The revolutionary advancements in industrial and agricultural sectors have helped to cope with escalating demands of ever growing populations. However, ecosystems and environments around the globe have been severely affected in response to these accomplishments. Severe nitrate (NO3-) pollution of water resources is one of the most notable consequences which resulted in intensive eutrophication, depletion of dissolved oxygen, and deterioration of vital drinkable water bodies. The enormous amount of NO3- polluted water bodies could be reclaimed by adopting novel, sustainable, and environmentally benign technologies and materials. Catalytic NO3- reduction is among most promising water treatment technologies which offers several advantages e.g., high removal capacities and environmentally benign conversion to N2 and simple remediation process. In this study we prepared three novel bimetallic catalysts (Sn-Pd-NBZ; In-Pd-NBZ; Cu-Pd-NBZ) comprising of nano-crystalline beta zeolite (NBZ) as support material, Sn, Cu, and In as promoter metals, and Pd as noble metal to investigate intermetallic and metallic-zeolite interactions for optimal catalytic nitrate removal. Investigation was carried out through experiments as well as characterization techniques including X-Ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), inductively coupled plasma mass spectroscopy (ICP-MS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and H2 pulse chemisorption. Sn-Pd-NBZ, In-Pd-NBZ, and Cu-Pd-NBZ successfully removed all NO3- in batch mode. However, the reduction kinetics were in the order of Sn-Pd-NBZ (k = 19.09×10-2×min-1) &gt; In-Pd-NBZ (k = 2.89×10-2×min-1) &gt; Cu-Pd-NBZ (k = 2.31×10-2×min-1). Interestingly, Cu-Pd-NBZ achieved highest N2 selectivity (i.e., 92.68%) followed by In-Pd-NBZ (82.93%) and Sn-Pd-NBZ (80.80%). The reduction kinetics and N2 selectivity have been found to be a function of hydrogenation capacity of Pd, metal-metal alloying, and surface charge of NZB supported bimetallic catalysts. Hydrogenation of Pd was affected by its alloying with Cu, In, and Sn. Cu greatly suppressed the hydrogenation capacity of Pd which resulted in high N2 selectivity and low NO3- reduction kinetics due to the limiting conditions of activated H, as compared to that of Sn- and In-Pd-NBZ.

Exploring the interaction between metals and nano-crystalline beta zeolite for enhanced nitrate reduction

256th National Meeting (2018)

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