Use of PdCu catalysts supported on zirconia-ceria based supports for the elimination of oxyanions present in water

Use of carbon from the agricultural industry for the synthesis of catalysts destined to oxyanions removal from water

Remediation of water contaminated with oxyanions is of great importance due to the toxicity and environmental persistence of these chemical species. The present work describes the elimination of different oxyanions in water using catalysts supported on active carbon obtained from an agricultural residue (peanut shells, CPeanut) and active commercial carbon (CCom) in order to compare their structural and catalytic properties. The synthesized CPeanut and CCom were fully characterized by surface analysis, TGA, TPR, SEM-EDX, FT-IR, and TEM. It was observed that CPeanut presented similar superficial characteristics to CCom, being an adequate support to synthesize catalysts. With both carbons, catalysts based on Cu, Pd, and PdCu were prepared and evaluated in the elimination of NO3-, NO2-, and BrO3- from water using H2 as a reducing agent. The bimetallic catalysts prepared on both supports were active in the oxyanions reduction, obtaining good selectivities to the products of interest. In this sense, this work presents a potential re-use of agricultural wastes by preparing activated carbon from peanut shell residues in order to reduce the waste volume generated. In addition, the material synthetized is low cost due to its large-scale production and great availability in Argentina. The carbon obtained from the peanut shells provides a potential application in the environmental remediation of water contaminated with oxyanions.

Enhanced Catalytic Denitrification Performance of Ruthenium-based Catalysts by Hydrogen Spillover from a Palladium Promoter

Catalytic denitrification, a promising technology for nitrate removal, is increasingly limited by the rising price of Pd. Replacing Pd with less-expensive Ru would significantly reduce the cost; however, Ru-based catalysts have been reported to perform inconsistently in denitrification applications, making their replacement prospects unclear. Herein, the surface oxidation of Ru catalysts was confirmed to be a key factor that inhibits activity. A series of Ru-Pd catalysts containing small amounts of Pd (0.5 wt%) was developed to eliminate the Ru surface-oxide layer through the spillover of hydrogen atoms activated on the Pd promoter. Ru-Pd/Fe₃O₄ exhibited superior catalytic activity to Ru-Pd/C and Ru-Pd/Al₂O₃ because the reducible carrier (Fe₃O₄) has a lower resistance to hydrogen spillover and diffusion, as determined experimentally and supported by density functional theory calculations. This study developed a method that eliminates ruthenium surface oxides in situ and restores its denitrification activity, further reducing the barrier to Ru replacing Pd in catalytic aqueous denitrification.