Study of Isothermal Equilibrium,Kinetics and Thermodynamics of Adsorptive Desulfurization on Synthesized Cu~ⅠY~ⅢY Zeolite

Deep adsorptive desulfurization of low sulfur content gasoline via zeolite is a promising process.Herein,the Cu~ⅠY~ⅢY zeolite was prepared and the effect of adsorption conditions and aromatics on the performance of adsorptive desulfurization was studied.And the isothermal equilibrium and kinetics were also investigated.The results showed that upon using 10 m L of model oil and 0.2 g of the Cu~ⅠY~ⅢY adsorbent during the adsorption reaction,which was carried out at 323 K for 60 min,the benzothiophene(BT) desulfurization rate reached 98.4%.The impact of aromatics on the adsorptive desulfurization over the Cu~ⅠY~ⅢY zeolite decreased in the following order:ortho-xylene > meta-xylene > para-xylene.The equilibrium isotherm shows that the adsorption of benzothiophene over the as-prepared CuIYIIIY zeolite can be represented by the Langmuir model.And the kinetics can be more perfectly represented by the pseudo-second-order model than that of the pseudo-first-order one.The thermodynamic parameters(ΔG,ΔH) were both negative,which suggested that the adsorption process is monostratal,mass transfer controlled,spontaneous,and exothermic.

Measurement and prediction of isothermal vapor–liquid equilibrium of a-pinene+camphene/longifolene+abietic acid+palustric acid+neoabietic acid systems

The vapor–liquid equilibrium(VLE)data of a-pinene+camphene+[abietic acid+palustric acid+neoabietic acid]and a-pinene+longifolene+[abietic acid+palustric acid+neoabietic acid]systems at 313.15 K,333.15 K and 358.15 K were measured by headspace gas chromatography(HSGC).These data was compared with the predictions value by conductor-like screening model for realistic solvation(COSMO-RS).Moreover,the calculated data of COSMO-RS and Non-Random Two-Liquids(NRTL)models showed good agreement with the experimental data.It was found that the three resin acids inhibited the volatility of a-pinene,camphene and longifolene and resulted in the decrease of total pressure.Moreover,HE(HB)contributes the most to the excess enthalpy and the hydrogen bonding interaction is the dominant intermolecular force of a-pinene,camphene and longifolene with the three resin acids.In addition,the geometric structures optimization and binding energy were obtained by the DFT to further illustrate the hydrogen bonding interaction and the effects of the addition of the three resin acids on the isothermal VLE.

Selective removal of phenol by spherical particles of α-,β- and γ-cyclodextrin polymers： kinetics and isothermal equilibrium

Spherical particles of α-,β- and γ-cyclodextrin （CD） polymers to efficiently remove phenol from waste water were prepared by reverse suspension polymerization with epichlorohydrin as crosslinker in liquid paraffin. By controlling the amounts of crosslinker and water, well- defined spherical polymer particles with controllable size were obtained. Due to the selective inclusion associations between CD groups and phenol, these CD spherical polymer particles were demonstrated to be ideal candidates for removal of phenol. Among them β-CD polymer particles showed the best performance. The kinetics and isothermal equilibrium models were used to fit the experimental data of phenol removal from aqueous solution using these CD polymer particles. It was found that the kinetics followed the Ho and Mckay equation, suggesting that the adsorption process of phenol was controlled by diffusion and the host-guest interaction between CD and phenol. Equilibrium isothermal data can be well fitted by the Freundlich equation. The negative free energy change indicated the spontaneous nature of adsorption of phenol by α-,β- and γ-CD spherical polymer particles, while the lowest free energy for β-CD polymer reflected its best adsorption ability, compared to α- and γ- CD polymer particles.

Adsorption equilibrium for Z-ligustilide on C18-bonded silica from supercritical carbon dioxide

Adsorption equilibrium is of great importance for the preparative supercritical fluid chromatography(pre-SFC) in defining supercritical adsorption behavior and the industrial amplification.This paper presents adsorption isotherms of Z-ligustilide from supercritical carbon dioxide(SC-CO_2) on C18-bonded silica.Adsorption behavior was studied at 305.15 K,313.15 K and 323.15 K with SC-CO_2 density varying from 0.687 g·cm^(-3) to0.863 g·cm^(-3) with the elution by characteristic points(ECP) method.The adsorption amount of Z-ligustilide from SC-CO_2 on C18-bonded silica decreased with the increasing density of the mobile phase as well as the increasing temperature.Adsorption equilibrium data were fitted by Langmuir and Freundlich isotherm models,and the Langmuir isotherm model performed better for describing the whole adsorption process on the column.The monolayer saturation adsorption capacity of Z-ligustilide is in the range of 3.0 × 10^(-4) mg·cm^(-3) to5.5 × 10^(-4) mg·cm^(-3) with an average value of 4.0 × 10^(-4) mg·cm^(-3).

Error Analysis of Adsorption Isotherm Models for Acid Dyes onto Bamboo Derived Activated Carbon

High surface area activated carbons were produced by thermal activation of waste bamboo scaffolding with phosphoric acid.Single component equilibrium dye adsorption was conducted on the carbons produced and compared with a commercially available carbon.Two acid dyes with different molecular sizes,namely Acid Yellow 117(AY117) and Acid Blue 25(AB25),were used to evaluate the adsorption capacity of the produced carbons.It was found that the dye with smaller molecular size,AB 25,was readily adsorbed onto the produced carbon,nearly three times higher than a commercially available carbon,while the larger size dye,AY117,showed little adsorption.The experimental data were analyzed using isotherm equations including Langmuir,Freundlich,Tempkin,Toth,Redlich-Peterson and Sips equations.The equilibrium data were then analyzed using five different non-linear error analysis methods.

Removal of diclofenac from aqueous solution with multi-walled carbon nanotubes modified by nitric acid

Modified multi-walled carbon nanotubes(MWCNTs) were used as adsorbents for removal of diclofenac. The reaction conditions were examined. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were applied to determine appropriate equilibrium expression. The results show that the experimental data fit the Freundlich equation well. Thermodynamic parameters show that the adsorption process is spontaneous and exothermic. The kinetic study indicates that the adsorption of diclofenac can be well described with the pseudo-second-order kinetic model and the process is controlled by multiple steps.

Competitive adsorption of Cu(II) and Pb(II) ions from aqueous solutions by Ca-alginate immobilized activated carbon and Saccharomyces cerevisiae

To establish a theoretical foundation for simultaneous removal of multi-heavy metals,the adsorption of Cu（Ⅱ） and Pb（Ⅱ） ions from their single and binary systems by Ca-alginate immobilized activated carbon and Saccharomyces cerevisiae （CAS） was investigated.The CAS beads were characterized by Scanning electron microscope （SEM） and Fourier transformed infrared spectroscopy （FTTR）.The effect of initial pH,adsorbent dosage,contact time and initial metal ions concentration on the adsorption process was systematically investigated.The experimental maximum contents of Cu（Ⅱ） and Pb（Ⅱ） uptake capacity were determined as 64.90 and 166.31 mg/g,respectively.The pseudo-second-order rate equation and Langmuir isotherm model could explain respectively the kinetic and isotherm experimental data of Cu（Ⅱ） and Pb（Ⅱ） ions in single-component systems with much satisfaction.The experimental adsorption data of Cu（Ⅱ） and Pb（Ⅱ） ions in binary system were best described by the extended Freundlich isotherm and the extended Langmuir isotherm,respectively.The removal of Cu（lⅡ） ions was more significantly influenced by the presence of the coexistent Pb（Ⅱ） species,while the Pb（Ⅱ） removal was affected slightly by varying the initial concentration of Cu（Ⅱ）.The CAS was successfully regenerated using 1 mol/L HNO3 solution.

Evaluation of Corrosion Inhibition of NO_(2)^(-) Intercalated LDHs on Steel Coated by Cement Paste

The purpose of this study is to apply the steel coated by cement paste to evaluate the corrosion inhibition of NO_(2)^(-) intercalated Mg-Al layered double hydroxides(LDHs),which was prepared by a conventional calcination-rehydration method.The chloride equilibrium isotherm,open-circuit potential(OCP)and electrochemical impedance spectroscopy(EIS)of steel in the saturated Ca(OH)_(2) solution contaminated by chloride ions were measured.The microstructures of as-obtained LDHs and cement paste containing the LDHs were observed by scanning electron microscope(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)and mercury intrusion porosimetry(MIP).It is found that the technique using the steel coated by the cement paste layer containing the LDHs to represent the steel in real concrete can be applied to accurately evaluate the corrosion inhibition performance of NO_(2)^(-) intercalated LDHs in a short duration.The addition of NO_(2)^(-) intercalated Mg-Al LDHs can improve the absorption capacity of Cl^(-) and the anti-corrosion property of cement paste layer.The combination actions of the refinement of pore structure,uptake of chloride ions and release of inhibitive NO_(2)^(-) contribute to the better corrosion protection property of cement paste layer.Moreover,a schematic mechanism of chloride intrusion for the steel specimen with cement paste layer is developed.

EXCHANGE ADSORPTION EQUILIBRIA OF AMMONIUM ON CATION-VERMICULITE MINERALS

Experiment was designed under different pH and temperature conditions to analysis the NH4+ exchange capacity of Na+-vermiculite,Ca2+-vermiculite and Mg2+-vermiculite clay minerals pre-treated using NaCl,CaCl2 and MgCl2 solutions respectively.The results indicated that the exchange reactions occurred most rapidly at the proceeding 80 minutes and approached to equilibrium by about 120 minutes.The exchange quantity of ammonium on the vermiculite(at initial ammonium concentration of 673mg/L)varied with pH with a peak value of 28.36mg/g on Na+-vermiculite,23.01mg/g on Ca2+-vermiculite,20.14mg/g on Mg2+-vermiculite,18.04mg/g on natural vermiculite at pH 7.The exchange and adsorption isotherm of NH4+ on cation-vermiculite can be described by Langmuir equation.