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Zhao Y.,Tianjin University | Jiang Z.,Tianjin University | Xiao L.,Tianjin University | Xu T.,Tianjin University | And 3 more authors.
Solid State Ionics | Year: 2011

Hydroxyapatite (BMHA) particles, using Ca(OH)2 and H 3PO4 as the reactants and chondroitin sulfate as the template/catalyst, are synthesized through a biomimetic mineralization approach. The BMHA particles are then incorporated into chitosan (CS) matrices to prepare the CS/BMHA hybrid membranes. Thermal stability of the hybrid membranes is enhanced owing to the formation of strong hydrogen bonds between the BMHA surface and CS molecules. The methanol crossover of the CS/BMHA membranes is decreased due to their prolonged methanol transfer pathways and the improved hydrophilicity. The hybrid membranes exhibit at most 127% higher proton conductivity than the pure CS membrane because of the high intrinsic proton conductivity of the BMHA particles, the strong hydrophilicity and the large free volume of the membranes. In particular, the hybrid membrane with BMHA content of 8 wt% exhibits1.8 times higher selectivity of proton to methanol than the pure CS membrane. © 2011 Elsevier B.V. All rights reserved. Source


Zhang J.,Tianjin University | He Z.,Tianjin University | Li W.,Tianjin University | Han Y.,Tianjin Key Laboratory of Membrane Science and Desalination Technology
RSC Advances | Year: 2012

The deactivation mechanism of AuCl 3 catalyst in the reaction of acetylene hydrochlorination was studied by using AuCl 3 dimer model and the density functional theory (DFT) method. Four possible paths for the acetylene hydrochlorination reaction catalyzed by AuCl 3 were illustrated with corresponding transition states. The activation free energies and reaction rate constants of the four paths were also analyzed. It is apparent that when HCl and C 2H 2 coadsorbed on the AuCl 3 dimer, the C 2H 2 was co-catalyzed by HCl and the AuCl 3 dimer to produce C 2H 3Cl and the reaction energy barrier was as low as 23.35 kcal mol -1. If the HCl in the gas phase could not adsorb on the Au site within the set time, the intermediate chlorovinyl was difficult to desorb from the AuCl 3 catalyst as its desorption energy was as high as 41.336 kcal mol -1. As the reaction temperature increased, C 2H 2 became easier to be adsorbed on the AuCl 3 catalyst prior to HCl, which resulted in the side reaction and the rapid deactivation of the AuCl 3 dimer due to the loss of Cl atoms. Our calculations are necessary for us to clearly understand the experimental results, which indicate a great dependence of activity and stability of AuCl 3 catalysts on the HCl:C 2H 2 ratio as well as the temperature. © 2012 The Royal Society of Chemistry. Source


Zhang L.,Tianjin University | Zhang L.,Tianjin Key Laboratory of Membrane Science and Desalination Technology | Xu L.,Tianjin University | Xu L.,Tianjin Key Laboratory of Membrane Science and Desalination Technology | And 2 more authors.
Electrochimica Acta | Year: 2014

A new type of Ti/SnO2-Sb electrode modified with carbon nanotube (CNT) has been fabricated using a pulse electrodeposition method. The electrode modified with CNT versus without CNT has larger surface area and smaller crystallite particles (41.9 nm versus 46.8 nm) as seen by scanning electron microscopy (SEM), and calculated through X-ray diffraction (XRD), respectively. It means that the CNT-modified electrode can provide more active sites for electrochemical oxidation of organic pollutants. Oxygen evolution potential of the CNT-modified electrode has 0.07 V higher overpotential in the Linear sweep voltammetry (LSV) curve. The service lifetime of Ti/SnO2-Sb-CNT electrode is 4.8 times longer than that of the Ti/SnO2-Sb electrode without CNT modifying. The Ti/SnO2-Sb-CNT electrode is demonstrated to have a superior electrochemical oxidation and degradation abilities using Acid Red 73 (AR 73) as a model organic pollutant. The CNT-modified electrode has higher kinetic rate constant, chemical oxygen demand (COD) and total organic carbon (TOC) removals, and mineralization current efficiency, which is 1.93, 1.27, 1.26, and 1.38 times those of the Ti/SnO2-Sb electrode, respectively. The repeated experiments prove the reproducibility of the data. Ti/SnO2-Sb-CNT electrode is 1.15 times more effective in permeation flux than the Ti/SnO2-Sb electrode when combining electro-catalytic oxidation and nanofiltration for treating dye wastewater. © 2013 Elsevier Ltd. Source


Xu L.,Tianjin University | Xu L.,Tianjin Key Laboratory of Membrane Science and Desalination Technology | Zhang L.,Tianjin University | Zhang L.,Tianjin Key Laboratory of Membrane Science and Desalination Technology | And 2 more authors.
Journal of Membrane Science | Year: 2014

The research was conducted to study the independent impact of electro-catalytic oxidation on the nanofiltration (NF) performance during the separation of C.I. Acid Red 73 (AR 73) wastewater. Ti/SnO2-Sb2O3 electrode modified with rare element yttrium (Y) was successfully prepared by the sol-gel technology, and then it was used as an anode for the degradation of azo dye AR 73 coupling with NF. The electro-catalytic oxidation could be restrained by painting insulating varnish on the surface of anode. Through comparing the permeation flux with the case of not using insulating varnish, we could identify the independent impact of electro-catalytic oxidation in the coupling process. The influence of operating parameters, e.g., applied voltage, initial feed concentration, operating pressure and cross flow velocity on the electro-catalytic oxidation flux and energy consumption was investigated respectively. The results indicated that the accelerated lifetime of the Ti/SnO2-Sb2O3-Y electrode reached 4.1h, which was 9.1 times longer than that of the Ti/SnO2-Sb2O3 electrode, and the electro-catalytic oxidation flux was enhanced to a great extent by choosing appropriate operating conditions and the coupling process could energy-effectively treat AR 73 wastewater. © 2013 Elsevier B.V. Source


Xu L.,Tianjin University | Xu L.,Tianjin Key Laboratory of Membrane Science and Desalination Technology | Guo Z.,Tianjin University | Guo Z.,Tianjin Key Laboratory of Membrane Science and Desalination Technology | And 2 more authors.
Electrochimica Acta | Year: 2013

This work is conducted to study ability of anodic oxidation treatment azo dye C.I. Acid Red 73 (AR73) using the electrodes of Y doped Ti/SnO 2-Sb electrodes prepared by thermal decomposition and Ti/SnO 2-Sb electrodes prepared by electrodeposition. It has been shown that doping Y can enhances the electrochemical activity of the electrodes, but the accelerated service life was slightly reduced. Both the lifetime and electrochemical activity of Ti/SnO2-Sb electrodes prepared by electrodeposition in a new Sn-Sb electrodeposition bath outperform the Ti/SnO2-Sb electrodes prepared by thermal decomposition. Moreover, the effect of varying wastewater process indexes (initial pH (4-10), the addition of NaCl (0-9 mM) and initial dye concentration (0.5-2.0 g L -1)) on the performance of anodic oxidation using Ti/SnO 2-Sb electrodes prepared by electrodeposition was investigated followed by the performance indicators analyses including color, chemical oxygen demand (COD), current efficiency and specific energy consumption. Finally, the synergy technology of anodic oxidation coupling nanofiltration was adopted to treat AR73 wastewater in order to overcome the low current efficiency of anodic oxidation. Preliminary results have shown that the synergy technology could cost-effectively treat AR73 wastewater. © 2013 Elsevier Ltd. Source

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