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Yang B.,Shenzhen University | Yang B.,Tsinghua University | Zhang F.,Shenzhen University | Deng S.,Tsinghua University | And 4 more authors.
Chemical Engineering Journal | Year: 2012

An integrated low-cost alloy and corrosive anion system was attempted to perform aqueous hydrodechlorination (HDC) of biorefractory chlorinated organics. Several influencing factors were investigated for HDC of 2-chlorophenol (2-CP) including anion species, alloy categories, and their dosages. Al-Ni alloy presented the remarkably highest reactivity to remove 2-CP under the action of aqueous fluorine ion (F-) compared with other anions and alloys used in this study. Increasing Al-Ni alloy dosage or initial concentration of F- could enhance of 2-CP HDC efficiency. The optimized results showed that 0.389mM of 2-CP in solution could be completely dechlorinated into phenol using 10gL-1 of Al-Ni alloy and 39.7mM initial concentration of F- within 120-min reaction. The used Al-Ni alloy after each HDC reaction could almost be reactivated to the original activity level of raw Al-Ni alloy for HDC after Ca(OH)2 treatment to remove the adsorbed species such as AlF3 on alloy surface during three cycle reaction. Moreover, after Ca(OH)2 activation, F- in the effluent solution could also be effectively removed to under 0.8mgL-1 due to the formation of insoluble CaF2. The maintenance and regeneration of Al-Ni alloy activity for HDC was mainly attributed to the effects of Ca(OH)2 activation to remove adsorbed species on Al-Ni surface, inherent structure of alloy with Ni droplets homogeneously dispersed into Al substrate, and the change of its surface morphology with more active sites produced by F- corrosion. © 2012. Source

Yang B.,Shenzhen University | Yang B.,Tsinghua University | Zhang Y.,Shenzhen University | Deng S.,Tsinghua University | And 7 more authors.
Chemical Engineering Journal | Year: 2013

The Pd/Al nanoparticles (NPs) prepared by aqueous cementation were employed to probe hydrodechlorination (HDC) efficiencies of 4-chlorophenol (4-CP) in aqueous solution and 2-chlorobiphenyl (2-PCB) in surfactant solution. Major factors affecting HDC performance were investigated including acidic types, pH conditions, and surfactant types and their concentrations. Among HCl, H2SO4, H3PO4, formic acid, and acetic acid, only HCl was the proper pH adjustor to initiate HDC reaction of 4-CP with Pd/Al NPs at pH 3.0 due to the particular penetration function of active Cl- on the compact oxide film of Al. Aqueous pH states obviously influenced HDC efficiency and its values stable at pH 3-4 were the optimum range for HDC with HCl adjustor. 0.389mM of 4-CP could be almost completely dechlorinated into phenol after 30-min reaction using 2g/L of Pd/Al NPs with 1.2wt.% of Pd loading. In addition, the effect of surfactants on HDC process of highly hydrophobic 2-PCB was explored, which were employed for its better solubilization. The addition of surfactants including SDS, CTAB, Tween 80, or Brij 30 had adverse effect on HDC activity of Pd/Al NPs due to their inhibiting effect on Al corrosion. The adverse effect was closely related with the concentrations of surfactants especially for each CMC level and molecular structures. © 2013. Source

Yang B.,Shenzhen University | Yang B.,Tsinghua University | Deng S.,Tsinghua University | Yu G.,Tsinghua University | And 6 more authors.
Chemical Engineering Journal | Year: 2013

Nanoscale Al particles with average diameter of about 100nm were employed to prepare Pd/Al nanoparticles (NPs) by chemical displacement deposition. It was proved that Pd2+ acidic deposition solution was superior to its alkaline deposition solution in terms of Pd loading rate on Al NPs. The Pd/Al NPs were characterized by ICP-OES, SEM, TEM, XRD, BET and then used to explore hydrodechlorination (HDC) performance of 3-chlorophenol (3-CP) in aqueous solution. Major factors affecting HDC efficiency were investigated including Al substrate sizes, pH, Pd loadings in Pd/Al NPs, dosage of Pd/Al NPs, and temperature. The optimal results indicated that nanoscale Pd/Al bimetallic particles were highly effective for 3-CP HDC. HDC efficiency was only about 30% in 50min reaction with micron sizes of Pd/Al particles (100-400 mesh), whereas it increased to 99.7% within 30min using Pd/Al NPs at 25°C. Aqueous pH presented remarkable effect on HDC and pH 3-4 was the optimum range for HDC as pH varied from 2 to 11. Pd loadings and Pd/Al dosages were optimized for highly effective HDC as 1.16wt.% and 2g/L, respectively. In addition, higher HDC performance was obtained while reaction temperature arrived at 45°C and 0.389mM of 3-CP could be completely dechlorinated into phenol only within 10min reaction. © 2012 Elsevier B.V. Source

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