Levi Juliana, Jung Bongyeon, Jacobs Hunter P, Luo Yihao, Lee Chung-Seop, Hong Kiheon, Long Min, Donoso Juan, Garcia-Segura Sergi, Wong Michael S, Rittmann Bruce E, Westerhoff Paul
Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT), School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, United States; Biodesign Swette Center for Environmental Biotechnology, School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-5701, United States.
Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT), School of Chemical and Biomolecular Engineering, Rice University, Houston, TX 77005, United States.
Sci Total Environ. 2024 Sep 15;943:173711. doi: 10.1016/j.scitotenv.2024.173711. Epub 2024 Jun 8.
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 mgNO-N-min L) 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.
地表水和地下水的硝酸盐污染是一项重大的全球挑战。当前大多数处理技术将硝酸盐与水分离，产生了需要管理的浓缩废水流。膜催化剂膜反应器（MCfR）利用附着在氢气渗透中空纤维膜上原位生成的纳米催化剂，为反硝化提供了一种有前景的替代方案，且不会产生浓缩废水流。在基于氢气的MCfR中，双金属纳米级催化剂将硝酸盐还原为亚硝酸盐，然后进一步还原为氮气或铵。本研究首先调查了不同铟与钯（In:Pd）摩尔比的催化膜如何影响间歇式MCfR中的反硝化速率。我们评估了11种In-Pd双金属催化剂膜，In:Pd摩尔比从0.0029到0.28。硝酸盐去除率对铟含量呈现出火山形状的依赖性，在0.045 mol In/mol Pd时硝酸盐去除率最高（0.19 mgNO-N-min L）。使用具有最佳In:Pd负载量的MCfR，我们对加标硝酸盐的自来水进行了连续60多天的处理。硝酸盐去除和还原分三个阶段进行：第一阶段大量反硝化，第二阶段反硝化效率下降，第三阶段反硝化稳定。导致反硝化减缓的因素包括：膜表面钯和铟催化剂的损失以及由于氢氧根离子产生导致的pH值升高。要持续去除硝酸盐，需要缓解这些因素。
