Huixin Zhang

Recovery of isoflavone aglycones from soy whey wastewater using foam fractionation and acidic hydrolysis.

The purpose of this work was to recover isoflavone aglycones from industrial soy whey wastewater, where the isoflavone aglycones mainly existed in the form of β-glycosides. First, foam fractionation was used for effectively concentrating the total soy isoflavones, including isoflavone aglycones and β-glycosides, from the wastewater. Fourier transform infrared spectroscopy indicated the existence of complexes of soy isoflavones and soy proteins. When soy proteins were used as the collectors, a high enrichment ratio of 3.68 was obtained under the optimal operating conditions of temperature of 50 °C, pH of 5.0, volumetric air flow rate of 100 mL/min, and loading liquid height of 400 mm. Subsequently, acidic hydrolysis was used for hydrolyzing β-glycosides in the foamate into aglycones. Using response surface methodology, a hydrolytic percentage could reach 96% under the optimum hydrolysis conditions of hydrolytic temperature of 80 °C, hydrochloric acid concentration of 1.37 mol/L, and hydrolytic time of 90 min.

Magnetic Pb(II) Ion-Imprinted Polymer Prepared by Surface Imprinting Technique and its Adsorption Properties

A novel magnetic Pb(II) ion-imprinted polymer was prepared via surface ion-imprinting technique by using magnetic Fe3O4@SiO2 microspheres as supporter, Pb(II) as template ion, methacrylic acid and salicylaldoxime as monomers, and ethylene glycol dimethacrylate as crosslinker. The product was characterized by FT-IR, VSM, XRD, and SEM. The adsorption experiments showed that the imprinted polymer was employed successfully in comparison with non-imprinted polymer. When the temperature was in a range of 277 K to 291 K the maximum adsorption was about 81.83 mg/g with an optimal pH 6.0. Its relative selectivity coefficient values of Pb(II)/Cu(II), Pb(II)/Zn(II), and Pb(II)/Cd(II) were 2.60, 6.38, and 7.89 times greater than the ones of the magnetic non-imprinted polymer. The Langmuir adsorption model was more favorable for M-IIP than Freundlich or Temkin adsorption models. The Scatchard analysis suggested that M-IIP was processed with two kinds of binding sites with different affinity. Thermodynamic experiment showed that the adsorption was a spontaneous and endothermic process for Pb(II). The mechanism for Pb(II) adsorption on the imprinted polymer was also investigated.

Chromium removal with cross-linked chitosan adsorption and base-precipitation combination

A novel technique for a complete removal of both Cr(VI) and Cr(III) ions, namely cross-linked chitosan (CCTS) adsorption and base-precipitation combination, was studied in this work in great detail. The optimum conditions for Cr(VI) adsorption onto CCTS were determined as a function of pH, CCTS dosage and contact time, while Cr(III) precipitation was investigated as a function of pH value. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the Cr(VI) adsorption isotherm on CCTS. The Langmuir model agreed much better with experimental data than the Freundlich and D-R by a correlation coefficient (R²) of 0.994. The capacity and ΔG° of CCTS for Cr(VI) were 70.4 mg/g and -26.6 kJ/mol respectively, indicating the feasible and spontaneous nature of the Cr(VI) sorption process. This combined technique was applied for real wastewater treatment from the electroplating industry and obtained a one-off retention in solution not more than 0.5 mg/L for both Cr(VI) and Cr total. These results meet the Chinese standards for effluent discharge.

Magnetic Zn (II) ion-imprinted polymer prepared by the surface imprinting technique and its adsorption properties

A novel magnetic Zn (II) ion-imprinted polymer was prepared by the surface ion-imprinted technique by using magnetic Fe3O4@SiO2 microspheres as supporter, methacrylic acid and salicylaldoxime as monomers, ethylene glycol dimethacrylate as the crosslinker. The products were characterized by Fourier transform infrared, X-ray photoelectron spectrometer, vibrating sample magnetometer and scanning electron microscope. The adsorption experiments showed that the imprinted polymer was employed successfully in comparison with non-imprinted polymer. When the temperature was in a range of 291–297 K, the maximum adsorption was about 52.69 mg g−1 with an optimal pH 6.0 for an equilibrium time of 40 min. The imprinted polymer possessed high selectivity and specific recognition towards Zn (II). The Langmuir adsorption model was more favourable than the Freundlich or the Temkin adsorption model. Thermodynamic experiment showed that the adsorption was a spontaneous and endothermic process for Zn (II). The mechanism for Zn (II) adsorption on the imprinted polymer was investigated.

Synthesis of [H22·Zr5·WO4·10 P2O7]n·26n H2O by response surface methodology to adsorb Ca(II) in manganiferous wastewater

The presence of calcium challenges the manganese recovery from manganiferous wastewater. In this paper, a kind of mesoporous material named [H22·Zr5·WO4·10 P2O7]n·6n H2O is investigated as an ion exchanger to remove calcium ion from manganese slag percolate. The synthesis of zirconium tungstopyrophosphate (ZWPP) was optimized by response surface methodology , and its adsorption capacity and equilibrium were tested. The adsorption data have been confirmed by the use of various techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy and Brunauer, Emmett and Teller. An empirical formula of ZWPP was obtained by X-ray diffraction and thermal analysis. The adsorption process conformed to pseudo-second-order kinetics and the Langmuir isotherm, which described the equilibrium powerfully. Furthermore, different thermodynamic parameters were evaluated. And it was found that Gibbs free energy change is negative, indicating the adsorption process was spontaneous, whereas the enthalpy change and entropy change are positive indicating endothermy and increased randomness nature of the adsorption process. As a result, ZWPP could be a possible ion exchanger material in the area of removing Ca2+ from processing water or wastewater.

Synthesis of [H22• Zr5• WO4•10 P2O7]n • 26n H2O by RSM to adsorb Ca(II) in manganiferous wastewater

The presence of calcium challenges the manganese recovery from manganiferous wastewater. In this paper, a kind of mesoporous material named [H22·Zr5·WO4·10 P2O7]n·6n H2O is investigated as an ion exchanger to remove calcium ion from manganese slag percolate. The synthesis of zirconium tungstopyrophosphate (ZWPP) was optimized by response surface methodology , and its adsorption capacity and equilibrium were tested. The adsorption data have been confirmed by the use of various techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy and Brunauer, Emmett and Teller. An empirical formula of ZWPP was obtained by X-ray diffraction and thermal analysis. The adsorption process conformed to pseudo-second-order kinetics and the Langmuir isotherm, which described the equilibrium powerfully. Furthermore, different thermodynamic parameters were evaluated. And it was found that Gibbs free energy change is negative, indicating the adsorption process was spontaneous, whereas the enthalpy change and entropy change are positive indicating endothermy and increased randomness nature of the adsorption process. As a result, ZWPP could be a possible ion exchanger material in the area of removing Ca2+ from processing water or wastewater.

Construction of adsorptive nanorods from polyoxometalates and ionic liquid and their adsorption properties for silver ion from AMD

A new structure of hybrid nanorods adsorbent ([n-BBIM]9PW9O34) was synthesized by a simple molecular assembly of polyoxometalates with ionic liquids (ILs). The nanocomposite was characterized by Fourier transform infrared (FT-IR), ultraviolet-visible (UV-Vis), scanning electron microscope, energy dispersive X-ray and X-ray diffractometer. Adsorption of silver from acid mine drainage (AMD) was studied using batch experiments. The impact of several parameters, like ion concentration, pH, adsorbent dosage, and temperature was elucidated and optimization was carried out by single-factor experiment and response surface methodology. Analysis of variance of the quadratic model suggested that experimental data were excellently fitted to the quadratic model. Optimum conditions for removal of Ag(+) from AMD were determined to be an initial concentration 143 mg/L, adsorbent dosage 2.69 g/L, temperature 35 °C to achieve the maximum adsorption of Ag(+) 99.03%, which was very close to the predicted value (100%). The adsorption was confirmed as oxidation-reduction mechanism following a complexation process, and has been verified according to results from FT-IR and UV-vis spectra. The selective experiment suggested that the nanorods adsorbent could adsorb silver ions in AMD well. Based on the adsorption/desorption study result, the adsorbent can be efficiently recovered.

Several salts of pyrophosphoric heteropoly acid: characterization and ion-exchange behavior for calcium removal from manganiferous water

AbstractIn this study, five salts of pyrophosphoric heteropoly acid were synthesized as ion exchanger to remove Ca2+ in manganiferous water and characterized by Fourier Transform Infrared spectroscopy and scanning electron microscope. Their performances like ion-exchange capacities, selectivities were tested and the results were compared with zirconium phosphate and molecular sieves (13X and 5A). It can be found that Ca exchange reaction is easy to occur on these ion exchangers. The outcomes for zirconium tungstophosphate (ZWPP) were the best among the mentioned salts, its dynamic exchange capacity has been verified through static and column experiments. The specific surface areas, pore structure, and particle size of ZWPP were also calculated, therein ZWPP being classified into materials with nanoparticles and mesoporosity. Therefore, the salts of pyrophosphoric heteropoly acids, especially ZWPP, can be used as a potential ion exchanger for Ca removal in processed water and effluents from metallurgical i...