TY - JOUR
T1 - Optimized bimetallic ratios for durable membrane catalyst-film reactors in treating nitrate-polluted water
AU - Levi, Juliana
AU - Jung, Bongyeon
AU - Jacobs, Hunter P.
AU - Luo, Yihao
AU - Lee, Chung Seop
AU - Hong, Kiheon
AU - Long, Min
AU - Donoso, Juan
AU - Garcia-Segura, Sergi
AU - Wong, Michael S.
AU - Rittmann, Bruce E.
AU - Westerhoff, Paul
N1 - Publisher Copyright:
© 2024 Elsevier B.V.
PY - 2024/9/15
Y1 - 2024/9/15
N2 - Nitrate contamination of surface and ground water is a significant global challenge. Most current treatment technologies separate nitrate from water, resulting in concentrated wastestreams that need to be managed. Membrane Catalyst-film Reactors (MCfR), which utilize in-situ produced nanocatalysts attached to hydrogen-gas-permeable hollow-fiber membranes, offer a promising alternative for denitrification without generating a concentrated wastestream. In hydrogen-based MCfRs, bimetallic nano-scale catalysts reduce nitrate to nitrite and then further to di-nitrogen or ammonium. This study first investigated how different molar ratios of indium-to-palladium (In:Pd) catalytic films influenced denitrification rates in batch-mode MCfRs. We evaluated eleven In-Pd bimetallic catalyst films, with In:Pd molar ratios from 0.0029 to 0.28. Nitrate-removal exhibited a volcano-shaped dependence on In content, with the highest nitrate removal (0.19 mgNO3−-N-min−1 L−1) occurring at 0.045 mol In/mol Pd. Using MCfRs with the optimal In:Pd loading, we treated nitrate-spiked tap water in continuous-flow for >60 days. Nitrate removal and reduction occurred in three stages: substantial denitrification in the first stage, a decline in denitrification efficiency in the second stage, and stabilized denitrification in the third stage. Factors contributing to the slowdown of denitrification were: loss of Pd and In catalysts from the membrane surface and elevated pH due to hydroxide ion production. Sustained nitrate removal will require that these factors be mitigated.
AB - Nitrate contamination of surface and ground water is a significant global challenge. Most current treatment technologies separate nitrate from water, resulting in concentrated wastestreams that need to be managed. Membrane Catalyst-film Reactors (MCfR), which utilize in-situ produced nanocatalysts attached to hydrogen-gas-permeable hollow-fiber membranes, offer a promising alternative for denitrification without generating a concentrated wastestream. In hydrogen-based MCfRs, bimetallic nano-scale catalysts reduce nitrate to nitrite and then further to di-nitrogen or ammonium. This study first investigated how different molar ratios of indium-to-palladium (In:Pd) catalytic films influenced denitrification rates in batch-mode MCfRs. We evaluated eleven In-Pd bimetallic catalyst films, with In:Pd molar ratios from 0.0029 to 0.28. Nitrate-removal exhibited a volcano-shaped dependence on In content, with the highest nitrate removal (0.19 mgNO3−-N-min−1 L−1) occurring at 0.045 mol In/mol Pd. Using MCfRs with the optimal In:Pd loading, we treated nitrate-spiked tap water in continuous-flow for >60 days. Nitrate removal and reduction occurred in three stages: substantial denitrification in the first stage, a decline in denitrification efficiency in the second stage, and stabilized denitrification in the third stage. Factors contributing to the slowdown of denitrification were: loss of Pd and In catalysts from the membrane surface and elevated pH due to hydroxide ion production. Sustained nitrate removal will require that these factors be mitigated.
KW - Catalysis
KW - Denitrification
KW - Membrane catalytic film reactor
KW - Nitrate
KW - Water treatment
UR - http://www.scopus.com/inward/record.url?scp=85195578838&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2024.173711
DO - 10.1016/j.scitotenv.2024.173711
M3 - Article
AN - SCOPUS:85195578838
SN - 0048-9697
VL - 943
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 173711
ER -