Pd-based catalytic hydrogenation has emerged as a promising and sustainable technology for waterborne contaminant removal. Supports are indispensable for Pd-based nanoparticles because they prevent nanoparticle aggregation and enhance catalyst recovery after use. Immobilization of extremely small NPs on supports enables catalyst reuse and largely reduces NP leaching, and it is more practical for water purification. Very recently, g-C3N4 has emerged as an innovative catalyst support because of its unique features. It is chemical and thermal stable in oxidative environment, it can be synthesized from earth-abundant materials, it exhibits highly tunable properties, and most importantly, it has abundant amino groups which are helpful for anchoring metal nanoparticles and their dispersion. The objective of this study is to develop Pd-based catalysts by using g-C3N4 as the catalyst support and employ them for waterborne contaminant removal (i.e., nitrite and nitrate). g-C3N4 was prepared by thermal polycondensation of different precursors (i.e., melamine (M), urea (U), and a mixture of melamine, cyanuric acid, and barbituric acid (MCB)). Pd was deposited on these g-C3N4 via wetness impregnation (noted as Pd/M, Pd/U, and Pd/MCB). Our preliminary results showed that Pd/MCB increased nitrite reduction rate by 3.3 fold, while Pd/U enhanced nitrite reduction rate by 3.7 fold compared to Pd/M. Liquid nitrogen adsorption indicated that the BET surface area of MCB, U, and M was 83.3, 52.2, and 9.8 m2/g, respectively. The high surface area of MCB and U may promote Pd dispersion and thus enhance catalytic activity. Though the surface area of U is smaller than that of MCB, higher activity on Pd/U than Pd/MCB suggests that other factors other than surface area could influence the catalytic activity (e.g., electronic properties of g-C3N4). TEM analysis showed that Pd/MCB and Pd/U have nanoparticle sizes smaller than Pd/M. CO chemisorption and ICP-MS tests will be conducted to determine Pd dispersion. XPS has confirmed the presence of elemental Pd on g-C3N4. g-C3N4 holds promise to act as new and environmentally benign support to increase catalytic activity and reusability for water purification.

Reduction of waterborne contaminants on graphitic carbon nitride supported Pd-based catalysts

253rd National Meeting (2017)

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