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Functionalized PVDF membrane platforms were developed for environmentally benign in-situ nanostructured Fe/Pd synthesis and remediation of chlorinated organic compounds. To prevent leaching and aggregation, nanoparticle catalysts were integrated into membrane domains functionalized with poly (acrylic acid). Nanoparticles of 16–19 nm were observed inside the membrane pores by using focused ion beam (FIB). This technique prevents mechanical deformation of the membrane, compared to the normal SEM preparation methods, thus providing a clean, smooth surface for nanoparticles characterization. This allowed quantification of nanoparticle properties (size and distribution) versus depth underneath the membrane surface (0–20 µm). The results showed that nanoparticles were uniformly sized and evenly distributed inside the membrane pores. However, the size of nanoparticles inside the membrane pores was 13.9% smaller than those nanoparticles located on the membrane surface. Investigating nanoparticles inside membrane pores increases the accuracy of kinetic analysis and modeling aspects. Furthermore, the Fe/Pd immobilized membranes showed excellent performance in the degradation of chlorinated organics: Over 96% degradation of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) was achieved in less than 15 s residence time in convective flow mode. The regeneration and reuse of this catalytic membrane system were also studied. Particles were examined in XRD upon formation, after deliberate oxidation, and after regeneration. The regenerated sample showed the same crystalline pattern as the original sample. Repeated degradation experiments demonstrated successful PCB 126 dechlorination with nanoparticles regenerated for four cycles with only a small loss in reactivity. It demonstrated that Fe/Pd immobilized membranes have the potential for large-scale remediation applications.

Temperature and pH responsive polymers (poly(N-isopropylacrylamide) (PNIPAAm), and polyacrylic acid, PAA) were synthesized in one common macrofiltration PVDF membrane platform by pore-filling method. The microstructure and morphology of the PNIPAAm-PVDF, and PNIPAAm-FPAA-PVDF membranes were studied by attenuated total reflectance Fourier transform infrared (ATR-FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The membrane pore size was controlled by the swelling and shrinking of the PNIPAAm at the temperature around lower critical solution temperature (LCST). The composite membrane demonstrated a rapid and reversible swelling and deswelling change within a small temperature range. The controllable flux makes it possible to utilize this temperature responsive membrane as a valve to regulate filtration properties by temperature change. Dextran solution (Mw=2,000,000g/mol, 26 nm diameter) was used to evaluate the separation performance of the temperature responsive membranes. The ranges of dextran rejection are from 4% to 95% depending on the temperature, monomer amount and pressure. The full-scale membrane was also developed to confirm the feasibility of our bench-scale experimental results. The full-scale membrane also exhibited both temperature and pH responsivity. This system was also used for controlled nanoparticles synthesis and for dechlorination reaction.

Fe−Pd nanoparticles are immobilized in stimuliresponsive poly-N-isopropylacrylamide (PNIPAm)-and polymethyl methacrylate-functionalized polyvinylidene fluoride membranes using ion exchange for 2-chlorobiphenyl (PCB-1) degradation via the reductive pathway. PNIPAm is introduced into the reactive membrane system, and its thermoresponsive behavior is leveraged to enhance PCB-1 diffusion and adsorption into the reactive domain. The surface area-normalized rate constant (k SA ) values were determined in the convective flow mode to be 0.13, 0.28, 0.72, and 1.36 L/m 2 /g at 15, 25, 35, and 45 °C, respectively, with an activation energy of 60 kJ/mol (3 wt % Pd). The diffusion coefficients for PCB-1 were 6.6 × 10 −11 and 8.7 × 10 −11 m 2 /s at 25 and 35 °C, respectively. The adsorption of PCB-1 onto PNIPAm hydrogels also increased from 40 to 70% as the temperature was increased above its lower critical solution temperature of 32 °C. The batch-mode k SA values were 0.12 L/m 2 /h at 25 °C and 0.35 L/m 2 /h at 35 °C.

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