Sorption of cesium on montmorillonite and effects of salt concentration

The sorption behavior of cesium on montmorillonite type clay was studied by using radioactivity measurements. Concentrations of Cs⁺ ions ranged from 10^–6 to 10^–2M. Cesium retention reduced with increasing salt concentration which was varied between 10^–4 and 10^–1M. Selectivity coefficients K_Cs–Na for the exchange between Cs and Na were calculated for different equivalent fractions of Cs on the solid phase. Using theK _Cs–Na values, free energy change was found to be 7.8 kJ/mol. The data could be fitted to a Freundlich isotherm, and empirical Freundlich parameters enabled the generation of a site distribution function. By fitting the data to the Dubinin-Radushkevich (D-R) isotherm, a mean energy of sorption of 8.6 kJ/mole was calculated which corresponds to the energy of ion exchange reactions. The values of energy changes calculated by using two different methods were in good agreement.     

Sorption and desorption of thorium from aqueous solutions by montmorillonite

The sorption and desorption of thorium on a West Anatolian montmorillonite has been studied by application of a batch technique. Experimental procedures are outlined and results for thorium contacted with montmorillonite are reported and discussed. The thorium concentration range was between 200–4000 ppm (8.5×10^–4–1.7×10^–2M). The sorption and desorption coefficients varied between 1.586–0.216 ml g^–1 and 0.829–0.168 ml g^–1, respectively, and sorption was not fully reversible. The data could be fitted to Freundlich and Langmuir isotherms. The quantity of the sorbed thorium was much lower than its theoretical CEC. This was attributed to a blocking of montmorillonite's CEC by thorium islands in the interlayer.     

Sorption kinetics of indium,iron, and zinc ions on modified montmorillonite

Adsorption integral kinetic curves of indium and iron(III) ions were obtained from model solutions on a montmorillonite Metosol modified with di(2-ethylhexyl)phosphoric acid. The adsorption kinetics can be reliably described with pseudofirst and pseudosecond order models. Adsorption of metal ions on a Metosol reagent occurs in a mixed diffusion mode. The rate constants of external and internal diffusion on the Metosol reagent are greater for In³⁺ ions than those for Fe³⁺ one, so that it can be used for the selective sorption of indium from complex technological solutions in zinc production.     

Sorption of phenols from water in column systems using surfactant-modified montmorillonite

The sorption of phenol, m-nitrophenol (m-NP), and o-cresol from water onto montmorillonite modified with cetyltrimethylammonium bromide (CTAB) in a column was studied. The sorption isotherms were fitted by the Langmuir equation. Column experiments were performed at 25 degrees C to determine the breakthrough curves at different flow rates, feed sorbate concentrations, and bed lengths. It was shown that the proposed constant-pattern wave approach with the Langmuir model could well describe the breakthrough curves. The time required when the effluent concentration reached half of the feed concentration (t(1/2)) decreased with increasing feed flow rate, but the mass transfer coefficient (KLa) increased. In addition, an increase in feed sorbate concentration led to a decrease of both values of t(1/2) and KLa. The effect of axial dispersion on breakthrough dynamics in these sorption systems was finally discussed.     

Sorption behavior of 2,4-dichlorophenol on marine sediment

The sorption behavior of 2,4-dichlorophenol on marine sediments treated by different methods was investigated systematically. The sorption of 2,4-dichlorophenol on marine sediments was completed mainly via ion exchange and surface polar sorption. Both the Freundlich and Langmuir isotherms were fit for describing its sorption behavior. The sorption behavior of 2,4-dichlorophenol was affected by various factors including aqueous salinity and temperature. The sorption amount of 2,4-dichlorophenol on marine sediments increased with increasing ion strength, but decreased with increasing temperature.     

Sorption behavior of acidic herbicides on carbon nanotubes

Carbon nanotubes and graphitized carbon are investigated as adsorbents for solid phase extraction of dicamba and 2,4,5-T, two phenoxyalkanoic acid herbicides. These adsorbents have much greater adsorption capability than that of C₁₈ bonded silica, which was also tested for comparison studies. The adsorption capacity increases remarkably at lower pH of the sample solution. Freundlich isotherms were applied to analyze the data. Our studies suggest that carbon nanotubes have great potential applications in environmental analysis.     

Adsorption behavior of Pb(II) on montmorillonite

The present work investigated the adsorption and desorption behaviors of Pb(II) on montmorillonite. The adsorption experiments were carried out using batch process. The results show that the adsorption is dependent on the pH value of the medium, and the uptake of Pb(II) increases with the pH increasing in the pH range of 2.0–10.0. The adsorption kinetics is in better agreement with pseudo-second order kinetics, and the adsorption data is a good fit with Langmuir isotherm. The presence of EDTA may result in a decrease of the amount of Pb(II) adsorbed. The presence of electrolyte and EDTA may enhance the desorption of Pb(II) ions adsorbed. The adsorption mechanism of Pb(II) on montmorillonite may be explained in two aspects: the chemical binding between Pb(II) ions and surface hydroxyl groups; and the electrostatic binding between Pb(II) ions and the permanent negatively charged sites of montmorillonite.     

Sorption behavior of gamma-irradiated silica gel

The effect of Pb(II) and non-ionic surfactants (oxyethylate alcohols OS-10 and ALM-10) on the rate of intraparticle diffusion and on to the equilibrium sorption on Purolite C 106 cation exchanger in hydrogen form was investigated. The sorption of Pb(II) cations and in free state and bonded to the surfactant was measured. The coefficients of intraparticle diffusion were also calculated.     

Sorption behavior of tritiated water on Armenian natural zeolites

Summary The sorptive behavior of tritiated water on natural, irradiated, chemically treated and heated at high temperatures Armenian zeolites was studied and their capacity for the separation and enrichment of tritiated water was evaluated. The distribution coefficients from the batch experiments were calculated for different zeolites and vary between 0.23 and 3.01. The influence of temperature, acidity, basicity, specific activity, electron and gamma-irradiation on sorption has been studied.     

Sorption and desorption of Co(II) on montmorillonite in presence and absence of fulvic acid

Sorption and desorption of Co(II) on montmorillonite under ambient conditions as a function of pH, ionic strength and fulvic acid are studied by batch technique. The results indicate that the sorption of Co(II) is dependent on pH, and ionic strength. The sorption-desorption hysteresis is found in the desorption tests. Surface complexation is considered as the main sorption mechanism of Co(II) on montmorillonite. The presence of fulvic acid (FA) enhances the sorption of Co(II) on montmorillonite. Montmorillonite is considered as a promising candidate for the solidification and pre-concentration of Co(II) from large volume of solutions.     

Viscoelastic behavior of epoxy prepolymer/organophilic montmorillonite dispersions

Dispersions of a bisphenol A‐based epoxy resin with an organophilic montmorillonite (Nanofil 919) were studied by X‐ray diffraction and oscillatory shear rheometry. X‐ray studies reveal that the clay is intercalated by the epoxy and forms stable dispersions. The viscoelastic behavior of the nanodispersions was measured as a function of the Nanofil concentration and temperature. An increase in both G′ and G″ moduli was detected as the concentration increases. Furthermore, a transition from a liquid‐like behavior, at low temperatures, to a solid‐like behavior, at higher temperatures, was observed for all the samples. This transition is accounted for the formation of a percolated structure of interconnected tactoids through hydrophobic interactions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1837–1844, 2008     

Sorption behavior of germanium(IV) on titanium dioxide nanoparticles

Titanium dioxide nanoparticles were employed for the sorption of Ge(IV) ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, and temperature. The sorption process was found to be fast, equilibrium was reached within 3 min. A maximum sorption could be achieved from solution when the pH ranges between 4.0 and 11.0. Sorbed Ge(IV) ions can be completely desorbed with 2 mL of 0.3 mol L⁻¹ K₃PO₄-1.0 mol L⁻¹ H₂SO₄ mixture solution. The kinetic experimental data properly correlate with the second-order kinetic model (k ₂ = 0.88 g mg⁻¹ min⁻¹ (25°C)), Reichenberg equation and Morris-Weber model. The estimated E _a for Ge(IV) adsorption on nano-TiO₂ was 19.66 kJ mol⁻¹. The overall rate process appears to be influenced by intra-particle diffusion. The sorption data could be well interpreted with the Langmuir and Dubinin-Radushkevich (D-R) type sorption isotherms. The D-R parameters were calculated to be K = −0.00321 mol₂ kJ⁻², q _m = 0.59 mmol g⁻¹ and E = 12.48 kJ mol⁻¹ at room temperature. Furthermore, the thermodynamic parameters were also determined, and the ΔH ⁰ and ΔG ⁰ values indicated a spontaneous exothermic behavior.     

Nonisothermal crystallization behavior of syndiotactic polystyrene/montmorillonite nanocomposites

X‐ray diffraction methods and differential scanning calorimetry were used to investigate the crystalline structure and crystallization kinetics of syndiotactic polystyrene (sPS)/clay nanocomposites. X‐ray diffraction data showed the presence of polymorphism in sPS/montmorillonite (MMT) nanocomposites, which was strongly dependent on the processing conditions (premelting temperature and cooling rate) of the sPS/MMT nanocomposites and on the content of MMT in the sPS/MMT nanocomposites. The α‐crystalline form could be transformed into β‐crystalline forms at higher premelting temperatures. The nonisothermal melt‐crystallization kinetics and melting behavior of the sPS/MMT nanocomposites were also studied at various cooling rates. The correlation of the crystallization kinetics, melting behavior, and crystalline structure of the sPS/MMT nanocomposites was examined. The results indicated that the addition of a small amount of MMT to sPS caused a change in the mechanism of nucleation and the crystal growth of the sPS crystallite. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 560–570, 2003     

Sorption behavior of Zn(II) ions on synthesized hydroxyapatites

Calcium hydroxyapatite (CaHAP) and barium hydroxyapatite (BaHAP) have been prepared by a wet method from aqueous solutions with cation/P molar ratio of 1.67. The prepared particles were characterized using XRD, IR, TG-DTA and BET-N(2) adsorption measurements. The potential of the synthesized hydroxyapatites to remove Zn(II) from aqueous solutions was investigated in batch reactor under different experimental conditions. Both hydroxyapatites remove Zn(II) from aqueous solutions with an efficiency higher than 98% at initial pH around 6-8. The data reveal that the initial uptake was rapid and equilibrium was established in 20 and 60 min for CaHAP and BaHAP. The sorption process follows the pseudo-first-order kinetic with a rate constant (k(ads)) equals to 1.06x10(-2) and 1.91x10(-2) min(-1) for CaHAP and BaHAP, respectively. Zn(II) removal was quantitatively evaluated using Langmuir isotherm model and the monolayer sorption capacity (Q(max)) shows the values 102.04 and 36.62 mg g(-1) for CaHAP and BaHAP clarifying the high affinity of these novel sorbents for Zn(II) ions. Kinetically, the prepared apatites are feasible sorbents retain Zn(II) ions through a favorable and spontaneous sorption process. The possibility of metal recovery and regeneration of hydroxyapatites were investigated using several eluting agents include hydrochloric acids, double distilled water, calcium chloride, barium hydroxide, and copper chloride. Different desorption levels were obtained with the different adsorbents and the maximum recovery yield was achieved with copper chloride.     

Sorption behavior of Am(III) onto granite

Sorption behavior of Am(III) onto granite was investigated. The distribution coefficient (K _d ) of Am(III) onto granite was determined in the solution of which pH was ranged from 2.9 to 11.4 and ionic strength was set at 10⁻² and 10⁻¹. TheK _d values were found to increase with increasing pH and with decreasing ionic strength. The obtained data were successfully analyzed by applying an electrical double layer model. The optimum parameter values of the double layer electrostatics and adsorption reactions were obtained, and the selective adsorption behavior of Am(III) onto the granite was discussed.     

Morphological and mechanical behavior of montmorillonite grafted block copolymer brushes

Here we report the phase behavior of a family of montmorillonite (MMT) block copolymer brushes (MBBs), a novel class of polymer nanocomposites. MBBs are comprised of discrete MMT platelets encapsulated with block copolymer brushes. These MBBs were synthesized via surface-initiated atom transfer radical polymerization using halogenated alkylammonium surfactants to localize initiation sites on the clay surfaces. Two styreninc MBB systems—poly(styrene-b-n-butyl acrylate) and poly(styrene-b-t-butyl acrylate)—were prepared varying the composition and total 80–250 kDa. MBB materials were compared with their non-clay bulk block copolymer counterparts via electron microscopy and a host of mechanical tests in both the solid and melt states. Notably, MBBs have similar melt-state rheological properties compared to neat block copolymers and are thus amenable to current processing techniques. MBBs were found to self-assemble into single grain morphologies across incredibly large areas (>3 μm) which resulted in extremely well-ordered, defect-free lamellar structures with applications in microelectronics. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 353–361     

Sorption mechanism of U(VI) on a reference montmorillonite: Binding to the internal and external surfaces

Batch type experiments of U(VI) sorption on a reference montmorillonite(SWy-2) were carried out over wide ranges of pH, ionic strength, and totalU(VI) concentration. The influences of these factors on the sorption behaviorof U(VI) were analyzed to gain a macroscopic understanding of the sorptionmechanism. The sorption of U(VI) on montmorillonite showed a distinct dependencyon ionic strength. When it was low (0.01 or 0.001M), almost all of the totalU(VI) was sorbed over the whole pH range studied, therefore, the dependencyon pH was not clear. But the sorption of U(VI) on montmorillonite showed asorption pH edge in the high ionic strength condition (0.1M), like those onother clay minerals, kaolinite and chlorite. A mechanistic model was establishedby considering the mineral structure of montmorillonite together with ourprevious EPR result, which successfully explained the U(VI) sorption on montmorilloniteover the whole range of experimental conditions. The model describes the U(VI)sorption on montmorillonite as simultaneous and competitive reactions of ionexchange and surface complexation, whose relative contribution to the totalsorption depends on pH and ionic strength. At low ionic strength and low pHconditions, ion exchange was the dominant mechanism for U(VI) sorption onmontmorillonite. At high ionic strength and high pH conditions, surface complexationwas the dominant     

丁香酚在改性蒙脱土修饰电极上的电化学行为及测定

制备了十八烷基三甲基溴化铵( STMAB)改性蒙脱土修饰电极,用循环伏安法和差分脉冲伏安法(DPV)研究了丁香酚在该电极上的电化学行为.在pH6.0 PBS电解液中,丁香酚在该电极上的电极反应受扩散控制,转移电子数等于质子数n=m=2,电极有效面积Aeff=0.034cm2,扩散系数D =2.58×10-6cm2/s....