A heterogeneous Re(hoz)2�Pd/C catalyst with high activity for perchlorate (ClO4-) reduction by H2 was synthesized and evaluated under various conditions relevant to water treatment. Inert anions inhibited ClO4- reduction activity to varying degrees, whereas cations did not affect the catalyst. Nitrate (NO3-) and elevated concentrations of ClO4- caused significant ReO4- leaching from Re(hoz)2�Pd/C. Through a comparative study of chlorate (ClO3-) reduction using Pd/C, Re leaching appears to depend on the relative rate of ReV oxidation (by oxyanions and other oxidizing species in water) and ReVII re-reduction (by Pd-generated adsorbed atomic H), where fast ReV oxidation and slow ReVII reduction leads to Re(hoz)2 decomposition and increased leaching. The effects of pH on ClO4- reduction with Re(hoz)2�Pd/C were evaluated; high activity was still observed at pH 5.9, and the optimum working pH is around 3. The Re(hoz)2�Pd/C catalyst also showed high ClO4- reduction activity in 1 M NaCl brine and after 54 days of continuous H2 sparging. The results demonstrate the necessity of developing highly active coordination complex catalysts for recalcitrant contaminants and the promising application potential of the heterogenized catalyst in water treatment.

Kinetics and stability of perchlorate reduction using a Re�Pd/C catalyst with immobilized oxorhenium complex under water treatment conditions

248th National Meeting (2014)

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