Manipulation of polymer layer characteristics by electrochemical polymerization from mixtures of aniline and ortho‐phenylenediamine monomers

The influence of adding ortho‐phenylenediamine (OPDA) during the polymerization of aniline on the characteristics of the resulting polymer film was examined. When using a platinum electrode, the deposits were obtained from solutions containing 0.1 mol dm^?3 aniline and 1, 5, or 10 mmol dm^?3 OPDA. The deposits were also prepared from solutions containing 0.5 mol dm^?3 aniline and 5, 10, or 50 mmol dm^?3 OPDA. In both cases, 3 mol dm^?3 phosphoric acid solution was used as a supporting electrolyte. The characteristics of the obtained layers were investigated through the catalytic effect of different polymer layers on hydroquinone/quinone (H₂Q/Q) test redox system. The results obtained confirm the earlier established catalytic effect on the potential of the redox reaction by shifting it to more reversible values. However, as the concentration of OPDA was increased, the resulting limiting current decreased, thus indicating in the presence of OPDA a lower population of the available active centers necessary for the catalytic reaction to proceed. The influence of OPDA on polymer characteristics was also studied by using scanning electron microscopy as well as electrochemical impedance spectroscopy. The polymer was synthesized on a stainless steel electrode (13% Cr) from a solution containing 0.5 mol dm^?3 aniline and 5, 10, or 50 mmol dm^?3 OPDA. The layers were tested in chloride‐containing solutions by monitoring the open circuit potential. The results obtained suggest that, by increasing the concentration of OPDA, the time of OCP in the passive region of stainless steel is prolonged. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modification of dextran through the grafting of N‐vinyl‐2‐pyrrolidone and studies of physicochemical phenomena in terms of metal‐ion uptake,swelling capacity,and flocculation

The optimum conditions for grafting N‐vinyl‐2‐pyrrolidone onto dextran initiated by a peroxydiphosphate/thiourea redox system were determined through the variation of the concentrations of N‐vinyl‐2‐pyrrolidone, hydrogen ion, potassium peroxydiphosphate, thiourea, and dextran along with the time and temperature. The grafting ratio increased as the concentration of N‐vinyl‐2‐pyrrolidone increased and reached the maximum value at 24 × 10^?2 mol/dm³. Similarly, when the concentration of hydrogen ion increased, the grafting parameters increased from 3 × 10^?3 to 5 × 10^?3 mol/dm³ and attained the maximum value at 5 × 10^?3 mol/dm³. The grafting ratio, add‐on, and efficiency increased continuously with the concentration of peroxydiphosphate increasing from 0.8 × 10^?2 to 2.4 × 10^?2 mol/dm³. When the concentration of thiourea increased from 0.4 × 10^?2 to 2.0 × 10^?2 mol/dm³, the grafting ratio attained the maximum value at 1.2 × 10^?2 mol/dm³. The grafting parameters decreased continuously as the concentration of dextran increased from 0.6 to 1.4 g/dm³. An attempt was made to study some physicochemical properties in terms of metal‐ion sorption, swelling, and flocculation. Dextran‐g‐N‐vinyl‐2‐pyrrolidone was characterized with infrared spectroscopy and thermogravimetric analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Potential of Rice Husk for the Decontamination of Silver Ions from Aqueous Media

The sorption behavior of silver ions on rice husk has been investigated in detail. Various physico-chemical parameters were optimized to simulate the best conditions in which this material can be used as an adsorbent. Maximum adsorption was observed at 0.001 mol L^?1 of acid solutions (HNO₃, H₂SO₄ and HClO₄) using 0.5 g of adsorbent for 9.27 × 10^?5 mol L^?1 silver concentration in fifteen minutes equilibration time. The adsorption of silver was decreased with the increase in the concentrations of all the acids used. The kinetic data indicated an intraparticle diffusion process with sorption being pseudo-second order. The determined rate constant k₂ was 14.707 ± 1.832 mol g^?1 min^?1. The adsorption data obeyed the Freundlich, Langmuir, and Dubinin-Radushkevich isotherms over the silver concentration range of 1.85 × 10^?4 to 1.16 × 10^?3 mol L^?1. The characteristic Freundlich constants, that is, 1/n = 0.38 ± 0.033 and K = 0.271 ± 0.104 m mol g^?1 whereas the Langmuir constants Q = (1.504 ± 0.054) × 10^?2 m mol g^?1 and b = (16.582 ± 2.227) × 10³ dm³ mol^?1 have been computed for the sorption system. The sorption mean free energy from the Dubinin-Radushkevich isotherm is 12.16 ± 0.82 kJ mol^?1 indicating ion-exchange mechanism of chemisorption. The uptake of silver increases with the rise in temperature (283–333 K). Thermodynamic quantities, namely, ΔG, ΔS, and ΔH have also been calculated for the system. The sorption process was found to be endothermic. The effect of other cations and anions on the adsorption of silver has also been studied.     

Removal of trivalent chromium(III) from solution by biosorption in cork powder

The removal of trivalent chromium from solutions using biosorption in cork powder is described. The adsorption isotherm was determined, along with the effect of different variables, such as biomass particle size, solid–liquid ratio, reaction time, metal concentration and pH, on the efficiency of chromium removal. It was concluded that the adsorption is slow and favoured by an increase in pH. Therefore, using a solid–liquid ratio of 4 g dm^?3 it is possible to reduce the chromium concentration in the solution from 10 mg dm^?3 to less than 1.5 mg dm^?3 in 2 h at 22 °C. The kinetic studies verified that the sorption of chromium by cork was described by a second‐order model. The elution results showed that 50% of the chromium bound to the cork was eluted using 0.5 mol dm^?3 H₂SO₄ and that cork maintains its binding capacity over four cycles of biosorption/elution. © 2002 Society of Chemical Industry     

Factors affecting silver biosorption by an industrial strain of Saccharomyces cerevisiae

Factors affecting silver biosorption by Saccharomyces cerevisiae biomass, obtained as a waste product from industry, were examined. Maximum removal of silver from solution was achieved within 5 min. Increasing the concentration of biomass in experimental flasks from 1 to 8 mg cm⁻³ decreased both silver accumulation, from 224·7 to 89·5 μmol Ag g⁻¹ dry wt, and associated H⁺ ion release, from 109·4 to 31·7 μmol H⁺ g⁻¹ dry wt. The presence of 1·0 mol dm⁻³ cadmium or methionine decreased silver biosorption by 40% and 93% respectively. Boiling in 100 mmol dm⁻³ NaOH or 10 mmol dm⁻³ sodium dodecyl sulphate decreased silver biosorption by 54% and 25% respectively. A temperature increase from 4°C to 55°C decreased silver biosorption by 9%. The metabolic state of the yeast had no effect on silver biosorption. Decreasing the pH of the silver solution caused a reduction in metal removal by the biomass.     

Graft copolymerization of acrylic acid onto xanthum gum using a potassium monopersulfate/Fe2+ redox pair

A previously unreported graft copolymer of xanthan gum (XOH) with acrylic acid was synthesized and the reaction conditions were optimized using a potassium monopersulfate (PMS)/Fe²⁺ redox pair. Grafting ratio, add on, and conversion increase with an increase in the ferrous ion concentration (2.0 × 10^?3 to 5.0 × 10^?3 mol dm^?3) and PMS concentration (1.0 × 10^?3 to 4.0 × 10^?3 mol dm^?3). It was observed that grafting takes place efficiently when the acrylic acid concentration and temperature were 5.0 × 10^?2 mol dm^?3 and 35°C, respectively. Samples of xanthan gum and xanthan gum–g–acrylic acid were subjected to thermogravimetric analysis with the objective of studying the effect of grafting of acrylic acid on the thermal stability of xanthan gum. The graft copolymer was found to be more thermally stable than xanthan gum. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1341–1346, 2003     

Fourier-transform infrared assay of bile salt-stimulated lipase activity in reversed micelles

A Fourier-transform infrared (FT-IR) spectroscopic method has been developed for assaying the bile salt-stimulated human milk lipase (BSSL, EC3.1) catalyzed hydrolysis of triolein in AOT reversed micelles in iso-octane. At 37°C in 50 mmol dm^?3 AOT the molar absorbtivities for the carbonyl stretching frequencies for triolein (at 1751 cm^?1) and oleic acid (at 1714 cm^?1) were 1646 dm³ mol^?1 cm^?1 and 743 dm^?3 mol^?1 cm^?1, respectively. The rate was linearly dependent upon the concentration of enzyme in the water pool up to 10 mg cm^?3 and maximum activity was observed at a ratio (w₀) of [H₂O]:[AOT] = 16·7. Using these conditions, and in the presence of 10 mmol dm^?3 sodium taurocholate (TC), the derived Michaelis–Menten parameters V_max and K_m were 57·5 μmol min^?1 mg^?1 and 5·53 mmol dm^?3, respectively. These results are compared with those obtained in an oil-in-water microemulsion system and are discussed in terms of the relative partitioning of the enzyme and the substrate in the aqueous and oil phases and the interfacial concentration of the substrate in the two systems.     

Synthesis and characterization of chitosan‐g‐methacrylic acid and studies of its additional physicochemical properties,such as swelling,metal‐ion sorption,and flocculation behavior

The aim of this study was to examine the synthesis of a graft copolymer of chitosan and methacrylic acid (MAA) by free‐radical polymerization with a potassium peroxymonosulfate/cyclohexanone (CY) redox system in an inert atmosphere. The optimum reaction conditions affording maximum grafting ratio (%G), grafting efficiency (%E), add on (%A), and conversion (%C) were determined. The grafting parameters were found to increase with increasing concentration of MAA up to 24 × 10^?2 mol/dm³, but thereafter, these parameters decreased. With increasing concentration of peroxymonosulfate from 0.6 × 10^?2 to 1.2 × 10^?2 mol/dm³, %G, %A, and %E increased continuously. All of these grafting parameters increased with increasing concentration of CY up to 1.2 × 10^?2 mol/dm³, but beyond this concentration, the grafting parameters decreased. With various concentrations of chitosan from 0.6 to 1.4 g/dm³, the maximum %G, %A, and %E were obtained at 1.4 g/dm³. %G, %A, and %C decreased continuously with various concentrations of hydrogen ions from 2 × 10^?3 to 6 × 10^?3 mol/dm³. The grafting parameters increased with increasing temperature up to 35°C, but thereafter, these parameters decreased. With increasing time period of reaction from 60 to 180 min, %G, %A, and %E increased up to 120 min, but thereafter, these parameters decreased. The graft copolymer was characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sorption of tannic acid on zirconium pillared clay

Zirconium pillared clay (PILC) was prepared using montmorillonite as the base clay. Adsorption of tannic acid (tannin) was studied by a batch equilibrium technique, as a function of adsorbate concentration, temperature, pH, agitation speed, particle size of the adsorbent and ionic strength. The process of uptake is governed by diffusion controlled first‐order reversible rate kinetics. The higher uptake for the pH range 4.0–6.0 was attributed to external hydrogen bonding between phenolic‐OH groups of tannin molecules and the hydrogen bonding sites on the clay. The removal of tannin by adsorption was found to be >99.0% depending on the initial concentration in the pH range of 4.0–6.0. The process involves both film and pore diffusion to different extents. The effects of solute concentration, temperature, agitation speed and particle size on the diffusion rate were investigated. Tannin uptake was found to increase with ionic strength due to the compression of diffuse double layers. The applicability of Langmuir and Freundlich isotherm models has been tested. The maximum adsorption capacity of PILC was found to be 45.8 µmol g^?1 of clay and the affinity constant is 2.9 × 10^?2 dm³ µmol^?1 at 30 °C. Thermodynamic parameters such as ΔG °,ΔH ° and ΔS ° were calculated to predict the nature of adsorption. The isosteric enthalpies of adsorption were also determined and found to decrease with increasing surface coverage. Regeneration with hot water (60 °C) has been investigated for several cycles with a view to recovering the adsorbed tannin and also restoring the sorbent to its original state. Copyright © 2001 Society of Chemical Industry     

Removal of phosphate by adsorption onto oyster shell powder—kinetic studies

Kinetic studies on the removal of phosphate by adsorption onto oyster shell powder have been investigated at 24 °C. The results showed that the equilibrium occurred in 10 min and the equilibrium data followed the Freundlich isotherm. Freundlich constants were found to be k_f, 1.4 × 10^?2, and n, 0.71. The phosphate removal was not influenced by pH over the range 5.0–10.5. Continuous agitation studies at 24 °C and 530 rpm reached equilibrium after 7.7 days, when 24 g dm^?3 of oyster shell powder reduced the phosphate concentration from 50 to 7.0 mg dm^?3. The Lagergren rate constant for the slow adsorption process was observed to be 3.81 × 10^?4 dm³ min^?1. Comparison with calcium carbonate, GR grade, showed that oyster shell powder and CaCO₃ behave more or less in the same way. Copyright © 2004 Society of Chemical Industry     

One pot synthesis of xanthan gum‐g‐N‐vinyl‐2‐pyrrolidone and study of their metal ion sorption behavior and water swelling property

In this article, graft copolymerization of N‐vinyl‐2‐pyrrolidone onto xanthan gum initiated by potassium peroxydiphosphate/Ag⁺ system in an aqueous medium has been studied under oxygen free nitrogen atmosphere. Grafting ratio, grafting efficiency, and add on increase on increasing the concentration of potassium peroxydiphosphate (2.0 × 10^?3 to 12 × 10^?3 mol dm^?3), Ag⁺(0.4 × 10^?3 to 2.8 × 10^?3 mol dm^?3), and hydrogen ion concentration from 2 × 10^?3 to 14.0 × 10^?3 mol dm^?3. Maximum grafting has been obtained when xanthan gum and monomer concentration were 0.4 g dm^?3 and 16 × 10^?2 mol dm^?3, respectively, at 35°C and 120 min. Water swelling capacity, swelling ratio, metal ion uptake, and metal retention capacity have also been studied, and it has been found that graft copolymer shows enhancement in these properties than pure xanthan gum. The graft copolymer has been characterized by FTIR and thermal analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Graft copolymerization of methacrylic acid onto xanthan gum by Fe2+/H2O2 redox initiator

The graft copolymer of xanthan gum with methacrylic acid was synthesized in inert atmosphere by using Fentos reagent as a redox initiator. The effect of reaction conditions on grafting parameters [G(%), E(%), C(%), A(%), H(%), and R_g] was investigated. Similar trend was observed on increasing the concentration of ferrous ion and hydrogen peroxide from 4.0 to 20.0 × 10^?3 mol dm^?3 and 2.5 to 10 × 10^?3 mol dm^?3 respectively, i.e., initially grafting parameters increased and after a certain range of concentration grafting parameters showed decreasing trend. Hydrogen ion shows influenced result i.e., small increment of concentration in hydrogen ion presents much increment in percent of grafting. It was observed that the [G(%), E(%), C(%), A(%), and R_g] increased upto 6.67 × 10^?2 mol dm^?3 concentration of methacylic acid after that it decreased. Maximum G(%) was obtained at minimum concentration of xanthan gum i.e., at 40 × 10^?2 g dm^?3. The optimum temperature and time duration of reaction for maximum percentage of grafting were found to be 45°C and 150 min respectively. Thermogravimetric analysis showed that the xanthan gum‐g‐methacrylic acid is thermally more stable than pure gum. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Anaerobic biodegradation of phenol in sulfide‐rich media

In the refinery industry, the washing processes of middle‐distillates using caustic solutions generate phenol‐ and sulfide‐containing waste streams. The spent caustic liquors generated contain phenols at concentrations higher than 60 g dm^?3(638.3 mmol dm^?3). For sulfur compounds, the average sulfide concentration was 48 g dm^?3(1500 mmol dm^?3) in these streams. The goal of this study was to evaluate the specific impact of phenol and sulfide concentrations towards the phenol‐biodegradation activity of a phenol‐acclimated anaerobic granular sludge. An inhibition model was used to calculate the phenol and sulfide inhibitory concentrations that completely stopped the phenol‐biodegradation activity (IC100). A maximum phenol‐biodegradation activity of 83 µmol g^?1 VSS h^?1 was assessed and the IC100 values were 21.8 mmol dm^?3 and 13.4 mmol dm^?3 for phenol and sulfide respectively. The limitation of the phenol biodegradation flow by phenol inhibition seemed to be related to the more important sensitivity of phenol‐degrading bacteria. The up‐flow anaerobic sludge bed reactor operating in a non‐phenol‐dependent inhibition condition did not present any sensitivity to sulfide concentrations below 9.6 mmol dm^?3. At this residual concentration, the pH and bisulfide ions' concentration might be responsible for the general collapsing of the reactor activity. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of polysaccharide based graft copolymer by using potassium peroxymonosulphate/ascorbic acid as an efficient redox initiator in inert atmosphere

Polysaccharide based graft copolymer (xanthan gum‐g‐4‐vinyl pyridine) was synthesized using potassium peroxymonosulphate/ascorbic acid redox initiator in inert atmosphere at 40°C. By studying the effect of the concentration of monomer, peroxymonosulphate (PMS), ascorbic acid (AA), xanthan gum (XOH), hydrogen ion along with effect of time and temperature on grafting characteristics: grafting ratio (%G), add on (%A), conversion (%C), efficiency (%E), homopolymer (%H), and rate of grafting (Rg), the reaction conditions for optimum grafting were determined. The optimum concentration of AA, H⁺ ion, 4‐VP for maximum grafting were found to be 10.0 × 10^?3 mol dm^?3, 2.5 × 10^?2 mol dm^?3, 10.0 × 10^?3 mol dm^?3, respectively. Maximum %G was obtained at minimum concentration of xanthan gum i.e., at 40.0 × 10^?2 g dm^?3 and at maximum concentration of PMS i.e., at 10.0 × 10^?3 mol dm^?3. The optimum temperature and time duration of reaction for maximum % of grafting were found to be 45°C and 120 min respectively. The synthesized graft copolymer was characterized by FTIR analysis. Thermogravimetric analysis showed that the xanthan gum‐g‐4‐vinyl pyridine is thermally more stable than pure gum. A probable mechanism was suggested for the graft copolymerization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Simultaneous influence of uni-univalent salt aqueous solutions and sodium dodecyl sulfate surfactant on interfacial tension of toluene-water

The simultaneous influence of NaCl, KCl and KI salts and well known sodium dodecyl sulfate (SDS) surfactant on the interfacial tension (IFT) of conventionally used chemical system of toluene-water was studied. The concentration range of salts was within (0.010 to 0.075) mol/dm³ and of surfactant within (1.7 to 26.0)×10^?5 mol/dm³. SDS adsorption on interface is highly intensified in the presence of salts and IFT can reach to 67.1% of its initial value. Accordingly, the role of ions was investigated and the order of salts effectiveness was revealed as KI?KCl>NaCl. The obtained data, with both effects, were nicely reproduced using an equation of state, based on Gibbs adsorption equation and the Langmuir isotherm. Two relevant important adsorption parameters exhibited reasonable variations. Furthermore, the general revealed linear variation of IFT with a previously defined “effective concentration” indicates the strong influence of the surfactant counterions.     

Synthesis of acrylamide/acrylic acid‐based aluminum flocculant for dye reduction and textile wastewater treatment

Aluminum hydroxide‐poly[acrylamide‐co‐(acrylic acid)], AHAMAA, was synthesized with a redox initiator by solution polymerization in which the effects of reactant contents were optimized. The effects of pH, temperature, and initial dye concentration on Congo red reduction were investigated. A mixture of Congo red and direct blue 71, and the composite textile dye wastewater were investigated. Adsorptions of both dyes were more effective in the nonbuffered solution than those in the buffered solution, and Congo red adsorbed more than direct blue 71 at all pHs. The adsorption of Congo red increased with increasing temperature and its initial concentration. Both dyes obeyed the Freundlich adsorption isotherm. The maximum adsorptions in 100 mg dm^?3 solution were 109 ± 0.5 mg g^?1 and 62 ± 6.6 mg g^?1 for Congo red and direct blue 71, respectively. At 150 mg dm^?3 of the mixed Congo red and direct blue 71, the adsorption was 142 ± 2 mg g^?1 by 643 ± 3 mg dm^?3 AHAMAA. The 40 mg g^?1 dyes of the textile effluent wastewater were adsorbed by 500 mg dm^?3 AHAMAA. AHAMAA could decrease turbidity of the composite wastewater containing a mixture of reactive and direct dyes from 405 to 23 NTU. POLYM. ENG. SCI., 50:1535–1546, 2010. © 2010 Society of Plastics Engineers     

Coupled Transport of Zr(IV) through Tri-n-butylphosphate-Xylene-Based Supported Liquid Membranes

Abstract

The transport of Zr(IV) through tri-n-butylphosphate-xylene-based liquid membranes, supported in a polypropylene hydrophobic microporous film, has been studied. The concentration of HNO₃ in the feed solution and tri-n-butylphosphate (TBP) carrier in the membrane were varied, and the flux and permeability coefficients were determined. The optimum conditions found for maximum flux were determined to be 10 mol/dm³ HNO₃ and 2.93 mol/dm³ TBP with a flux value of 12.9 × 10^?6 mol · m^?2 · s^?1. The solvent extraction study revealed that 1.25 to 3.5 protons are involved in zirconium transport, and that two molecules of TBP are involved in the complex formation. The value of protons involved varies with acid concentration. The zirconium ion transport is coupled with nitrate ions transport.     

Chemical decolorization of the azo dye CI Reactive Orange 96 by various organic/inorganic compounds

Batch experiments were performed to investigate the possibility and kinetics of chemical decolorization of the reactive mono‐azo dye CI Reactive Orange 96 (RO 96) with various compounds such as cysteine, ascorbate, Ti(III)‐citrate, Fe(II)‐sulfate, and yeast extract. Cysteine and ascorbate (10 mmol dm^?3 respectively) decolorized RO 96 (0.19 mmol dm^?3) in the absence of oxygen. Increasing the concentration of either reductant (to 20 or 38 mmol dm^?3) enhanced the decolorization rate, showing first‐order kinetics with respect to both the concentration of the dye and of cysteine or ascorbate. The rate constants, k, for cysteine and ascorbate were 0.0003 and 0.0010 dm³mmol^?1 h^?1 respectively at pH 7.1 and 33 °C. Ti(III)‐citrate (10 mmol dm^?3) decolorized RO 96 (0.20 mmol dm^?3) within 5 min, independent of the presence of oxygen. Fe(II)‐sulfate was not effective in the decolorization of RO 96 at pH 8, whereas a rapid decolorization occurred at pH 12. This study suggests that a variety of abiotic processes may be involved in decolorization under anaerobic conditions. © 2002 Society of Chemical Industry     

Adsorption of chlorophyll-a from acetone solution on natural and activated bentonite

The adsorption of chlorophyll-a on bentonite desiccated at 110°C, untreated and acid-treated with H₂SO₄ solutions over a concentration range between 0·25 and 2·50 mol dm^?3, from acetone solution at 25°C has been studied. The adsorption isotherms may be classified as using Giles' classification, as type S (untreated sample and 0·25 mol dm^?3 H₂SO₄-treated sample), type H (0·50 mol dm^?3 H₂SO₄-treated sample) and type L (1·00 and 2·50 mol dm^?3 H₂SO₄-treated samples). This fact suggests that the bentonite surfaces (low, high and medium affinity, respectively) behave in differently relation to the adsorption of the chlorophyll-a molecules. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K_f) of the samples; K_f values range from 0·43 mg kg^?1 for the untreated bentonite up to 108·89 mg kg^?1 for the 0·50 M H₂SO₄-treated bentonite. The removal efficiencies (R) have also been calculated and range from 5·71% for the untreated bentonite up to 85·18% for the 0·50 M H₂SO₄-treated bentonite.