Preparation Of PVDF Modification Supported Pd/fe Catalyst Reducer To Dechlorination Of Monochloroacetic Acid

Nanoparticles iron plays an important role in reducing chlorinated organics for their efficiency and convenience, but these nanoparticles can't retrieve effectively which lead to secondary pollution . Therefore it is necessary to find some supporter for metallic nanoparticles to be immobilized in. In this paper, PVDF membranes were prepared by the phase inversion method and used as the support of catalytic reductor. PVDF membranes were modified by mixing nano-TiO₂ into casting solution, and by using the surface chemical modification. Membrane-immobilized Pd/Fe nanoparticles were prepared in this study, and their characteristic and dechlorination effect of monochloracetic acid (MCAA) that was used as a targot were examed.Particle shape ,and specific surface area of membrane-immobilized Pd/Fe nanoparti-cles were studied by Fourier Transform Infrared (FT-IR) spectrometer,Sc anning Electron Microscope (SEM), Enengy Distribution Spectra (EDS) , X-ray photoelectron spectroscopy(XPS) and Contace angle methods, which were also used in the study of chemical and physical change on the PVDF embranes surface during the modification.Nano-TiO₂ modification membrane (TiO₂/PVDF) was prepared, and nano-TiO₂ content in the casting solution was optimized. When the nano-TiO₂ content reached 1wt% in casting solution, Fe loading in unit area (cm2) of the TiO₂/PVDF membrane reached 0.8032g/cm2. FT-IR and Contact angle tests studies indicated that the hydrophilicity of TiO₂/PVDF membrane was improved obviously. Pd/Fe bimetallic particles supported by TiO₂/PVDF membrane were prepared, and Pd and Fe contents loading on membrane were also optimized by dechlorinating MCAA. The result showed that 0.831 wt% Pd loading exhibited the highest dechlorination efficiency which could reach 59.75% in the first 25min and respectively reached 99.9%,87%,68.88% with different MCAA concentration (5mg/L, 10mg/L and 20mg/L) in 120min. Therefore the catalytic dechlorination of MCAA by Pd/Fe-TiO₂/PVDF was effective, and MCAA concentration has the essential effect on the dechlorination efficiency, that dechlorination efficiency decreased with the increase of concentration of MCAA . The surface chemical modification of the PVDF membrane had three steps: (1) alkaline treatment to remove HF from PVDF molecular chain; (2) nucleophilic addition reaction to creat the hydrophilcity for the surface of PVDF membrane; (3) grafting acrylic acid (AA) into the PVDF molecular chain. First, the alkaline treatment was optimized by orthogonal tests, and the best condationswere confirmed as follow: KOH concentration is 0.5mol/L, KMnO4 concentration is 2wt%, reaction temperature is 40℃, reaction time is 15min. Second, the AA concentration in the graft process was also optimized by dechlorination efficiency of MCAA, which reached 67.31% when AA concentration was20wt%. Finally, Pd/Fe bimetallic particles supported by PVDF-g-AA membrane were prepared, and Pd and Fe contents loading on membrane were optimized by dechlorinating MCAA. The result indicated that 0.501 wt% Pd loading exhibited the highest dechlorination efficiency, which could reach 67.31% in the first 30min and respectively reached 84%,62.09%,53.4% with different MCAA concentration (5mg/L, 10mg/L and 20mg/L) in 120min.