Treatment of Chlorinated Organic Compounds by Carbon Nanotubes Modified with Nanoscale Palladium Metal Hema Vijwani 1 , Sushil R. Kanel 2,3 , Sharmila M. Mukhopadhyay 1 , Abinash Agrawal 2 , Mark N. Goltz 3 1 Center for Nanoscale Multifunctional Materials, Wright State University, Dayton OH 2 Department of Earth & Environmental Sciences, Wright State University, Dayton OH 3 Air Force Institute of Technology, Wright Patterson AFB OH References 1. S. M Mukhopadhyay, Anil Karumuri and Ian T Barney, J. Phys. D: Appl. Phys. 42 (2009) 2. S. M. Mukhopadhyay, P. Joshi, S. Datta and J. MacDaniel, Applied Surface Science, 201, 219-226 (2002) 3d 5/2 3d 3/2 5.25 eV Pd Research Innovation in Treatment of Contaminated Water Aquifer contamination by chlorinated organic compounds (COC) is of great environmental concern worldwide. One approach to degrade/treat COC found in drinking water sources is by catalytic reductive dechlorination using highly reactive supported metal catalysts. Carbon nanotubes (CNTs) have extremely high specific surface area (expressed as m 2 /g), which makes them attractive as catalyst supports, and they can also be effective as pollutant adsorbents in water treatment applications. The application of metal nanoparticles in water treatment technologies presents certain challenges; if the nanoparticles to be applied in water treatment are in suspended form, the recovery of the catalyst from the treated water and its reusability can be difficult. Nanoparticles, if not recovered from the treated water, may pose toxicity to the receptors, and the treatment process can also become cost-prohibitive. We present a new class of hybrid supports for anchoring Pd nanoparticles, which combine the high surface area and structural robustness in the micro-cellular carbon foam and CNTs in designing flexibility and high catalytic activity. Objectives The present work investigates the catalytic reductive dechlorination of carbon tetrachloride (CT) by supported palladium metal nanoparticles. Palladium (Pd 0 ) is a well-known catalyst that promotes dehalogenation reactions in the presence of H 2 gas as reductant/electron donor. The bench-scale investigation currently in progress has the following objectives: 1. Examine how different supports for Pd nanoparticles affect CT transformation a. Microcellular carbon foam (Foam) b. Carbon nanotubes grafted on microcellular carbon foam (CNT) c. Pd 0 nanoparticles supported on carbon foam (Pd-Foam) d. Pd 0 nanoparticles supported on grafted carbon nanotubes (Pd-CNT) 2. Study the attachment of Pd 0 particles on carbon foam and CNT by scanning electron microscopy and energy dispersive spectroscopy 3. Study the changes in Pd 0 before and after reactions with CT with X-ray photoelectron spectroscopy (XPS) in order to assess the longevity of the Pd-CNT system The base structure is microcellular carbon foam, an open cell structure, with 3-dimensional arrays of interconnected pores resulting in high specific surface area. The surface area can be further increased by several orders of magnitude by grafting carbon nanotubes (CNTs) onto the base carbon foam to create a multi-scale hierarchical structure. Pd 0 nanoparticles supported on such carbon structure can be compact (smaller size) and cost-effective due to their extremely high surface activity. Batch experiments were conducted at bench-scale that showed no CT degradation by carbon foam and CNT-grafted carbon foam. However, CT degradation was observed with supported Pd 0 nanoparticles, as Pd-foam and Pd-CNT. CT was mostly transformed to chloroform and other less-toxic byproducts such as methane. Element Wt% At% CK 56.16 79.93 OK 11.20 11.97 SiK 05.33 03.24 PdL 24.25 03.90 VK 00.89 00.30 FeK 02.17 00.66 Matrix Correction ZAF Element Wt% At% CK 56.46 81.18 OK 08.96 09.68 SiK 05.75 03.54 PdL 22.72 03.69 FeK 05.69 01.76 Matrix Correction ZAF XPS ANALYSIS EDS ANALYSIS At% Wt% At% Wt% Pd/Bare/Grap hite C 1s 98.87 97.34 96.99 94.28 O 1s 0.97 1.27 2.76 3.57 Pd 3d 0.16 1.39 0.25 2.15 Pd/CNT/Graph ite C 1s 92.69 80.44 83.67 64.07 O 1s 4.65 5.38 10.05 10.25 Si 2p 0.75 1.52 1.57 2.82 Fe 2p 0.55 2.23 2.82 10.04 Pd 3d 1.36 10.44 1.89 12.82 Block of Carbon foam (a) Porous structure of Micro-cellular Carbon foam (b) CNT coating on Microcellular Carbon foam (c) CNT coating on carbon foam (100K ) (d) SEM: Pd 0 NPs on Carbon foam SEM: Palladium-NPs on CNT grafted Carbon Foam EDAX: Pd 0 NPs on Carbon Foam First pore Top Ligament Second pore Pd 0 NPs on Carbon Foam at 20,000x (e) Pd 0 NPs attached to microcellular carbon foam Pd 0 NPs attached to CNTs grafted on carbon foam Pd 0 NPs on Carbon Foam at 100,000x (f) Pd 0 NP on CNT/Foam at 20,000x (g) Pd 0 NPs on CNT/Foam at 100,000x (h) Figure 1: SEM images of carbon supports used in this study; (a-b) microcellular carbon foam, (c-d) CNTs grafted on microcellular carbon foam, (e-f) Palladium NPs fabricated on the microcellular carbon foam, and (g-h) Palladium NPs fabricated on CNTs attached to microcellular carbon foam Figure 2: SEM images of Pd 0 NPs at different pores on carbon foam Figure 4: SEM images of Pd 0 NPs attached to CNT- grafted microcellular foam at different pores Figure 3: SEM (20,000x magnification), EDAX, and XPS of Pd 0 NPs attached to (i) carbon foam , (ii) CNT-grafted microcellular foam EDAX: Pd 0 NPs on CNT XPS: Comparison of Pd-3d Peak Pd/Graphite vs Pd/CNT Graphite Table 1.Compositional Analysis Figure 4: CT degradation kinetics with Pd-Foam vs Pd-CNT Pd on CNT/Foam BEFORE CT Degradation XPS : Palladium - Pd 3d Peak Pd on CNT/Foam AFTER CT Degradation Figure 6: SEM and compositional analysis (from EDAX) of Pd 0 NPs bound to CNT-grafted carbon foam (i) BEFORE and (ii) AFTER CT Degradation Figure 7: XPS (a) Pd – 3d Peak of Pd 0 NPs attached to CNT grafted carbon foam (i) BEFORE and (ii) AFTER CT degradation, (b) Cl -2p Peak of Pd 0 NPs attached to CNT grafted carbon foam AFTER CT degradation XPS : Chlorine - Cl 2p Peak XPS Pd-3d 5/2 and 3/2 Peaks  BEFORE CT Degradation  AFTER CT Degradation Figure 5: CT degradation and CF formation through time with Pd-CNT 1. Pd-CNT catalyst is highly effective in the degradation/treatment of CT and similar organic pollutants found commonly in drinking water sources. 2. Pd-CNT can be used repeatedly as the valence state of Pd does not change, and thus can be cost-effective. BACKGROUND First pore Second pore Top Ligament RESULTS Conclusions y = -0.0102x + 0.1068 R² = 0.9954 y = 0.1055e -0.107x R² = 0.9953 y = -0.0217x + 0.1108 R² = 0.9633 y = 0.0809e -0.304x R² = 0.9945 0.00 0.02 0.04 0.06 0.08 0.10 -10 0 10 20 30 CT mass (mmoles) Time (Hrs) Pd-NPs Fabricated on Carbon Foam Pd-NPs Fabricated on CNTgrafted Foam 0 0.02 0.04 0.06 0.08 0.1 0 5 10 15 20 25 30 CT mass (µmoles) Time (hrs) Carbon Tetrachloride Degradation Chloroform Formation View publication stats View publication stats