Da-Wei Fang

Study on Physicochemical Properties of Ionic Liquids Based on Alanine [Cnmim][Ala] (n = 2,3,4,5,6)

According to Fukumotos method, a new series of ionic liquids (ILs) based on alanine, [Cnmim][Ala] ( n=2,3,4,5,6), which comprise 1-alkyl-3-methylimidazolium cation ([Cnmim](+)) and alanine anions ([Ala] (-)), were prepared and characterized. In terms of standard addition method, the density and surface tension of amino acid ILs [Cnmim][Ala] (1-alkyl-3-methylimidazolium alpha-aminopropionic acid salt) were measured in the temperature range 293.15-343.15+/-0.05 K. The volume and surface properties of the ILs [Cnmim][Ala] were discussed. A new method of determining parachor of ionic compound was proposed and was applied to estimate the physicochemical properties of amino acid ionic liquids (AAILs): molecular volume, surface tension, molar enthalpy of vaporization, and thermal expansion coefficient. In comparison with Deetlefss method of using neutral parachor contribution, the method proposed in this work makes smaller error in estimating properties of AAILs.

Ionic Parachor and Its Application in Acetic Acid Ionic Liquid Homologue 1-Alkyl-3-methylimidazolium Acetate {[Cnmim][OAc](n = 2,3,4,5,6)}

Five acetic acid ionic liquids (AcAILs) [C(n)mim][OAc](n = 2,3,4,5,6) (1-alkyl-3-methylimidazolium acetate) were prepared by the neutralization method and characterized by (1)HNMR spectroscopy and differential scanning calorimetry (DSC). The values of their density and surface tension were measured at 298.15 ± 0.05 K. Since the AcAILs can strongly form hydrogen bonds with water, the small amounts of water are difficult to remove from the AcAILs by common methods. In order to eliminate the effect of the trace water, the standard addition method (SAM) was applied to these measurements. As a new concept, ionic parachor was put forward. [OAc](-) was seen as a reference ion, and its individual value of ionic parachor was determined in terms of two extrathermodynamic assumptions. Then, the values of ionic parachors of a number of anions, [NTf(2)](-), [Ala](-), [AlCl(4)](-), and [GaCl(4)](-), were obtained by using the value of the ionic parachor of the reference ion; the parachor and surface tension of the investigated ionic liquids in literature were estimated. In comparison, the estimated values correlate quite well with their matching experimental values.

Selective adsorption of molybdenum(VI) from Mo-Re bearing effluent by chemically modified astringent persimmon.

Astringent persimmon was chemically cross-linked by formaldehyde to obtain a novel kind of adsorption gel, which was named as APF gel. The adsorption behaviors of Mo(VI) and Re(VII) along with other coexisting metals onto the APF gel were studied in the present paper. The APF gel was found to be effective for the adsorption of Mo(VI) while the gel is almost completely inert toward rhenium and calcium over the whole hydrochloric acid concentration region. The APF gel has a low affinity for iron, copper, lead, nickel, manganese and zinc ions when the concentration of HCl is higher than 1 mol/L. The gel exhibited selectivity only for Mo(VI) with a remarkably high adsorption capacity 1.05 mol/kg, and the adsorption behavior obeys the Langmuir model. According to the thermodynamic and kinetic studies, the endothermic adsorption process followed pseudo-second order kinetics. Also, its excellent adsorption characteristics for Mo(VI) were confirmed by the adsorption and elution tests using a column packed with the APF gel. The result provides a new approach for the recovery of Mo(VI) from a industrial waste effluent.

Contribution of tertiary amino groups to Re(VII) biosorption on modified corn stalk: competitiveness and regularity.

The effects of basic strength and steric hindrance of gels modified by dimethylamine, diethylamine, di-n-octylamine and di-2-ethylhexylamine, respectively, on rhenium (Re(VII)) adsorption capacity and selectivity were discussed. By comparing with the adsorption of other coexisting metals, such as Mo(VI), Cu(II), Pb(II), Fe(III), Zn(II), Mn(VII) and Ni(II), the gel modified by di-n-octylamine (DNOA-OCS) showed a high affinity for Re(VII) at higher hydrochloric acid concentration (C(H)(+)≥1.0 mol L(-1)), and the maximum adsorption capacity was 98.69 mg g(-1). This article not only described the adsorption behavior but also suggested isotherms, kinetics and thermodynamics of Re(VII) onto the DNOA-OCS gel in an aqueous medium using several models. Further study on adsorption of rhenium in a fixed-bed column packed with the DNOA-OCS gel under continuous and recirculating modes could confirm that the corn stalk gel modified by di-n-octylamine could be used as the adsorbent of Re(VII) from Mo-containing wastewater.

Predicting Properties of Amino Acid Ionic Liquid Homologue of 1-Alkyl-3-methylimidazolium Glycine

Amino acid ionic liquids (AAILs) [C(5)mim][Gly] (1-pentyl-3-methylimidazolium glycine) and [C(6)mim][Gly] (1-hexyl-3-methylimidazolium glycine) were prepared by the neutralization method and characterized by (1)H NMR spectroscopy and differential scanning calorimetry (DSC). The values of their density, surface tension, and refractive index were measured in the temperature range of 293.15-343.15 (±0.05) K. Since the AAILs can strongly form hydrogen bonds with water, the small amounts of water are difficult to remove from the AAILs by common methods. In order to eliminate the effect of the impurity water, the standard addition method (SAM) was applied to these measurements. In terms of semiempirical method, physicochemical properties molecular volume V(m), standard molar entropy S(0), parachor P, surface tension γ, thermal expansion coefficients α, molar refraction R(m), and refractive index n(D) of the homologue of [C(n)mim][Gly] (n = 2-6) were predicted. In comparison with the values of [C(2)mim][Gly] in literature, the predicted results were in good agreement within an order of magnitude.

A new approach for rhenium(VII) recovery by using modified brown algae Laminaria japonica adsorbent

Brown algae Laminaria japonica was chemically modified with sulfuric acid to obtain a crosslinked brown algae gel (CAS). The CAS gel showed a high affinity for Re(VII) comparing with other biomass gels, and the maximum adsorption capacity was evaluated as 37.20 mg g(-1) in case of pH 6, which could be explained by their different adsorption mechanisms. The adsorption equilibrium, kinetics and thermodynamic study for Re(VII) on the CAS gel was discussed in detail by the several models, such as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich model for kinetics analysis, the pseudo first, the second-order, the Elovich and intraparticle diffusion equation for equilibrium analysis. Reutilization of the CAS gel was confirmed up to three adsorption-elution cycles in column-mode operation with no damage of gel, packed in the column. The result also provides a new approach for the recovery of Re(VII) from Re-containing wastewater by using the modified brown algae gel.

Investigation on the removal of Mo(VI) from Mo-Re containing wastewater by chemically modified persimmon residua.

Persimmon waste was chemically modified by crosslinking with concentrated sulfuric acid to obtain a novel kind of adsorption gel, which was termed as crosslinked persimmon tannin (CPT), hereinafter. The adsorption behaviors of Mo(VI) with other coexisting metal ions onto the CPT gel were investigated. The gel exhibited selectivity only for Mo(VI) ions evidenced by the high value of separation factor of molybdenum and rhenium (β(Mo/Re)=164.37), and the adsorption mechanism of Mo(VI) as a multispecies was studied. The molybdenum adsorption behavior conforms to the Langmuir model with a remarkably high adsorption capacity of 0.56 mol/kg. A kinetic study for the adsorption of molybdenum at various temperatures confirmed that the endothermic adsorption process followed pseudo-second order kinetics. Moreover, its excellent adsorption properties and applicability for Mo(VI) were demonstrated by the removal and separation of Mo(VI) from different Mo-Re containing industrial wastewaters.

Estimation of Physicochemical Properties of Ionic Liquid HPReO4 Using Surface Tension and Density

An ionic liquid (IL) HPReO 4 (N-hexylpyridine rheniumate) was prepared. The density and surface tension of the IL were determined in the temperature range of (293.15 to 343.15) K. The ionic volume and surface entropy of the IL were estimated by extrapolation. In terms of Glassers theory, the standard molar entropy and lattice energy of the IL were estimated. Using Kabos method and Rebelos method, the molar enthalpy of vaporization of the IL, Δ l g H m 0 (298 K), at 298 K and Δ l g H m 0 (T b ), at hypothetical normal boiling point, were estimated, respectively. According to the interstice model, the thermal expansion coefficient of IL HPRe0 4 , α, was calculated, and in comparison with experimental value, the magnitude order is in good agreement by 3.32 %.

Physicochemical properties of air and water stable rhenium ionic liquids.

Air and water stable ionic liquids (ILs) based on catalytic functional metal rhenium, [C(n)mim][ReO(4)](n = 2,4,5,6)(1-alkyl-3-methylimidazolium perrhenate), are designed and synthesized. Their density and surface tension are measured in the temperature range of 293.15-343.15 ± 0.05 K. Some physical-chemical properties of the ILs have been calculated or estimated by the empirical methods. The ion parachor is put forward and calculated by two extrathermodynamic assumptions. According to the interstice model, the thermal expansion coefficient of ILs [C(n)mim][ReO(4)], α, are calculated and in comparison with experimental values, their magnitude order is in good agreement.

Measurement of vaporization enthalpy by isothermogravimetrical method and prediction of the polarity for 1-alkyl-3-methylimidazolium acetate {[Cnmim][OAc] (n = 4, 6)} ionic liquids

Ionic liquids 1-butyl-3-methylimidazolium acetate [C4mim][OAc] and 1-hexyl-3-methylimidazolium acetate [C6mim][OAc] were prepared by the neutralization method and confirmed by 1H NMR spectroscopy and differential scanning calorimetry (DSC). Using isothermogravimetrical analysis, the enthalpy of vaporization, ΔglH°m(Tav), at the average temperature, Tav, for [Cnmim][OAc] (n = 4, 6) were determined. Using the established method, the difference of heat capacities between the vapor phase and the liquid phase, ΔglC°pm, for [Cnmim][OAc] (n = 4, 6) were calculated based on the statistical thermodynamics. Therefore, the value of ΔglH°m(Tav) can be transformed into ΔglH°m(298) by using ΔglC°pm. The vaporization enthalpies were also further tested by molecular dynamic (MD) simulations, and the results were in good agreement with the corresponding experimental values. In terms of the new scale of polarity for ILs, the order of the polarity of [Cnmim][OAc] (n = 4, 6) was also predicted and good agreement with our experiences.