Catalytic Denitrification in a Trickle Bed Reactor: Ion Exchange Waste Brine Treatment

Abstract

Catalytic reduction of nitrate in ion exchange (IX) waste brine for reuse is a promising option for reducing IX costs and environmental impacts. A recycling trickle bed reactor (TBR) was designed and optimized using 0.5 percent by weight (wt%) palladium–0.05 wt% indium catalysts supported on US mesh size 12 × 14 or 12 × 30 activated carbon particles. Various liquid superficial velocities (U r ) and hydrogen gas superficial velocities (U g‐H2 ) were evaluated to assess performance in different flow regimes; catalyst activity increased with U g‐H2 at all U r for both catalysts and was greatest for the 12 × 30 catalyst at the lowest U r (8.9 m/h). The 12 × 30 catalyst demonstrated up to 100% higher catalytic activity and 280% higher mass transfer rate compared with the 12 × 14 catalyst. Optimal TBR performance was achieved with both catalysts in the trickle flow regime. The results indicate that the TBR is a promising step forward, and continued improvements are possible to overcome remaining mass transfer limitations.