the dependence of hydrogen pressure. The standard potential of iron at 293 K is estimated at E° = ?0,356 (±0,010)V in 0.1 M NH₄NO₃. Standard potentials of other electrodes are reevaluated and shown to be consistent with earlier measurements except for the standard potential of lead. Steady state and transient polarization curves indicate in simple mechanism of the iron electrode involving transfer of iron(II) in one step. The temperature-independent anodic transfer coefficient is α₊ = 0.41 (±0.02), the cathodic transfer coefficient α_? = 0.61 (±0.03). The standard exchange current density at E° is j°_° = 7.10^?7 Acm^?2 for 293 K. Exchange current densities of the hydrogen electrode are j_° = 1.6·10^?9 Acm^?2 at platinized platinum in 0.1 M NH₄Cl both for 293 K.