Scale-up of a palladium-coated hydrogen membrane catalyst-film reactor for nitrite reduction: In situ catalyst deposition and performance evaluation

초록

The hydrogen (H2)-based membrane catalyst-film reactor (H2-MCfR) has been demonstrated at bench-scale (38 mL volume and < 0.01 m2 membrane) to denitrify nitrate and nitrite and to remove and defluorinated perfluoroalkyl substances. This work evaluated a > 2000-fold scale up (to 85 L with over 11 m2 of membrane surface area) and demonstrated it for nitrite reduction. A key technical challenge was real-time determination that in-situ palladium deposition on the hollow-fiber membranes was efficient in the upscaled-module MCfR. For this, we developed a novel UV–visible spectroscopy method for real-time monitoring of Pd2+ reduction. Material characterization on the coating validated the coating efficacy to produce Pd0. Once coated with Pd0, the upscaled-module MCfR achieved denitrification rates that increased from 1.4 to 3.7 mg∙L−1∙h−1 with increasing H2 pressures from 0.06 to 0.17 bar when dissolved oxygen (DO) was in the influent. Deoxygenating the feed water yielded even higher denitrification rates, up to 7.5 mg∙L−1∙h−1. Higher H2 pressure also promoted selectivity toward NH4+ instead of N2. The findings point out that scaled-up MCfRs should minimize DO input and optimize the H2 pressure and recirculation flow rate. © 2026 Elsevier B.V.

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