Application of a Re-Pd bimetallic catalyst for treatment of perchlorate in waste ion-exchange regenerant brine

作者：Liu Jinyong^*; Choe Jong Kwon; Sasnow Zachary; Werth Charles J; Strathmann Timothy J

来源：Water Research, 2013, 47(1): 91-101.

DOI：10.1016/j.watres.2012.09.031

• Perchlorate
• Nitrate
• Ion exchange
• Brine reuse
• Catalytic reduction
• Palladium
• Rhenium

Concentrated sodium chloride (NaCl) brines are often used to regenerate ion-exchange (IX) resins applied to treat drinking water sources contaminated with perchlorate (ClO4-), generating large volumes of contaminated waste brine. Chemical and biological processes for ClO4- reduction are often inhibited severely by high salt levels, making it difficult to recycle waste brines. Recent work demonstrated that novel rhenium-palladium bimetallic catalysts on activated carbon support (Re-Pd/C) can efficiently reduce ClO4- to chloride (Cl-) under acidic conditions, and here the applicability of the process for treating waste IX brines was examined. Experiments conducted in synthetic NaCl-only brine (6-12 wt%) showed higher Re-Pd/C catalyst activity than in comparable freshwater solutions, but the rate constant for ClO4- reduction measured in a real IX waste brine was found to be 65 times lower than in the synthetic NaCl brine. Through a series of experiments, co-contamination of the IX waste brine by excess NO3- (which the catalyst reduces principally to NF4+) was found to be the primary cause for deactivation of the Re-Pd/C catalyst, most likely by altering the immobilized Re component. Pre-treatment of NO3- using a different bimetallic catalyst (In-Pd/Al2O3) improved selectivity for N-2 over NH4- and enabled facile ClO4- reduction by the Re-Pd/C catalyst. Thus, sequential catalytic treatment may be a promising strategy for enabling reuse of waste IX brine containing NO3- and ClO4-.

• 出版日期2013-1-1